Particle size affects short-term preference behavior of brown-egg laying hens fed diets based on corn or barley

Particle size affects short-term preference behavior of brown-egg laying hens fed diets based on... Abstract We studied the influence of particle size of the main cereal of the diet on preference behavior by laying hens. Diets formed a 2 × 5 factorial with 2 main cereals (corn vs. barley) and 5 grinding sizes of the cereal (4, 6, 8, 10, and 12 mm screen). Each treatment was replicated 5 times (10 hens each). After a fasting period of 8 h, hens received their respective experimental diets from 06.00 to 14.00 hours. The geometric mean diameter (GMD) and the geometric standard deviation of the residuals in the feeder were determined every 2 hours. In addition, CP, ash, and Ca contents of the feeds were determined at the start and at the end of the experimental period. The experimental design was completely randomized with data analyzed as repeated measures with particle size and cereal as main effects. The GMD of the original feeds increased with increases in screen size and was greater for the barley than for the corn diets. The difference in GMD between the original diets and the residuals measured at 2 h intervals decreased as the experiment progressed (P < 0.001 for the interaction). Crude protein, ash, and Ca concentrated in the coarse fraction of the original diets and of the uneaten feed, an effect more pronounced for the minerals. Independent of the coarseness of the feed sieve, ash and Ca contents were higher in the uneaten feed at 14.00 h than in the original diets. Hens showed a clear preference for coarse particles irrespective of the concentration of CP, ash, or Ca in the different fractions of the diets. Data showed that birds under-consumed Ca during the morning, a period in which the requirements for mineral deposition are low. In summary, hens showed a significant preference for coarser particles, an effect that was more evident when the cereals were ground coarse. Hens, however, did not show any preference for consuming those feed fractions with greater CP, ash, or Ca contents. INTRODUCTION Several researchers (Benabdeljelil and Arbaoui, 1994; Lázaro et al., 2003; Herrera et al. 2017) have compared the effects of diets based on corn or barley on feed intake (FI), egg production, and egg quality in laying hens. In most cases, the main cereal of the diet did not affect egg production, provided that the feed was supplemented with an adequate enzyme complex. Berg (1959) reported also similar egg production but greater BW gain and lower FI in hens fed corn than in hens fed barley. Pérez-Bonilla et al. (2011) compared diets based on corn or barley and reported similar egg production but greater BW gain in hens fed corn. In contrast, Coon et al. (1988) reported higher FI, lower egg size, and reduced feed efficiency and BW gain in hens fed a barley diet than in hens fed a corn diet, probably because in this research the diets were not supplemented with exogenous enzymes. The information available on particle size preference by laying hens is limited. Schiffman (1968) and Allen and Perry (1977) observed that poultry had a pecking preference for coarse textured feed over non-textured feed, a preference that increased with age. ISA Brown (1999) recorded a 3.4% increase in FI and egg production in hens fed coarsely ground feeds compared with hens fed finely ground feeds (9 vs. 31% of particles smaller than 0.5 mm, respectively). More recently, Safaa et al. (2009) recorded higher FI in hens fed diets with a geometric mean diameter (GMD) of 1,375 μm than in hens fed diets with a GMD of 1,007 μm. In fact, most guidelines for laying hens (ISA Brown, 2010; Lohmann, 2016) recommend feeding coarse diets with less than 15 to 20% particles smaller than 0.5 mm when the objective is to increase FI. However, Herrera et al. (2017) did not detect any difference in FI or egg production in brown-egg laying hens fed diets in which the cereal was ground using sieves varying in screen size from 6 to 12 mm (GMD of 1,003 μm and 1,427 μm, respectively). The physico-chemical characteristics of the cereal and the diameter of the screen used to grind the cereal affect diet structure (Amerah et al., 2007; Jiménez-Moreno et al., 2016) and FI (Schiffman, 1968; Xu et al., 2015). The mechanoreceptors located in the beak of the bird detect differences in feed texture and discriminate against the consumption of fine particles (Gentle, 1979; González-Alvarado et al., 2007; Pérez-Bonilla et al., 2014), which may reduce voluntary FI. On the other hand, coarse particles are retained for a longer time in the upper part of the gastrointestinal tract (GIT) than fine particles, which might result in better development and function of the gizzard and in an improvement in nutrient utilization (Jiménez-Moreno et al., 2010; Svihus, 2011). The relative smaller surface area of the coarse particles, however, penalizes the contact between digestive enzymes and nutrients, reducing feed utilization (Amerah et al., 2007). Moreover, coarse grinding reduces feed uniformity and might induce a preference of the hens for coarse particles, resulting in the consumption of unbalanced diets and a reduction in feed efficiency (Davis et al., 1951; Nir et al., 1994). In this respect, mash diets based on cereals with different physico-chemical characteristics might result in feeds with different particle size distributions and GMD, even when ground using the same screen size (Douglas et al., 1990; Nir et al., 1995; Jiménez-Moreno et al., 2009; Perez-Bonilla et al., 2014). All these contrasting effects might counteract each other and the final outcome might depend on other uncontrolled variables, such as age of the bird, management practices, and nutritional characteristics of the diet (Mateos and Sell, 1980; Grobas et al., 1999; González-Alvarado et al., 2010). Laying hens show a specific appetite for some components of the diet, such as protein, fiber, and Ca. When given a choice, birds might be able to balance the final diet by selecting nutrients and increasing the consumption of those feed particles rich in the deficient nutrient (Hughes and Wood-Gush, 1971; Mongin and Sauveur, 1974; Holcombe et al., 1975; Abdollahi et al., 2016). For example, Forbes and Shariatmadari (1994) showed that poultry offered diets differing in CP content choose the correct amount of the different feeds to meet protein requirements. Poultry also show an appetite for structural dietary components, and when fed low fiber diets, they consume extra amounts of fibrous components if they have free access to the litter (Hetland et al., 2003; Mateos et al., 2012). We hypothesized that grinding size could affect FI and preference behavior in laying hens, with effects that could depend on the physico-chemical characteristics of the main cereal used. Also, it was hypothesized that differences in the nutritional composition of the coarse and the fine fractions of the diets could affect the feeding behavior of the hens. The objective of this research was to compare the effect of the size of the screen used to grind the cereal on the preference behavior of brown-egg laying hens fasted for 8 h and then fed diets based on corn or barley from 06.00 to 14.00 hours. MATERIALS AND METHODS Husbandry, Diets, and Experiment Design All procedures were approved by the Animal Ethics Committee of the Universidad Politécnica de Madrid and were in compliance with the Spanish guidelines for the care and use of animals in research (Boletín Oficial del Estado, 2007). Details on husbandry, ingredient composition, feeding program, and nutrient content of the diets were reported by Herrera et al. (2017). Briefly, 2 diets with similar nutrient content but differing in the main cereal used (corn vs. barley) were formulated. The moisture content of the cereals was 13.5% for the corn and 10.1% for the barley. Before feed manufacturing, the batches of the 2 cereals were divided into 5 portions, and each portion was ground using a horizontal hammer mill (Mecafa S.A., Ciudad Real, Spain) provided with a 4, 6, 8, 10, or 12 mm screen and included in their respective experimental diets. Each of the 10 diets was fed to 5 replicates that consisted of an enriched cage (120 cm × 63 cm and 45 cm height; Facco S.p.A., Padova, Italy) with 10 brown egg-laying hens. The soybean meal used in the manufacturing of the diets was used as received, whereas the sunflower meal (received in pellets) was ground using a 10-mm screen. The GMD ± geometric standard deviation (GSD; log normal SD) of the soybean meal and sunflower meal were 1,069 ± 1.79 and 699 ± 2.23 μm, respectively (Table 1). The limestone included in the diets was presented as 50% powder (GMD = 597 ± 2.31 μm) and 50% in granular (GMD = 2166 ± 1.39 μm) form. This ratio was representative of diets used in laying hens under Spanish commercial conditions (Pérez-Bonilla et al., 2014). The ingredient composition and the calculated (FEDNA, 2010) and determined nutrient content of the experimental diets are shown in Table 2. As reported by Herrera et al. (2017), FI, egg production, and BW gain of the hens from 17 to 48 wk of age (prior to the start of the experiment) were not affected by the main cereal or the screen size used to grind the cereal. Table 1. Particle size distribution and geometric mean diameter (GMD) and log normal SD (GSD) of the main ingredients.1       Calcium carbonate    Soybean meal  Sunflower meal        (47% CP)  (34% CP)  Powder  Granular  Sieve diameter, μm   5,000  0.0  0.5  0.0  0.2   2,500  3.6  3.6  0.1  29.2   1,250  36.0  18.5  18.5  70.3   630  47.7  34.6  35.2  0.2   315  10.2  27.3  23.4  0.0   160  1.4  11.8  14.8  0.0   80  0.7  3.2  6.0  0.1   40  0.4  0.5  1.9  0.0   0  0.0  0.0  0.1  0.0  GMD  1,069  699  597  2,166  GSD  1.79  2.23  2.31  1.39        Calcium carbonate    Soybean meal  Sunflower meal        (47% CP)  (34% CP)  Powder  Granular  Sieve diameter, μm   5,000  0.0  0.5  0.0  0.2   2,500  3.6  3.6  0.1  29.2   1,250  36.0  18.5  18.5  70.3   630  47.7  34.6  35.2  0.2   315  10.2  27.3  23.4  0.0   160  1.4  11.8  14.8  0.0   80  0.7  3.2  6.0  0.1   40  0.4  0.5  1.9  0.0   0  0.0  0.0  0.1  0.0  GMD  1,069  699  597  2,166  GSD  1.79  2.23  2.31  1.39  1Measured in the original ingredients before the manufacturing of the diets. View Large Table 2. Ingredient composition and chemical analyses (% as-fed basis) of the experimental diets.   Corn  Barley  Ingredient   Corn  45.00  12.50   Barley  8.80  45.00   Soybean meal, 47% CP  20.80  25.20   Sunflower meal, 34% CP  10.00  1.20   Soy oil soapstocks  4.70  5.30   Dicalcium phosphate  1.49  1.42   Calcium carbonate (powder)  4.11  4.18   Calcium carbonate (granular size)  4.11  4.18   Sodium chloride  0.35  0.35   DL-methionine, 99%  0.14  0.17   Vitamin and mineral premix1  0.50  0.50  Calculated analyses2   AMEn (Kcal/kg)  2750  2750   Crude fiber  4.4  3.6   Digestible amino acids2    Lys  0.80  0.80    Met  0.35  0.35    Met + cys  0.59  0.59    Thr  0.56  0.56  Determined analyses3   Dry matter  89.6  90.3   Gross energy (Kcal/kg)  4,305  4,290   Crude protein  17.7  17.9   Neutral detergent fiber  10.0  11.3   Ether extract  7.1  7.5   Linoleic acid (C18:2)  3.75  3.40   Ash  12.3  12.8   Calcium  3.85  3.94   Total phosphorus  0.65  0.62    Corn  Barley  Ingredient   Corn  45.00  12.50   Barley  8.80  45.00   Soybean meal, 47% CP  20.80  25.20   Sunflower meal, 34% CP  10.00  1.20   Soy oil soapstocks  4.70  5.30   Dicalcium phosphate  1.49  1.42   Calcium carbonate (powder)  4.11  4.18   Calcium carbonate (granular size)  4.11  4.18   Sodium chloride  0.35  0.35   DL-methionine, 99%  0.14  0.17   Vitamin and mineral premix1  0.50  0.50  Calculated analyses2   AMEn (Kcal/kg)  2750  2750   Crude fiber  4.4  3.6   Digestible amino acids2    Lys  0.80  0.80    Met  0.35  0.35    Met + cys  0.59  0.59    Thr  0.56  0.56  Determined analyses3   Dry matter  89.6  90.3   Gross energy (Kcal/kg)  4,305  4,290   Crude protein  17.7  17.9   Neutral detergent fiber  10.0  11.3   Ether extract  7.1  7.5   Linoleic acid (C18:2)  3.75  3.40   Ash  12.3  12.8   Calcium  3.85  3.94   Total phosphorus  0.65  0.62  1Provided the following (per kilogram of diet): vitamin A (trans-retinyl acetate), 10,000 IU; vitamin D3 (cholecalciferol), 3,750 IU; vitamin E (dl-α-tocopheryl acetate), 10 mg; vitamin B1, 1.3 mg; vitamin B2, 5 mg; vitamin B6, 2 mg; vitamin B12 (cyanocobalamin), 13 mg; niacin, 25 mg; pantothenic acid (d-calcium pantothenate), 10 mg; folic acid, 1 mg; biotin, 0.13 mg; choline (choline chloride), 250 mg; manganese (MnO), 90 mg; zinc (ZnO), 65 mg; iron (FeSO4.H2O), 40 mg; copper (CuSO4 5H2O), 8 mg; iodine [Ca(IO3)2], 0.7 mg; selenium (Na2SeO3), 0.3 mg; Roxazyme, 200 mg [1600 U of endo-1,4-β-glucanase (EC 3.2.1.4), 3600 U of endo-1,3 (4)-β-glucanase (EC 3.2.1.6), and 5200 U of endo-1,4-β-xylanase (EC 3.2.1.8)] supplied by DSM S.A., Madrid, Spain; Natuphos 5000 (300 FTU/kg supplied by Basf Española, S.A., Tarragona, Spain), 60 mg. 2According to FEDNA (2010). 3Data correspond to the average of duplicate analyses of the 5 diets ground with different screen sizes of each cereal. Within each cereal type, the determined chemical analyses were similar for all the diets (CV below 5%), independent of the screen size. View Large The night before the start of the experiment, feeders were emptied at 22.00 h and the hens fasted for 8 hours. At 06.00 h the following d, all replicates were offered 2.2 kg of their respective experimental feeds for ad libitum consumption. The amount of feed supplied at the start of the experiment was chosen to allow a complete filling of the feeders while avoiding feed wastage. Consequently, hens consumed the different fractions of the original feeds according to their preference throughout the experiment. Representative samples (300 g) of the feed remaining in the feeders were collected every 2 h during the experiment (from 06.00 to 14.00 h), and the particle size distribution and the GMD ± GSD were determined per cage at the end of each interval. The experiment was conducted as a completely randomized design with 10 diets in a factorial arrangement with 2 cereals and 5 screen sizes. Each treatment was replicated 5 times, and the experimental unit was the cage with 10 hens for all measurements. Laboratory Analysis The particle size distribution of the main ingredients, the original diets, and the uneaten feed remaining in the feeders was determined in triplicate in representative samples (100 g) every 2 h (Tables 1 and 3, and Figure 1). The data were expressed as GMD ± GSD (ASAE, 1995). Representative samples of the feeds were ground with a laboratory mill (Retsch Model Z-I, Stuttgart, Germany) equipped with a 1-mm screen and analyzed in duplicate for major nutrients, as indicated by AOAC International (2005) (Table 2). Figure 1. View largeDownload slide Particle size distribution1 of the original diets at the start of the experiment.2 1The percentage of particles smaller than 160 μm and bigger than 2,500 μm were negligible for all diets. 2The average geometric mean diameter and geometric standard deviation (GMD ± GSD), across sieve diameters, were 1,143 ± 2.16 μm for the corn diets and 1,311 ± 2.06 μm for the barley diets. Figure 1. View largeDownload slide Particle size distribution1 of the original diets at the start of the experiment.2 1The percentage of particles smaller than 160 μm and bigger than 2,500 μm were negligible for all diets. 2The average geometric mean diameter and geometric standard deviation (GMD ± GSD), across sieve diameters, were 1,143 ± 2.16 μm for the corn diets and 1,311 ± 2.06 μm for the barley diets. Table 3. Geometric mean diameter (GMD, μm) and geometric standard deviation (GSD) of the experimental diets.1   Cereal    Screen size (mm)  Corn  Barley  Average  4  960 ± 2.07  1,045 ± 2.01  1,003 ± 2.04  6  1,041 ± 2.12  1,165 ± 2.07  1,103 ± 2.10  8  1,180 ± 2.20  1,335 ± 2.06  1,258 ± 2.13  10  1,232 ± 2.21  1,458 ± 2.08  1,345 ± 2.15  12  1,302 ± 2.20  1,551 ± 2.07  1,427 ± 2.14  Average  1,143 ± 2.16  1,311 ± 2.06      Cereal    Screen size (mm)  Corn  Barley  Average  4  960 ± 2.07  1,045 ± 2.01  1,003 ± 2.04  6  1,041 ± 2.12  1,165 ± 2.07  1,103 ± 2.10  8  1,180 ± 2.20  1,335 ± 2.06  1,258 ± 2.13  10  1,232 ± 2.21  1,458 ± 2.08  1,345 ± 2.15  12  1,302 ± 2.20  1,551 ± 2.07  1,427 ± 2.14  Average  1,143 ± 2.16  1,311 ± 2.06    1Determined before the start of the experiment. View Large At the end of the experiment (14.00 h.), the feed remaining in the feeders of all the replicates was collected and pooled by treatment. The reason for pooling the uneaten feed of the 5 replicates of each of the 10 treatments was the limited amount of residual feed present in some replicates, which did not allow to estimate precisely the nutrient composition of each of the sieve fractions in the replicates. Representative samples of the 5 sieve fractions of each of the 10 original diets and of the 50 composite uneaten feed samples collected at 14.00 h (10 treatments and 5 sieve fractions per treatment) were ground (1-mm screen) and analyzed for moisture, CP, total ash, and Ca, as indicated by Herrera et al. (2017). Statistical Analysis The experiment was conducted as a completely randomized design with 10 treatments arranged as a 2 × 5 factorial with 2 main cereals (corn and barley) and 5 mean particle sizes of the cereal (4, 6, 8, 10, and 12 mm screen). The effects of type of cereal and grinding size of the cereal on FI and their interactions were analyzed by the GLM procedure of SAS (SAS Institute, 2004). For particle size selection, the same effects and the interaction between sampling time and the main effects were analyzed by the MIXED procedure of SAS (SAS Institute, 2004), using time as the repeated measure. The individual cage represented the experimental unit for all measurements. When the model was significant, treatment means were separated using the Tukey test. Results in tables are presented as means, and differences were considered significant at P < 0.05. For data on CP, ash, and Ca content of the different sieve fractions of the original diets and of the residual feeds at 14.00 h, no replicates were available and therefore only average values per treatment are presented. RESULTS The effects of the cereal and screen size on the GMD and the GSD of the diets are shown in Table 3. Independent of the screen used, the GMD of the feeds was greater (average of 1,311 μm vs. 1,143 μm) for the barley than for the corn diets. However, an opposite effect was observed for the GSD (2.06 vs. 2.16). FI from 06.00 to 14.00 h (56.6 ± 5.4 g) was not affected by the main cereal or the screen size used to grind the cereal (data not shown). The effects of the main cereal, screen size, and time on particle size distribution of diets and feed refusals are shown in Table 4. The GMD and the GSD of the diets decreased (P < 0.001) as the experiment progressed, irrespective of the size of the screen used to grind the cereal. The differences in GMD between the corn and barley based diets decreased with time (P < 0.001 for the interaction; Figure 2A). For the GSD, the decrease with sampling time observed was more pronounced for the corn than for the barley diets (P < 0.001 for the interaction; Figure 2B). Figure 2. View largeDownload slide Interaction between the main cereal of the diet and sampling time on geometric mean diameter (GMD) and log normal SD (GSD) of the diets. (A) Geometric mean diameter (GMD, μm). (B) Geometric standard deviation (GSD, μm). Figure 2. View largeDownload slide Interaction between the main cereal of the diet and sampling time on geometric mean diameter (GMD) and log normal SD (GSD) of the diets. (A) Geometric mean diameter (GMD, μm). (B) Geometric standard deviation (GSD, μm). Table 4. Influence of the main cereal and the particle size distribution of the diet on preference behavior of the hens.     Cereal  Screen size (mm)  Time  SD1  Probability2,3      Corn  Barley  4  6  8  10  12      1  2  3  4  5  GMD4                  88.5  <.001  <.001  <.001  <.001  <.001    06.00 h  1,143  1,311  1,003  1,103  1,258  1,345  1,427  1,227x                08.00 h  1,060  1,202  950  1,109  1,103  1,239  1,255  1,131y                10.00 h  1,048  1,149  936  1,076  1,063  1,206  1,212  1,098y                12.00 h  1,023  1,158  933  1,070  1,079  1,165  1,206  1,091y                14.00 h  928  1,053  884  991  981  1,036  1,061  991z                Average  1,048b  1,175a  948c  1,069b  1,108b  1,198a  1,246a                GSD5                  0.051  <.001  <.001  <.001  <.001  0.601    06.00 h  2.16  2.06  2.04  2.10  2.13  2.15  2.14  2.11y                08.00 h  2.13  2.06  2.03  2.07  2.12  2.12  2.14  2.10x                10.00 h  2.08  2.04  2.01  2.04  2.09  2.09  2.09  2.06y                12.00 h  2.03  1.98  1.96  1.98  2.01  2.02  2.06  2.01z                14.00 h  2.03  1.99  1.97  1.99  2.01  2.02  2.05  2.01z                Average  2.09a  2.03b  2.00c  2.04b  2.07a  2.08a  2.10a                    Cereal  Screen size (mm)  Time  SD1  Probability2,3      Corn  Barley  4  6  8  10  12      1  2  3  4  5  GMD4                  88.5  <.001  <.001  <.001  <.001  <.001    06.00 h  1,143  1,311  1,003  1,103  1,258  1,345  1,427  1,227x                08.00 h  1,060  1,202  950  1,109  1,103  1,239  1,255  1,131y                10.00 h  1,048  1,149  936  1,076  1,063  1,206  1,212  1,098y                12.00 h  1,023  1,158  933  1,070  1,079  1,165  1,206  1,091y                14.00 h  928  1,053  884  991  981  1,036  1,061  991z                Average  1,048b  1,175a  948c  1,069b  1,108b  1,198a  1,246a                GSD5                  0.051  <.001  <.001  <.001  <.001  0.601    06.00 h  2.16  2.06  2.04  2.10  2.13  2.15  2.14  2.11y                08.00 h  2.13  2.06  2.03  2.07  2.12  2.12  2.14  2.10x                10.00 h  2.08  2.04  2.01  2.04  2.09  2.09  2.09  2.06y                12.00 h  2.03  1.98  1.96  1.98  2.01  2.02  2.06  2.01z                14.00 h  2.03  1.99  1.97  1.99  2.01  2.02  2.05  2.01z                Average  2.09a  2.03b  2.00c  2.04b  2.07a  2.08a  2.10a                a–cWithin a line, means without a common superscript differ significantly. x–zWithin a column, means without a common superscript differ significantly. 125 replicates for the main cereal effect and 10 replicates for the screen size effect. 21 = Effect of type of cereal; 2 = effect of screen size; 3 = effect of time; 4 = interaction between type of cereal and time; 5 = interaction between screen size and time. 3Interaction between type of cereal and screen size was not significant (P > 0.10). 4Geometric mean diameter. 5Geometric standard deviation. View Large As an average of the corn and barley diets, both GMD (from 948 μm to 1,246 μm) and the GSD (from 2.00 to 2.10) increased (P < 0.001) as the screen size used to grind the cereal increased from 4 to 12 mm (Table 4). The differences in GMD among screen sizes of the corn and barley diets decreased with time (P < 0.001 for the interaction; Figure 3), but no interactions were detected for the GSD. Figure 3. View largeDownload slide Interaction between the screen size (mm) used to grind the cereal and sampling time on the geometric mean diameter (GMD) of the diet. Figure 3. View largeDownload slide Interaction between the screen size (mm) used to grind the cereal and sampling time on the geometric mean diameter (GMD) of the diet. The CP content of the sieved fractions of the original diets and of the residual feeds, measured after 8 h of ad libitum feeding, is shown in Table 5. When the cereal, either corn or barley, was finely ground (4 and 6 mm screen), the protein accumulated primarily in the coarser fraction (average of the 1,250 and 2,500 μm sieves) of the original diets. However, no such an effect was observed when the cereal was coarsely ground (10 and 12 mm screen), with more protein accumulating in the finer fraction (160 and 315 μm sieves). In fact, the CP content of the coarser fraction was 18.6 and 19.2% for the corn and barley diets, when the cereal was ground with a 4 mm screen but 14.3 and 14.4% when ground with a 12 mm screen. Similar but less pronounced effects were observed in the residual feeds after 8 h of ad libitum feeding; the CP content of the coarser fractions was 17.1 and 16.8% for the corn and barley diets when the cereal was finely ground (4 mm screen) but 15.0 and 16.6% when the cereal was coarsely ground (12 mm screen). Table 5. Crude protein content (%) of the sieved fractions of the original diets at the start of the experiment (06.00 h) and of the residual feeds at the end of the experiment (14.00 h). Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm                       160  15.0  14.7  15.1  15.5  16.0  13.0  13.4  13.7  14.3  16.9   315  15.9  16.6  16.2  17.1  19.3  14.6  14.6  16.0  16.2  18.3   630  17.4  18.4  19.3  20.9  20.9  17.9  18.4  19.0  21.2  21.6   1,250  17.4  17.6  19.8  18.8  18.5  18.9  18.2  19.1  21.0  18.9   2,500  19.9  19.5  12.3  11.4  10.1  19.4  15.2  13.4  11.0  9.8  Pooled fractions   Fine fraction2  15.5  15.7  15.7  16.3  17.7  13.8  14.0  14.9  15.3  17.6   Coarse fraction3  18.6  18.5  16.1  15.1  14.3  19.2  16.7  16.3  16.0  14.4    Residual feed4  Sieve diameter, μm                       160  14.1  15.0  15.7  15.5  15.7  12.4  12.8  13.2  13.4  13.5   315  16.3  17.7  18.1  17.4  19.2  14.9  16.6  17.1  17.6  19.5   630  19.4  20.1  20.6  21.0  22.2  19.2  21.4  21.2  23.5  23.5   1,250  19.0  18.3  18.7  19.9  17.9  18.8  18.9  18.9  18.7  19.4   2,500  15.1  13.7  15.9  13.2  12.1  14.7  12.4  15.0  13.9  13.8  Pooled fractions   Fine fraction  15.2  16.4  16.9  16.5  17.5  13.7  14.7  15.2  15.5  16.5   Coarse fraction  17.1  16.0  17.3  16.6  15.0  16.8  15.7  17.0  16.3  16.6  Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm                       160  15.0  14.7  15.1  15.5  16.0  13.0  13.4  13.7  14.3  16.9   315  15.9  16.6  16.2  17.1  19.3  14.6  14.6  16.0  16.2  18.3   630  17.4  18.4  19.3  20.9  20.9  17.9  18.4  19.0  21.2  21.6   1,250  17.4  17.6  19.8  18.8  18.5  18.9  18.2  19.1  21.0  18.9   2,500  19.9  19.5  12.3  11.4  10.1  19.4  15.2  13.4  11.0  9.8  Pooled fractions   Fine fraction2  15.5  15.7  15.7  16.3  17.7  13.8  14.0  14.9  15.3  17.6   Coarse fraction3  18.6  18.5  16.1  15.1  14.3  19.2  16.7  16.3  16.0  14.4    Residual feed4  Sieve diameter, μm                       160  14.1  15.0  15.7  15.5  15.7  12.4  12.8  13.2  13.4  13.5   315  16.3  17.7  18.1  17.4  19.2  14.9  16.6  17.1  17.6  19.5   630  19.4  20.1  20.6  21.0  22.2  19.2  21.4  21.2  23.5  23.5   1,250  19.0  18.3  18.7  19.9  17.9  18.8  18.9  18.9  18.7  19.4   2,500  15.1  13.7  15.9  13.2  12.1  14.7  12.4  15.0  13.9  13.8  Pooled fractions   Fine fraction  15.2  16.4  16.9  16.5  17.5  13.7  14.7  15.2  15.5  16.5   Coarse fraction  17.1  16.0  17.3  16.6  15.0  16.8  15.7  17.0  16.3  16.6  1Analyzed CP content was 17.7 and 17.9% for the corn and barley diets, respectively. 2Fine fraction was defined as the proportion of particles with a geometric mean diameter no more than 315 μm. 3Coarse fraction was defined as the proportion of particles with a geometric mean diameter of at least 1,250 μm. 4Feed remaining in the feeders of all the replicates of each of the 10 experimental diets was collected and pooled by treatment. Consequently, only average data are presented. View Large The ash and Ca contents of the sieving of the original diets and of the residual feeds, measured after 8 h of ad libitum feeding are shown in Tables 6 and 7, respectively. Ash and Ca concentrated in the coarser fractions of the original and the residual feeds in both sets of diets, with differences being more pronounced when the cereals were ground fine than when ground coarse. In fact, the Ca content of the coarser fraction (1,250 and 2,500 μm sieves) of the original corn and barley diets was 8.2 and 7.8% when the cereal was ground at 4 mm but 4.4 and 3.7% when ground at 12 mm (Table 7). Similarly, the Ca content of the coarser fraction (1,250 and 2,500 μm sieves) of the residual feed after 8 h of ad libitum feeding was 13.2 and 11.7% for the corn and barley diets when the cereal was ground at 4 mm but 9.7 and 6.7% when ground at 12 mm. A similar response was observed for the ash, which concentrated in the coarser fraction of the original and of the residual feeds, with more pronounced effects when the cereal was ground fine (4 and 6 mm screen) than when ground coarse (10 and 12 mm screen). Table 6. Ash content (%) of the sieved fractions of the original diets at the start of the experiment (06.00 h) and of the residual feeds at the end of the experiment (14.00 h). Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  7.3  7.5  8.7  8.3  8.7  10.5  10.8  10.8  12.3  12.6   315  6.6  7.3  7.4  7.7  7.6  8.3  9.1  8.9  9.7  9.7   630  11.3  12.1  12.2  12.7  12.9  11.2  13.6  12.9  14.6  14.7   1,250  12.7  15.0  12.1  16.4  15.5  10.4  17.2  12.3  14.8  14.2   2,500  34.1  21.5  22.1  16.5  14.7  33.2  20.2  15.1  15.3  10.3  Pooled fractions   Fine fraction2  7.0  7.4  8.1  8.0  8.2  9.4  10.0  9.9  11.0  11.2   Coarse fraction3  23.4  18.3  17.1  16.5  15.1  21.8  18.7  13.7  15.1  12.3    Residual feed4  Sieve diameter, μm   160  9.7  10.6  10.9  10.5  9.3  11.3  14.7  16.0  17.1  15.7   315  9.3  9.4  9.8  9.1  10.4  8.9  11.5  11.9  12.7  12.2   630  11.8  12.0  13.3  12.5  13.7  12.1  15.6  15.2  15.8  15.5   1,250  21.7  19.6  24.0  18.3  19.8  18.1  19.2  17.6  16.8  18.2   2,500  47.9  36.0  42.7  33.0  33.0  45.4  29.1  27.4  27.6  21.4  Pooled fractions   Fine fraction  9.5  10.0  10.4  9.8  9.9  10.1  13.1  14.0  14.9  14.0   Coarse fraction  34.8  27.8  33.4  25.7  26.4  31.8  24.2  22.5  22.2  19.8  Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  7.3  7.5  8.7  8.3  8.7  10.5  10.8  10.8  12.3  12.6   315  6.6  7.3  7.4  7.7  7.6  8.3  9.1  8.9  9.7  9.7   630  11.3  12.1  12.2  12.7  12.9  11.2  13.6  12.9  14.6  14.7   1,250  12.7  15.0  12.1  16.4  15.5  10.4  17.2  12.3  14.8  14.2   2,500  34.1  21.5  22.1  16.5  14.7  33.2  20.2  15.1  15.3  10.3  Pooled fractions   Fine fraction2  7.0  7.4  8.1  8.0  8.2  9.4  10.0  9.9  11.0  11.2   Coarse fraction3  23.4  18.3  17.1  16.5  15.1  21.8  18.7  13.7  15.1  12.3    Residual feed4  Sieve diameter, μm   160  9.7  10.6  10.9  10.5  9.3  11.3  14.7  16.0  17.1  15.7   315  9.3  9.4  9.8  9.1  10.4  8.9  11.5  11.9  12.7  12.2   630  11.8  12.0  13.3  12.5  13.7  12.1  15.6  15.2  15.8  15.5   1,250  21.7  19.6  24.0  18.3  19.8  18.1  19.2  17.6  16.8  18.2   2,500  47.9  36.0  42.7  33.0  33.0  45.4  29.1  27.4  27.6  21.4  Pooled fractions   Fine fraction  9.5  10.0  10.4  9.8  9.9  10.1  13.1  14.0  14.9  14.0   Coarse fraction  34.8  27.8  33.4  25.7  26.4  31.8  24.2  22.5  22.2  19.8  1Analyzed ash content was 12.3 and 12.8% for the corn and barley diets, respectively. 2Fine fraction was defined as the proportion of particles with a geometric mean diameter no more than 315 μm. 3Coarse fraction was defined as the proportion of particles with a geometric mean diameter of at least 1,250 μm. 4Feed remaining in the feeders of all the replicates of each of the 10 experimental diets was collected and pooled by treatment. Consequently, only average data are presented. View Large Table 7. Calcium content (%) of the sieved fractions of the original diets at the start of the experiment (06.00 h) and of the residual feeds at the end of the experiment (14.00 h). Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  1.3  1.3  1.6  1.5  1.7  2.2  2.3  2.3  2.8  2.9   315  0.9  1.2  1.1  1.7  1.5  1.8  1.9  1.7  1.9  2.0   630  3.2  3.2  3.2  3.3  3.3  3.0  3.8  3.5  4.2  4.0   1,250  4.0  4.2  3.3  4.6  4.3  3.5  5.3  3.7  4.5  4.3   2,500  12.4  7.1  7.4  5.5  4.5  12.1  8.1  4.4  4.9  3.0  Pooled fractions   Fine fraction2  1.1  1.3  1.4  1.6  1.6  2.0  2.1  2.0  2.4  2.5   Coarse fraction3  8.2  5.7  5.4  5.1  4.4  7.8  6.7  4.1  4.7  3.7    Residual feed4  Sieve diameter, μm   160  2.5  3.0  3.1  2.9  3.5  3.1  4.3  4.6  5.0  4.2   315  2.3  2.4  2.4  2.4  2.5  2.1  3.2  3.1  3.5  3.1   630  3.6  3.5  4.0  3.7  4.0  3.7  4.8  4.4  4.9  4.5   1,250  7.8  6.9  9.0  6.4  7.0  6.0  7.1  5.6  5.5  6.2   2,500  18.6  13.8  16.4  12.6  12.3  17.4  11.4  10.5  10.7  7.2   Fine fraction  2.4  2.7  2.8  2.7  3.0  2.6  3.8  3.9  4.3  3.7   Coarse fraction  13.2  10.4  12.7  9.5  9.7  11.7  9.3  8.1  8.1  6.7  Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  1.3  1.3  1.6  1.5  1.7  2.2  2.3  2.3  2.8  2.9   315  0.9  1.2  1.1  1.7  1.5  1.8  1.9  1.7  1.9  2.0   630  3.2  3.2  3.2  3.3  3.3  3.0  3.8  3.5  4.2  4.0   1,250  4.0  4.2  3.3  4.6  4.3  3.5  5.3  3.7  4.5  4.3   2,500  12.4  7.1  7.4  5.5  4.5  12.1  8.1  4.4  4.9  3.0  Pooled fractions   Fine fraction2  1.1  1.3  1.4  1.6  1.6  2.0  2.1  2.0  2.4  2.5   Coarse fraction3  8.2  5.7  5.4  5.1  4.4  7.8  6.7  4.1  4.7  3.7    Residual feed4  Sieve diameter, μm   160  2.5  3.0  3.1  2.9  3.5  3.1  4.3  4.6  5.0  4.2   315  2.3  2.4  2.4  2.4  2.5  2.1  3.2  3.1  3.5  3.1   630  3.6  3.5  4.0  3.7  4.0  3.7  4.8  4.4  4.9  4.5   1,250  7.8  6.9  9.0  6.4  7.0  6.0  7.1  5.6  5.5  6.2   2,500  18.6  13.8  16.4  12.6  12.3  17.4  11.4  10.5  10.7  7.2   Fine fraction  2.4  2.7  2.8  2.7  3.0  2.6  3.8  3.9  4.3  3.7   Coarse fraction  13.2  10.4  12.7  9.5  9.7  11.7  9.3  8.1  8.1  6.7  1Analyzed Ca content was 3.85 and 3.94% for the corn and barley diets, respectively. 2Fine fraction was defined as the proportion of particles with a geometric mean diameter no more than 315 μm. 3Coarse fraction was defined as the proportion of particles with a geometric mean diameter of at least 1,250 μm. 4Feed remaining in the feeders of all the replicates of each of the 10 experimental diets was collected and pooled by treatment. Consequently, only average data are presented. View Large DISCUSSION The GMD of the original diets was greater for the barley than for the corn diets (1,311 vs. 1,143 μm), consistent with data of Pérez-Bonilla et al. (2011) comparing the 2 cereals. The glumes of the barley grains are quite flexible, and when ground, a high proportion passes intact through the screen, resulting in an increase in the GMD of diets based on barley compared with diets based on corn. These results confirm that the structure of the feed depends not only on the size of the sieve but also on the main cereal of the diet, consistent with data of Douglas et al. (1990) and Nir et al. (1995). The beak of the chicken is not well adapted to consume fine particles, and, consequently, coarse particles tended to be preferred (Picard et al., 1997; Mateos et al., 2002). In fact, most management guides (ISA Brown, 2010; Lohmann, 2016) recommended coarse grinding when the objective is to maximize FI. In this respect, Safaa et al. (2009) observed a significant 2.5% increase in FI in hens fed corn or wheat ground with a 10-mm screen compared with hens fed the same cereals ground with a 6-mm screen. However, in the current research in which diets based on corn or barley were compared, no differences in FI because of particle size were observed. The reasons for the discrepancy among experiments is not apparent but could be related to the proportion of very fine particles present in the diets rather than to their GMD. In this respect, Portella et al. (1988a) suggested that hen preference for coarse particles might be altered not only by the average size of the particles of the diet but also by the proportion of very fine particles. Herrera et al. (2017) suggested that supplemental fat might agglomerate the fines of the diet, improving palatability and reducing the rejection rate for fine particles. In the current research, supplemental fat was high in both corn and barley diets (4.7 and 5.3%, respectively) which might have reduced the preference of the hens for coarse vs. fine particles. The GMD of the diets decreased with time, reflecting the preference behavior of the hens for coarse particles, in agreement with previous studies with broilers (Schiffman, 1968; Portella et al., 1988b; Xu et al., 2015) and laying hens (Portella et al., 1988a; Safaa et al., 2009). The data confirm that when allowed to choose, laying hens prefer coarse particles. In contrast, Herrera et al. (2017) reported no differences in FI of brown-egg laying hens fed diets from 17 to 49 wk of age when the cereal was ground using screens varying in size from 4 to 12 mm. The reasons for the discrepancy among researches are not known but might depend on the chemical composition of the experimental diets as well as on the feeding strategy used (i.e., frequency of feeding) and feeder design, which might affect feed particle size distribution. When allowed to choose, hens might prefer coarse particles as observed in the current experiment. However, when new feed is constantly added to the uneaten feed or when the hens are obliged to clean the feeders at specific times, as occurred often under practical conditions, the effects might be less pronounced or even disappear. The differences in GMD of the residual feeds between the 2 cereal-based diets and among screen sizes decreased with time, reflecting the increased uniformity of the particles in the uneaten feed. Portella et al. (1988a) reported also that the disappearance of coarse particles was overwhelming when the feed had an excess of large particles (>2.36 mm). However, the preference was less obvious as the experiment progressed and the percentage of coarse particle was reduced, consistent with the results reported herein. The GSD of the diets was greater for the corn than for the barley diets, differences that increased with increases in the size of the screen. In contrast, the differences in GSD for both main effects (type of cereal and screen size) decreased with time, reflecting the higher rate of disappearance of the coarser particles of the uneaten feed for the first h after the start of the experiment. Birds show a specific appetite for some components of the diet, such as CP, fiber, or Ca (Hughes and Wood-Gush, 1971; Mongin and Sauveur, 1974; Holcombe et al., 1975). When the diet is deficient in a given nutrient, birds might choose to eat those sieving fractions richer in the deficient nutrient (Portella et al., 1988a). As a result, hen preference might depend not only on particle size but also on the physical distribution of the limiting nutrient within the sieving fractions. In the current research, however, the differences in CP, ash, and Ca content among the sieving fractions of the original diets were similar to those of the residuals at the end of the experiment, suggesting that feed preference was not modulated by differences in nutrient content of the sieve fractions of the diet. An observation that deserves further attention is the difference in Ca concentration between the original diets and the residual feeds after 8 h of ad libitum consumption. For the corn diet, the percentage of Ca across fractions of the diet, independent of the sieving fraction considered and of the screen size used to grind the corn, was 8.6 to 63.4% higher in the residual feeds than in the original diets. Similar data were observed for the barley diets, in which the percentage of Ca was 11.1 to 58.3% higher in the residual feed than in the original diets. A similar distribution pattern was observed for ash content but not for CP. The reasons for these contrasting observations are unknown but might be related to the timing at which the feed (and the Ca included in the feed) was available for consumption and the Ca needs for shell formation according to the period of the day. Hughes (1972) reported that laying hens under-consume Ca during the morning but tend to over-consume Ca late in the d, when most of the shell formation process occurs. In the evening, hens try to balance Ca intake and Ca requirements, giving preference to those particles rich in the deficient nutrient, regardless of feed coarseness, whereas an opposite pattern might occur during the morning. The current research was conducted from 06.00 to 14.00 h, a period of the da in which Ca deposition is relatively low (Hughes, 1972; Molnár et al., 2018). Consequently, hens chose to under-consume Ca because Ca requirements are lower. The higher Ca concentration of the residual feeds after 8 h of ad libitum consumption, compared to that of the original diets observed, is consistent with this suggestion. Also, it was noticed that Ca concentrated in the coarse fractions of the original feeds, probably because 50% of the CaCO3 of the diets was supplied in granular form. A similar Ca distribution pattern was observed in the residual feeds of all diets after 8 h of ad libitum consumption, confirming that hens’ preference for coarse particles was independent of its Ca content. In contrast, Portella et al. (1988a) observed that the proportion of Ca in the different sieving fractions of a mash diet was not homogenous and decreased as the GMD of the diet increased, opposite to the results reported herein. The reasons for the discrepancy are not known. We do not have information on the time of the d and the size of the Ca carbonate used by Portella et al. (1988a), and, thus, no comparison of the results of the 2 experiments can be made. The consumption pattern observed was different for CP than for Ca. Hens showed a clear preference for consuming coarse particles and were unable to choose those fractions of the feed with a higher or lower protein content. Traineau et al. (2015), however, reported that when hens were allowed to choose between 2 feeds varying in CP content, they over-consumed the diet rich in protein after oviposition, early in the morning, a period in which the albumen of the egg is formed. In the research of Traineau et al. (2015), hens were offered 2 different feeds to choose, whereas a single feed was supplied in the current research, limiting the capacity of the hens for selecting feed particles based on its protein content. In this respect, Forbes and Shariatmadari (1994) showed that the ability of the hens to choose ingredients according to its CP needs, when offered a single diet, was limited. Moreover, Pousga et al. (2005) reported that hens offered a single conventional feed were not able to choose those feed fractions with higher CP content, consistent with the data reported herein. In conclusion, type of cereal and size of the screen used to grind the cereal affected feed preference behavior of the hens. The CP, ash, and Ca contents of the diet were not uniform and varied with the screen used to grind the cereal and with the sieving fraction (fine vs. coarse) of the diets. The data demonstrate that under the condition of the current research, hen preference for coarse particles was not modulated by the desire to meet any potential requirement for the missing nutrient. In fact, in relative terms, the concentration of CP, ash, and Ca of the sieve fractions of the original diets and the residuals after 8 h of ad libitum consumption followed a similar pattern, demonstrating that the composition of the sieving fractions of the diet did not affect the preference behavior of the hens for coarse particles. When allowed to choose, and no extra quantities of feed were added to the feeder during the experimental period, hens showed a clear preference for consuming coarse particles. Crude protein content of the different sieve fractions did not affect hen preference behavior. In fact, hens did not show any preference for consuming extra amounts of protein during the early part of the day. In contrast, Ca intake of the hens was reduced during the morning, resulting in residual feeds with greater concentration of ash and Ca than in the original diets, irrespective of the size of the feed fractions. It should be noticed that in the current research, hens were offered at all times the leftovers of the previous feeding periods, reducing its potential capacity to choose coarse particles. Hen preference behavior might be different under commercial conditions, when the residuals are remixed constantly with new feed coming from the auger and the hens are obliged often to consume the fine particles previously refused. Footnotes 1 Financial support was provided by the Ministerio de Economía y Competitividad (Project AGL 2014–56139). REFERENCES Abdollahi M. R., Duangnumsawang Y., Kwakkel R. P., Steenfeldt S., Bootwalla S. M., Ravindran V.. 2016. Investigation of the interaction between separate calcium feeding and phytase supplementation on growth performance, calcium intake, nutrient digestibility and energy utilisation in broiler starters. Anim. Feed Sci. Technol.  219: 48– 58. Google Scholar CrossRef Search ADS   Allen J., Perry G. C. 1977. Feeding patterns and food selection of caged birds. Br. Vet. J.  133: 99 (Abstr.) Amerah A. M., Ravindran V., Lentle R. G., Thomas D. G.. 2007. Feed particle size: Implications on the digestion and performance of poultry. World's Poult. Sci. J.  63: 439– 455. Google Scholar CrossRef Search ADS   AOAC International. 2005. Official Methods of Analysis of the AOAC International . 18th ed. AOAC Int., Gaithersburg, MD. ASAE. 1995. Standard S319.2: Method of determining and expressing fineness of feed material by sieving. 461– 462 in Agriculture Engineers Yearbook of Standards . Am. Soc. Agric. Eng., St. Joseph, MO. Benabdeljelil K., Arbaoui M. I.. 1994. Effects of enzyme supplementation of barley-based diets on hen performance and egg quality. Anim. Feed Sci. Technol.  48: 325– 334. Google Scholar CrossRef Search ADS   Berg L. R. 1959. Enzyme supplementation of barley diets for laying hens. Poult. Sci.  38: 1132– 1139 Google Scholar CrossRef Search ADS   Boletín Oficial del Estado. 2007. Ley 32/2007 de 7 de Noviembre para el cuidado de los animales, en su explotación, transporte, experimentación y sacrificio. BOE . 268: 45914– 45920. Coon C. N., Obi, Hamre, 1988. Use of barley in laying hen diets. Poult. Sci.  67, 1306– 1313. Google Scholar CrossRef Search ADS   Davis R. L., Hill E. G., Sloan H. J., Briggs G. M.. 1951. Detrimental effect of corn of coarse particle size in rations for chicks. Poult. Sci.  30: 325– 328. Google Scholar CrossRef Search ADS   Douglas J. H., Sullivan T. W., Bond P. L., Struwe F. J., Baier J. G., Robeson L. G.. 1990. Influence of grinding, rolling, and pelleting on the nutritional-value of grain sorghums and yellow corn for broilers. Poult. Sci.  69: 2150– 2156. Google Scholar CrossRef Search ADS   FEDNA (Fundación Española Desarrollo Nutrición Animal). 2010. Normas FEDNA para la Formulación de Piensos Compuestos . 3rd ed. In: De Blas C., Mateos G. G., Rebollar P. G. (Eds). Fund. Esp. Desarro. Nutr. Anim., Madrid, Spain. Forbes J. M., Shariatmadari F. S.. 1994. Diet selection for protein by poultry. Word's Poult. Sci. J.  50: 7– 24. Google Scholar CrossRef Search ADS   Gentle M. J. 1979. Sensory control of feed intake. 259– 273 In: Food Intake Regulation in Poultry , Boorman K. N., Freeman B. M., eds. Br. Poult. Sci. Ltd, Edinburg. González-Alvarado J. M., Jiménez-Moreno E., Lázaro R., Mateos G. G.. 2007. Effect of type of cereal, heat processing of the cereal, and inclusion of fiber in the diet on productive performance and digestive traits of broilers. Poult. Sci.  86: 1705– 1715. Google Scholar CrossRef Search ADS PubMed  González-Alvarado J. M., Jiménez-Moreno E., González-Sánchez D., Lázaro R., Mateos G. G.. 2010. Effect of inclusion of oat hulls and sugar beet pulp in the diet on productive performance and digestive traits of broilers from 1 to 42 days of age. Anim. Feed Sci. Technol.  162: 37– 46. Google Scholar CrossRef Search ADS   Grobas S., Méndez S., de Blas J. C., Mateos G. G.. 1999. Influence of dietary energy, supplemental fat and linoleic acid concentration on performance of laying hens at two ages. Br. Poult. Sci.  40: 681– 687. Google Scholar CrossRef Search ADS PubMed  Herrera J., Saldaña B., Guzmán P., Cámara L., Mateos G. G.. 2017. Influence of particle size of the main cereal of the diet on egg production, gastrointestinal tract traits, and body measurements of brown laying hens. Poult. Sci.  96: 440– 448. Google Scholar CrossRef Search ADS PubMed  Hetland H., Svihus B., Krögdahl Å.. 2003. Effects of oat hulls and wood shavings on digestion in broilers and layers fed diets based on whole or ground wheat. Br. Poult. Sci.  44: 275– 282. Google Scholar CrossRef Search ADS PubMed  Holcombe D. J., Roland D. A., Harms R. H.. 1975. The ability of hens to adjust calcium intake when given a choice of diets containing two levels of calcium. Poult. Sci.  54: 552– 561. Google Scholar CrossRef Search ADS PubMed  Hughes B. O., Wood-Gush D. G. M.. 1971. A specific appetite for calcium in domestic chickens. Anim. Behav.  19: 490– 499. Google Scholar CrossRef Search ADS PubMed  Hughes B. O., 1972. A circadian rhythm of calcium intake in the domestic fowl. Br. Poult. Sci.  13: 485– 493. Google Scholar CrossRef Search ADS PubMed  ISA Brown. 1999. Energy levels and feed presentation for laying hens: Effects on performance and intake. Institut de Selection Animale. B. V, Boxmeer, The Netherlands. ISA Brown. 2010. Nutrition Management Guide. Isa Brown Commercial Layer. Institut de Selection Animale. B. V, Boxmeer, The Netherlands. Jiménez-Moreno E., González-Alvarado J. M., Lázaro R., Mateos G. G.. 2009. Effects of type of cereal, heat processing of the cereal, and fiber inclusion in the diet on gizzard pH and nutrient utilization in broilers at different ages. Poult. Sci.  88: 1925– 1933. Google Scholar CrossRef Search ADS PubMed  Jiménez-Moreno E., González-Alvarado J. M., González-Sánchez D., Lázaro R., Mateos G. G.. 2010. Effects of type and particle size of dietary fiber on growth performance and digestive traits of broilers from 1 to 21 days of age. Poult. Sci.  89: 2197– 2212. Google Scholar CrossRef Search ADS PubMed  Jiménez-Moreno E., De Coca-Sinova A., González-Alvarado J. M., Mateos G. G.. 2016. Inclusion of insoluble fiber sources in mash or pellet diets for young broilers. 1. Effects on growth performance and water intake. Poult. Sci.  95: 41– 52. Google Scholar CrossRef Search ADS PubMed  Lázaro R., García M., Araníbar M. J., Mateos G. G.. 2003. Effect of enzyme addition to wheat-, barley- and rye-based diets on nutrient digestibility and performance of laying hens. Br. Poult. Sci.  44: 256– 265. Google Scholar CrossRef Search ADS PubMed  Lohmann. 2016. Management Guide for Lohmann Brown-Classic . Lohmann Tierzucht. GMBH. Cuxhaven, Germany. Mateos G. G., Sell J. L.. 1980. Influence of carbohydrate and supplemental fat source of the metabolizable energy of the diet. Poult. Sci.  59: 2129– 2135. Google Scholar CrossRef Search ADS PubMed  Mateos G. G., Lázaro R., Gracia M. I.. 2002. The feasibility of using nutritional modifications to replace drugs in poultry feeds. J. Appl. Poult. Res.  11: 437– 452. Google Scholar CrossRef Search ADS   Mateos G. G., Jiménez-Moreno E., Serrano M. P., Lázaro R.. 2012. Poultry response to high levels of dietary fiber sources varying in physical and chemical characteristics. J. Appl. Poult. Res.  21: 156– 174. Google Scholar CrossRef Search ADS   Molnár A., Maertens L., Ampe B., Buyse J., Zoons J., Delezie E.. 2018. Effect of different split-feeding treatments on performance, egg quality, and bone quality of individually housed aged laying hens. Poult. Sci.  97: 88– 101. Google Scholar CrossRef Search ADS PubMed  Mongin P., Sauveur B.. 1974. Volundary food and calcium intake by the laying hens. Br. Poult. Sci.  15: 349– 359. Google Scholar CrossRef Search ADS PubMed  Nir I., Hiller R., Shefet G., Nitsan Z.. 1994. Effect of grain particle size on performance. 2. Grain texture interactions. Poult. Sci.  73: 781– 791. Google Scholar CrossRef Search ADS PubMed  Nir I., Hillel R., Ptichi I., Shefet G.. 1995. Effect of particle size on performance. 3. Grinding pelleting interactions. Poult. Sci.  74: 771– 783. Google Scholar CrossRef Search ADS PubMed  Pérez-Bonilla A., Frikha M., Mirzaie S., García J., Mateos G. G.. 2011. Effects of the main cereal and type of fat of the diet on productive performance and egg quality of brown-egg laying hens from 22 to 54 weeks of age. Poult. Sci.  90: 2801– 2810. Google Scholar CrossRef Search ADS PubMed  Pérez-Bonilla A., Frikha M., Lázaro R., Mateos G. G.. 2014. Type of grinding of the main cereal of the diet affects production of brown egg-laying hens. Anim. Feed Sci. Technol.  194: 121– 130. Google Scholar CrossRef Search ADS   Picard M., Melcion J. P., Bouchot C., Faure J. M.. 1997. Picorage et préhensibilité des particules alimentaires chez les volailles. INRA Prod. Anim.  10: 403– 414. Portella F. J., Caston L. J., Leeson S.. 1988a. Apparent feed particle size preference by laying hens. Can. J. Anim. Sci.  68: 915– 922. Google Scholar CrossRef Search ADS   Portella F. J., Caston L. J., Leeson S.. 1988b. Apparent feed particle size preference by broilers. Can. J. Anim. Sci.  68: 923– 930. Google Scholar CrossRef Search ADS   Pousga S., Boly H., Ogle B.. 2005. Choice feeding of poultry: A review. Liv. Res. Rural Develop.  Vol. 17, Article 45. Retrieved from http://www.lrrd.org/lrrd17/4/pous17045.htm. Safaa H. M., Jimenéz-Moreno E., Valencia D. G., Frikha M., Serrano M. P., Mateos G. G.. 2009. Effect of main cereal of the diet and particle size of the cereal on productive performance and egg quality of brown egg-laying hens in early phase of production. Poult. Sci.  88: 608– 614. Google Scholar CrossRef Search ADS PubMed  SAS Institute. 2004. SAS/STAT User's Guide . Version 9.1. SAS Inst. Inc., Cary, NC. Schiffman H. R. 1968. Texture preference in the domestic chick. J. Comp. Physiol. Psychol.  66: 540– 541. Google Scholar CrossRef Search ADS PubMed  Svihus B. 2011. The gizzard: Function, influence of diet structure and effects on nutrient availability. World's Poult. Sci. J.  67: 207– 223. Google Scholar CrossRef Search ADS   Traineau M., Bouvarel I., Mulsant C., Roffidal L., Launay C., Lescoat P.. 2015. Modulation of energy and protein supplies in sequential feeding in laying hens. Animal . 9: 49– 57. Google Scholar CrossRef Search ADS PubMed  Xu Y., Stark C. R., Ferket P. R., Williams C. M., Brake J.. 2015. Effects of feed form and dietary coarse ground corn on broiler live performance, body weight uniformity, relative gizzard weight, excreta nitrogen, and particle size preference behaviors. Poult. Sci.  94: 1549– 1556. Google Scholar CrossRef Search ADS PubMed  © 2018 Poultry Science Association Inc. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Poultry Science Oxford University Press

Particle size affects short-term preference behavior of brown-egg laying hens fed diets based on corn or barley

Loading next page...
 
/lp/ou_press/particle-size-affects-short-term-preference-behavior-of-brown-egg-hB3JaVi36x
Publisher
Oxford University Press
Copyright
© 2018 Poultry Science Association Inc.
ISSN
0032-5791
eISSN
1525-3171
D.O.I.
10.3382/ps/pex441
Publisher site
See Article on Publisher Site

Abstract

Abstract We studied the influence of particle size of the main cereal of the diet on preference behavior by laying hens. Diets formed a 2 × 5 factorial with 2 main cereals (corn vs. barley) and 5 grinding sizes of the cereal (4, 6, 8, 10, and 12 mm screen). Each treatment was replicated 5 times (10 hens each). After a fasting period of 8 h, hens received their respective experimental diets from 06.00 to 14.00 hours. The geometric mean diameter (GMD) and the geometric standard deviation of the residuals in the feeder were determined every 2 hours. In addition, CP, ash, and Ca contents of the feeds were determined at the start and at the end of the experimental period. The experimental design was completely randomized with data analyzed as repeated measures with particle size and cereal as main effects. The GMD of the original feeds increased with increases in screen size and was greater for the barley than for the corn diets. The difference in GMD between the original diets and the residuals measured at 2 h intervals decreased as the experiment progressed (P < 0.001 for the interaction). Crude protein, ash, and Ca concentrated in the coarse fraction of the original diets and of the uneaten feed, an effect more pronounced for the minerals. Independent of the coarseness of the feed sieve, ash and Ca contents were higher in the uneaten feed at 14.00 h than in the original diets. Hens showed a clear preference for coarse particles irrespective of the concentration of CP, ash, or Ca in the different fractions of the diets. Data showed that birds under-consumed Ca during the morning, a period in which the requirements for mineral deposition are low. In summary, hens showed a significant preference for coarser particles, an effect that was more evident when the cereals were ground coarse. Hens, however, did not show any preference for consuming those feed fractions with greater CP, ash, or Ca contents. INTRODUCTION Several researchers (Benabdeljelil and Arbaoui, 1994; Lázaro et al., 2003; Herrera et al. 2017) have compared the effects of diets based on corn or barley on feed intake (FI), egg production, and egg quality in laying hens. In most cases, the main cereal of the diet did not affect egg production, provided that the feed was supplemented with an adequate enzyme complex. Berg (1959) reported also similar egg production but greater BW gain and lower FI in hens fed corn than in hens fed barley. Pérez-Bonilla et al. (2011) compared diets based on corn or barley and reported similar egg production but greater BW gain in hens fed corn. In contrast, Coon et al. (1988) reported higher FI, lower egg size, and reduced feed efficiency and BW gain in hens fed a barley diet than in hens fed a corn diet, probably because in this research the diets were not supplemented with exogenous enzymes. The information available on particle size preference by laying hens is limited. Schiffman (1968) and Allen and Perry (1977) observed that poultry had a pecking preference for coarse textured feed over non-textured feed, a preference that increased with age. ISA Brown (1999) recorded a 3.4% increase in FI and egg production in hens fed coarsely ground feeds compared with hens fed finely ground feeds (9 vs. 31% of particles smaller than 0.5 mm, respectively). More recently, Safaa et al. (2009) recorded higher FI in hens fed diets with a geometric mean diameter (GMD) of 1,375 μm than in hens fed diets with a GMD of 1,007 μm. In fact, most guidelines for laying hens (ISA Brown, 2010; Lohmann, 2016) recommend feeding coarse diets with less than 15 to 20% particles smaller than 0.5 mm when the objective is to increase FI. However, Herrera et al. (2017) did not detect any difference in FI or egg production in brown-egg laying hens fed diets in which the cereal was ground using sieves varying in screen size from 6 to 12 mm (GMD of 1,003 μm and 1,427 μm, respectively). The physico-chemical characteristics of the cereal and the diameter of the screen used to grind the cereal affect diet structure (Amerah et al., 2007; Jiménez-Moreno et al., 2016) and FI (Schiffman, 1968; Xu et al., 2015). The mechanoreceptors located in the beak of the bird detect differences in feed texture and discriminate against the consumption of fine particles (Gentle, 1979; González-Alvarado et al., 2007; Pérez-Bonilla et al., 2014), which may reduce voluntary FI. On the other hand, coarse particles are retained for a longer time in the upper part of the gastrointestinal tract (GIT) than fine particles, which might result in better development and function of the gizzard and in an improvement in nutrient utilization (Jiménez-Moreno et al., 2010; Svihus, 2011). The relative smaller surface area of the coarse particles, however, penalizes the contact between digestive enzymes and nutrients, reducing feed utilization (Amerah et al., 2007). Moreover, coarse grinding reduces feed uniformity and might induce a preference of the hens for coarse particles, resulting in the consumption of unbalanced diets and a reduction in feed efficiency (Davis et al., 1951; Nir et al., 1994). In this respect, mash diets based on cereals with different physico-chemical characteristics might result in feeds with different particle size distributions and GMD, even when ground using the same screen size (Douglas et al., 1990; Nir et al., 1995; Jiménez-Moreno et al., 2009; Perez-Bonilla et al., 2014). All these contrasting effects might counteract each other and the final outcome might depend on other uncontrolled variables, such as age of the bird, management practices, and nutritional characteristics of the diet (Mateos and Sell, 1980; Grobas et al., 1999; González-Alvarado et al., 2010). Laying hens show a specific appetite for some components of the diet, such as protein, fiber, and Ca. When given a choice, birds might be able to balance the final diet by selecting nutrients and increasing the consumption of those feed particles rich in the deficient nutrient (Hughes and Wood-Gush, 1971; Mongin and Sauveur, 1974; Holcombe et al., 1975; Abdollahi et al., 2016). For example, Forbes and Shariatmadari (1994) showed that poultry offered diets differing in CP content choose the correct amount of the different feeds to meet protein requirements. Poultry also show an appetite for structural dietary components, and when fed low fiber diets, they consume extra amounts of fibrous components if they have free access to the litter (Hetland et al., 2003; Mateos et al., 2012). We hypothesized that grinding size could affect FI and preference behavior in laying hens, with effects that could depend on the physico-chemical characteristics of the main cereal used. Also, it was hypothesized that differences in the nutritional composition of the coarse and the fine fractions of the diets could affect the feeding behavior of the hens. The objective of this research was to compare the effect of the size of the screen used to grind the cereal on the preference behavior of brown-egg laying hens fasted for 8 h and then fed diets based on corn or barley from 06.00 to 14.00 hours. MATERIALS AND METHODS Husbandry, Diets, and Experiment Design All procedures were approved by the Animal Ethics Committee of the Universidad Politécnica de Madrid and were in compliance with the Spanish guidelines for the care and use of animals in research (Boletín Oficial del Estado, 2007). Details on husbandry, ingredient composition, feeding program, and nutrient content of the diets were reported by Herrera et al. (2017). Briefly, 2 diets with similar nutrient content but differing in the main cereal used (corn vs. barley) were formulated. The moisture content of the cereals was 13.5% for the corn and 10.1% for the barley. Before feed manufacturing, the batches of the 2 cereals were divided into 5 portions, and each portion was ground using a horizontal hammer mill (Mecafa S.A., Ciudad Real, Spain) provided with a 4, 6, 8, 10, or 12 mm screen and included in their respective experimental diets. Each of the 10 diets was fed to 5 replicates that consisted of an enriched cage (120 cm × 63 cm and 45 cm height; Facco S.p.A., Padova, Italy) with 10 brown egg-laying hens. The soybean meal used in the manufacturing of the diets was used as received, whereas the sunflower meal (received in pellets) was ground using a 10-mm screen. The GMD ± geometric standard deviation (GSD; log normal SD) of the soybean meal and sunflower meal were 1,069 ± 1.79 and 699 ± 2.23 μm, respectively (Table 1). The limestone included in the diets was presented as 50% powder (GMD = 597 ± 2.31 μm) and 50% in granular (GMD = 2166 ± 1.39 μm) form. This ratio was representative of diets used in laying hens under Spanish commercial conditions (Pérez-Bonilla et al., 2014). The ingredient composition and the calculated (FEDNA, 2010) and determined nutrient content of the experimental diets are shown in Table 2. As reported by Herrera et al. (2017), FI, egg production, and BW gain of the hens from 17 to 48 wk of age (prior to the start of the experiment) were not affected by the main cereal or the screen size used to grind the cereal. Table 1. Particle size distribution and geometric mean diameter (GMD) and log normal SD (GSD) of the main ingredients.1       Calcium carbonate    Soybean meal  Sunflower meal        (47% CP)  (34% CP)  Powder  Granular  Sieve diameter, μm   5,000  0.0  0.5  0.0  0.2   2,500  3.6  3.6  0.1  29.2   1,250  36.0  18.5  18.5  70.3   630  47.7  34.6  35.2  0.2   315  10.2  27.3  23.4  0.0   160  1.4  11.8  14.8  0.0   80  0.7  3.2  6.0  0.1   40  0.4  0.5  1.9  0.0   0  0.0  0.0  0.1  0.0  GMD  1,069  699  597  2,166  GSD  1.79  2.23  2.31  1.39        Calcium carbonate    Soybean meal  Sunflower meal        (47% CP)  (34% CP)  Powder  Granular  Sieve diameter, μm   5,000  0.0  0.5  0.0  0.2   2,500  3.6  3.6  0.1  29.2   1,250  36.0  18.5  18.5  70.3   630  47.7  34.6  35.2  0.2   315  10.2  27.3  23.4  0.0   160  1.4  11.8  14.8  0.0   80  0.7  3.2  6.0  0.1   40  0.4  0.5  1.9  0.0   0  0.0  0.0  0.1  0.0  GMD  1,069  699  597  2,166  GSD  1.79  2.23  2.31  1.39  1Measured in the original ingredients before the manufacturing of the diets. View Large Table 2. Ingredient composition and chemical analyses (% as-fed basis) of the experimental diets.   Corn  Barley  Ingredient   Corn  45.00  12.50   Barley  8.80  45.00   Soybean meal, 47% CP  20.80  25.20   Sunflower meal, 34% CP  10.00  1.20   Soy oil soapstocks  4.70  5.30   Dicalcium phosphate  1.49  1.42   Calcium carbonate (powder)  4.11  4.18   Calcium carbonate (granular size)  4.11  4.18   Sodium chloride  0.35  0.35   DL-methionine, 99%  0.14  0.17   Vitamin and mineral premix1  0.50  0.50  Calculated analyses2   AMEn (Kcal/kg)  2750  2750   Crude fiber  4.4  3.6   Digestible amino acids2    Lys  0.80  0.80    Met  0.35  0.35    Met + cys  0.59  0.59    Thr  0.56  0.56  Determined analyses3   Dry matter  89.6  90.3   Gross energy (Kcal/kg)  4,305  4,290   Crude protein  17.7  17.9   Neutral detergent fiber  10.0  11.3   Ether extract  7.1  7.5   Linoleic acid (C18:2)  3.75  3.40   Ash  12.3  12.8   Calcium  3.85  3.94   Total phosphorus  0.65  0.62    Corn  Barley  Ingredient   Corn  45.00  12.50   Barley  8.80  45.00   Soybean meal, 47% CP  20.80  25.20   Sunflower meal, 34% CP  10.00  1.20   Soy oil soapstocks  4.70  5.30   Dicalcium phosphate  1.49  1.42   Calcium carbonate (powder)  4.11  4.18   Calcium carbonate (granular size)  4.11  4.18   Sodium chloride  0.35  0.35   DL-methionine, 99%  0.14  0.17   Vitamin and mineral premix1  0.50  0.50  Calculated analyses2   AMEn (Kcal/kg)  2750  2750   Crude fiber  4.4  3.6   Digestible amino acids2    Lys  0.80  0.80    Met  0.35  0.35    Met + cys  0.59  0.59    Thr  0.56  0.56  Determined analyses3   Dry matter  89.6  90.3   Gross energy (Kcal/kg)  4,305  4,290   Crude protein  17.7  17.9   Neutral detergent fiber  10.0  11.3   Ether extract  7.1  7.5   Linoleic acid (C18:2)  3.75  3.40   Ash  12.3  12.8   Calcium  3.85  3.94   Total phosphorus  0.65  0.62  1Provided the following (per kilogram of diet): vitamin A (trans-retinyl acetate), 10,000 IU; vitamin D3 (cholecalciferol), 3,750 IU; vitamin E (dl-α-tocopheryl acetate), 10 mg; vitamin B1, 1.3 mg; vitamin B2, 5 mg; vitamin B6, 2 mg; vitamin B12 (cyanocobalamin), 13 mg; niacin, 25 mg; pantothenic acid (d-calcium pantothenate), 10 mg; folic acid, 1 mg; biotin, 0.13 mg; choline (choline chloride), 250 mg; manganese (MnO), 90 mg; zinc (ZnO), 65 mg; iron (FeSO4.H2O), 40 mg; copper (CuSO4 5H2O), 8 mg; iodine [Ca(IO3)2], 0.7 mg; selenium (Na2SeO3), 0.3 mg; Roxazyme, 200 mg [1600 U of endo-1,4-β-glucanase (EC 3.2.1.4), 3600 U of endo-1,3 (4)-β-glucanase (EC 3.2.1.6), and 5200 U of endo-1,4-β-xylanase (EC 3.2.1.8)] supplied by DSM S.A., Madrid, Spain; Natuphos 5000 (300 FTU/kg supplied by Basf Española, S.A., Tarragona, Spain), 60 mg. 2According to FEDNA (2010). 3Data correspond to the average of duplicate analyses of the 5 diets ground with different screen sizes of each cereal. Within each cereal type, the determined chemical analyses were similar for all the diets (CV below 5%), independent of the screen size. View Large The night before the start of the experiment, feeders were emptied at 22.00 h and the hens fasted for 8 hours. At 06.00 h the following d, all replicates were offered 2.2 kg of their respective experimental feeds for ad libitum consumption. The amount of feed supplied at the start of the experiment was chosen to allow a complete filling of the feeders while avoiding feed wastage. Consequently, hens consumed the different fractions of the original feeds according to their preference throughout the experiment. Representative samples (300 g) of the feed remaining in the feeders were collected every 2 h during the experiment (from 06.00 to 14.00 h), and the particle size distribution and the GMD ± GSD were determined per cage at the end of each interval. The experiment was conducted as a completely randomized design with 10 diets in a factorial arrangement with 2 cereals and 5 screen sizes. Each treatment was replicated 5 times, and the experimental unit was the cage with 10 hens for all measurements. Laboratory Analysis The particle size distribution of the main ingredients, the original diets, and the uneaten feed remaining in the feeders was determined in triplicate in representative samples (100 g) every 2 h (Tables 1 and 3, and Figure 1). The data were expressed as GMD ± GSD (ASAE, 1995). Representative samples of the feeds were ground with a laboratory mill (Retsch Model Z-I, Stuttgart, Germany) equipped with a 1-mm screen and analyzed in duplicate for major nutrients, as indicated by AOAC International (2005) (Table 2). Figure 1. View largeDownload slide Particle size distribution1 of the original diets at the start of the experiment.2 1The percentage of particles smaller than 160 μm and bigger than 2,500 μm were negligible for all diets. 2The average geometric mean diameter and geometric standard deviation (GMD ± GSD), across sieve diameters, were 1,143 ± 2.16 μm for the corn diets and 1,311 ± 2.06 μm for the barley diets. Figure 1. View largeDownload slide Particle size distribution1 of the original diets at the start of the experiment.2 1The percentage of particles smaller than 160 μm and bigger than 2,500 μm were negligible for all diets. 2The average geometric mean diameter and geometric standard deviation (GMD ± GSD), across sieve diameters, were 1,143 ± 2.16 μm for the corn diets and 1,311 ± 2.06 μm for the barley diets. Table 3. Geometric mean diameter (GMD, μm) and geometric standard deviation (GSD) of the experimental diets.1   Cereal    Screen size (mm)  Corn  Barley  Average  4  960 ± 2.07  1,045 ± 2.01  1,003 ± 2.04  6  1,041 ± 2.12  1,165 ± 2.07  1,103 ± 2.10  8  1,180 ± 2.20  1,335 ± 2.06  1,258 ± 2.13  10  1,232 ± 2.21  1,458 ± 2.08  1,345 ± 2.15  12  1,302 ± 2.20  1,551 ± 2.07  1,427 ± 2.14  Average  1,143 ± 2.16  1,311 ± 2.06      Cereal    Screen size (mm)  Corn  Barley  Average  4  960 ± 2.07  1,045 ± 2.01  1,003 ± 2.04  6  1,041 ± 2.12  1,165 ± 2.07  1,103 ± 2.10  8  1,180 ± 2.20  1,335 ± 2.06  1,258 ± 2.13  10  1,232 ± 2.21  1,458 ± 2.08  1,345 ± 2.15  12  1,302 ± 2.20  1,551 ± 2.07  1,427 ± 2.14  Average  1,143 ± 2.16  1,311 ± 2.06    1Determined before the start of the experiment. View Large At the end of the experiment (14.00 h.), the feed remaining in the feeders of all the replicates was collected and pooled by treatment. The reason for pooling the uneaten feed of the 5 replicates of each of the 10 treatments was the limited amount of residual feed present in some replicates, which did not allow to estimate precisely the nutrient composition of each of the sieve fractions in the replicates. Representative samples of the 5 sieve fractions of each of the 10 original diets and of the 50 composite uneaten feed samples collected at 14.00 h (10 treatments and 5 sieve fractions per treatment) were ground (1-mm screen) and analyzed for moisture, CP, total ash, and Ca, as indicated by Herrera et al. (2017). Statistical Analysis The experiment was conducted as a completely randomized design with 10 treatments arranged as a 2 × 5 factorial with 2 main cereals (corn and barley) and 5 mean particle sizes of the cereal (4, 6, 8, 10, and 12 mm screen). The effects of type of cereal and grinding size of the cereal on FI and their interactions were analyzed by the GLM procedure of SAS (SAS Institute, 2004). For particle size selection, the same effects and the interaction between sampling time and the main effects were analyzed by the MIXED procedure of SAS (SAS Institute, 2004), using time as the repeated measure. The individual cage represented the experimental unit for all measurements. When the model was significant, treatment means were separated using the Tukey test. Results in tables are presented as means, and differences were considered significant at P < 0.05. For data on CP, ash, and Ca content of the different sieve fractions of the original diets and of the residual feeds at 14.00 h, no replicates were available and therefore only average values per treatment are presented. RESULTS The effects of the cereal and screen size on the GMD and the GSD of the diets are shown in Table 3. Independent of the screen used, the GMD of the feeds was greater (average of 1,311 μm vs. 1,143 μm) for the barley than for the corn diets. However, an opposite effect was observed for the GSD (2.06 vs. 2.16). FI from 06.00 to 14.00 h (56.6 ± 5.4 g) was not affected by the main cereal or the screen size used to grind the cereal (data not shown). The effects of the main cereal, screen size, and time on particle size distribution of diets and feed refusals are shown in Table 4. The GMD and the GSD of the diets decreased (P < 0.001) as the experiment progressed, irrespective of the size of the screen used to grind the cereal. The differences in GMD between the corn and barley based diets decreased with time (P < 0.001 for the interaction; Figure 2A). For the GSD, the decrease with sampling time observed was more pronounced for the corn than for the barley diets (P < 0.001 for the interaction; Figure 2B). Figure 2. View largeDownload slide Interaction between the main cereal of the diet and sampling time on geometric mean diameter (GMD) and log normal SD (GSD) of the diets. (A) Geometric mean diameter (GMD, μm). (B) Geometric standard deviation (GSD, μm). Figure 2. View largeDownload slide Interaction between the main cereal of the diet and sampling time on geometric mean diameter (GMD) and log normal SD (GSD) of the diets. (A) Geometric mean diameter (GMD, μm). (B) Geometric standard deviation (GSD, μm). Table 4. Influence of the main cereal and the particle size distribution of the diet on preference behavior of the hens.     Cereal  Screen size (mm)  Time  SD1  Probability2,3      Corn  Barley  4  6  8  10  12      1  2  3  4  5  GMD4                  88.5  <.001  <.001  <.001  <.001  <.001    06.00 h  1,143  1,311  1,003  1,103  1,258  1,345  1,427  1,227x                08.00 h  1,060  1,202  950  1,109  1,103  1,239  1,255  1,131y                10.00 h  1,048  1,149  936  1,076  1,063  1,206  1,212  1,098y                12.00 h  1,023  1,158  933  1,070  1,079  1,165  1,206  1,091y                14.00 h  928  1,053  884  991  981  1,036  1,061  991z                Average  1,048b  1,175a  948c  1,069b  1,108b  1,198a  1,246a                GSD5                  0.051  <.001  <.001  <.001  <.001  0.601    06.00 h  2.16  2.06  2.04  2.10  2.13  2.15  2.14  2.11y                08.00 h  2.13  2.06  2.03  2.07  2.12  2.12  2.14  2.10x                10.00 h  2.08  2.04  2.01  2.04  2.09  2.09  2.09  2.06y                12.00 h  2.03  1.98  1.96  1.98  2.01  2.02  2.06  2.01z                14.00 h  2.03  1.99  1.97  1.99  2.01  2.02  2.05  2.01z                Average  2.09a  2.03b  2.00c  2.04b  2.07a  2.08a  2.10a                    Cereal  Screen size (mm)  Time  SD1  Probability2,3      Corn  Barley  4  6  8  10  12      1  2  3  4  5  GMD4                  88.5  <.001  <.001  <.001  <.001  <.001    06.00 h  1,143  1,311  1,003  1,103  1,258  1,345  1,427  1,227x                08.00 h  1,060  1,202  950  1,109  1,103  1,239  1,255  1,131y                10.00 h  1,048  1,149  936  1,076  1,063  1,206  1,212  1,098y                12.00 h  1,023  1,158  933  1,070  1,079  1,165  1,206  1,091y                14.00 h  928  1,053  884  991  981  1,036  1,061  991z                Average  1,048b  1,175a  948c  1,069b  1,108b  1,198a  1,246a                GSD5                  0.051  <.001  <.001  <.001  <.001  0.601    06.00 h  2.16  2.06  2.04  2.10  2.13  2.15  2.14  2.11y                08.00 h  2.13  2.06  2.03  2.07  2.12  2.12  2.14  2.10x                10.00 h  2.08  2.04  2.01  2.04  2.09  2.09  2.09  2.06y                12.00 h  2.03  1.98  1.96  1.98  2.01  2.02  2.06  2.01z                14.00 h  2.03  1.99  1.97  1.99  2.01  2.02  2.05  2.01z                Average  2.09a  2.03b  2.00c  2.04b  2.07a  2.08a  2.10a                a–cWithin a line, means without a common superscript differ significantly. x–zWithin a column, means without a common superscript differ significantly. 125 replicates for the main cereal effect and 10 replicates for the screen size effect. 21 = Effect of type of cereal; 2 = effect of screen size; 3 = effect of time; 4 = interaction between type of cereal and time; 5 = interaction between screen size and time. 3Interaction between type of cereal and screen size was not significant (P > 0.10). 4Geometric mean diameter. 5Geometric standard deviation. View Large As an average of the corn and barley diets, both GMD (from 948 μm to 1,246 μm) and the GSD (from 2.00 to 2.10) increased (P < 0.001) as the screen size used to grind the cereal increased from 4 to 12 mm (Table 4). The differences in GMD among screen sizes of the corn and barley diets decreased with time (P < 0.001 for the interaction; Figure 3), but no interactions were detected for the GSD. Figure 3. View largeDownload slide Interaction between the screen size (mm) used to grind the cereal and sampling time on the geometric mean diameter (GMD) of the diet. Figure 3. View largeDownload slide Interaction between the screen size (mm) used to grind the cereal and sampling time on the geometric mean diameter (GMD) of the diet. The CP content of the sieved fractions of the original diets and of the residual feeds, measured after 8 h of ad libitum feeding, is shown in Table 5. When the cereal, either corn or barley, was finely ground (4 and 6 mm screen), the protein accumulated primarily in the coarser fraction (average of the 1,250 and 2,500 μm sieves) of the original diets. However, no such an effect was observed when the cereal was coarsely ground (10 and 12 mm screen), with more protein accumulating in the finer fraction (160 and 315 μm sieves). In fact, the CP content of the coarser fraction was 18.6 and 19.2% for the corn and barley diets, when the cereal was ground with a 4 mm screen but 14.3 and 14.4% when ground with a 12 mm screen. Similar but less pronounced effects were observed in the residual feeds after 8 h of ad libitum feeding; the CP content of the coarser fractions was 17.1 and 16.8% for the corn and barley diets when the cereal was finely ground (4 mm screen) but 15.0 and 16.6% when the cereal was coarsely ground (12 mm screen). Table 5. Crude protein content (%) of the sieved fractions of the original diets at the start of the experiment (06.00 h) and of the residual feeds at the end of the experiment (14.00 h). Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm                       160  15.0  14.7  15.1  15.5  16.0  13.0  13.4  13.7  14.3  16.9   315  15.9  16.6  16.2  17.1  19.3  14.6  14.6  16.0  16.2  18.3   630  17.4  18.4  19.3  20.9  20.9  17.9  18.4  19.0  21.2  21.6   1,250  17.4  17.6  19.8  18.8  18.5  18.9  18.2  19.1  21.0  18.9   2,500  19.9  19.5  12.3  11.4  10.1  19.4  15.2  13.4  11.0  9.8  Pooled fractions   Fine fraction2  15.5  15.7  15.7  16.3  17.7  13.8  14.0  14.9  15.3  17.6   Coarse fraction3  18.6  18.5  16.1  15.1  14.3  19.2  16.7  16.3  16.0  14.4    Residual feed4  Sieve diameter, μm                       160  14.1  15.0  15.7  15.5  15.7  12.4  12.8  13.2  13.4  13.5   315  16.3  17.7  18.1  17.4  19.2  14.9  16.6  17.1  17.6  19.5   630  19.4  20.1  20.6  21.0  22.2  19.2  21.4  21.2  23.5  23.5   1,250  19.0  18.3  18.7  19.9  17.9  18.8  18.9  18.9  18.7  19.4   2,500  15.1  13.7  15.9  13.2  12.1  14.7  12.4  15.0  13.9  13.8  Pooled fractions   Fine fraction  15.2  16.4  16.9  16.5  17.5  13.7  14.7  15.2  15.5  16.5   Coarse fraction  17.1  16.0  17.3  16.6  15.0  16.8  15.7  17.0  16.3  16.6  Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm                       160  15.0  14.7  15.1  15.5  16.0  13.0  13.4  13.7  14.3  16.9   315  15.9  16.6  16.2  17.1  19.3  14.6  14.6  16.0  16.2  18.3   630  17.4  18.4  19.3  20.9  20.9  17.9  18.4  19.0  21.2  21.6   1,250  17.4  17.6  19.8  18.8  18.5  18.9  18.2  19.1  21.0  18.9   2,500  19.9  19.5  12.3  11.4  10.1  19.4  15.2  13.4  11.0  9.8  Pooled fractions   Fine fraction2  15.5  15.7  15.7  16.3  17.7  13.8  14.0  14.9  15.3  17.6   Coarse fraction3  18.6  18.5  16.1  15.1  14.3  19.2  16.7  16.3  16.0  14.4    Residual feed4  Sieve diameter, μm                       160  14.1  15.0  15.7  15.5  15.7  12.4  12.8  13.2  13.4  13.5   315  16.3  17.7  18.1  17.4  19.2  14.9  16.6  17.1  17.6  19.5   630  19.4  20.1  20.6  21.0  22.2  19.2  21.4  21.2  23.5  23.5   1,250  19.0  18.3  18.7  19.9  17.9  18.8  18.9  18.9  18.7  19.4   2,500  15.1  13.7  15.9  13.2  12.1  14.7  12.4  15.0  13.9  13.8  Pooled fractions   Fine fraction  15.2  16.4  16.9  16.5  17.5  13.7  14.7  15.2  15.5  16.5   Coarse fraction  17.1  16.0  17.3  16.6  15.0  16.8  15.7  17.0  16.3  16.6  1Analyzed CP content was 17.7 and 17.9% for the corn and barley diets, respectively. 2Fine fraction was defined as the proportion of particles with a geometric mean diameter no more than 315 μm. 3Coarse fraction was defined as the proportion of particles with a geometric mean diameter of at least 1,250 μm. 4Feed remaining in the feeders of all the replicates of each of the 10 experimental diets was collected and pooled by treatment. Consequently, only average data are presented. View Large The ash and Ca contents of the sieving of the original diets and of the residual feeds, measured after 8 h of ad libitum feeding are shown in Tables 6 and 7, respectively. Ash and Ca concentrated in the coarser fractions of the original and the residual feeds in both sets of diets, with differences being more pronounced when the cereals were ground fine than when ground coarse. In fact, the Ca content of the coarser fraction (1,250 and 2,500 μm sieves) of the original corn and barley diets was 8.2 and 7.8% when the cereal was ground at 4 mm but 4.4 and 3.7% when ground at 12 mm (Table 7). Similarly, the Ca content of the coarser fraction (1,250 and 2,500 μm sieves) of the residual feed after 8 h of ad libitum feeding was 13.2 and 11.7% for the corn and barley diets when the cereal was ground at 4 mm but 9.7 and 6.7% when ground at 12 mm. A similar response was observed for the ash, which concentrated in the coarser fraction of the original and of the residual feeds, with more pronounced effects when the cereal was ground fine (4 and 6 mm screen) than when ground coarse (10 and 12 mm screen). Table 6. Ash content (%) of the sieved fractions of the original diets at the start of the experiment (06.00 h) and of the residual feeds at the end of the experiment (14.00 h). Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  7.3  7.5  8.7  8.3  8.7  10.5  10.8  10.8  12.3  12.6   315  6.6  7.3  7.4  7.7  7.6  8.3  9.1  8.9  9.7  9.7   630  11.3  12.1  12.2  12.7  12.9  11.2  13.6  12.9  14.6  14.7   1,250  12.7  15.0  12.1  16.4  15.5  10.4  17.2  12.3  14.8  14.2   2,500  34.1  21.5  22.1  16.5  14.7  33.2  20.2  15.1  15.3  10.3  Pooled fractions   Fine fraction2  7.0  7.4  8.1  8.0  8.2  9.4  10.0  9.9  11.0  11.2   Coarse fraction3  23.4  18.3  17.1  16.5  15.1  21.8  18.7  13.7  15.1  12.3    Residual feed4  Sieve diameter, μm   160  9.7  10.6  10.9  10.5  9.3  11.3  14.7  16.0  17.1  15.7   315  9.3  9.4  9.8  9.1  10.4  8.9  11.5  11.9  12.7  12.2   630  11.8  12.0  13.3  12.5  13.7  12.1  15.6  15.2  15.8  15.5   1,250  21.7  19.6  24.0  18.3  19.8  18.1  19.2  17.6  16.8  18.2   2,500  47.9  36.0  42.7  33.0  33.0  45.4  29.1  27.4  27.6  21.4  Pooled fractions   Fine fraction  9.5  10.0  10.4  9.8  9.9  10.1  13.1  14.0  14.9  14.0   Coarse fraction  34.8  27.8  33.4  25.7  26.4  31.8  24.2  22.5  22.2  19.8  Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  7.3  7.5  8.7  8.3  8.7  10.5  10.8  10.8  12.3  12.6   315  6.6  7.3  7.4  7.7  7.6  8.3  9.1  8.9  9.7  9.7   630  11.3  12.1  12.2  12.7  12.9  11.2  13.6  12.9  14.6  14.7   1,250  12.7  15.0  12.1  16.4  15.5  10.4  17.2  12.3  14.8  14.2   2,500  34.1  21.5  22.1  16.5  14.7  33.2  20.2  15.1  15.3  10.3  Pooled fractions   Fine fraction2  7.0  7.4  8.1  8.0  8.2  9.4  10.0  9.9  11.0  11.2   Coarse fraction3  23.4  18.3  17.1  16.5  15.1  21.8  18.7  13.7  15.1  12.3    Residual feed4  Sieve diameter, μm   160  9.7  10.6  10.9  10.5  9.3  11.3  14.7  16.0  17.1  15.7   315  9.3  9.4  9.8  9.1  10.4  8.9  11.5  11.9  12.7  12.2   630  11.8  12.0  13.3  12.5  13.7  12.1  15.6  15.2  15.8  15.5   1,250  21.7  19.6  24.0  18.3  19.8  18.1  19.2  17.6  16.8  18.2   2,500  47.9  36.0  42.7  33.0  33.0  45.4  29.1  27.4  27.6  21.4  Pooled fractions   Fine fraction  9.5  10.0  10.4  9.8  9.9  10.1  13.1  14.0  14.9  14.0   Coarse fraction  34.8  27.8  33.4  25.7  26.4  31.8  24.2  22.5  22.2  19.8  1Analyzed ash content was 12.3 and 12.8% for the corn and barley diets, respectively. 2Fine fraction was defined as the proportion of particles with a geometric mean diameter no more than 315 μm. 3Coarse fraction was defined as the proportion of particles with a geometric mean diameter of at least 1,250 μm. 4Feed remaining in the feeders of all the replicates of each of the 10 experimental diets was collected and pooled by treatment. Consequently, only average data are presented. View Large Table 7. Calcium content (%) of the sieved fractions of the original diets at the start of the experiment (06.00 h) and of the residual feeds at the end of the experiment (14.00 h). Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  1.3  1.3  1.6  1.5  1.7  2.2  2.3  2.3  2.8  2.9   315  0.9  1.2  1.1  1.7  1.5  1.8  1.9  1.7  1.9  2.0   630  3.2  3.2  3.2  3.3  3.3  3.0  3.8  3.5  4.2  4.0   1,250  4.0  4.2  3.3  4.6  4.3  3.5  5.3  3.7  4.5  4.3   2,500  12.4  7.1  7.4  5.5  4.5  12.1  8.1  4.4  4.9  3.0  Pooled fractions   Fine fraction2  1.1  1.3  1.4  1.6  1.6  2.0  2.1  2.0  2.4  2.5   Coarse fraction3  8.2  5.7  5.4  5.1  4.4  7.8  6.7  4.1  4.7  3.7    Residual feed4  Sieve diameter, μm   160  2.5  3.0  3.1  2.9  3.5  3.1  4.3  4.6  5.0  4.2   315  2.3  2.4  2.4  2.4  2.5  2.1  3.2  3.1  3.5  3.1   630  3.6  3.5  4.0  3.7  4.0  3.7  4.8  4.4  4.9  4.5   1,250  7.8  6.9  9.0  6.4  7.0  6.0  7.1  5.6  5.5  6.2   2,500  18.6  13.8  16.4  12.6  12.3  17.4  11.4  10.5  10.7  7.2   Fine fraction  2.4  2.7  2.8  2.7  3.0  2.6  3.8  3.9  4.3  3.7   Coarse fraction  13.2  10.4  12.7  9.5  9.7  11.7  9.3  8.1  8.1  6.7  Main cereal  Corn  Barley  Screen size (mm)  4  6  8  10  12  4  6  8  10  12    Original diet1  Sieve diameter, μm   160  1.3  1.3  1.6  1.5  1.7  2.2  2.3  2.3  2.8  2.9   315  0.9  1.2  1.1  1.7  1.5  1.8  1.9  1.7  1.9  2.0   630  3.2  3.2  3.2  3.3  3.3  3.0  3.8  3.5  4.2  4.0   1,250  4.0  4.2  3.3  4.6  4.3  3.5  5.3  3.7  4.5  4.3   2,500  12.4  7.1  7.4  5.5  4.5  12.1  8.1  4.4  4.9  3.0  Pooled fractions   Fine fraction2  1.1  1.3  1.4  1.6  1.6  2.0  2.1  2.0  2.4  2.5   Coarse fraction3  8.2  5.7  5.4  5.1  4.4  7.8  6.7  4.1  4.7  3.7    Residual feed4  Sieve diameter, μm   160  2.5  3.0  3.1  2.9  3.5  3.1  4.3  4.6  5.0  4.2   315  2.3  2.4  2.4  2.4  2.5  2.1  3.2  3.1  3.5  3.1   630  3.6  3.5  4.0  3.7  4.0  3.7  4.8  4.4  4.9  4.5   1,250  7.8  6.9  9.0  6.4  7.0  6.0  7.1  5.6  5.5  6.2   2,500  18.6  13.8  16.4  12.6  12.3  17.4  11.4  10.5  10.7  7.2   Fine fraction  2.4  2.7  2.8  2.7  3.0  2.6  3.8  3.9  4.3  3.7   Coarse fraction  13.2  10.4  12.7  9.5  9.7  11.7  9.3  8.1  8.1  6.7  1Analyzed Ca content was 3.85 and 3.94% for the corn and barley diets, respectively. 2Fine fraction was defined as the proportion of particles with a geometric mean diameter no more than 315 μm. 3Coarse fraction was defined as the proportion of particles with a geometric mean diameter of at least 1,250 μm. 4Feed remaining in the feeders of all the replicates of each of the 10 experimental diets was collected and pooled by treatment. Consequently, only average data are presented. View Large DISCUSSION The GMD of the original diets was greater for the barley than for the corn diets (1,311 vs. 1,143 μm), consistent with data of Pérez-Bonilla et al. (2011) comparing the 2 cereals. The glumes of the barley grains are quite flexible, and when ground, a high proportion passes intact through the screen, resulting in an increase in the GMD of diets based on barley compared with diets based on corn. These results confirm that the structure of the feed depends not only on the size of the sieve but also on the main cereal of the diet, consistent with data of Douglas et al. (1990) and Nir et al. (1995). The beak of the chicken is not well adapted to consume fine particles, and, consequently, coarse particles tended to be preferred (Picard et al., 1997; Mateos et al., 2002). In fact, most management guides (ISA Brown, 2010; Lohmann, 2016) recommended coarse grinding when the objective is to maximize FI. In this respect, Safaa et al. (2009) observed a significant 2.5% increase in FI in hens fed corn or wheat ground with a 10-mm screen compared with hens fed the same cereals ground with a 6-mm screen. However, in the current research in which diets based on corn or barley were compared, no differences in FI because of particle size were observed. The reasons for the discrepancy among experiments is not apparent but could be related to the proportion of very fine particles present in the diets rather than to their GMD. In this respect, Portella et al. (1988a) suggested that hen preference for coarse particles might be altered not only by the average size of the particles of the diet but also by the proportion of very fine particles. Herrera et al. (2017) suggested that supplemental fat might agglomerate the fines of the diet, improving palatability and reducing the rejection rate for fine particles. In the current research, supplemental fat was high in both corn and barley diets (4.7 and 5.3%, respectively) which might have reduced the preference of the hens for coarse vs. fine particles. The GMD of the diets decreased with time, reflecting the preference behavior of the hens for coarse particles, in agreement with previous studies with broilers (Schiffman, 1968; Portella et al., 1988b; Xu et al., 2015) and laying hens (Portella et al., 1988a; Safaa et al., 2009). The data confirm that when allowed to choose, laying hens prefer coarse particles. In contrast, Herrera et al. (2017) reported no differences in FI of brown-egg laying hens fed diets from 17 to 49 wk of age when the cereal was ground using screens varying in size from 4 to 12 mm. The reasons for the discrepancy among researches are not known but might depend on the chemical composition of the experimental diets as well as on the feeding strategy used (i.e., frequency of feeding) and feeder design, which might affect feed particle size distribution. When allowed to choose, hens might prefer coarse particles as observed in the current experiment. However, when new feed is constantly added to the uneaten feed or when the hens are obliged to clean the feeders at specific times, as occurred often under practical conditions, the effects might be less pronounced or even disappear. The differences in GMD of the residual feeds between the 2 cereal-based diets and among screen sizes decreased with time, reflecting the increased uniformity of the particles in the uneaten feed. Portella et al. (1988a) reported also that the disappearance of coarse particles was overwhelming when the feed had an excess of large particles (>2.36 mm). However, the preference was less obvious as the experiment progressed and the percentage of coarse particle was reduced, consistent with the results reported herein. The GSD of the diets was greater for the corn than for the barley diets, differences that increased with increases in the size of the screen. In contrast, the differences in GSD for both main effects (type of cereal and screen size) decreased with time, reflecting the higher rate of disappearance of the coarser particles of the uneaten feed for the first h after the start of the experiment. Birds show a specific appetite for some components of the diet, such as CP, fiber, or Ca (Hughes and Wood-Gush, 1971; Mongin and Sauveur, 1974; Holcombe et al., 1975). When the diet is deficient in a given nutrient, birds might choose to eat those sieving fractions richer in the deficient nutrient (Portella et al., 1988a). As a result, hen preference might depend not only on particle size but also on the physical distribution of the limiting nutrient within the sieving fractions. In the current research, however, the differences in CP, ash, and Ca content among the sieving fractions of the original diets were similar to those of the residuals at the end of the experiment, suggesting that feed preference was not modulated by differences in nutrient content of the sieve fractions of the diet. An observation that deserves further attention is the difference in Ca concentration between the original diets and the residual feeds after 8 h of ad libitum consumption. For the corn diet, the percentage of Ca across fractions of the diet, independent of the sieving fraction considered and of the screen size used to grind the corn, was 8.6 to 63.4% higher in the residual feeds than in the original diets. Similar data were observed for the barley diets, in which the percentage of Ca was 11.1 to 58.3% higher in the residual feed than in the original diets. A similar distribution pattern was observed for ash content but not for CP. The reasons for these contrasting observations are unknown but might be related to the timing at which the feed (and the Ca included in the feed) was available for consumption and the Ca needs for shell formation according to the period of the day. Hughes (1972) reported that laying hens under-consume Ca during the morning but tend to over-consume Ca late in the d, when most of the shell formation process occurs. In the evening, hens try to balance Ca intake and Ca requirements, giving preference to those particles rich in the deficient nutrient, regardless of feed coarseness, whereas an opposite pattern might occur during the morning. The current research was conducted from 06.00 to 14.00 h, a period of the da in which Ca deposition is relatively low (Hughes, 1972; Molnár et al., 2018). Consequently, hens chose to under-consume Ca because Ca requirements are lower. The higher Ca concentration of the residual feeds after 8 h of ad libitum consumption, compared to that of the original diets observed, is consistent with this suggestion. Also, it was noticed that Ca concentrated in the coarse fractions of the original feeds, probably because 50% of the CaCO3 of the diets was supplied in granular form. A similar Ca distribution pattern was observed in the residual feeds of all diets after 8 h of ad libitum consumption, confirming that hens’ preference for coarse particles was independent of its Ca content. In contrast, Portella et al. (1988a) observed that the proportion of Ca in the different sieving fractions of a mash diet was not homogenous and decreased as the GMD of the diet increased, opposite to the results reported herein. The reasons for the discrepancy are not known. We do not have information on the time of the d and the size of the Ca carbonate used by Portella et al. (1988a), and, thus, no comparison of the results of the 2 experiments can be made. The consumption pattern observed was different for CP than for Ca. Hens showed a clear preference for consuming coarse particles and were unable to choose those fractions of the feed with a higher or lower protein content. Traineau et al. (2015), however, reported that when hens were allowed to choose between 2 feeds varying in CP content, they over-consumed the diet rich in protein after oviposition, early in the morning, a period in which the albumen of the egg is formed. In the research of Traineau et al. (2015), hens were offered 2 different feeds to choose, whereas a single feed was supplied in the current research, limiting the capacity of the hens for selecting feed particles based on its protein content. In this respect, Forbes and Shariatmadari (1994) showed that the ability of the hens to choose ingredients according to its CP needs, when offered a single diet, was limited. Moreover, Pousga et al. (2005) reported that hens offered a single conventional feed were not able to choose those feed fractions with higher CP content, consistent with the data reported herein. In conclusion, type of cereal and size of the screen used to grind the cereal affected feed preference behavior of the hens. The CP, ash, and Ca contents of the diet were not uniform and varied with the screen used to grind the cereal and with the sieving fraction (fine vs. coarse) of the diets. The data demonstrate that under the condition of the current research, hen preference for coarse particles was not modulated by the desire to meet any potential requirement for the missing nutrient. In fact, in relative terms, the concentration of CP, ash, and Ca of the sieve fractions of the original diets and the residuals after 8 h of ad libitum consumption followed a similar pattern, demonstrating that the composition of the sieving fractions of the diet did not affect the preference behavior of the hens for coarse particles. When allowed to choose, and no extra quantities of feed were added to the feeder during the experimental period, hens showed a clear preference for consuming coarse particles. Crude protein content of the different sieve fractions did not affect hen preference behavior. In fact, hens did not show any preference for consuming extra amounts of protein during the early part of the day. In contrast, Ca intake of the hens was reduced during the morning, resulting in residual feeds with greater concentration of ash and Ca than in the original diets, irrespective of the size of the feed fractions. It should be noticed that in the current research, hens were offered at all times the leftovers of the previous feeding periods, reducing its potential capacity to choose coarse particles. Hen preference behavior might be different under commercial conditions, when the residuals are remixed constantly with new feed coming from the auger and the hens are obliged often to consume the fine particles previously refused. Footnotes 1 Financial support was provided by the Ministerio de Economía y Competitividad (Project AGL 2014–56139). REFERENCES Abdollahi M. R., Duangnumsawang Y., Kwakkel R. P., Steenfeldt S., Bootwalla S. M., Ravindran V.. 2016. Investigation of the interaction between separate calcium feeding and phytase supplementation on growth performance, calcium intake, nutrient digestibility and energy utilisation in broiler starters. Anim. Feed Sci. Technol.  219: 48– 58. Google Scholar CrossRef Search ADS   Allen J., Perry G. C. 1977. Feeding patterns and food selection of caged birds. Br. Vet. J.  133: 99 (Abstr.) Amerah A. M., Ravindran V., Lentle R. G., Thomas D. G.. 2007. Feed particle size: Implications on the digestion and performance of poultry. World's Poult. Sci. J.  63: 439– 455. Google Scholar CrossRef Search ADS   AOAC International. 2005. Official Methods of Analysis of the AOAC International . 18th ed. AOAC Int., Gaithersburg, MD. ASAE. 1995. Standard S319.2: Method of determining and expressing fineness of feed material by sieving. 461– 462 in Agriculture Engineers Yearbook of Standards . Am. Soc. Agric. Eng., St. Joseph, MO. Benabdeljelil K., Arbaoui M. I.. 1994. Effects of enzyme supplementation of barley-based diets on hen performance and egg quality. Anim. Feed Sci. Technol.  48: 325– 334. Google Scholar CrossRef Search ADS   Berg L. R. 1959. Enzyme supplementation of barley diets for laying hens. Poult. Sci.  38: 1132– 1139 Google Scholar CrossRef Search ADS   Boletín Oficial del Estado. 2007. Ley 32/2007 de 7 de Noviembre para el cuidado de los animales, en su explotación, transporte, experimentación y sacrificio. BOE . 268: 45914– 45920. Coon C. N., Obi, Hamre, 1988. Use of barley in laying hen diets. Poult. Sci.  67, 1306– 1313. Google Scholar CrossRef Search ADS   Davis R. L., Hill E. G., Sloan H. J., Briggs G. M.. 1951. Detrimental effect of corn of coarse particle size in rations for chicks. Poult. Sci.  30: 325– 328. Google Scholar CrossRef Search ADS   Douglas J. H., Sullivan T. W., Bond P. L., Struwe F. J., Baier J. G., Robeson L. G.. 1990. Influence of grinding, rolling, and pelleting on the nutritional-value of grain sorghums and yellow corn for broilers. Poult. Sci.  69: 2150– 2156. Google Scholar CrossRef Search ADS   FEDNA (Fundación Española Desarrollo Nutrición Animal). 2010. Normas FEDNA para la Formulación de Piensos Compuestos . 3rd ed. In: De Blas C., Mateos G. G., Rebollar P. G. (Eds). Fund. Esp. Desarro. Nutr. Anim., Madrid, Spain. Forbes J. M., Shariatmadari F. S.. 1994. Diet selection for protein by poultry. Word's Poult. Sci. J.  50: 7– 24. Google Scholar CrossRef Search ADS   Gentle M. J. 1979. Sensory control of feed intake. 259– 273 In: Food Intake Regulation in Poultry , Boorman K. N., Freeman B. M., eds. Br. Poult. Sci. Ltd, Edinburg. González-Alvarado J. M., Jiménez-Moreno E., Lázaro R., Mateos G. G.. 2007. Effect of type of cereal, heat processing of the cereal, and inclusion of fiber in the diet on productive performance and digestive traits of broilers. Poult. Sci.  86: 1705– 1715. Google Scholar CrossRef Search ADS PubMed  González-Alvarado J. M., Jiménez-Moreno E., González-Sánchez D., Lázaro R., Mateos G. G.. 2010. Effect of inclusion of oat hulls and sugar beet pulp in the diet on productive performance and digestive traits of broilers from 1 to 42 days of age. Anim. Feed Sci. Technol.  162: 37– 46. Google Scholar CrossRef Search ADS   Grobas S., Méndez S., de Blas J. C., Mateos G. G.. 1999. Influence of dietary energy, supplemental fat and linoleic acid concentration on performance of laying hens at two ages. Br. Poult. Sci.  40: 681– 687. Google Scholar CrossRef Search ADS PubMed  Herrera J., Saldaña B., Guzmán P., Cámara L., Mateos G. G.. 2017. Influence of particle size of the main cereal of the diet on egg production, gastrointestinal tract traits, and body measurements of brown laying hens. Poult. Sci.  96: 440– 448. Google Scholar CrossRef Search ADS PubMed  Hetland H., Svihus B., Krögdahl Å.. 2003. Effects of oat hulls and wood shavings on digestion in broilers and layers fed diets based on whole or ground wheat. Br. Poult. Sci.  44: 275– 282. Google Scholar CrossRef Search ADS PubMed  Holcombe D. J., Roland D. A., Harms R. H.. 1975. The ability of hens to adjust calcium intake when given a choice of diets containing two levels of calcium. Poult. Sci.  54: 552– 561. Google Scholar CrossRef Search ADS PubMed  Hughes B. O., Wood-Gush D. G. M.. 1971. A specific appetite for calcium in domestic chickens. Anim. Behav.  19: 490– 499. Google Scholar CrossRef Search ADS PubMed  Hughes B. O., 1972. A circadian rhythm of calcium intake in the domestic fowl. Br. Poult. Sci.  13: 485– 493. Google Scholar CrossRef Search ADS PubMed  ISA Brown. 1999. Energy levels and feed presentation for laying hens: Effects on performance and intake. Institut de Selection Animale. B. V, Boxmeer, The Netherlands. ISA Brown. 2010. Nutrition Management Guide. Isa Brown Commercial Layer. Institut de Selection Animale. B. V, Boxmeer, The Netherlands. Jiménez-Moreno E., González-Alvarado J. M., Lázaro R., Mateos G. G.. 2009. Effects of type of cereal, heat processing of the cereal, and fiber inclusion in the diet on gizzard pH and nutrient utilization in broilers at different ages. Poult. Sci.  88: 1925– 1933. Google Scholar CrossRef Search ADS PubMed  Jiménez-Moreno E., González-Alvarado J. M., González-Sánchez D., Lázaro R., Mateos G. G.. 2010. Effects of type and particle size of dietary fiber on growth performance and digestive traits of broilers from 1 to 21 days of age. Poult. Sci.  89: 2197– 2212. Google Scholar CrossRef Search ADS PubMed  Jiménez-Moreno E., De Coca-Sinova A., González-Alvarado J. M., Mateos G. G.. 2016. Inclusion of insoluble fiber sources in mash or pellet diets for young broilers. 1. Effects on growth performance and water intake. Poult. Sci.  95: 41– 52. Google Scholar CrossRef Search ADS PubMed  Lázaro R., García M., Araníbar M. J., Mateos G. G.. 2003. Effect of enzyme addition to wheat-, barley- and rye-based diets on nutrient digestibility and performance of laying hens. Br. Poult. Sci.  44: 256– 265. Google Scholar CrossRef Search ADS PubMed  Lohmann. 2016. Management Guide for Lohmann Brown-Classic . Lohmann Tierzucht. GMBH. Cuxhaven, Germany. Mateos G. G., Sell J. L.. 1980. Influence of carbohydrate and supplemental fat source of the metabolizable energy of the diet. Poult. Sci.  59: 2129– 2135. Google Scholar CrossRef Search ADS PubMed  Mateos G. G., Lázaro R., Gracia M. I.. 2002. The feasibility of using nutritional modifications to replace drugs in poultry feeds. J. Appl. Poult. Res.  11: 437– 452. Google Scholar CrossRef Search ADS   Mateos G. G., Jiménez-Moreno E., Serrano M. P., Lázaro R.. 2012. Poultry response to high levels of dietary fiber sources varying in physical and chemical characteristics. J. Appl. Poult. Res.  21: 156– 174. Google Scholar CrossRef Search ADS   Molnár A., Maertens L., Ampe B., Buyse J., Zoons J., Delezie E.. 2018. Effect of different split-feeding treatments on performance, egg quality, and bone quality of individually housed aged laying hens. Poult. Sci.  97: 88– 101. Google Scholar CrossRef Search ADS PubMed  Mongin P., Sauveur B.. 1974. Volundary food and calcium intake by the laying hens. Br. Poult. Sci.  15: 349– 359. Google Scholar CrossRef Search ADS PubMed  Nir I., Hiller R., Shefet G., Nitsan Z.. 1994. Effect of grain particle size on performance. 2. Grain texture interactions. Poult. Sci.  73: 781– 791. Google Scholar CrossRef Search ADS PubMed  Nir I., Hillel R., Ptichi I., Shefet G.. 1995. Effect of particle size on performance. 3. Grinding pelleting interactions. Poult. Sci.  74: 771– 783. Google Scholar CrossRef Search ADS PubMed  Pérez-Bonilla A., Frikha M., Mirzaie S., García J., Mateos G. G.. 2011. Effects of the main cereal and type of fat of the diet on productive performance and egg quality of brown-egg laying hens from 22 to 54 weeks of age. Poult. Sci.  90: 2801– 2810. Google Scholar CrossRef Search ADS PubMed  Pérez-Bonilla A., Frikha M., Lázaro R., Mateos G. G.. 2014. Type of grinding of the main cereal of the diet affects production of brown egg-laying hens. Anim. Feed Sci. Technol.  194: 121– 130. Google Scholar CrossRef Search ADS   Picard M., Melcion J. P., Bouchot C., Faure J. M.. 1997. Picorage et préhensibilité des particules alimentaires chez les volailles. INRA Prod. Anim.  10: 403– 414. Portella F. J., Caston L. J., Leeson S.. 1988a. Apparent feed particle size preference by laying hens. Can. J. Anim. Sci.  68: 915– 922. Google Scholar CrossRef Search ADS   Portella F. J., Caston L. J., Leeson S.. 1988b. Apparent feed particle size preference by broilers. Can. J. Anim. Sci.  68: 923– 930. Google Scholar CrossRef Search ADS   Pousga S., Boly H., Ogle B.. 2005. Choice feeding of poultry: A review. Liv. Res. Rural Develop.  Vol. 17, Article 45. Retrieved from http://www.lrrd.org/lrrd17/4/pous17045.htm. Safaa H. M., Jimenéz-Moreno E., Valencia D. G., Frikha M., Serrano M. P., Mateos G. G.. 2009. Effect of main cereal of the diet and particle size of the cereal on productive performance and egg quality of brown egg-laying hens in early phase of production. Poult. Sci.  88: 608– 614. Google Scholar CrossRef Search ADS PubMed  SAS Institute. 2004. SAS/STAT User's Guide . Version 9.1. SAS Inst. Inc., Cary, NC. Schiffman H. R. 1968. Texture preference in the domestic chick. J. Comp. Physiol. Psychol.  66: 540– 541. Google Scholar CrossRef Search ADS PubMed  Svihus B. 2011. The gizzard: Function, influence of diet structure and effects on nutrient availability. World's Poult. Sci. J.  67: 207– 223. Google Scholar CrossRef Search ADS   Traineau M., Bouvarel I., Mulsant C., Roffidal L., Launay C., Lescoat P.. 2015. Modulation of energy and protein supplies in sequential feeding in laying hens. Animal . 9: 49– 57. Google Scholar CrossRef Search ADS PubMed  Xu Y., Stark C. R., Ferket P. R., Williams C. M., Brake J.. 2015. Effects of feed form and dietary coarse ground corn on broiler live performance, body weight uniformity, relative gizzard weight, excreta nitrogen, and particle size preference behaviors. Poult. Sci.  94: 1549– 1556. Google Scholar CrossRef Search ADS PubMed  © 2018 Poultry Science Association Inc.

Journal

Poultry ScienceOxford University Press

Published: Apr 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