Effects of split feeding on performance, egg quality, and bone strength in brown laying hens in aviary system

Effects of split feeding on performance, egg quality, and bone strength in brown laying hens in... SUMMARY Brown laying hens are kept in production on average until 80 weeks. In the last phase of the production cycle, however, egg production decreases, and there is a proportional increase in cracked eggs due to decreased shell quality. Laying hens are expected to produce 500 first-quality eggs until 100 wk of age without being molted in extended production cycles. Therefore, problems related to decreased shell quality have to be addressed by genetic selection and also by optimizing nutrition and management. Conventional feeding systems in laying hens might need to be re-evaluated regarding daily Ca requirement, time, and source of its supplementation and absorption. In this experiment, feeding different diets in the first and second half of the d in a split feeding system was tested as a potential strategy to improve shell quality by offering a better match between Ca supplementation and requirements in the laying hen. Although the aim was to keep hens for an extended laying cycle, the flock had to be depopulated at 85 wk due to increased cracked eggs and low performance in the last phase of the experiment. The split feeding system could not maintain shell quality; however, it did show some potential to improve relative shell weight. The practical application of split feeding was challenging in the aviary system, and the flock also experienced health and welfare problems before and during the experiment, which influenced overall performance and the outcome of the experiment. Further long-term studies are needed to address these issues related to shell quality and health of laying hens kept in extended laying cycles. DESCRIPTION OF THE PROBLEM Brown laying hens are kept in production on average until 80 wk [1]. In the last phase of the production cycle, however, egg production decreases, and there is a proportional increase of second-grade eggs due to an increased number of cracked eggs [2, 3]. Relative shell weight, shell thickness, and breaking strength decrease towards the end of the production cycle, as a result of changes in ultrastructural organization of the shell and less efficient Ca metabolism in old laying hens [4, 5]. In addition, bone quality also decreases progressively throughout the laying cycle. As not only the medullary bone provides Ca for shell formation, in addition to the dietary sources, structural bone also may be subject to daily resorption, which can result in osteoporosis in aged laying hens [6–8]. Breeding companies predict that the production cycle will be extended to 100 wk of age, and hens will be able to produce 500 first-quality eggs in a single laying cycle without being molted [9]. The most important concerns remain, however, to maintain shell quality and bone integrity in extended production cycles. In order to do so, nutrition of laying hens might need to be re-evaluated, most importantly, regarding daily Ca requirement and time and source of its supplementation and absorption. In a conventional feeding system, laying hens are fed one diet during the d, offering a constant Ca level [10]. However, this approach might not be ideal, as Ca absorption varies during the day. During the first 5 to 6 h of egg formation when ovulation and albumen formation take place, only ∼40% of the available Ca is absorbed from the diet, whereas during shell formation, this ratio increases up to 70 to 80% [11]. In addition, it has been shown that hens have a higher Ca appetite in the last h of the light period [12], which suggests that Ca requirement is also changing during the day. However, not only the amount and time of Ca supplementation but also its form is important in the diet. Fine and coarse limestone sources are widely used as a Ca supplement, differing not only in particle size but also in solubility. Coarse limestone particles (>0.8 mm) solubilize more slowly in the gizzard, allowing a more constant Ca release, whereas fine particles due to the powdery texture provide immediately available Ca for absorption [13]. Therefore, fine limestone could be used in the morning diet to support Ca reabsorption to bone, and coarse limestone could be fed in the afternoon diet to supply Ca for longer for shell formation during the night. These factors are considered in a so-called split feeding system, where hens receive a different diet in the morning vs. afternoon. The morning diet has a lower Ca content, exclusively in the form of fine limestone, and the protein and energy levels also are increased to provide more protein for albumen formation [14]. In contrast, in the afternoon diet, hens receive a diet lower in protein and energy and a higher amount of Ca, fed exclusively in coarse form. This feeding system attempts to improve shell quality by offering a better match between Ca supplementation and requirements in the laying hen. In addition, hens might rely less on their bone reserves when provided an increased amount of Ca in the form of coarse limestone in the afternoon diet. To the authors’ knowledge, there are no studies available that investigate the practical application of split feeding in large-scale trials. Therefore, in this experiment, conventional and split feeding were compared for their effects on performance and egg and bone strength in brown laying hens kept in aviaries for an extended production cycle. MATERIALS AND METHODS Pre-experimental Period The experimental protocol was approved by the Ethical Committee of ILVO (under authorization number 2015/255; Merelbeke, Belgium). In total, 10,600 Isa Brown pullets were reared at a commercial farm and were transferred at 17 wk of age to the Experimental Poultry Center (EPC; Geel, Belgium). Hens were housed in a 2-row aviary system in 4 separate house departments (Figure 1) [15]. Figure 1. View largeDownload slide Housing and experimental setup. Figure 1. View largeDownload slide Housing and experimental setup. In the pre-experimental period (17 to 38 wk), all hens received a commercial diet based on wheat, corn, soybean, and rapeseed meal. Feed and water were provided ad libitum, and daily intake was recorded per experimental group (mean of 1325 birds). Experimental Treatments Two types of feeding systems—conventional and split—were compared. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 separate house departments. A replicate is referred to as an “experimental group” further on. Within one department, both feeding systems were tested. In the conventional system, hens received the same diet throughout the d, whereas in the split system, different morning and afternoon diets were provided. To offer the same quality raw materials to all hens at a given moment, a base feed without added limestone was formulated to create the experimental diets (Table 1). In the conventional diet, both fine and coarse limestone were added in a ratio 30:70. In the split morning diet, the amount of base feed was increased compared to the conventional diet, and a reduced amount of limestone was added (30% of the total limestone). In the split afternoon diet, the amount of base feed was reduced, and a higher amount of limestone was used (70% of the total limestone). The total daily ratio of fine and coarse limestone was also 30:70 in the split system. Table 1. Experimental diet formulation. Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 1M=morning diet available between 2:35 and 11:30. 2A=afternoon diet available between 11:30 and 18:30. 3Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. Vitamin premix added to the base diet included: Vitamin A 8000 IE/kg; 25-hydroxycholecalciferol 0.038 mg/kg; vitamin D3 (E671) 1500 IE/kg; vitamin E 30 mg/kg; cholinechloride 1000 mg/kg; Fe (II) sulphate monohydrate, Fe 55 mg/kg; calcium iodate, Iodine 1.8 mg/kg; Cu(II)sulphate pentahydrate, Cu 15 mg/kg; Mn(II)oxide, Mn100 mg/kg; Zn sulphate monohydrate, Zn 100 mg/kg; sodium selenite, selenium 0.35 mg/kg. 4Average particle sizes were 0.42 mm and 2.22 mm for the fine and coarse limestone, respectively. View Large Table 1. Experimental diet formulation. Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 1M=morning diet available between 2:35 and 11:30. 2A=afternoon diet available between 11:30 and 18:30. 3Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. Vitamin premix added to the base diet included: Vitamin A 8000 IE/kg; 25-hydroxycholecalciferol 0.038 mg/kg; vitamin D3 (E671) 1500 IE/kg; vitamin E 30 mg/kg; cholinechloride 1000 mg/kg; Fe (II) sulphate monohydrate, Fe 55 mg/kg; calcium iodate, Iodine 1.8 mg/kg; Cu(II)sulphate pentahydrate, Cu 15 mg/kg; Mn(II)oxide, Mn100 mg/kg; Zn sulphate monohydrate, Zn 100 mg/kg; sodium selenite, selenium 0.35 mg/kg. 4Average particle sizes were 0.42 mm and 2.22 mm for the fine and coarse limestone, respectively. View Large The experiment lasted from 39 to 85 wk and consisted of a 3-phase feeding system: phase 1 (39 to 55 wk), phase 2 (56 to 75 wk), and phase 3 (76 to 85 wk). In each phase, feed composition was changed to meet requirements as hens became older: the total percentage of limestone was increased to provide more Ca with advancing age of hens. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal and were isocaloric and isonitrogenous (Table 2). Table 2. Calculated nutrient composition of the experimental diets.1 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 separate house departments. 2In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 3In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 4In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). 5Ash content calculated in the base diet, without added limestone. View Large Table 2. Calculated nutrient composition of the experimental diets.1 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 separate house departments. 2In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 3In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 4In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). 5Ash content calculated in the base diet, without added limestone. View Large Feed Distribution A total of 130 g feed/hen was provided daily in both feeding systems. In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. The ratio of morning and afternoon diet had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). Distribution of 40% of the total daily feed amount was insufficient in the morning, whereas 60% of the afternoon diet provided excess amounts that were not consumed but accumulated in the feeder by the end of the day. Feed was distributed by automatic auger feeder systems: 2 at the middle and 2 at the top level of the aviary system in every experimental group. Each auger feeder was connected to its own feed hopper (Figure 1). A total of 32 hoppers was used in the experiment (16/feeding system, 4/experimental group). The base feed and limestone sources of fine, coarse, or both were weighed, mixed, and transported to the designated feed hoppers within closed tubes by an automated system. Each hopper was filled 5 times daily. Analysis of Feed and Limestone Sources Feed samples were analyzed for nitrogen, crude fat, crude fiber, crude ash, Ca, total P, and phytate P [16–22]. Particle size of the fine and coarse limestone was analyzed by sieving 3 subsamples of 100 g [23]. The calculated Ca content of the supplemented fine and coarse limestone was 38% Ca. Solubility of limestone sources was determined according to the method of Zhang and Coon [24] with a modification of using a water bath that oscillates at 50 to 60 Hz. Data Collection The F-Central FarmManager 11.10 software [25] was used to collect data of total daily feed, water intake, and mean bodyweight in every experimental group. The eggs from the 2 experimental groups within one house department were collected on the same collection belt (Figure 1). Eggs from the frontal experimental group were separated by a 1.1 m long empty belt section from the eggs of the experimental group at the back. Colored magnetic eggs were used to identify the eggs belonging to the different experimental groups. Eggs were sorted daily by the Sanovo Staalkat Alpha egg grader [26]. Eggs were weighed and also screened for blood spots, cracks, and dirtiness and were sorted and packed as first- or second-grade quality. Leakers among cracked eggs were discarded. Egg production was recorded per experimental group (mean of 1,325 hens) during the collection and grading process. During daily control of the experimental groups, dead, weak, or sick birds were removed from the flock. Feed and water intake, laying percentage, egg weight, egg mass, FCR, percentage of first- and second-grade, cracked, and dirty eggs were recorded daily, and the averages were calculated weekly on the basis of hen days. All data were gathered into one database by the Lay Insight application [27]. At the end of the experiment, the total number of eggs, cumulative FCR, and total mortality and culling were calculated. Egg Quality Assessment In total, 3,360 eggs were collected and analyzed during the experiment. A total of 120 eggs was collected per feeding system (n = 30/experimental group) on a regular basis directly from the nests (at 28, 38, 46, 52, 55, 59, 65, 70, 75, 80, and 85 wk of age) to determine external and internal quality traits. Egg weight and dynamic stiffness were determined on the d of collection; pending further analysis, eggs were stored at 10°C for 48 hours. Shell breaking strength, yolk, albumen and shell weight, albumen height and Haugh unit, and shell thickness were determined as previously described [28]. At 55 wk, only egg weight, dynamic stiffness, and breaking strength were determined, because this assessment was used to evaluate whether Ca level in the diet should be increased. At 75, 80, and 85 wk, an additional 30 eggs were collected from each replicate, but these eggs were assessed only for egg weight, dynamic stiffness, and breaking strength. Bone Strength Measurement From every experimental group, 2 laying hens were selected (n = 8/feeding system) at 21, 29, 47, 59, 71, and 85 wk of age—in total, 8 hens per feeding system—and were killed by cervical dislocation to collect right tibias for the determination of breaking strength. Breaking strength was measured using a VersaTest motorized stand [29] equipped with a 2000 N force gauge [30]. Statistical Analysis Data were analyzed using R 3.1.0 [31]. Mean performance traits (feed intake, laying %, egg weight, egg mass, and FCR) in the 2 different feeding systems were calculated for the pre-experimental phase (17 to 38 wk), and for 4 periods in the experimental phase (39 to 55, 56 to 65, 66 to 75, and 76 to 85 wk). Mean laying %, egg weight, and cracked eggs % were calculated per wk during the experimental phase (39 to 85 wk), and bone breaking strength was compared at different time points to analyze the effect of age, feeding system, and their interaction. Egg quality traits in the 2 different feeding systems were compared per week. Performance traits in the feeding systems were compared within a period using a non-parametric Wilcoxon Rank Sum test. Significance was declared at P ≤ 0.05. For mean laying%, egg weight, cracked eggs %, bone strength, and for egg quality traits, linear mixed models were used (lme4 package of R) with experimental group as random effect to correct for repeated measurements within groups. Results are presented as least square means (lsmeans). The analyzed data used for the linear models were considered sufficiently normally distributed, based on the graphical evaluation (histogram and QQ-plot) of the residuals. RESULTS AND DISCUSSION Analyzed Nutrient Composition of the Experimental Diets, Particle Size of Limestone Sources The analyzed and calculated crude protein and P content were comparable, whereas analyzed fat content was in all phases lower than the calculated values. Similarly, the analyzed crude fiber content was lower in phase 1, but in phases 2 and 3, the analyzed and the calculated values were comparable. Analyzed Ca content, however, was in every phase higher compared to the calculated content (Table 3). This could be attributed to the higher analyzed Ca content in the limestone sources, which was 40.97%. Table 3. Analyzed nutrient content of the experimental diets. Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 1In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 2Analyzed nutrient content in the base feed is given unless otherwise stated. The base diet was included in each diet in different percentages as given in Table 1. 3In the conventional system, the feed contained both fine and coarse limestone as calcium source, whereas in the split system, only fine limestone was fed in the morning diet, and only coarse limestone in the afternoon diet. 4In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 5In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). View Large Table 3. Analyzed nutrient content of the experimental diets. Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 1In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 2Analyzed nutrient content in the base feed is given unless otherwise stated. The base diet was included in each diet in different percentages as given in Table 1. 3In the conventional system, the feed contained both fine and coarse limestone as calcium source, whereas in the split system, only fine limestone was fed in the morning diet, and only coarse limestone in the afternoon diet. 4In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 5In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). View Large Mean particle sizes of the fine and coarse limestone were 0.42 mm and 2.22 mm, respectively (Table 4). More than half (66.46%) of the fine limestone particles were smaller than 0.3 mm, whereas only 1% of the coarse limestone particles had a diameter of less than 0.3 mm. In the coarse limestone source, 94.88% of the particles ranged between 1.18 and 3.35 mm in diameter. In vitro solubility was 86.11 and 50.87% for the fine and coarse limestone, respectively. Mean particle size and in vitro solubility of the fine limestone suggest that this source was probably retained for only a short period in the gizzard. The coarse limestone source, however, due to its higher mean particle size and lower in vitro solubility, could remain in the gizzard for longer, which allowed better solubilization of this Ca source. Therefore, these sources were suitable for the aim of the study, and the utilization of Ca could be adjusted to the requirements at different times of the day. Table 4. Particle size and solubility of the limestone sources. Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 View Large Table 4. Particle size and solubility of the limestone sources. Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 View Large Pre-experimental Period (17 to 38 wk) Performance of hens in the experimental groups allocated to the different feeding systems was comparable (Table 5). Total number of eggs produced per hen was non-significantly higher in the groups allocated to the conventional feeding system (112 ± 2 eggs) compared to the split feeding system (111 ± 1 egg). First-grade eggs %, cracked eggs %, and dirty eggs % were also comparable in the experimental groups (Table 6). Relative shell weight of eggs at 28 wk was higher in hens that were assigned to the conventional system compared to hens assigned to the split feeding system (P = 0.021; Figure 3a). Other shell quality and internal quality traits were similar in the experimental groups (Figures 3b, c, d and 4a, b, c). Total mortality did not differ significantly, but it was considerably higher in the groups allocated to the conventional system (1.75 ± 1.21%) compared to the groups allocated to the split system (0.94 ± 0.23%). The differences in tibia breaking strength were not significant between the experimental groups; however, the groups that were allocated to the split system had lower tibia breaking strength at 21 and 29 wk compared to the groups of the conventional system, while all hens still received the same diet (Figure 5). Experimental Period (39 to 85 wk) Practical Implementation of Split Feeding. When feeding a different morning and afternoon diet, feed portions have to be planned carefully in order to have the feed hopper empty twice a d: before the afternoon diet is dosed and before the morning diet is dosed for the next d in order to avoid mixing of the 2 diets. Constant follow-up of hoppers and feed portions is necessary, as feed intake can be influenced by stress, ambient temperature changes, diseases, and also by plumage condition [10, 32]. In case of any changes in feed intake, immediate reaction is needed to avoid that the wrong type of feed is distributed at the wrong moment of the day. In the experiment, the following measures were taken to minimize the mixing of the morning and afternoon diets in the feeders: 1) control of feeders and hoppers twice daily, 2) additional feeding times, and 3) gap feeding. Although the control of feeders and hoppers was necessary, it probably disturbed the hens and triggered stress reactions, such as aggressive feather pecking. Due to the specificity of the feeding system, 2 extra feeding times had to be added: at 8:45 and at 17:30, in addition to those at 2:35, 8:00, 11:30, 14:15, and 16:30. This was necessary because in the loop of the auger feeder (Figure 1), a certain amount of feed was always out of reach from the hens (∼16 kg). Therefore, the feeders had to be switched on for a short period of time to distribute the feed from the loop at 8:45 (before the afternoon diet was dosed) and at 17:30 (before the morning diet was dosed to the hopper). Joly [33] recommended to limit feeding times, because the more often the feeders are filled, the more competition will be between birds to pick the larger particles out of the feeder. The use of 7 feeding times daily in this experiment probably increased competition among birds and negatively affected uniformity of the flock. However, a compromise had to be made between potential mixing of the morning and afternoon diets and the total feeding times per day. Gap feeding is also a useful management practice, which is applied to make sure that hens consume all feed ingredients, including the small particles containing amino acids and vitamins [34]. During the experiment, leaving feeders empty for 1 to 2 h during the first half of the d was useful to minimize the mixing of morning and afternoon diet portions. Although it is recommended to have empty feeders only once a d, we had to aim for at least half-empty feeders by 11:30 before the afternoon diet was distributed, to make sure that the mixing of morning and afternoon diets was limited. This limited feed availability might also have caused stress and competition among hens, resulting in decreased uniformity and increased occurrence of feather pecking. In the afternoon, less time was left between feed distributions (11:30, 14:15, and 16:30) to compensate for the limited availability in the morning. During the first feed distribution (2:35), mixing of the diets could not be avoided because the feeders supposedly still contained a certain amount of leftover afternoon diet from the previous day. Therefore, the first feed distribution was always a mixture of the leftover afternoon and morning diets. In addition to minimizing the mixing of the morning and afternoon diets, the most challenging task was to fine-tune the exact amount and ratio of feed portions dosed during the day. At the start of the experiment, 40% of the total daily feed was supplied in the morning (2:35 to 11:30), and 60% in the afternoon (11:30 to 18:30), but this pattern had to be changed gradually to 45:55 and eventually to 50:50 in the last phase of the production period (76 to 85 wk), because in the morning, 40% of the total amount was not sufficient, and especially higher consumption was noticed between 8:00 and 11:30. Although Keshavarz [35] reported that 40% of the feed is consumed in the first half of the d and 60% in the second half, this might not always be applicable under practical conditions. In addition, his observation was made in a battery cage system, whereas our study was conducted in an aviary system, where birds may be more active during the first half of the d, and this might result in a higher feed consumption than in the cage systems. The ratio of feed portions dosed at different levels (middle vs. top) of the aviary also had to be established. Based on the feed consumption in the pre-experimental period, 40% of the total daily amount was dosed in the hoppers on the top level and 60% in the hoppers on the middle level. This ratio, however, had to be changed: as hens became older, they moved less in the system, and the proportion of the feed on the middle level had to be increased. The specificities of the feeding system of this semi-practical housing system (32 hoppers: 4/experimental group) made it challenging to implement split feeding during this experiment. Although the experiment was conducted on a large scale, the experimental groups were relatively small compared to those under commercial conditions. The feeding system in commercial layer houses is also less complex: the amount of hoppers is limited compared to that at the experimental facilities of EPC. Therefore, larger-scale studies are needed to test how split feeding could be applied under field conditions. Performance In general, it should be noted that we used only 4 experimental groups per feeding system, and therefore the number of replicates was limited. This resulted in a lower statistical power. In this case, a non-significant difference does not mean that there is no effect: lack of significance means either that the feeding system indeed does not have an effect on a specific trait, or it can be that there is not enough power to show the differences between feeding systems. Therefore, when considerable (non-significant) differences were found between the feeding systems, these are stated in the discussion. Feed intake did not differ significantly in the feeding systems (Table 5). However, between 76 and 80 wk of age, feed intake in the split system was considerably higher with higher variation between the experimental groups (139.8 ± 7.6 g/d) compared to the conventional system (137.9 ± 5.5 g/d). We intended to dose the same amount of feed to the hoppers in all experimental groups, based on the number of hens present and a daily feed supply of 130 g/hen/day. The total feed amount dosed was always adjusted to mortality rates. However, a certain amount of feed was needed to fill the whole length of the auger feeders. Therefore—even though mortality increased, and fewer hens were present in an experimental group—feed portions could not be lowered under a threshold amount; otherwise, feed could not have been presented equally in the whole length of the feeders. This resulted in feed intake of more than 130 g/hen/day. Table 5. Effect1 of feeding system2 on performance traits (means ± SD). Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 1No significant differences were found between treatments. 2Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 3All laying hens received the same diet between 17 and 38 wk. View Large Table 5. Effect1 of feeding system2 on performance traits (means ± SD). Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 1No significant differences were found between treatments. 2Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 3All laying hens received the same diet between 17 and 38 wk. View Large Laying % was also comparable between the feeding systems, but in the first 3 periods (39 to 75 wk), it was approximately 1% lower in the split compared to the conventional feeding system. In addition, considerable, non-significant differences were observed between the feeding systems in the total number of eggs produced per hen. Hens in the C system laid 290 ± 7 eggs, whereas hens in the S system laid 287 ± 2 eggs between 39 and 85 weeks. In the conventional system, 3 eggs more were produced per hen, but the variation was also high among the 4 experimental groups receiving the conventional diet. It should be noted that there were problems with the collection of eggs during the experiment. Laying % was followed up on a daily basis, and occasionally there was up to 10 % difference among the experimental groups housed in one house department. The eggs from the experimental groups within a house department were collected on the same collection belt. A few eggs from the first experimental group might have remained on the belt and were counted with the eggs of the group in the back or vice versa. Therefore, we assume that feeding system alone cannot account for the difference in egg production between the split and the conventional systems. Egg weight was comparable in the feeding systems, but at 76 to 80 wk, it tended to be higher in the split system compared to the conventional feeding system (P = 0.057, Table 5). Mean laying % and egg weight also were calculated per wk to compare the effect of age in the different feeding systems (Figure 2a, b). No interaction effect was found between age and feeding system. Laying % decreased significantly by 0.66% weekly between 39 and 85 wk in both feeding systems (P ≤ 0.001, Figure 2a), whereas egg weight significantly increased by 0.06 g weekly between 39 and 85 wk in both feeding systems (P ≤ 0.001, Figure 2b). Figure 2. View largeDownload slide Effect of age on laying1 %, egg weight,2 and cracked eggs3 % in the conventional and split feeding systems4. 1Laying % was calculated on the basis of hen days. 2Egg weight of all eggs produced daily was measured during the automatic grading process. 3Cracked eggs % was recorded daily during the automatic grading process. 4Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. Figure 2. View largeDownload slide Effect of age on laying1 %, egg weight,2 and cracked eggs3 % in the conventional and split feeding systems4. 1Laying % was calculated on the basis of hen days. 2Egg weight of all eggs produced daily was measured during the automatic grading process. 3Cracked eggs % was recorded daily during the automatic grading process. 4Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. Egg mass and FCR were comparable between feeding systems (Table 5). Split feeding has been reported to improve feed efficiency on a small experimental scale [36], but in our study, such improvement was not observed. However, it should be noted that early on after placement of birds, during the pre-experimental period, several health problems occurred in the flock, mainly related to gut health. Feather loss around the neck and pale combs signaled that liver lipid metabolism and intestinal digestive processes were compromised [37]. Autopsies showed necrotic enteritis in the duodenum and E.coli infection. All experimental groups were treated by a spray vaccine against E.coli and received a Cu-containing supplement in the drinking water, as it has been described that this mineral contributes to the acute phase response in case of inflammation [38]. If there had been any potential positive effects of split feeding on feed efficiency, these were masked by the symptoms—such as increased feed intake—of gut health problems. However, it cannot be excluded that split feeding did not improve feed efficiency in this trial. In addition to health problems, aggressive feather pecking was a constant problem during the experiment. Although light intensity was decreased gradually, and alfalfa and pecking stones were placed in each experimental group, already from 24 wk of age, it could not be completely eliminated from the flock [39]. As a result of gut health and E.coli problems, and injurious feather pecking, total mortality between 39 and 85 wk of age was 10.6 ± 3.0 and 11.8 ± 2.6% in the conventional and split feeding systems, respectively. Although we intended to keep layers for an extended production cycle, the flock had to be depopulated at 85 wk of age due to low performance and increased % of cracked eggs in the last phase of the production cycle. In addition, health and welfare problems also led to earlier depopulation of hens. This highlights that extended production cycles can be realized only if, in addition to persistency and shell quality, health and uniformity of the flock can be maintained and stress can be minimized [40]. Egg Quality Only small, non-significant differences were found in the percentage of first-grade, cracked, and dirty eggs produced in the conventional and split feeding systems (Table 6). As hens aged, cracked eggs % increased by 0.14 % weekly between 39 and 85 wk in both feeding systems (P ≤ 0.001; Figure 2c). Approximately from 65 wk, cracked eggs % increased and reached a level up to 8% by 85 weeks. One of the strategies to maintain eggshell quality is to control egg weight in the last phase of the laying cycle. In general, high egg weight was observed (>65 g) in both feeding systems, but until 65 wk, it was comparable to the Isa brown standard [41]. However, after 65 to 85 wk, egg weight increased by 4 g, and in the same period, cracked eggs % increased from 2 to 8%. As egg weight increased, both relative shell weight and shell thickness decreased in the last phase of the production cycle (Figure 3a, b). If energy and protein level of the diet had been adjusted to the high feed intake of hens (>130 g/d), perhaps egg weight could have been controlled. In that case, providing different levels of Ca in the morning and afternoon diets may have resulted in improvements in shell quality. But it seems that old hens (>65 wk) laying larger eggs could not form proportionally more shell, even if they were provided adjusted Ca levels in a split feeding system. Figure 3. View largeDownload slide Effect of feeding systems1 on shell quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. For dynamic stiffness and breaking strength, a total of 60 eggs was analyzed per replicate per time point between 70 and 85 wk of age. †P ≤ 0.1, * P ≤ 0.05. Figure 3. View largeDownload slide Effect of feeding systems1 on shell quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. For dynamic stiffness and breaking strength, a total of 60 eggs was analyzed per replicate per time point between 70 and 85 wk of age. †P ≤ 0.1, * P ≤ 0.05. Figure 4. View largeDownload slide Effect of feeding systems1 on internal egg quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. †P ≤ 0.1, *P ≤ 0.05. Figure 4. View largeDownload slide Effect of feeding systems1 on internal egg quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. †P ≤ 0.1, *P ≤ 0.05. Table 6. Effect of feeding system1 on egg quality. First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2Intact, clean, first-quality table eggs. 3Cracked and dirty eggs % was recorded daily during the automatic grading process. 4All laying hens received the same diet between 17 and 38 wk. 5Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. View Large Table 6. Effect of feeding system1 on egg quality. First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2Intact, clean, first-quality table eggs. 3Cracked and dirty eggs % was recorded daily during the automatic grading process. 4All laying hens received the same diet between 17 and 38 wk. 5Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. View Large However, some observations suggest that split feeding did have a positive effect on shell quality. In the pre-experimental period (28 wk), when all hens received the same diet, relative shell weight was significantly lower in the groups that were assigned to the split feeding system compared to hens assigned to the conventional feeding system. But during the experimental period at 46 wk, relative shell weight tended to be higher in the split compared to the conventional system (P = 0.085, Figure 3a). This suggests that hens having a lower relative shell weight could catch up and even improve relative shell weight, when fed an adjusted Ca level in the morning and afternoon diets in the split system. Dynamic stiffness of eggs was also higher in the split feeding system compared to the conventional system at 65 wk of age (P = 0.043, Figure 3c). Although this suggests that the probability of cracks during collection and handling would be lower in eggs from the split system, no differences were found in cracked eggs % between the feeding systems. Despite the small improvements in relative shell weight and dynamic stiffness in the split system, shell thickness and breaking strength of eggs did not differ between the feeding systems (Figure 3b, d). To the authors’ knowledge, there are no studies available investigating the effect of split feeding specifically on shell quality in laying hens throughout the whole production cycle. Furthermore, all published studies that tested split feeding were conducted on a small experimental scale. For instance, Ahmad and Balander [42] focused on reducing the P level in the afternoon diet by 20% (from 0.66 to 0.53%) and also adding 50% of coarse oyster shell to this diet. They reported that the combination of reduced P level and coarse oyster shell improved shell specific gravity (but not shell thickness). Supposedly, due to longer availability of Ca from the coarse oyster shell, less bone Ca had to be mobilized. As the diet also contained a lower amount of P, it did not interfere with Ca utilization, hence the improved egg specific gravity. In our study, P level in the afternoon diet was lower compared to the morning diet in each phase of the experiment. Nevertheless, the difference was small, only a 4% reduction in the afternoon, and perhaps this level could have been reduced more to create a higher Ca:P ratio in the afternoon diet. The relative weight of egg components differed only at 80 wk when albumen weight tended to be higher and yolk weight of eggs was significantly lower in the split system compared to the conventional feeding (P = 0.052, P = 0.043). This might be the result of higher feed intake and 5% higher protein content of the morning diet in the split system compared to the conventional diet. Haugh unit of eggs was not affected by feeding systems during the experiment (Figure 4). All in all, neither the conventional nor the split feeding system could maintain shell quality in brown hens kept in an aviary system between 38 and 85 wk of age. Bone Breaking Strength Tibia breaking strength was not affected significantly by age, feeding system, or by their interaction (Figure 5). However, a similar effect was observed as for relative shell weight of eggs. Groups assigned to the split feeding system had lower bone breaking strength in the pre-experimental period, but after 47 wk of age, split feeding seemed to improve bone strength of hens, but the differences were not significant. To the authors’ knowledge, there are no studies available investigating the effect of split feeding on bone quality. Figure 5. View largeDownload slide Effect of feeding system1 on tibia breaking strength of brown laying hens (21 to 85 wk). 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. Figure 5. View largeDownload slide Effect of feeding system1 on tibia breaking strength of brown laying hens (21 to 85 wk). 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. CONCLUSIONS AND APPLICATIONS Split feeding did not improve performance or shell quality in brown laying hens kept for an extended production cycle (until 85 wk). However, the flock experienced health and welfare problems, such as necrotic enteritis, colibacillosis, and aggressive feather pecking before and during the experiment. These confounding factors certainly influenced the performance of hens and the outcome of the experiment. Further long-term large-scale studies are needed with more replicates per feeding system to address issues related to shell quality and health in extended laying cycles. Improvement in relative shell weight in the split system at the start of the experiment suggests that split feeding can have positive effects on shell quality. However, hens were not able to form proportionally more shell when egg weight increased in the last phase of the production cycle. The application of split feeding was challenging in the aviary system under experimental conditions. Larger-scale studies are needed to test how split feeding could be applied under field conditions. When applying split feeding on farm level, a test period is certainly necessary using a conventional diet before the actual split diet feeding is applied. Attempts have to be made to reduce the potential mixing of the diets, possibly by the application of gap feeding. The optimization of feeding times and the fine-tuning of the feed portions are necessary throughout the d without compromising flock uniformity. Footnotes Primary Audience: Nutritionists, Egg Producers, Flock Advisors REFERENCES AND NOTES 1. Van Sambeek F. 2011 . Longer production cycles from a genetic perspective . Int. Poult. Prod. 19 : 27 – 29 . 2. Bain M. M. , Dunn I. C. , Wilson P. W. , Joseph N. , De Ketelaere B. , De Baerdemaeker J. , Waddington D. . 2006 . Probability of an egg cracking during packing can be predicted using a simple non-destructive acoustic test . Br. Poult. Sci. 47 : 462 – 469 . Google Scholar CrossRef Search ADS PubMed 3. Wistedt A. 2013 . Shell Formation and Bone Strength in Laying Hens . PhD. Diss . Swedish University of Agricultural Sciences . 4. Bar A. , Striem S. , Rosenberg J. , Hurwitz S. . 1988 . Egg shell quality and cholecalciferol metabolism in aged laying hens . J. Nutr. 118 : 1018 – 1023 . Google Scholar CrossRef Search ADS PubMed 5. Rodriguez-Navarro A. , Kalin O. , Nys Y. , Garcia-Ruiz J. M. . 2002 . Influence of the microstructure on the shell strength of eggs laid by hens of different ages . Br. Poult. Sci. 43 : 395 – 403 . Google Scholar CrossRef Search ADS PubMed 6. Dacke C. G. , Arkle S. , Cook D. J. , Wormstone I. M. , Jones S. , Zaidi M. , Bascal Z. A. . 1993 . Medullary Bone and Avian Calcium Regulation . J. Exp. Biol. 88 : 63 – 88 . 7. Riczu C. M. , Saunders-Blades J. L. , Yngvesson K. , Robinson F. E. , Korver D. R. . 2004 . End-of-cycle bone quality in white- and brown-egg laying hens . Poult. Sci. 83 : 375 – 383 . Google Scholar CrossRef Search ADS PubMed 8. Whitehead C. C. 2004 . Overview of bone biology in the egg-laying hen . Poult. Sci. 83 : 193 – 199 . Google Scholar CrossRef Search ADS PubMed 9. Van Sambeek F. 2011 . Breeding for 500 eggs in 100 weeks . World Poultry . Available at: http://www.poultryworld.net/Breeders/General/2011/3/Breeding-for-500-eggs-in-100-weeks-WP008564W/ . 10. Leeson S. , Summers J. D. . 2009 . Phase Feeding. Page 413 in Commercial Poultry Nutrition . Nottingham University Press , Nottingham, UK . 11. Hurwitz S. , Bar A. . 1965 . Absorption of calcium and phosphorus along the gastrointestinal tract of the laying fowl as influenced by dietary calcium and egg shell formation . J. Nutr. 86 : 433 – 438 . Google Scholar CrossRef Search ADS PubMed 12. Mongin P. , Sauveur B. . 1974 . Voluntary food and calcium intake by the laying hen . Br. Poult. Sci. 15 : 349 – 359 . Google Scholar CrossRef Search ADS PubMed 13. Zhang B. , Coon C. N. . 1997 . The relationship of calcium intake, source, size, solubility in vitro and in vivo, and gizzard limestone retention in laying hens . Poult. Sci. 76 : 1702 – 1706 . Google Scholar CrossRef Search ADS PubMed 14. Hiramoto K. , Muramatsu T. , Okumura J. . 1990 . Protein synthesis in tissues and in the whole body of laying hens during egg formation . Poult. Sci. 264 – 269 . 15. Each department housed 2 experimental groups of 1,325 birds each. Within a house department, the experimental groups (8.45 m long × 9.2 m wide) were separated by wire net walls and an intermediate section of 1.1 m. Stocking density was 9 hens per m2 . 16. International Organization for Standardization (ISO) . 2009 . ISO 5983-2, Animal feeding stuffs - Determination of nitrogen content and calculation of crude protein content - Part 2: Block digestion and steam distillation method. (last reviewed in 2014) . 17. International Organization for Standardization (ISO) . 1999 . ISO 6492, Animal Feeding Stuffs - Determination of fat content. (last reviewed in 2016) . 18. American Oil Chemists' Society (AOCS) . 2001 . Crude fiber analysis in feeds by filter bag technique . 19. International Organization for Standardization (ISO) . 2002 . ISO 5984, Animal Feeding Stuffs- Determination of crude ash. (last reviewed in 2013) . 20. International Organization for Standardization (ISO) . 1985 . ISO 6490–1, Animal feeding stuffs - Determination of calcium content - Part 1: Titrimetric method. (last reviewed in 2016) . 21. Haugh W. , Lantzsch H. . 1983 . Sensitive method for the rapid determination of phytate in cereals and cereal products . J. Sci. Food Agric. 12 : 1423 – 1426 . Google Scholar CrossRef Search ADS 22. International Organization for Standardization (ISO) . 1998 . ISO 6491, Animal feeding stuffs - Determination of phosphorus content - Spectrometric method. (last reviewed in 2014) . 23. American Society of Agricultural Engineers (ASAE) . 1995 . Standard S319.2 Method of determining and expressing fineness of feed materials by sieving. Pages 461–462 in Agricultural Engineers Yearbook of Standards, St. Joseph, Michigan: American Society of Agricultural and Biological Engineers . 24. Zhang B. , Coon C. N. . 1997 . Improved in vitro methods for determining limestone and oyster shell solubility1 . J. Appl. Poult. Res. 6 : 94 – 99 . Google Scholar CrossRef Search ADS 25. Fancom. F-Central FarmManager 11.10 . 2013 . Fancom BV, Panningen, The Netherlands . 26. Sanovo Technology Netherlands . 2014 . EGG-it Touch 4.1. Aalten, The Netherlands . 27. Porphyrio . 2013 . LayInsight Smart Farm Assistant. Porphyrio, Leuven-Herent, Belgium . 28. Molnar A. , Maertens L. , Ampe B. , Buyse J. , Zoons J. , Delezie E. . 2017 . Supplementation of fine and coarse limestone in different ratios in a split feeding system: Effects on performance , egg quality , and bone strength in old laying hens . Poult. Sci. 96 : 1659 – 1671 . Google Scholar PubMed 29. VersaTest . 1997 . Mecmesin Limited , Slinfold, United Kingdom . 30. Emperor Lite . 1977 . Mecmesin Limited , Slinfold, United Kingdom . Tibias were stored at –20°C pending analysis. For the determination of breaking strength, bones were first thawed, and all tissue and muscle were removed. The force was applied to the midpoint of each tibia with 1 cm distance between the 2 fixed points supporting the bone. The crosshead speed was 200 mm/min throughout the measurements . 31. R Core Team . 2014 . R: A language and environment for statistical computing . R Foundation for Statistical Computing , Vienna, Austria . Performance traits in the feeding systems were compared within a period using a non-parametric Wilcoxon Rank Sum test. Significance was declared at P ≤ 0.05. For mean laying %, egg weight, cracked eggs %, bone quality, and for egg quality traits, linear mixed models were used (lme4 package of R) with experimental group as random effect to correct for repeated measurements within groups. Results are presented as least square means (lsmeans). The analyzed data used for the linear models were considered sufficiently normally distributed, based on the graphical evaluation (histogram and QQ-plot) of the residuals . 32. Glatz P. C. 2001 . Effect of poor feather cover on feed intake and production of aged laying hens . Asian Australas. J. Anim. Sci 14 : 553 – 558 . Google Scholar CrossRef Search ADS 33. Joly P. 1999 . Feeding and Feeding Times. Pages 1–13 in Journèes ITAVI , Tours, France . 34. Institut de Sélection Animale (ISA) . 2009 . Nutrition Management Guide . Boxmeer, The Netherlands . 35. Keshavarz K. 1998 . Investigation on the possibility of reducing protein, phosphorus, and calcium requirements of laying hens by manipulation of time of access to these nutrients . Poult. Sci. 77 : 1320 – 1332 . Google Scholar CrossRef Search ADS PubMed 36. Lee K. H. , Ohh Y. S. . 2002 . Effects of nutrient levels and feeding regimen of a.m. and p.m. diets on laying hen performances and feed cost . Korean J. Poult. Sci. 29 : 195 – 204 . 37. Wilson M. 2013 . An Overview of Focal Duodenal Necrosis (FDN) . Hy-Line International . Available from: http://www.hyline.com/userdocs/pages/TU_FDN_ENG.pdf 38. O’Reilly E. L. , Eckersall P. D. . 2014 . Acute phase proteins: A review of their function, behaviour and measurement in chickens . Worlds Poult. Sci. J. 70 : 27 – 44 . Google Scholar CrossRef Search ADS 39. Nicol C. J. , Bestman M. , Gilani A-M. , De Haas E. N. , De Jong I. C. , Lambton S. , Wagenaar J. P. , Weeks C. A. , Rodenburg T. B. . 2013 . The prevention and control of feather pecking: Application to commercial systems . Worlds Poult. Sci. J. 69 : 775 – 788 . Google Scholar CrossRef Search ADS 40. Bain M. M. , Nys Y. , Dunn I. C. . 2016 . Increasing persistency in lay and stabilising egg quality in longer laying cycles. What are the challenges? Br. Poult. Sci. 57 : 330 – 338 . Google Scholar CrossRef Search ADS PubMed 41. Institut de Sélection Animale (ISA) . 2017 . ISA Brown Product Guide . Management Guide . Available at: http://www.isapoultry.com/es-es/products/isa/isa-brown/ . 42. Ahmad H. A. , Balander R. J. . 2003 . Alternative feeding regimen of calcium source and phosphorus level for better eggshell quality in commercial layers . J. Appl. Poult. Res. 12 : 509 – 514 . Google Scholar CrossRef Search ADS Acknowledgments The animal caretakers at EPC are greatly acknowledged for their dedicated work during this long-term experiment. The technical assistance of Ivo Hoekx, Chris Smets, and Kris De Baere are appreciated, as well as the assistance of Jos De Deken during egg quality assessment. Thanks go to flock advisors Paul Swennen and Christophe Decroos (Vepymo) for the useful suggestions and guidance. Orffa Belgium NV and Carmeuse are acknowledged for the collaboration. The technical support of Dirk Bax (VSI) is greatly acknowledged. © 2017 Poultry Science Association Inc. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Poultry Research Oxford University Press

Effects of split feeding on performance, egg quality, and bone strength in brown laying hens in aviary system

Loading next page...
 
/lp/ou_press/effects-of-split-feeding-on-performance-egg-quality-and-bone-strength-nAgeYUT5sK
Publisher
Applied Poultry Science, Inc.
Copyright
© 2017 Poultry Science Association Inc.
ISSN
1056-6171
eISSN
1537-0437
D.O.I.
10.3382/japr/pfy011
Publisher site
See Article on Publisher Site

Abstract

SUMMARY Brown laying hens are kept in production on average until 80 weeks. In the last phase of the production cycle, however, egg production decreases, and there is a proportional increase in cracked eggs due to decreased shell quality. Laying hens are expected to produce 500 first-quality eggs until 100 wk of age without being molted in extended production cycles. Therefore, problems related to decreased shell quality have to be addressed by genetic selection and also by optimizing nutrition and management. Conventional feeding systems in laying hens might need to be re-evaluated regarding daily Ca requirement, time, and source of its supplementation and absorption. In this experiment, feeding different diets in the first and second half of the d in a split feeding system was tested as a potential strategy to improve shell quality by offering a better match between Ca supplementation and requirements in the laying hen. Although the aim was to keep hens for an extended laying cycle, the flock had to be depopulated at 85 wk due to increased cracked eggs and low performance in the last phase of the experiment. The split feeding system could not maintain shell quality; however, it did show some potential to improve relative shell weight. The practical application of split feeding was challenging in the aviary system, and the flock also experienced health and welfare problems before and during the experiment, which influenced overall performance and the outcome of the experiment. Further long-term studies are needed to address these issues related to shell quality and health of laying hens kept in extended laying cycles. DESCRIPTION OF THE PROBLEM Brown laying hens are kept in production on average until 80 wk [1]. In the last phase of the production cycle, however, egg production decreases, and there is a proportional increase of second-grade eggs due to an increased number of cracked eggs [2, 3]. Relative shell weight, shell thickness, and breaking strength decrease towards the end of the production cycle, as a result of changes in ultrastructural organization of the shell and less efficient Ca metabolism in old laying hens [4, 5]. In addition, bone quality also decreases progressively throughout the laying cycle. As not only the medullary bone provides Ca for shell formation, in addition to the dietary sources, structural bone also may be subject to daily resorption, which can result in osteoporosis in aged laying hens [6–8]. Breeding companies predict that the production cycle will be extended to 100 wk of age, and hens will be able to produce 500 first-quality eggs in a single laying cycle without being molted [9]. The most important concerns remain, however, to maintain shell quality and bone integrity in extended production cycles. In order to do so, nutrition of laying hens might need to be re-evaluated, most importantly, regarding daily Ca requirement and time and source of its supplementation and absorption. In a conventional feeding system, laying hens are fed one diet during the d, offering a constant Ca level [10]. However, this approach might not be ideal, as Ca absorption varies during the day. During the first 5 to 6 h of egg formation when ovulation and albumen formation take place, only ∼40% of the available Ca is absorbed from the diet, whereas during shell formation, this ratio increases up to 70 to 80% [11]. In addition, it has been shown that hens have a higher Ca appetite in the last h of the light period [12], which suggests that Ca requirement is also changing during the day. However, not only the amount and time of Ca supplementation but also its form is important in the diet. Fine and coarse limestone sources are widely used as a Ca supplement, differing not only in particle size but also in solubility. Coarse limestone particles (>0.8 mm) solubilize more slowly in the gizzard, allowing a more constant Ca release, whereas fine particles due to the powdery texture provide immediately available Ca for absorption [13]. Therefore, fine limestone could be used in the morning diet to support Ca reabsorption to bone, and coarse limestone could be fed in the afternoon diet to supply Ca for longer for shell formation during the night. These factors are considered in a so-called split feeding system, where hens receive a different diet in the morning vs. afternoon. The morning diet has a lower Ca content, exclusively in the form of fine limestone, and the protein and energy levels also are increased to provide more protein for albumen formation [14]. In contrast, in the afternoon diet, hens receive a diet lower in protein and energy and a higher amount of Ca, fed exclusively in coarse form. This feeding system attempts to improve shell quality by offering a better match between Ca supplementation and requirements in the laying hen. In addition, hens might rely less on their bone reserves when provided an increased amount of Ca in the form of coarse limestone in the afternoon diet. To the authors’ knowledge, there are no studies available that investigate the practical application of split feeding in large-scale trials. Therefore, in this experiment, conventional and split feeding were compared for their effects on performance and egg and bone strength in brown laying hens kept in aviaries for an extended production cycle. MATERIALS AND METHODS Pre-experimental Period The experimental protocol was approved by the Ethical Committee of ILVO (under authorization number 2015/255; Merelbeke, Belgium). In total, 10,600 Isa Brown pullets were reared at a commercial farm and were transferred at 17 wk of age to the Experimental Poultry Center (EPC; Geel, Belgium). Hens were housed in a 2-row aviary system in 4 separate house departments (Figure 1) [15]. Figure 1. View largeDownload slide Housing and experimental setup. Figure 1. View largeDownload slide Housing and experimental setup. In the pre-experimental period (17 to 38 wk), all hens received a commercial diet based on wheat, corn, soybean, and rapeseed meal. Feed and water were provided ad libitum, and daily intake was recorded per experimental group (mean of 1325 birds). Experimental Treatments Two types of feeding systems—conventional and split—were compared. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 separate house departments. A replicate is referred to as an “experimental group” further on. Within one department, both feeding systems were tested. In the conventional system, hens received the same diet throughout the d, whereas in the split system, different morning and afternoon diets were provided. To offer the same quality raw materials to all hens at a given moment, a base feed without added limestone was formulated to create the experimental diets (Table 1). In the conventional diet, both fine and coarse limestone were added in a ratio 30:70. In the split morning diet, the amount of base feed was increased compared to the conventional diet, and a reduced amount of limestone was added (30% of the total limestone). In the split afternoon diet, the amount of base feed was reduced, and a higher amount of limestone was used (70% of the total limestone). The total daily ratio of fine and coarse limestone was also 30:70 in the split system. Table 1. Experimental diet formulation. Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 1M=morning diet available between 2:35 and 11:30. 2A=afternoon diet available between 11:30 and 18:30. 3Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. Vitamin premix added to the base diet included: Vitamin A 8000 IE/kg; 25-hydroxycholecalciferol 0.038 mg/kg; vitamin D3 (E671) 1500 IE/kg; vitamin E 30 mg/kg; cholinechloride 1000 mg/kg; Fe (II) sulphate monohydrate, Fe 55 mg/kg; calcium iodate, Iodine 1.8 mg/kg; Cu(II)sulphate pentahydrate, Cu 15 mg/kg; Mn(II)oxide, Mn100 mg/kg; Zn sulphate monohydrate, Zn 100 mg/kg; sodium selenite, selenium 0.35 mg/kg. 4Average particle sizes were 0.42 mm and 2.22 mm for the fine and coarse limestone, respectively. View Large Table 1. Experimental diet formulation. Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 Feeding phases 39 to 55 wk 56 to 75 wk 76 to 85 wk Ingredient (%) Conventional Split M1 Split A2 Conventional Split M Split A Conventional Split M Split A Base diet3 91.5 93.62 90.08 89.8 92.35 88.1 88.5 93.1 83.9 Including: Wheat 36.0 36.86 35.46 37.87 38.94 37.15 37.32 39.26 35.38 Corn 17.5 17.92 17.24 17.51 18.01 17.18 17.26 18.15 16.36 Soybean meal 11.1 11.37 10.94 8.22 8.45 8.06 8.10 8.52 7.68 Rapeseed meal 4.00 4.10 3.95 8.00 8.23 7.85 7.89 8.30 7.48 Salt 0.156 0.159 0.153 0.153 0.157 0.150 0.150 0.158 0.143 L-Lysine 50% liquid 0.110 0.112 0.108 0.171 0.175 0.167 0.168 0.177 0.159 DL-Methionine 98% 0.137 0.140 0.135 0.117 0.120 0.115 0.115 0.121 0.109 Fine limestone4 2.55 6.38 - 3.06 7.65 - 3.45 6.9 - Coarse limestone4 5.95 - 9.92 7.14 - 11.9 8.05 - 16.1 1M=morning diet available between 2:35 and 11:30. 2A=afternoon diet available between 11:30 and 18:30. 3Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. Vitamin premix added to the base diet included: Vitamin A 8000 IE/kg; 25-hydroxycholecalciferol 0.038 mg/kg; vitamin D3 (E671) 1500 IE/kg; vitamin E 30 mg/kg; cholinechloride 1000 mg/kg; Fe (II) sulphate monohydrate, Fe 55 mg/kg; calcium iodate, Iodine 1.8 mg/kg; Cu(II)sulphate pentahydrate, Cu 15 mg/kg; Mn(II)oxide, Mn100 mg/kg; Zn sulphate monohydrate, Zn 100 mg/kg; sodium selenite, selenium 0.35 mg/kg. 4Average particle sizes were 0.42 mm and 2.22 mm for the fine and coarse limestone, respectively. View Large The experiment lasted from 39 to 85 wk and consisted of a 3-phase feeding system: phase 1 (39 to 55 wk), phase 2 (56 to 75 wk), and phase 3 (76 to 85 wk). In each phase, feed composition was changed to meet requirements as hens became older: the total percentage of limestone was increased to provide more Ca with advancing age of hens. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal and were isocaloric and isonitrogenous (Table 2). Table 2. Calculated nutrient composition of the experimental diets.1 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 separate house departments. 2In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 3In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 4In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). 5Ash content calculated in the base diet, without added limestone. View Large Table 2. Calculated nutrient composition of the experimental diets.1 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 Feeding phases2 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients (%) Conventional Split M3 Split A4 Conventional Split M Split A Conventional Split M Split A Crude protein 16.01 16.38 15.76 15.50 15.94 15.21 15.27 16.07 14.48 Crude fat 6.50 6.65 6.40 5.77 5.93 5.66 5.68 5.98 5.39 Crude fiber 5.00 5.12 4.93 3.62 3.72 3.55 3.57 3.76 3.38 Crude ash5 3.52 3.61 3.47 3.29 3.39 3.23 3.24 3.41 3.08 Ca 3.50 2.68 4.04 4.15 3.17 4.81 4.65 2.88 6.43 P 0.48 0.49 0.47 0.47 0.48 0.46 0.46 0.49 0.44 P available 0.32 0.33 0.32 0.30 0.31 0.29 0.29 0.31 0.28 ME (kcal) 2799.17 2864.02 2755.73 2783.65 2862.69 2730.95 2743.35 2885.942 2600.76 Lysine 0.76 0.78 0.75 0.71 0.73 0.70 0.70 0.74 0.66 Methionine 0.39 0.40 0.38 0.37 0.38 0.36 0.36 0.38 0.34 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 separate house departments. 2In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 3In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 4In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). 5Ash content calculated in the base diet, without added limestone. View Large Feed Distribution A total of 130 g feed/hen was provided daily in both feeding systems. In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. The ratio of morning and afternoon diet had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). Distribution of 40% of the total daily feed amount was insufficient in the morning, whereas 60% of the afternoon diet provided excess amounts that were not consumed but accumulated in the feeder by the end of the day. Feed was distributed by automatic auger feeder systems: 2 at the middle and 2 at the top level of the aviary system in every experimental group. Each auger feeder was connected to its own feed hopper (Figure 1). A total of 32 hoppers was used in the experiment (16/feeding system, 4/experimental group). The base feed and limestone sources of fine, coarse, or both were weighed, mixed, and transported to the designated feed hoppers within closed tubes by an automated system. Each hopper was filled 5 times daily. Analysis of Feed and Limestone Sources Feed samples were analyzed for nitrogen, crude fat, crude fiber, crude ash, Ca, total P, and phytate P [16–22]. Particle size of the fine and coarse limestone was analyzed by sieving 3 subsamples of 100 g [23]. The calculated Ca content of the supplemented fine and coarse limestone was 38% Ca. Solubility of limestone sources was determined according to the method of Zhang and Coon [24] with a modification of using a water bath that oscillates at 50 to 60 Hz. Data Collection The F-Central FarmManager 11.10 software [25] was used to collect data of total daily feed, water intake, and mean bodyweight in every experimental group. The eggs from the 2 experimental groups within one house department were collected on the same collection belt (Figure 1). Eggs from the frontal experimental group were separated by a 1.1 m long empty belt section from the eggs of the experimental group at the back. Colored magnetic eggs were used to identify the eggs belonging to the different experimental groups. Eggs were sorted daily by the Sanovo Staalkat Alpha egg grader [26]. Eggs were weighed and also screened for blood spots, cracks, and dirtiness and were sorted and packed as first- or second-grade quality. Leakers among cracked eggs were discarded. Egg production was recorded per experimental group (mean of 1,325 hens) during the collection and grading process. During daily control of the experimental groups, dead, weak, or sick birds were removed from the flock. Feed and water intake, laying percentage, egg weight, egg mass, FCR, percentage of first- and second-grade, cracked, and dirty eggs were recorded daily, and the averages were calculated weekly on the basis of hen days. All data were gathered into one database by the Lay Insight application [27]. At the end of the experiment, the total number of eggs, cumulative FCR, and total mortality and culling were calculated. Egg Quality Assessment In total, 3,360 eggs were collected and analyzed during the experiment. A total of 120 eggs was collected per feeding system (n = 30/experimental group) on a regular basis directly from the nests (at 28, 38, 46, 52, 55, 59, 65, 70, 75, 80, and 85 wk of age) to determine external and internal quality traits. Egg weight and dynamic stiffness were determined on the d of collection; pending further analysis, eggs were stored at 10°C for 48 hours. Shell breaking strength, yolk, albumen and shell weight, albumen height and Haugh unit, and shell thickness were determined as previously described [28]. At 55 wk, only egg weight, dynamic stiffness, and breaking strength were determined, because this assessment was used to evaluate whether Ca level in the diet should be increased. At 75, 80, and 85 wk, an additional 30 eggs were collected from each replicate, but these eggs were assessed only for egg weight, dynamic stiffness, and breaking strength. Bone Strength Measurement From every experimental group, 2 laying hens were selected (n = 8/feeding system) at 21, 29, 47, 59, 71, and 85 wk of age—in total, 8 hens per feeding system—and were killed by cervical dislocation to collect right tibias for the determination of breaking strength. Breaking strength was measured using a VersaTest motorized stand [29] equipped with a 2000 N force gauge [30]. Statistical Analysis Data were analyzed using R 3.1.0 [31]. Mean performance traits (feed intake, laying %, egg weight, egg mass, and FCR) in the 2 different feeding systems were calculated for the pre-experimental phase (17 to 38 wk), and for 4 periods in the experimental phase (39 to 55, 56 to 65, 66 to 75, and 76 to 85 wk). Mean laying %, egg weight, and cracked eggs % were calculated per wk during the experimental phase (39 to 85 wk), and bone breaking strength was compared at different time points to analyze the effect of age, feeding system, and their interaction. Egg quality traits in the 2 different feeding systems were compared per week. Performance traits in the feeding systems were compared within a period using a non-parametric Wilcoxon Rank Sum test. Significance was declared at P ≤ 0.05. For mean laying%, egg weight, cracked eggs %, bone strength, and for egg quality traits, linear mixed models were used (lme4 package of R) with experimental group as random effect to correct for repeated measurements within groups. Results are presented as least square means (lsmeans). The analyzed data used for the linear models were considered sufficiently normally distributed, based on the graphical evaluation (histogram and QQ-plot) of the residuals. RESULTS AND DISCUSSION Analyzed Nutrient Composition of the Experimental Diets, Particle Size of Limestone Sources The analyzed and calculated crude protein and P content were comparable, whereas analyzed fat content was in all phases lower than the calculated values. Similarly, the analyzed crude fiber content was lower in phase 1, but in phases 2 and 3, the analyzed and the calculated values were comparable. Analyzed Ca content, however, was in every phase higher compared to the calculated content (Table 3). This could be attributed to the higher analyzed Ca content in the limestone sources, which was 40.97%. Table 3. Analyzed nutrient content of the experimental diets. Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 1In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 2Analyzed nutrient content in the base feed is given unless otherwise stated. The base diet was included in each diet in different percentages as given in Table 1. 3In the conventional system, the feed contained both fine and coarse limestone as calcium source, whereas in the split system, only fine limestone was fed in the morning diet, and only coarse limestone in the afternoon diet. 4In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 5In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). View Large Table 3. Analyzed nutrient content of the experimental diets. Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 Feeding phases1 39 to 55 wk 56 to 75 wk 76 to 85 wk Nutrients2 (%) Conventional3 Split2 M4 Split A5 Conventional Split M Split A Conventional Split M Split A Crude protein 16.43 16.81 16.18 15.64 16.09 15.35 15.42 16.22 14.62 Crude fat 5.87 6.00 5.77 4.58 4.71 4.49 4.51 4.74 4.27 Crude fiber 4.15 4.25 4.09 3.90 4.01 3.83 3.85 4.05 3.65 Crude ash 4.39 4.49 4.32 3.26 3.36 3.20 3.22 3.38 3.05 Ca in base diet 0.81 0.82 0.79 0.26 0.27 0.26 0.26 0.27 0.25 Ca from limestone 3.48 2.61 4.06 4.18 3.13 4.88 4.71 2.83 6.60 Ca total 4.29 3.43 4.85 4.44 3.40 5.14 5.16 3.10 6.85 Ptotal 0.45 0.46 0.44 0.46 0.47 0.45 0.45 0.47 0.43 1In each phase, feed composition was changed to meet requirements as hens became older. The composition of the diets at a given phase in the conventional and split feeding systems was kept identical throughout the whole experiment. Diets in all phases during the experiment were based on wheat, corn, soybean, and rapeseed meal. 2Analyzed nutrient content in the base feed is given unless otherwise stated. The base diet was included in each diet in different percentages as given in Table 1. 3In the conventional system, the feed contained both fine and coarse limestone as calcium source, whereas in the split system, only fine limestone was fed in the morning diet, and only coarse limestone in the afternoon diet. 4In the morning, 40% of the total daily feed amount was provided in 2 portions: at 2:35 and at 8:00 and was available until 11:30. 5In the afternoon, the remaining 60% of the feed was distributed in 3 portions: at 11:30, 14:15, and 16:30 and was available until 18:30. This ratio had to be changed to 50:50 in the last phase of the experiment (76 to 85 wk). View Large Mean particle sizes of the fine and coarse limestone were 0.42 mm and 2.22 mm, respectively (Table 4). More than half (66.46%) of the fine limestone particles were smaller than 0.3 mm, whereas only 1% of the coarse limestone particles had a diameter of less than 0.3 mm. In the coarse limestone source, 94.88% of the particles ranged between 1.18 and 3.35 mm in diameter. In vitro solubility was 86.11 and 50.87% for the fine and coarse limestone, respectively. Mean particle size and in vitro solubility of the fine limestone suggest that this source was probably retained for only a short period in the gizzard. The coarse limestone source, however, due to its higher mean particle size and lower in vitro solubility, could remain in the gizzard for longer, which allowed better solubilization of this Ca source. Therefore, these sources were suitable for the aim of the study, and the utilization of Ca could be adjusted to the requirements at different times of the day. Table 4. Particle size and solubility of the limestone sources. Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 View Large Table 4. Particle size and solubility of the limestone sources. Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 Limestone Fine Coarse Sieve opening (mm) Retained (%) <0.3 66.46 1.00 0.30 14.43 2.46 0.60 14.40 1.30 1.18 2.27 48.90 2.36 1.54 45.98 3.35 0.60 0.37 4.75 0.30 0.00 Average 0.42 2.22 In vitro solubility (%) 86.11 50.87 View Large Pre-experimental Period (17 to 38 wk) Performance of hens in the experimental groups allocated to the different feeding systems was comparable (Table 5). Total number of eggs produced per hen was non-significantly higher in the groups allocated to the conventional feeding system (112 ± 2 eggs) compared to the split feeding system (111 ± 1 egg). First-grade eggs %, cracked eggs %, and dirty eggs % were also comparable in the experimental groups (Table 6). Relative shell weight of eggs at 28 wk was higher in hens that were assigned to the conventional system compared to hens assigned to the split feeding system (P = 0.021; Figure 3a). Other shell quality and internal quality traits were similar in the experimental groups (Figures 3b, c, d and 4a, b, c). Total mortality did not differ significantly, but it was considerably higher in the groups allocated to the conventional system (1.75 ± 1.21%) compared to the groups allocated to the split system (0.94 ± 0.23%). The differences in tibia breaking strength were not significant between the experimental groups; however, the groups that were allocated to the split system had lower tibia breaking strength at 21 and 29 wk compared to the groups of the conventional system, while all hens still received the same diet (Figure 5). Experimental Period (39 to 85 wk) Practical Implementation of Split Feeding. When feeding a different morning and afternoon diet, feed portions have to be planned carefully in order to have the feed hopper empty twice a d: before the afternoon diet is dosed and before the morning diet is dosed for the next d in order to avoid mixing of the 2 diets. Constant follow-up of hoppers and feed portions is necessary, as feed intake can be influenced by stress, ambient temperature changes, diseases, and also by plumage condition [10, 32]. In case of any changes in feed intake, immediate reaction is needed to avoid that the wrong type of feed is distributed at the wrong moment of the day. In the experiment, the following measures were taken to minimize the mixing of the morning and afternoon diets in the feeders: 1) control of feeders and hoppers twice daily, 2) additional feeding times, and 3) gap feeding. Although the control of feeders and hoppers was necessary, it probably disturbed the hens and triggered stress reactions, such as aggressive feather pecking. Due to the specificity of the feeding system, 2 extra feeding times had to be added: at 8:45 and at 17:30, in addition to those at 2:35, 8:00, 11:30, 14:15, and 16:30. This was necessary because in the loop of the auger feeder (Figure 1), a certain amount of feed was always out of reach from the hens (∼16 kg). Therefore, the feeders had to be switched on for a short period of time to distribute the feed from the loop at 8:45 (before the afternoon diet was dosed) and at 17:30 (before the morning diet was dosed to the hopper). Joly [33] recommended to limit feeding times, because the more often the feeders are filled, the more competition will be between birds to pick the larger particles out of the feeder. The use of 7 feeding times daily in this experiment probably increased competition among birds and negatively affected uniformity of the flock. However, a compromise had to be made between potential mixing of the morning and afternoon diets and the total feeding times per day. Gap feeding is also a useful management practice, which is applied to make sure that hens consume all feed ingredients, including the small particles containing amino acids and vitamins [34]. During the experiment, leaving feeders empty for 1 to 2 h during the first half of the d was useful to minimize the mixing of morning and afternoon diet portions. Although it is recommended to have empty feeders only once a d, we had to aim for at least half-empty feeders by 11:30 before the afternoon diet was distributed, to make sure that the mixing of morning and afternoon diets was limited. This limited feed availability might also have caused stress and competition among hens, resulting in decreased uniformity and increased occurrence of feather pecking. In the afternoon, less time was left between feed distributions (11:30, 14:15, and 16:30) to compensate for the limited availability in the morning. During the first feed distribution (2:35), mixing of the diets could not be avoided because the feeders supposedly still contained a certain amount of leftover afternoon diet from the previous day. Therefore, the first feed distribution was always a mixture of the leftover afternoon and morning diets. In addition to minimizing the mixing of the morning and afternoon diets, the most challenging task was to fine-tune the exact amount and ratio of feed portions dosed during the day. At the start of the experiment, 40% of the total daily feed was supplied in the morning (2:35 to 11:30), and 60% in the afternoon (11:30 to 18:30), but this pattern had to be changed gradually to 45:55 and eventually to 50:50 in the last phase of the production period (76 to 85 wk), because in the morning, 40% of the total amount was not sufficient, and especially higher consumption was noticed between 8:00 and 11:30. Although Keshavarz [35] reported that 40% of the feed is consumed in the first half of the d and 60% in the second half, this might not always be applicable under practical conditions. In addition, his observation was made in a battery cage system, whereas our study was conducted in an aviary system, where birds may be more active during the first half of the d, and this might result in a higher feed consumption than in the cage systems. The ratio of feed portions dosed at different levels (middle vs. top) of the aviary also had to be established. Based on the feed consumption in the pre-experimental period, 40% of the total daily amount was dosed in the hoppers on the top level and 60% in the hoppers on the middle level. This ratio, however, had to be changed: as hens became older, they moved less in the system, and the proportion of the feed on the middle level had to be increased. The specificities of the feeding system of this semi-practical housing system (32 hoppers: 4/experimental group) made it challenging to implement split feeding during this experiment. Although the experiment was conducted on a large scale, the experimental groups were relatively small compared to those under commercial conditions. The feeding system in commercial layer houses is also less complex: the amount of hoppers is limited compared to that at the experimental facilities of EPC. Therefore, larger-scale studies are needed to test how split feeding could be applied under field conditions. Performance In general, it should be noted that we used only 4 experimental groups per feeding system, and therefore the number of replicates was limited. This resulted in a lower statistical power. In this case, a non-significant difference does not mean that there is no effect: lack of significance means either that the feeding system indeed does not have an effect on a specific trait, or it can be that there is not enough power to show the differences between feeding systems. Therefore, when considerable (non-significant) differences were found between the feeding systems, these are stated in the discussion. Feed intake did not differ significantly in the feeding systems (Table 5). However, between 76 and 80 wk of age, feed intake in the split system was considerably higher with higher variation between the experimental groups (139.8 ± 7.6 g/d) compared to the conventional system (137.9 ± 5.5 g/d). We intended to dose the same amount of feed to the hoppers in all experimental groups, based on the number of hens present and a daily feed supply of 130 g/hen/day. The total feed amount dosed was always adjusted to mortality rates. However, a certain amount of feed was needed to fill the whole length of the auger feeders. Therefore—even though mortality increased, and fewer hens were present in an experimental group—feed portions could not be lowered under a threshold amount; otherwise, feed could not have been presented equally in the whole length of the feeders. This resulted in feed intake of more than 130 g/hen/day. Table 5. Effect1 of feeding system2 on performance traits (means ± SD). Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 1No significant differences were found between treatments. 2Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 3All laying hens received the same diet between 17 and 38 wk. View Large Table 5. Effect1 of feeding system2 on performance traits (means ± SD). Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 Feed intake (g/d) Laying % Egg weight (g) Egg mass (g) FCR Period (wk)3 Conventional Split Conventional Split Conventional Split Conventional Split Conventional Split 17 to 38 111.8 ± 0.6 112.4 ± 0.9 84.8 ± 1.4 83.9 ± 0.9 59.2 ± 0.1 59.3 ± 0.2 54.1 ± 0.9 53.6 ± 0.8 2.056 ± 0.038 2.087 ± 0.027 39 to 55 126.9 ± 3.9 127.2 ± 4.0 94.5 ± 2.2 93.3 ± 1.5 65.2 ± 0.4 65.2 ± 0.5 61.6 ± 1.4 60.8 ± 1.0 2.062 ± 0.081 2.092 ± 0.077 56 to 65 131.1 ± 4.2 131.2 ± 3.5 90.6 ± 2.5 89.5 ± 2.1 65.0 ± 0.4 65.1 ± 0.4 58.9 ± 1.7 58.2 ± 1.5 2.227 ± 0.070 2.255 ± 0.061 66 to 75 135.1 ± 6.3 135.3 ± 5.4 83.8 ± 3.6 82.5 ± 3.5 66.4 ± 0.6 66.5 ± 0.7 55.4 ± 2.1 54.7 ± 2.0 2.441 ± 0.154 2.479 ± 0.180 76 to 80 137.9 ± 5.5 139.8 ± 7.6 72.6 ± 4.4 73.0 ± 3.7 67.2 ± 0.3 67.5 ± 0.3 48.4 ± 2.9 48.9 ± 2.4 2.856 ± 0.164 2.868 ± 0.242 81 to 85 136.3 ± 6.7 136.0 ± 7.0 67.1 ± 2.9 67.0 ± 1.6 67.4 ± 0.4 67.6 ± 0.5 44.7 ± 1.8 44.8 ± 1.2 3.054 ± 0.183 3.033 ± 0.143 1No significant differences were found between treatments. 2Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 3All laying hens received the same diet between 17 and 38 wk. View Large Laying % was also comparable between the feeding systems, but in the first 3 periods (39 to 75 wk), it was approximately 1% lower in the split compared to the conventional feeding system. In addition, considerable, non-significant differences were observed between the feeding systems in the total number of eggs produced per hen. Hens in the C system laid 290 ± 7 eggs, whereas hens in the S system laid 287 ± 2 eggs between 39 and 85 weeks. In the conventional system, 3 eggs more were produced per hen, but the variation was also high among the 4 experimental groups receiving the conventional diet. It should be noted that there were problems with the collection of eggs during the experiment. Laying % was followed up on a daily basis, and occasionally there was up to 10 % difference among the experimental groups housed in one house department. The eggs from the experimental groups within a house department were collected on the same collection belt. A few eggs from the first experimental group might have remained on the belt and were counted with the eggs of the group in the back or vice versa. Therefore, we assume that feeding system alone cannot account for the difference in egg production between the split and the conventional systems. Egg weight was comparable in the feeding systems, but at 76 to 80 wk, it tended to be higher in the split system compared to the conventional feeding system (P = 0.057, Table 5). Mean laying % and egg weight also were calculated per wk to compare the effect of age in the different feeding systems (Figure 2a, b). No interaction effect was found between age and feeding system. Laying % decreased significantly by 0.66% weekly between 39 and 85 wk in both feeding systems (P ≤ 0.001, Figure 2a), whereas egg weight significantly increased by 0.06 g weekly between 39 and 85 wk in both feeding systems (P ≤ 0.001, Figure 2b). Figure 2. View largeDownload slide Effect of age on laying1 %, egg weight,2 and cracked eggs3 % in the conventional and split feeding systems4. 1Laying % was calculated on the basis of hen days. 2Egg weight of all eggs produced daily was measured during the automatic grading process. 3Cracked eggs % was recorded daily during the automatic grading process. 4Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. Figure 2. View largeDownload slide Effect of age on laying1 %, egg weight,2 and cracked eggs3 % in the conventional and split feeding systems4. 1Laying % was calculated on the basis of hen days. 2Egg weight of all eggs produced daily was measured during the automatic grading process. 3Cracked eggs % was recorded daily during the automatic grading process. 4Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. Egg mass and FCR were comparable between feeding systems (Table 5). Split feeding has been reported to improve feed efficiency on a small experimental scale [36], but in our study, such improvement was not observed. However, it should be noted that early on after placement of birds, during the pre-experimental period, several health problems occurred in the flock, mainly related to gut health. Feather loss around the neck and pale combs signaled that liver lipid metabolism and intestinal digestive processes were compromised [37]. Autopsies showed necrotic enteritis in the duodenum and E.coli infection. All experimental groups were treated by a spray vaccine against E.coli and received a Cu-containing supplement in the drinking water, as it has been described that this mineral contributes to the acute phase response in case of inflammation [38]. If there had been any potential positive effects of split feeding on feed efficiency, these were masked by the symptoms—such as increased feed intake—of gut health problems. However, it cannot be excluded that split feeding did not improve feed efficiency in this trial. In addition to health problems, aggressive feather pecking was a constant problem during the experiment. Although light intensity was decreased gradually, and alfalfa and pecking stones were placed in each experimental group, already from 24 wk of age, it could not be completely eliminated from the flock [39]. As a result of gut health and E.coli problems, and injurious feather pecking, total mortality between 39 and 85 wk of age was 10.6 ± 3.0 and 11.8 ± 2.6% in the conventional and split feeding systems, respectively. Although we intended to keep layers for an extended production cycle, the flock had to be depopulated at 85 wk of age due to low performance and increased % of cracked eggs in the last phase of the production cycle. In addition, health and welfare problems also led to earlier depopulation of hens. This highlights that extended production cycles can be realized only if, in addition to persistency and shell quality, health and uniformity of the flock can be maintained and stress can be minimized [40]. Egg Quality Only small, non-significant differences were found in the percentage of first-grade, cracked, and dirty eggs produced in the conventional and split feeding systems (Table 6). As hens aged, cracked eggs % increased by 0.14 % weekly between 39 and 85 wk in both feeding systems (P ≤ 0.001; Figure 2c). Approximately from 65 wk, cracked eggs % increased and reached a level up to 8% by 85 weeks. One of the strategies to maintain eggshell quality is to control egg weight in the last phase of the laying cycle. In general, high egg weight was observed (>65 g) in both feeding systems, but until 65 wk, it was comparable to the Isa brown standard [41]. However, after 65 to 85 wk, egg weight increased by 4 g, and in the same period, cracked eggs % increased from 2 to 8%. As egg weight increased, both relative shell weight and shell thickness decreased in the last phase of the production cycle (Figure 3a, b). If energy and protein level of the diet had been adjusted to the high feed intake of hens (>130 g/d), perhaps egg weight could have been controlled. In that case, providing different levels of Ca in the morning and afternoon diets may have resulted in improvements in shell quality. But it seems that old hens (>65 wk) laying larger eggs could not form proportionally more shell, even if they were provided adjusted Ca levels in a split feeding system. Figure 3. View largeDownload slide Effect of feeding systems1 on shell quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. For dynamic stiffness and breaking strength, a total of 60 eggs was analyzed per replicate per time point between 70 and 85 wk of age. †P ≤ 0.1, * P ≤ 0.05. Figure 3. View largeDownload slide Effect of feeding systems1 on shell quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. For dynamic stiffness and breaking strength, a total of 60 eggs was analyzed per replicate per time point between 70 and 85 wk of age. †P ≤ 0.1, * P ≤ 0.05. Figure 4. View largeDownload slide Effect of feeding systems1 on internal egg quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. †P ≤ 0.1, *P ≤ 0.05. Figure 4. View largeDownload slide Effect of feeding systems1 on internal egg quality2 traits. 1Conventional system: the same diet was fed throughout the d; split system: different morning and afternoon diets were provided. Each feeding system had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2A total of 30 eggs was analyzed per replicate per time point. †P ≤ 0.1, *P ≤ 0.05. Table 6. Effect of feeding system1 on egg quality. First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2Intact, clean, first-quality table eggs. 3Cracked and dirty eggs % was recorded daily during the automatic grading process. 4All laying hens received the same diet between 17 and 38 wk. 5Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. View Large Table 6. Effect of feeding system1 on egg quality. First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 First grade eggs2 % Cracked eggs3 % Dirty eggs2 % Period4 (wk) Conventional5 Split4 Conventional Split Conventional Split 17 to 38 96.3 ± 0.3 96.2 ± 0.4 0.79 ± 0.02 0.81 ± 0.08 2.66 ± 0.31 2.76 ± 0.32 39 to 55 97.52 ± 0.54 97.27 ± 0.49 0.81 ± 0.23 0.90 ± 0.28 1.59 ± 0.42 1.74 ± 0.34 56 to 65 96.94 ± 0.57 96.65 ± 0.66 1.42 ± 0.34 1.45 ± 0.35 1.56 ± 0.40 1.81 ± 0.42 66 to 75 94.24 ± 1.73 94.00 ± 2.15 3.01 ± 1.07 3.04 ± 1.07 2.50 ± 0.80 2.68 ± 0.98 76 to 80 89.54 ± 1.33 89.66 ± 1.63 5.04 ± 0.91 5.01 ± 0.84 4.65 ± 1.27 4.50 ± 1.21 81 to 85 83.40 ± 4.10 85.32 ± 2.56 7.13 ± 1.31 7.15 ± 1.30 8.43 ± 4.12 6.50 ± 1.92 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. 2Intact, clean, first-quality table eggs. 3Cracked and dirty eggs % was recorded daily during the automatic grading process. 4All laying hens received the same diet between 17 and 38 wk. 5Conventional system: hens received the same diet throughout the d; split system: different morning and afternoon diets were provided. View Large However, some observations suggest that split feeding did have a positive effect on shell quality. In the pre-experimental period (28 wk), when all hens received the same diet, relative shell weight was significantly lower in the groups that were assigned to the split feeding system compared to hens assigned to the conventional feeding system. But during the experimental period at 46 wk, relative shell weight tended to be higher in the split compared to the conventional system (P = 0.085, Figure 3a). This suggests that hens having a lower relative shell weight could catch up and even improve relative shell weight, when fed an adjusted Ca level in the morning and afternoon diets in the split system. Dynamic stiffness of eggs was also higher in the split feeding system compared to the conventional system at 65 wk of age (P = 0.043, Figure 3c). Although this suggests that the probability of cracks during collection and handling would be lower in eggs from the split system, no differences were found in cracked eggs % between the feeding systems. Despite the small improvements in relative shell weight and dynamic stiffness in the split system, shell thickness and breaking strength of eggs did not differ between the feeding systems (Figure 3b, d). To the authors’ knowledge, there are no studies available investigating the effect of split feeding specifically on shell quality in laying hens throughout the whole production cycle. Furthermore, all published studies that tested split feeding were conducted on a small experimental scale. For instance, Ahmad and Balander [42] focused on reducing the P level in the afternoon diet by 20% (from 0.66 to 0.53%) and also adding 50% of coarse oyster shell to this diet. They reported that the combination of reduced P level and coarse oyster shell improved shell specific gravity (but not shell thickness). Supposedly, due to longer availability of Ca from the coarse oyster shell, less bone Ca had to be mobilized. As the diet also contained a lower amount of P, it did not interfere with Ca utilization, hence the improved egg specific gravity. In our study, P level in the afternoon diet was lower compared to the morning diet in each phase of the experiment. Nevertheless, the difference was small, only a 4% reduction in the afternoon, and perhaps this level could have been reduced more to create a higher Ca:P ratio in the afternoon diet. The relative weight of egg components differed only at 80 wk when albumen weight tended to be higher and yolk weight of eggs was significantly lower in the split system compared to the conventional feeding (P = 0.052, P = 0.043). This might be the result of higher feed intake and 5% higher protein content of the morning diet in the split system compared to the conventional diet. Haugh unit of eggs was not affected by feeding systems during the experiment (Figure 4). All in all, neither the conventional nor the split feeding system could maintain shell quality in brown hens kept in an aviary system between 38 and 85 wk of age. Bone Breaking Strength Tibia breaking strength was not affected significantly by age, feeding system, or by their interaction (Figure 5). However, a similar effect was observed as for relative shell weight of eggs. Groups assigned to the split feeding system had lower bone breaking strength in the pre-experimental period, but after 47 wk of age, split feeding seemed to improve bone strength of hens, but the differences were not significant. To the authors’ knowledge, there are no studies available investigating the effect of split feeding on bone quality. Figure 5. View largeDownload slide Effect of feeding system1 on tibia breaking strength of brown laying hens (21 to 85 wk). 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. Figure 5. View largeDownload slide Effect of feeding system1 on tibia breaking strength of brown laying hens (21 to 85 wk). 1Each feeding system—conventional and split—had 4 replicates (4 × 1,325 birds) housed in 4 different house departments. CONCLUSIONS AND APPLICATIONS Split feeding did not improve performance or shell quality in brown laying hens kept for an extended production cycle (until 85 wk). However, the flock experienced health and welfare problems, such as necrotic enteritis, colibacillosis, and aggressive feather pecking before and during the experiment. These confounding factors certainly influenced the performance of hens and the outcome of the experiment. Further long-term large-scale studies are needed with more replicates per feeding system to address issues related to shell quality and health in extended laying cycles. Improvement in relative shell weight in the split system at the start of the experiment suggests that split feeding can have positive effects on shell quality. However, hens were not able to form proportionally more shell when egg weight increased in the last phase of the production cycle. The application of split feeding was challenging in the aviary system under experimental conditions. Larger-scale studies are needed to test how split feeding could be applied under field conditions. When applying split feeding on farm level, a test period is certainly necessary using a conventional diet before the actual split diet feeding is applied. Attempts have to be made to reduce the potential mixing of the diets, possibly by the application of gap feeding. The optimization of feeding times and the fine-tuning of the feed portions are necessary throughout the d without compromising flock uniformity. Footnotes Primary Audience: Nutritionists, Egg Producers, Flock Advisors REFERENCES AND NOTES 1. Van Sambeek F. 2011 . Longer production cycles from a genetic perspective . Int. Poult. Prod. 19 : 27 – 29 . 2. Bain M. M. , Dunn I. C. , Wilson P. W. , Joseph N. , De Ketelaere B. , De Baerdemaeker J. , Waddington D. . 2006 . Probability of an egg cracking during packing can be predicted using a simple non-destructive acoustic test . Br. Poult. Sci. 47 : 462 – 469 . Google Scholar CrossRef Search ADS PubMed 3. Wistedt A. 2013 . Shell Formation and Bone Strength in Laying Hens . PhD. Diss . Swedish University of Agricultural Sciences . 4. Bar A. , Striem S. , Rosenberg J. , Hurwitz S. . 1988 . Egg shell quality and cholecalciferol metabolism in aged laying hens . J. Nutr. 118 : 1018 – 1023 . Google Scholar CrossRef Search ADS PubMed 5. Rodriguez-Navarro A. , Kalin O. , Nys Y. , Garcia-Ruiz J. M. . 2002 . Influence of the microstructure on the shell strength of eggs laid by hens of different ages . Br. Poult. Sci. 43 : 395 – 403 . Google Scholar CrossRef Search ADS PubMed 6. Dacke C. G. , Arkle S. , Cook D. J. , Wormstone I. M. , Jones S. , Zaidi M. , Bascal Z. A. . 1993 . Medullary Bone and Avian Calcium Regulation . J. Exp. Biol. 88 : 63 – 88 . 7. Riczu C. M. , Saunders-Blades J. L. , Yngvesson K. , Robinson F. E. , Korver D. R. . 2004 . End-of-cycle bone quality in white- and brown-egg laying hens . Poult. Sci. 83 : 375 – 383 . Google Scholar CrossRef Search ADS PubMed 8. Whitehead C. C. 2004 . Overview of bone biology in the egg-laying hen . Poult. Sci. 83 : 193 – 199 . Google Scholar CrossRef Search ADS PubMed 9. Van Sambeek F. 2011 . Breeding for 500 eggs in 100 weeks . World Poultry . Available at: http://www.poultryworld.net/Breeders/General/2011/3/Breeding-for-500-eggs-in-100-weeks-WP008564W/ . 10. Leeson S. , Summers J. D. . 2009 . Phase Feeding. Page 413 in Commercial Poultry Nutrition . Nottingham University Press , Nottingham, UK . 11. Hurwitz S. , Bar A. . 1965 . Absorption of calcium and phosphorus along the gastrointestinal tract of the laying fowl as influenced by dietary calcium and egg shell formation . J. Nutr. 86 : 433 – 438 . Google Scholar CrossRef Search ADS PubMed 12. Mongin P. , Sauveur B. . 1974 . Voluntary food and calcium intake by the laying hen . Br. Poult. Sci. 15 : 349 – 359 . Google Scholar CrossRef Search ADS PubMed 13. Zhang B. , Coon C. N. . 1997 . The relationship of calcium intake, source, size, solubility in vitro and in vivo, and gizzard limestone retention in laying hens . Poult. Sci. 76 : 1702 – 1706 . Google Scholar CrossRef Search ADS PubMed 14. Hiramoto K. , Muramatsu T. , Okumura J. . 1990 . Protein synthesis in tissues and in the whole body of laying hens during egg formation . Poult. Sci. 264 – 269 . 15. Each department housed 2 experimental groups of 1,325 birds each. Within a house department, the experimental groups (8.45 m long × 9.2 m wide) were separated by wire net walls and an intermediate section of 1.1 m. Stocking density was 9 hens per m2 . 16. International Organization for Standardization (ISO) . 2009 . ISO 5983-2, Animal feeding stuffs - Determination of nitrogen content and calculation of crude protein content - Part 2: Block digestion and steam distillation method. (last reviewed in 2014) . 17. International Organization for Standardization (ISO) . 1999 . ISO 6492, Animal Feeding Stuffs - Determination of fat content. (last reviewed in 2016) . 18. American Oil Chemists' Society (AOCS) . 2001 . Crude fiber analysis in feeds by filter bag technique . 19. International Organization for Standardization (ISO) . 2002 . ISO 5984, Animal Feeding Stuffs- Determination of crude ash. (last reviewed in 2013) . 20. International Organization for Standardization (ISO) . 1985 . ISO 6490–1, Animal feeding stuffs - Determination of calcium content - Part 1: Titrimetric method. (last reviewed in 2016) . 21. Haugh W. , Lantzsch H. . 1983 . Sensitive method for the rapid determination of phytate in cereals and cereal products . J. Sci. Food Agric. 12 : 1423 – 1426 . Google Scholar CrossRef Search ADS 22. International Organization for Standardization (ISO) . 1998 . ISO 6491, Animal feeding stuffs - Determination of phosphorus content - Spectrometric method. (last reviewed in 2014) . 23. American Society of Agricultural Engineers (ASAE) . 1995 . Standard S319.2 Method of determining and expressing fineness of feed materials by sieving. Pages 461–462 in Agricultural Engineers Yearbook of Standards, St. Joseph, Michigan: American Society of Agricultural and Biological Engineers . 24. Zhang B. , Coon C. N. . 1997 . Improved in vitro methods for determining limestone and oyster shell solubility1 . J. Appl. Poult. Res. 6 : 94 – 99 . Google Scholar CrossRef Search ADS 25. Fancom. F-Central FarmManager 11.10 . 2013 . Fancom BV, Panningen, The Netherlands . 26. Sanovo Technology Netherlands . 2014 . EGG-it Touch 4.1. Aalten, The Netherlands . 27. Porphyrio . 2013 . LayInsight Smart Farm Assistant. Porphyrio, Leuven-Herent, Belgium . 28. Molnar A. , Maertens L. , Ampe B. , Buyse J. , Zoons J. , Delezie E. . 2017 . Supplementation of fine and coarse limestone in different ratios in a split feeding system: Effects on performance , egg quality , and bone strength in old laying hens . Poult. Sci. 96 : 1659 – 1671 . Google Scholar PubMed 29. VersaTest . 1997 . Mecmesin Limited , Slinfold, United Kingdom . 30. Emperor Lite . 1977 . Mecmesin Limited , Slinfold, United Kingdom . Tibias were stored at –20°C pending analysis. For the determination of breaking strength, bones were first thawed, and all tissue and muscle were removed. The force was applied to the midpoint of each tibia with 1 cm distance between the 2 fixed points supporting the bone. The crosshead speed was 200 mm/min throughout the measurements . 31. R Core Team . 2014 . R: A language and environment for statistical computing . R Foundation for Statistical Computing , Vienna, Austria . Performance traits in the feeding systems were compared within a period using a non-parametric Wilcoxon Rank Sum test. Significance was declared at P ≤ 0.05. For mean laying %, egg weight, cracked eggs %, bone quality, and for egg quality traits, linear mixed models were used (lme4 package of R) with experimental group as random effect to correct for repeated measurements within groups. Results are presented as least square means (lsmeans). The analyzed data used for the linear models were considered sufficiently normally distributed, based on the graphical evaluation (histogram and QQ-plot) of the residuals . 32. Glatz P. C. 2001 . Effect of poor feather cover on feed intake and production of aged laying hens . Asian Australas. J. Anim. Sci 14 : 553 – 558 . Google Scholar CrossRef Search ADS 33. Joly P. 1999 . Feeding and Feeding Times. Pages 1–13 in Journèes ITAVI , Tours, France . 34. Institut de Sélection Animale (ISA) . 2009 . Nutrition Management Guide . Boxmeer, The Netherlands . 35. Keshavarz K. 1998 . Investigation on the possibility of reducing protein, phosphorus, and calcium requirements of laying hens by manipulation of time of access to these nutrients . Poult. Sci. 77 : 1320 – 1332 . Google Scholar CrossRef Search ADS PubMed 36. Lee K. H. , Ohh Y. S. . 2002 . Effects of nutrient levels and feeding regimen of a.m. and p.m. diets on laying hen performances and feed cost . Korean J. Poult. Sci. 29 : 195 – 204 . 37. Wilson M. 2013 . An Overview of Focal Duodenal Necrosis (FDN) . Hy-Line International . Available from: http://www.hyline.com/userdocs/pages/TU_FDN_ENG.pdf 38. O’Reilly E. L. , Eckersall P. D. . 2014 . Acute phase proteins: A review of their function, behaviour and measurement in chickens . Worlds Poult. Sci. J. 70 : 27 – 44 . Google Scholar CrossRef Search ADS 39. Nicol C. J. , Bestman M. , Gilani A-M. , De Haas E. N. , De Jong I. C. , Lambton S. , Wagenaar J. P. , Weeks C. A. , Rodenburg T. B. . 2013 . The prevention and control of feather pecking: Application to commercial systems . Worlds Poult. Sci. J. 69 : 775 – 788 . Google Scholar CrossRef Search ADS 40. Bain M. M. , Nys Y. , Dunn I. C. . 2016 . Increasing persistency in lay and stabilising egg quality in longer laying cycles. What are the challenges? Br. Poult. Sci. 57 : 330 – 338 . Google Scholar CrossRef Search ADS PubMed 41. Institut de Sélection Animale (ISA) . 2017 . ISA Brown Product Guide . Management Guide . Available at: http://www.isapoultry.com/es-es/products/isa/isa-brown/ . 42. Ahmad H. A. , Balander R. J. . 2003 . Alternative feeding regimen of calcium source and phosphorus level for better eggshell quality in commercial layers . J. Appl. Poult. Res. 12 : 509 – 514 . Google Scholar CrossRef Search ADS Acknowledgments The animal caretakers at EPC are greatly acknowledged for their dedicated work during this long-term experiment. The technical assistance of Ivo Hoekx, Chris Smets, and Kris De Baere are appreciated, as well as the assistance of Jos De Deken during egg quality assessment. Thanks go to flock advisors Paul Swennen and Christophe Decroos (Vepymo) for the useful suggestions and guidance. Orffa Belgium NV and Carmeuse are acknowledged for the collaboration. The technical support of Dirk Bax (VSI) is greatly acknowledged. © 2017 Poultry Science Association Inc. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

Journal of Applied Poultry ResearchOxford University Press

Published: Sep 1, 2018

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off