Influence of feed form and conditioning time on pellet quality, performance and ileal nutrient digestibility in broilers

Influence of feed form and conditioning time on pellet quality, performance and ileal nutrient... Abstract An experiment was conducted to investigate the effects of the feed form and conditioning time of pelleted diets on pellet quality, broiler performance and nutrient digestibility during the starter phase. A total of 480 male Cobb broilers were distributed according to a completely randomized experimental design into six treatments with eight replicates each. Treatments consisted of a mash diet and five crumbled diets submitted to different conditioning times (zero, 60, 80, 100, or 120 seconds). The broilers fed pelleted diets submitted to steam conditioning presented higher feed intake and BW gain (P ≤ 0.05), higher coefficient of ileal apparent digestibility (CIAD) of DM and CP, as well as higher ileal digestible energy (IDE) (P ≤ 0.05) than those fed the mash diet. However, treatments did not influence FCR or starch digestibility (P > 0.05). Feed intake increased linearly (P ≤ 0.05) with conditioning time while a quadratic response (P ≤ 0.05) was noted for IDE. Conditioning time did not affect the amount of intact pellets or protein solubility (P > 0.05), but increased pellet durability index (P ≤ 0.01), pellet hardness (P ≤ 0.05), and water activity (P ≤ 0.05). It was concluded that feed physical form and conditioning time influence the performance and nutrient digestibility in starter broilers. and that increasing conditioning times promote better pellet quality. DESCRIPTION OF PROBLEM Pelleting is widely applied in the poultry industry. Pelleted diets can promote higher feed intake than mash diets because they allow easier feed apprehension by the birds [1], better digestibility of the different dietary fractions [2], and increase the availability of energy for production, as less energy is spent for feed intake [3], ultimately improving broiler performance. However, this can only be achieved if the pellets produced maintain their integrity until they are consumed by the birds. According to Reimer [4], the physical quality of pelleted feeds is influenced by several factors, particularly by feed formulation (40%), particle size (20%), conditioning (20%), general specifications of the pellet-mill die (15%), as well as by pellet cooling and drying (5%). Steam conditioning of the mash before pelleting also plays an important role in dietary nutrient utilization. For instance, conditioning temperature, moisture, pressure, and time can cause the breakdown of amylose and amylopectin chains, favoring the action of the enzyme amylase, thereby increasing carbohydrate digestibility [5–7]. Those conditioning factors can also change the tertiary structure of proteins, increasing their digestibility [8–10]. On the other hand, some findings suggest that pellet feeding may cause poor digestibility under some conditions [11]. Moreover, increasing conditioning times improve pellet physical quality [12–14]. However, the effect of steam-conditioning time of pelleted diets on the live performance and nutrient digestibility in broilers has not been well studied yet. The objective of the present study was to evaluate the effects of two feed forms (mash or pelleted/crumbled) and steam-conditioning time of pelleted-crumbled diets (zero, 60, 80, 100, or 120 s) on pellet quality and on broiler live performance and dietary nutrient digestibility during the starter phase. MATERIALS AND METHODS Diet Composition and Feed Manufacturing Six diets were evaluated: a mash diet, a pelleted-crumbled diet not submitted to steam-conditioning (time zero), and four pelleted-crumbled diets submitted to four different conditioning times (60, 80, 100, and 120 s). A basal diet based on corn and soybean meal was formulated to supply the nutritional requirements of Cobb 500 broilers during the starter phase (1–21 days), according to the recommendations of the genetic company manual [15]. The ingredients and calculated nutritional composition of the basal diet are presented in Table 1. The mash diet was conditioned in a conditioner [16] with a capacity of 40 metric tons/h. The following conditioning parameters were applied: maximum steam injection at 1.3 kgf, 2.7% water addition, and 83°C constant temperature. The nonconditioned pelleted diet bypassed the conditioner, and presented a temperature of 58.7 °C at the exit of the pelleting die. The different retention times in the conditioner were obtained by using frequency inverters. Table 1. Composition and calculated analysis (%) of the diets. Ingredients  Composition  Corn  59.36  Hi-pro soybean meal  30.49  Gluten 60%  3.99  Dicalcium phosphate  1.64  Soybean oil  1.53  Limestone  1.01  Salt (NaCl)  0.49  Trace mineral and vitamin premix1  0.41  L-lysine  0.40  Mycotoxin adsorbent2  0.20  DL-methionine  0.12  Choline chloride  0.11  Betaine  0.11  Anti-salmonella product3  0.10  Calculated analysis  Values  Metabolizable energy (kcal/kg)  3050  Crude protein  22.0  Ether extract  3.60  Crude fiber  2.40  Ashes  4.50  Calcium  0.81  Available phosphorus  0.54  Sodium  0.22  Chlorine  0.36  Digestible lysine  1.30  Digestible methionine  0.60  Methionine + cysteine  0.97  Digestible threonine  0.79  Digestible tryptophan  0.20  Ingredients  Composition  Corn  59.36  Hi-pro soybean meal  30.49  Gluten 60%  3.99  Dicalcium phosphate  1.64  Soybean oil  1.53  Limestone  1.01  Salt (NaCl)  0.49  Trace mineral and vitamin premix1  0.41  L-lysine  0.40  Mycotoxin adsorbent2  0.20  DL-methionine  0.12  Choline chloride  0.11  Betaine  0.11  Anti-salmonella product3  0.10  Calculated analysis  Values  Metabolizable energy (kcal/kg)  3050  Crude protein  22.0  Ether extract  3.60  Crude fiber  2.40  Ashes  4.50  Calcium  0.81  Available phosphorus  0.54  Sodium  0.22  Chlorine  0.36  Digestible lysine  1.30  Digestible methionine  0.60  Methionine + cysteine  0.97  Digestible threonine  0.79  Digestible tryptophan  0.20  1Supplied per kilogram of diet: biotin, 0.2 mg; cyanocobalamin, 45 mg; cholecalciferol, 3.0 IU; folic acid, 1.6 mg; menadione 4.0 mg; nicotinic acid, 40 mg; pantothenic acid, 16 mg; pyridoxine, 3.2 mg; riboflavin, 6.4 mg; thiamin, 2.1 IU; trans-retinol, 9.6 IU; DL-tocopheryl acetate 48 IU; copper, 12 mg; iron, 48 mg; iodine, 0.8 mg; manganese, 72 g; selenium, 0.3 g; zinc, 72 mg; coccidiostat, 100 mg. 2Calibrin®—Elanco. 3Salmex®—Btech. View Large Diets were pelleted in a pellet mill [17], with a capacity of 30 metric tons/h, ring-shaped die with 4.0-mm diameter holes, and speed of 8.2 m/s. After pelleting, feeds were dried and cooled to an average temperature of 37 °C, and then crumbled in a roller mill with 2.0 mm of roll space. The mash diet presented 850 μm geometric mean diameter (GMD), and pelleted diets, 2135 μm GMD. At the end of the diet manufacturing process, samples of each experimental diet were collected and submitted to physical and chemical analyses. Birds and Housing Experimental procedures were conducted in accordance with the guidelines of the Committee of Ethics on Animal Use of the Federal University of Parana (UFPR), as approved in protocol n. 034/2012. In total, 480 one-d-old male Cobb 500 broilers were obtained from a commercial hatchery. Chicks were transported to the metabolism room of the department of Animal Science, UFPR, Curitiba, Paraná, Brazil, and individually weighed at arrival. Birds were housed in 48 metabolic cages measuring 0.90 m2 each (10 birds per cage), equipped with trough feeders and drinkers, and electric brooders. Water and feed were supplied ad libitum during the entire experimental period of 25 days. During the first 14 d, birds were maintained under constant incandescent light (24 h) and after this period approximately 12 h of light per day were used. Environmental temperature was maintained at 32°C on day 1 and then gradually reduced to approximately 22°C on day 25. Physical and Chemical Parameters In order to determine the amount of intact pellets, eight 500 g samples of each pelleted feed were passed through a 3.0-mm sieve, the feed remaining on top of the sieve was weighed, and its weight calculated as a percentage of the initial weight. Similarly, eight 500 g samples, with no fines, of each treatment were submitted to tumbling time of ten minutes, and a rotating speed of 50 revolutions per minute (RPM) to determine the pellet durability index (PDI). Pellet hardness was determined in a pellet-hardness tester [18] with individual pellets (eight per treatment) and expressed in kgf. The feeds and the ileal contents obtained after bird euthanasia, as described below, were ground to 1-mm particle size and analyzed for DM content by burning in a muffle at 105°C for 12 hours; for CP content (method 954.01); for acid insoluble ash (AIA) content (method 942.05), according to the AOAC [19]. Total starch content was analyzed using the method 996.11* of the AOAC adapted by Walter et al. [20]. Gross energy (GE) content was determined in a bomb calorimeter [21]. Diets were also analyzed for protein solubility in potassium hydroxide (KOH) according to Parsons et al. [22] and starch gelatinization degree according to method 27 of Compêndio Brasileiro de Nutrição Animal [23] as described in Table 2. Dietary water activity (Wa) was determined in water activity meter [24]. Table 2. Starch gelatinization degree of the experimental diets. Diet  Moisture (%)  Starch gelatinization degree (%)  Mash  13.36  30.10  P (0)  12.47  34.17  P (60)  12.59  32.47  P (80)  11.98  31.27  P (100)  12.61  33.75  P (120)  12.56  33.54  Diet  Moisture (%)  Starch gelatinization degree (%)  Mash  13.36  30.10  P (0)  12.47  34.17  P (60)  12.59  32.47  P (80)  11.98  31.27  P (100)  12.61  33.75  P (120)  12.56  33.54  View Large Performance Parameters Birds were weekly weighed per replicate to determine average weight gain (WG). Feed offer and residues per replicate were weekly weighed to determine average feed intake (FI). The FCR was calculated as the ratio between FI and WG (g/g). Birds were daily inspected for mortality, and the dead birds were removed and weighed for subsequent correction of WG for mortality. Digestibility Determination On day 25 of the experimental period, five birds per replicate were euthanized by cervical dislocation for the collection of ileal content. Ileal content samples were pooled per experimental unit, and each pool was individually homogenized, lyophilized, and ground for subsequent analyses. The content of AIA in the diets and in the ileal contents was used as internal indigestible marker for digestibility calculations, and determined according to the methodology described by Scott and Boldaji [25]. The coefficients of ileal apparent digestibility (CIAD) of the nutrients were estimated according to the equations below:   \begin{eqnarray*} \text{CIAD of diet nutrient} = \frac{\text{(nutrient in the diet)} - (\text{nutrient in the ileal digesta} \times \text{IF})}{\text{nutrient in the diet}} \end{eqnarray*} where (IF) is the ratio of dietary AIA content to the ileal digesta AIA content. Ileal digestible energy (IDE) values were calculated according to the equation:   \begin{eqnarray*} \text{IDE (Kcal/kg DM) = dietary GE level - (ileal digesta GE level } \times \text{ IF content in the ileal digesta)} \end{eqnarray*} Statistical Analysis A completely randomized experimental design, involving six treatments with eight replicates of 10 birds each, was applied. The obtained data were firstly tested for normality (Shapiro-Wilk's test) and homoscedasticity (Bartlett's test). Data complied with those assumptions, and were then submitted to analysis of variance using the GLM procedure of SAS statistical software [26]. Means were compared by the Dunnett's test at 5% probability level, using the mash diet as control treatment. Dependent treatments (pelleted diets conditioned for zero, 60, 80, 100, and 120 s) were submitted to analysis of regression. RESULTS Physical and Chemical Parameters There was a quadratic effect of conditioning time on PDI and pellet hardness (P ≤ 0.05), as shown in Table 3, with optimal values obtained at 89 and 51 s, respectively. Water activity linearly increased with conditioning time (P ≤ 0.05), whereas the amount of intact pellets was not affected (P > 0.05). Table 3. Percentage of intact pellets (IP), pellet durability index (PDI), pellet hardness, water activity (Wa), and KOH-soluble protein (PS) of pelleted diets submitted to different conditioning times.   Treatments1    P-value    P (0)  P (60)  P (80)  P (100)  P (120)  SEM  L  Q  IP (%)  95.07  95.67  96.37  95.47  96.45  0.298  0.20  0.90  PDI (%)  90.41  95.78  95.43  95.16  95.07  0.438  <0.001  <0.01  Hardness (kgf)  4.23  5.11  5.24  3.98  4.85  0.133  0.39  0.04  Wa  0.63  0.64  0.66  0.65  0.65  0.004  0.04  0.58  PS (%)  14.21  13.91  13.97  14.05  13.86  0.089  0.32  0.73    Treatments1    P-value    P (0)  P (60)  P (80)  P (100)  P (120)  SEM  L  Q  IP (%)  95.07  95.67  96.37  95.47  96.45  0.298  0.20  0.90  PDI (%)  90.41  95.78  95.43  95.16  95.07  0.438  <0.001  <0.01  Hardness (kgf)  4.23  5.11  5.24  3.98  4.85  0.133  0.39  0.04  Wa  0.63  0.64  0.66  0.65  0.65  0.004  0.04  0.58  PS (%)  14.21  13.91  13.97  14.05  13.86  0.089  0.32  0.73  1Conditioning times of the pelleted diets (0, 60, 80, 100, and 120 s) L = linear; Q = quadratic. View Large The content of KOH-soluble protein was not influenced by steam-conditioning times (Table 3). Bird Performance The pelleted diets promoted higher FI (P ≤ 0.05), except for the nonconditioned pelleted feed, and higher WG (P ≤ 0.05) compared with the control mash diet; however, FCR was not influenced (P > 0.05) by the treatments (Table 4). The diets submitted to increasing conditioning times linearly increased FI (P ≤ 0.05), but did not affect WG or FCR (P > 0.05), as shown in Table 4. Table 4. Performance of 1- to 25-d-old broilers fed mash or pelleted-crumbled diets submitted to different conditioning times.   Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  Feed intake (g)2  1269  1312  1351*  1339*  1360*  1362*  0.008  0.0027  Weight gain (g)  962  1027*  1049*  1030*  1071*  1046*  0.008  0.0014  FCR (g/g)  1.320  1.278  1.289  1.302  1.270  1.302  0.005  0.1206    Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  Feed intake (g)2  1269  1312  1351*  1339*  1360*  1362*  0.008  0.0027  Weight gain (g)  962  1027*  1049*  1030*  1071*  1046*  0.008  0.0014  FCR (g/g)  1.320  1.278  1.289  1.302  1.270  1.302  0.005  0.1206  1Mash diet (control) and pelleted diets submitted to different conditioning times (0, 60, 80, 100, and 120 s). 2Linear effect of conditioning times (P = 0.04). Y = 0.4118x + 1315.2; R² = 0.859. *Indicates difference from the control (P ≤ 0.05) by Dunnett's test. View Large Digestibility Higher CIAD of DM and CP (pelleted diets conditioned for 80 and 120 s), as well as higher IDE content, were obtained in the pelleted diets compared with the mash diet (P ≤ 0.01). However, the treatments did not affect (P > 0.05) the CIAD of starch (Table 5). Table 5. Coefficients of ileal apparent digestibility (CIAD) of dry matter (DM), starch, and crude protein (CP), and ileal digestible energy content (IDE) determined in 25-d-old broilers fed starter mash (control) or pelleted-crumbled diets submitted to different conditioning times (0, 60, 80, 100, and 120 s).   Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  CIAD of DM (%)  57.14  62.90*  65.80*  64.85*  65.59*  66.30*  0.729  <0.0001  CIAD of starch (%)  84.21  84.79  86.32  87.19  85.00  85.65  0.389  0.258  CIAD of CP (%)  71.77  71.53  74.09  74.22*  74.19  76.08*  0.549  0.011  IDE (kcal/kg DM) 2  2731  2966*  3113*  3094*  3160*  3187*  32.734  <0.0001    Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  CIAD of DM (%)  57.14  62.90*  65.80*  64.85*  65.59*  66.30*  0.729  <0.0001  CIAD of starch (%)  84.21  84.79  86.32  87.19  85.00  85.65  0.389  0.258  CIAD of CP (%)  71.77  71.53  74.09  74.22*  74.19  76.08*  0.549  0.011  IDE (kcal/kg DM) 2  2731  2966*  3113*  3094*  3160*  3187*  32.734  <0.0001  1Mash diet (control) and pelleted diets submitted to different conditioning times (0, 60, 80, 100, and 120 s). 2Quadratic effect of conditioning times (P = 0.04). Y = −0.0036x2 + 2.2155x + 2969.3 R² = 0.952. *Indicates difference from the control (P ≤ 0.05) by Dunnett's test. View Large No differences in the CIAD of DM, CP or starch were detected (P > 0.05) among pelleted diets submitted to the different conditioning times, but IDE content presented a quadratic response (P ≤ 0.05), as shown in Table 5. DISCUSSION All pelleted diets presented more than 95% intact pellets (Table 3), indicating good physical quality. Different results were obtained by Skoch et al. [5], who found higher percentage of fines in pelleted diets not submitted to conditioning (9.1%) compared with those conditioned at 65°C (3.8%) and at 80°C (3.2%); however, the percentage of fines was not affected by steam addition. Abdollahi et al. [27] reported that nonconditioned pelleted diets presented 10% less intact pellets than those submitted to heat, but not to steam-conditioning. In the present study, no pellet integrity differences were observed among pelleted diets, even at the longest conditioning time (120 s). Briggs et al. [12] found a negative correlation between the level of fines and PDI, which was not observed in the present study. Pellet durability index (PDI) presented a quadratic response to increasing conditioning time, which were more evident in the diets submitted to conditioning. The PDI of pelleted diet conditioned for 60 s was 5.9% higher compared with the nonconditioned diet. These results are in agreement with the findings of Abdollahi et al. [27], who found higher pellet durability in steam-conditioned pelleted diets than in dry-conditioned pelleted feeds. The poorer physical quality of the nonconditioned pelleted diet compared with the other pelleted diets may be explained by its low moisture, as that feed bypassed the steam conditioner. Fahrenholz [14], evaluating the influence of different conditioning times (30 and 60 s), observed that increasing mash retention time in the conditioner improved pellet durability; however, this effect was more significant when associated to other factors, such as conditioning temperature. Among the variables studied by Fahrenholz [14], conditioning time had the least influence on pellet quality. Likewise, Briggs et al. [12] observed that increasing the retention time from 5 to 15 s increased pellet durability in 4.5%. Pellet hardness responded quadratically to conditioning time up to 120 seconds. However, Fahrenholz [14] states that the PDI is a better expression of pellet physical quality than hardness, because it uses for its determination a large sample, and therefore, better represents the actual handling procedures than those used for determining pellet hardness. Thomas and Van der Poel [28] evaluated the hardness and durability of pelleted diets and found that durability results were more consistent to express pellet physical quality than hardness because they presented lower CV. There was a linear effect of conditioning time on Wa, as increasing steam exposure time during conditioning resulted in greater moisture incorporation to the feed. As all the diets were submitted to the same drying time, moisture content was similarly removed. Therefore, pelleted diets submitted to longer conditioning times presented higher Wa. However, the obtained values are close to the recommendations (nearby 0.6), and did not compromise the quality of the finished product. Protein solubility in KOH is applied especially for assessing soybean meal quality and nutrient availability, and it may be affected by inadequate heat processing of soybeans, reducing its nutritional value. The results of the present study show that even long conditioning times at 83°C did not affect protein solubility. In contrast, Muramatsu et al. [29] found that most intensive processing methods, such as expansion (110°C), reduced protein solubility in KOH from 68.6% to 64.3% during pelleting (80–82°C). The benefits of pelleting on animal performance are widely reported in the literature [3, 7, 30, 31]. These benefits were confirmed in the present study, as shown by the higher WG obtained with the pelleted diets compared with the mash diet. However, this better performance can only be achieved if the pellets produced maintain their integrity until they are consumed by the birds. Although the birds fed the steam-conditioned pelleted diets presented higher FI than those fed the mash diet, the FI values obtained with the nonconditioned pelleted diet and the mash diet were not statistically different. This probably occurred because the quality of this pelleted diet was lower (i.e., its PDI was 5% lower, on average) compared with those submitted to steam conditioning (Table 3). However, FI increased with conditioning time. Fahrenholz [14], evaluating the influence of different conditioning times (30 and 60 s), observed that longer retention times in the conditioner resulted in improved pellet durability. According to Skoch et al. [5], the addition of moisture using steam improves pellet quality by reducing the proportion of fines and increasing pellet durability. Based on these results, it is suggested that long retention times allow moisture to penetrate more efficiently into the feed particles, allowing greater adhesion among pellet components, and thereby, increasing feed intake. The pelleted diets presented better CIAD of DM, which is consistent with the findings of Zatari and Sell [32], who observed a significant increase in DM digestibility in pelleted diets compared with mash diets. Pelleted diets conditioned for 80 and 120 s presented higher protein digestibility rates than the other evaluated diets. The increase in protein digestibility may be explained by the breakdown of disulfide bridges of the protein molecule, causing its denaturation, and thereby, its easier access of proteases [9, 10]. In the present study, the steam-conditioning temperature (83°C), associated with exposure time, may have promoted these changes in the pelleted diets. The higher protein digestibility determined in those diets may also explain the higher WG obtained. Pelleting did not improve starch digestibility, as previously observed by Abdollahi et al. [31], working with corn-based diets. According to Svihus et al. [33], pelleting has marginal effects on starch availability, whereas more intensive processes such as extrusion, which includes water addition and applies higher temperatures than pelleting, result in greater starch gelatinization. Several studies have shown that only a small amount of starch is gelatinized during pelleting [5, 7, 34, 35] and that its effect on starch digestibility seems to be negligible [36]. Pelleted diets contained higher ileal digestible energy levels (IDE) compared with the mash diet. Jimenez-Moreno et al. [37] reported higher AMEn levels in broilers fed steam-cooked corn relative to raw corn. In the present study, the IDE level of the nonconditioned pelleted diet was 235 kcal/kg of DM higher compared with the mash diet. This may be attributed to the mechanical action of the feed inside the pellet mill, because the temperature measured at the exit of the due was 58.7°C. According to Abdollahi et al. [38], part of the starch gelatinization occurs after conditioning at pelleting press due to an increase in temperature and friction. This mechanical action may also be responsible for the greater availability of the other dietary fractions. Moreover, pelleted diets submitted to 60 s of steam-conditioning contained more 146 kcal/kg DM of IDE relative to the nonconditioned pelleted diet. The combination of moisture, temperature and time during conditioning may have improved the digestibility of the different dietary fractions, resulting in an increase in IDE value. The ileal digestibility of DM, CP, or starch of the pelleted diets was not influenced by conditioning times. Kokić et al. [39], evaluating different types of corn processing, determined lower degrees of starch gelatinization for flocculation (21.33%) and pelleting (25.47%), while more intensive processes, such as micronization and extrusion, yielded higher degrees of gelatinization, of 63.58 and 100%, respectively. The results obtained in the present study suggest that the steam-conditioning times employed before pelleting may not have been sufficiently to change the structures of the feedstuffs, leading to an increase in the digestibility of the diet fractions. Ileal digestible energy level presented a quadratic response to conditioning time. The behavior of IDE was similar to that of the PDI, suggesting a possible association between pellet durability and digestible energy values. McKinney and Teeter [3], feeding broilers with diets with different proportions of intact and fine pellets (with 100%, 80%, 60%, 40%, and 20% pellets, and mash), found an increase in the effective caloric value and in the resting frequency of broilers, because the birds spent less energy and time to consume pelleted feeds. Energy digestibility is influenced by many processing factors, such as temperature, time, pressure, and moisture and their interaction. In addition, it is affected by the feedstuffs included in diet and their energy contents, making it difficult to evaluate the effects of individual factors. For instance, according to Skoch et al. [5] and Voragen et al. [6], the heat treatment of starch causes granules to “swell”, and after continued heating, they disintegrate, solubilizing the individual starch molecules. Zelenka [2] mentions that one of the benefits of feeding pelleted feeds to broilers is the increase in dietary metabolizable energy value due to higher digestibility of dietary fractions. Furthermore, in the present study, FI increased as steam-conditioning time increased, which may have affected the obtained IDE values. CONCLUSIONS AND APPLICATIONS Feeding pelleted diets resulted in broilers with superior feed intake and weight gain, as well as greater ileal digestibility of dry matter, crude protein and energy compared with those fed the mash diet. Increasing conditioning time of pelleted diets improved feed intake, but weight gain and feed conversion ratio were not affected. Dry matter, starch, and crude protein ileal digestibility were not influenced by conditioning times, but the ileal digestible energy quadratically increased. It may be possible to improve pellet quality increasing steam-conditioning times. The combined effects of time, temperature, and moisture during conditioning should be further evaluated. Footnotes Primary Audience: Feed Mill Managers, Nutritionists, Broiler Producers, Researchers REFERENCES AND NOTES 1. Meinerz C., Ribeiro A. M. L., Penz A. M. Jr, Kessler A. M.. 2001. Níveis de energia e peletização no desempenho e rendimento de carcaça de frangos de corte com oferta alimentar equalizada. Rev. Bras. de Zootec.  30: 2026– 2032. Google Scholar CrossRef Search ADS   2. Zelenka J. 2003. Effect of pelleting on digestibility and metabolizable energy values of poultry diets. Czech J. Anim. Sci.  48: 239– 242. 3. Mckinney L. J., Teeter R. G.. 2004. Predicting effective caloric value of nonnutritive factors: I. Pellet quality and II. Prediction of consequential formulation dead zones. Poult. Sci.  83: 1165– 1174. Google Scholar CrossRef Search ADS PubMed  4. Reimer L.. 1992. Conditioning. Proc. Northern Crops Institute Feed Mill Management and Feed Manufacturing Technol. Short Course . p. 7. California Pellet Mill Co. Crawfordsville. 5. Skoch E. R., Behnke K. C., Deyoe C. W., Binder S. F.. 1981. The effect of steam-conditioning rate on the pelleting process. Anim. Feed Sci. Technol.  6: 83– 90. Google Scholar CrossRef Search ADS   6. Voragen A. G. J., Gruppen H., Marsmanl G. J. P., Mul A. J.. 1995. Effect of some manufacturing technologies on chemical, physical and nutritional properties of feed. Pages 93– 126 in Recent Advances in Animal Nutrition . Garnsworthy P. C., Cole D. J. A., eds. Nottingham University Press, Nottingham, UK. 7. Svihus B., Kløvstad K. H., Perez V., Zimonja O., Sahlström S., Schüller R. B., Jeksrud W. K., Prestløkken E.. 2004. Nutritional effects of pelleting of broiler chicken diets made from wheat ground to different coarsenesses by the use of roller mill and hammer mill. Anim. Feed Sci. Technol.  117: 281– 293. Google Scholar CrossRef Search ADS   8. Moran E. T. Jr. 1987. Pelleting: affects feed and its consumption. Poult. Sci.  5: 30– 31. 9. Scott T. A., Swift M. L., Bedford M. R.. 1997. The influence of feed milling, enzyme supplementation, and nutrient regimen on broiler chick performance. J. Appl. Poult. Res.  6: 391– 398. Google Scholar CrossRef Search ADS   10. Dozier W. A. 2001. Pelet de calidad para obtener carne de ave más economica. Alim. Balanc. Anim.  8: 16– 19. 11. Svihus B., Hetland H.. 2001. Ileal starch digestibility in growing broiler chickens fed on a wheat-based diet is improved by mash feeding, dilution with cellulose or whole wheat inclusion. Br. Poult. Sci.  42: 633– 637. Google Scholar CrossRef Search ADS PubMed  12. Briggs J. L., Maier D. E., Watkins B. A., Behnke K. C.. 1999. Effect of ingredients and processing parameters on pellet quality. Poult. Sci.  78: 1464– 1471. Google Scholar CrossRef Search ADS PubMed  13. Gilpin A. S., Herrman T. J., Behnke K. C., Fairchild F. J.. 2002. Feed moisture, retention time, and steam as quality and energy utilization determinants in the pelleting process. App. Eng. in Ag.  18: 331– 338. 14. Fahrenholz A. C. 2012. Evaluating factors affecting pellet durability and energy consumption in a pilot feed mill and comparing methods for evaluating pellet durability . PhD Diss. Kansas State University, Kansas. 15. Cobb. 2013. Cobb 500 Broiler: Broiler performance and nutrition supplement , Cobb-Vantress Inc., Siloam Springs, AR. 16. Van Aarsen LTV1200 Conditioner, Van Aarsen International B.V, Panheel, the Netherlands. 17. Van Aarsen C900 Standard Pellet Mill, Van Aarsen International B.V, Panheel, the Netherlands. 18. Nova Ética 298DGP Hardness Tester, Ethiktechnology, São Paulo, Brazil. 19. AOAC International. 1995. Official and tentative methods of analysis . 16th ed. Arlington, Virginia. 20. Walter M., Silva L. P., Perdomo D. M. X.. 2005. Amido disponível e resistente em alimentos: adaptação do método da AOAC 996.11*. Alimentos e Nutrição. 16: 39– 43. 21. Ika Werke C 2000. Control Oxygen Bomb Calorimeter , Ika-Werke GmbH&Co, Staufen, Germany. 22. Parsons C. M., Hashimoto K., Wedekind K. J., Baker D. H.. 1991. Soybean protein solubility in potassium hydroxide: an in vitro test of in vivo protein quality. J. Anim. Sci.  69: 2918– 2924. Google Scholar CrossRef Search ADS PubMed  23. Sindirações. 2009. Brazilian Compendium in Animal Nutrition. 24. Aqualab S3TE Water Activity Meter, Decagon Devices Inc., Washington, USA. 25. Scott T. A., Boldaji F.. 1997. Comparison of inert markers [chromic oxide or insoluble ash (CeliteTM)] for determining apparent metabolizable energy of wheat- or barley- based broiler diets with or without enzymes. Poult. Sci.  76: 594– 598. Google Scholar CrossRef Search ADS PubMed  26. SAS User's Guide. 2004. Version 9.0. ed  SAS Inst. Inc., Cary, NC. 27. Abdollahi M. R., Ravindran V., Wester T. J., Ravindran G., Thomas D. V.. 2011. Influence of feed form and conditioning temperature on performance, apparent metabolisable energy and ileal digestibility of starch and nitrogen in broiler starters fed wheat-based diet. Anim. Feed Sci. Technol.  168: 88– 99. Google Scholar CrossRef Search ADS   28. Thomas M., Van der Poel A. F. B.. 1996. Physical quality of pelleted animal feed. Anim. Feed Sci. Technol.  61: 89– 112. Google Scholar CrossRef Search ADS   29. Muramatsu K., Maiorka A., Vaccari I. C. M., Reis R. N., Dahlke F., Pinto A. A., Orlando U. A. D., Bueno M., Imagawa M.. 2013. Impact of particle size, thermal processing, fat inclusion and moisture addition on pellet quality and protein solubility of broiler feeds. J. Agric. Sci. Technol. A.  3: 1017– 1028. 30. Oliveira A. A., Gomes A. V. C., Oliveira G. R., Lima M. F., Dias G. E. A., Agostinho T. S. P., Sousa F. D. R., Lima C. A. R.. 2011. Desempenho e características da carcaça de frangos de corte alimentados com rações de diferentes formas físicas. Rev. Bras. de Zootec. 40: 2450– 2455. 31. Abdollahi M. R., Ravindran V., Svihus B.. 2013. Influence of grain type and feed form on performance, apparent metabolisable energy and ileal digestibility of nitrogen, starch, fat, calcium and phosphorus in broiler starters. Anim. Feed Sci. Technol.  186: 193– 203. Google Scholar CrossRef Search ADS   32. Zatari I. M., Sell J. L.. 1990. Effects of pelleting diets containing sunflower meal on performance of broiler chickens. Anim. Feed Sci. Technol.  30: 121– 129. Google Scholar CrossRef Search ADS   33. Svihus B., Uhlen A. K., Harstad O. M.. 2005. Effect of starch granule structure, associated components and processing on nutritive value of cereal starch: A review. Animal Feed Science and Technology . 122: 303– 320. Google Scholar CrossRef Search ADS   34. Moritz J. S., Wilson K. J., Cramer K. R., Beyer R. S., Mckinney L. J., Cavalcanti B., Mo X.. 2002. Effect of formulation density, moisture, and surfactant on feed manufacturing, pellet quality and broiler performance. J. Appl. Poult. Res.  11: 155– 163. Google Scholar CrossRef Search ADS   35. Moritz J. S., Cramer K. R., Wilson K. J., Beyer R. S.. 2003. Feed manufacture and feeding of rations with graded levels of added moisture formulated to different energy densities. J. Appl. Poult. Res.  12: 371– 381. Google Scholar CrossRef Search ADS   36. Zimonja O., Hetland H., Lazarevic N., Edvardsen D. H., Svihus B.. 2008. Effects of fiber content in pelleted wheat and oat diets on technical pellet quality and nutritional value for broiler chickens. Can. J. Anim. Sci.  88: 613– 622. Google Scholar CrossRef Search ADS   37. Jimenez-Moreno E., Gonzalez-Alvarado J. M., Lazaro R., Mateos G. G.. 2009. Effects of type of cereal, heat processing of the cereal, and fibre inclusion in the diet on gizzard pH and nutrient utilisation in broilers at different ages. Poult. Sci.  88: 1925– 1933. Google Scholar CrossRef Search ADS PubMed  38. Abdollahi M. R., Ravindran V., Wester T. J., Ravindran G., Thomas D. V.. 2010. Influence of conditioning temperature on performance, apparent metabolisable energy, ileal digestibility of starch and nitrogen and the quality of pellets, in broiler starters fed maize and sorghum-based diets. Anim. Feed Sci. Technol.  162: 106– 115. Google Scholar CrossRef Search ADS   39. Kokić B. M., Lević J. D., Chrenková M., Formelová Z., Poláĉiková M., Rajský M., Jovanović R. D.. 2013. Influence of thermal treatments on starch gelatinization and in vitro organic matter digestibility of corn. Food and Feed Research . 40: 93– 99. © 2017 Poultry Science Association Inc. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Poultry Research Oxford University Press

Influence of feed form and conditioning time on pellet quality, performance and ileal nutrient digestibility in broilers

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Applied Poultry Science, Inc.
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© 2017 Poultry Science Association Inc.
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1056-6171
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1537-0437
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10.3382/japr/pfx039
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Abstract

Abstract An experiment was conducted to investigate the effects of the feed form and conditioning time of pelleted diets on pellet quality, broiler performance and nutrient digestibility during the starter phase. A total of 480 male Cobb broilers were distributed according to a completely randomized experimental design into six treatments with eight replicates each. Treatments consisted of a mash diet and five crumbled diets submitted to different conditioning times (zero, 60, 80, 100, or 120 seconds). The broilers fed pelleted diets submitted to steam conditioning presented higher feed intake and BW gain (P ≤ 0.05), higher coefficient of ileal apparent digestibility (CIAD) of DM and CP, as well as higher ileal digestible energy (IDE) (P ≤ 0.05) than those fed the mash diet. However, treatments did not influence FCR or starch digestibility (P > 0.05). Feed intake increased linearly (P ≤ 0.05) with conditioning time while a quadratic response (P ≤ 0.05) was noted for IDE. Conditioning time did not affect the amount of intact pellets or protein solubility (P > 0.05), but increased pellet durability index (P ≤ 0.01), pellet hardness (P ≤ 0.05), and water activity (P ≤ 0.05). It was concluded that feed physical form and conditioning time influence the performance and nutrient digestibility in starter broilers. and that increasing conditioning times promote better pellet quality. DESCRIPTION OF PROBLEM Pelleting is widely applied in the poultry industry. Pelleted diets can promote higher feed intake than mash diets because they allow easier feed apprehension by the birds [1], better digestibility of the different dietary fractions [2], and increase the availability of energy for production, as less energy is spent for feed intake [3], ultimately improving broiler performance. However, this can only be achieved if the pellets produced maintain their integrity until they are consumed by the birds. According to Reimer [4], the physical quality of pelleted feeds is influenced by several factors, particularly by feed formulation (40%), particle size (20%), conditioning (20%), general specifications of the pellet-mill die (15%), as well as by pellet cooling and drying (5%). Steam conditioning of the mash before pelleting also plays an important role in dietary nutrient utilization. For instance, conditioning temperature, moisture, pressure, and time can cause the breakdown of amylose and amylopectin chains, favoring the action of the enzyme amylase, thereby increasing carbohydrate digestibility [5–7]. Those conditioning factors can also change the tertiary structure of proteins, increasing their digestibility [8–10]. On the other hand, some findings suggest that pellet feeding may cause poor digestibility under some conditions [11]. Moreover, increasing conditioning times improve pellet physical quality [12–14]. However, the effect of steam-conditioning time of pelleted diets on the live performance and nutrient digestibility in broilers has not been well studied yet. The objective of the present study was to evaluate the effects of two feed forms (mash or pelleted/crumbled) and steam-conditioning time of pelleted-crumbled diets (zero, 60, 80, 100, or 120 s) on pellet quality and on broiler live performance and dietary nutrient digestibility during the starter phase. MATERIALS AND METHODS Diet Composition and Feed Manufacturing Six diets were evaluated: a mash diet, a pelleted-crumbled diet not submitted to steam-conditioning (time zero), and four pelleted-crumbled diets submitted to four different conditioning times (60, 80, 100, and 120 s). A basal diet based on corn and soybean meal was formulated to supply the nutritional requirements of Cobb 500 broilers during the starter phase (1–21 days), according to the recommendations of the genetic company manual [15]. The ingredients and calculated nutritional composition of the basal diet are presented in Table 1. The mash diet was conditioned in a conditioner [16] with a capacity of 40 metric tons/h. The following conditioning parameters were applied: maximum steam injection at 1.3 kgf, 2.7% water addition, and 83°C constant temperature. The nonconditioned pelleted diet bypassed the conditioner, and presented a temperature of 58.7 °C at the exit of the pelleting die. The different retention times in the conditioner were obtained by using frequency inverters. Table 1. Composition and calculated analysis (%) of the diets. Ingredients  Composition  Corn  59.36  Hi-pro soybean meal  30.49  Gluten 60%  3.99  Dicalcium phosphate  1.64  Soybean oil  1.53  Limestone  1.01  Salt (NaCl)  0.49  Trace mineral and vitamin premix1  0.41  L-lysine  0.40  Mycotoxin adsorbent2  0.20  DL-methionine  0.12  Choline chloride  0.11  Betaine  0.11  Anti-salmonella product3  0.10  Calculated analysis  Values  Metabolizable energy (kcal/kg)  3050  Crude protein  22.0  Ether extract  3.60  Crude fiber  2.40  Ashes  4.50  Calcium  0.81  Available phosphorus  0.54  Sodium  0.22  Chlorine  0.36  Digestible lysine  1.30  Digestible methionine  0.60  Methionine + cysteine  0.97  Digestible threonine  0.79  Digestible tryptophan  0.20  Ingredients  Composition  Corn  59.36  Hi-pro soybean meal  30.49  Gluten 60%  3.99  Dicalcium phosphate  1.64  Soybean oil  1.53  Limestone  1.01  Salt (NaCl)  0.49  Trace mineral and vitamin premix1  0.41  L-lysine  0.40  Mycotoxin adsorbent2  0.20  DL-methionine  0.12  Choline chloride  0.11  Betaine  0.11  Anti-salmonella product3  0.10  Calculated analysis  Values  Metabolizable energy (kcal/kg)  3050  Crude protein  22.0  Ether extract  3.60  Crude fiber  2.40  Ashes  4.50  Calcium  0.81  Available phosphorus  0.54  Sodium  0.22  Chlorine  0.36  Digestible lysine  1.30  Digestible methionine  0.60  Methionine + cysteine  0.97  Digestible threonine  0.79  Digestible tryptophan  0.20  1Supplied per kilogram of diet: biotin, 0.2 mg; cyanocobalamin, 45 mg; cholecalciferol, 3.0 IU; folic acid, 1.6 mg; menadione 4.0 mg; nicotinic acid, 40 mg; pantothenic acid, 16 mg; pyridoxine, 3.2 mg; riboflavin, 6.4 mg; thiamin, 2.1 IU; trans-retinol, 9.6 IU; DL-tocopheryl acetate 48 IU; copper, 12 mg; iron, 48 mg; iodine, 0.8 mg; manganese, 72 g; selenium, 0.3 g; zinc, 72 mg; coccidiostat, 100 mg. 2Calibrin®—Elanco. 3Salmex®—Btech. View Large Diets were pelleted in a pellet mill [17], with a capacity of 30 metric tons/h, ring-shaped die with 4.0-mm diameter holes, and speed of 8.2 m/s. After pelleting, feeds were dried and cooled to an average temperature of 37 °C, and then crumbled in a roller mill with 2.0 mm of roll space. The mash diet presented 850 μm geometric mean diameter (GMD), and pelleted diets, 2135 μm GMD. At the end of the diet manufacturing process, samples of each experimental diet were collected and submitted to physical and chemical analyses. Birds and Housing Experimental procedures were conducted in accordance with the guidelines of the Committee of Ethics on Animal Use of the Federal University of Parana (UFPR), as approved in protocol n. 034/2012. In total, 480 one-d-old male Cobb 500 broilers were obtained from a commercial hatchery. Chicks were transported to the metabolism room of the department of Animal Science, UFPR, Curitiba, Paraná, Brazil, and individually weighed at arrival. Birds were housed in 48 metabolic cages measuring 0.90 m2 each (10 birds per cage), equipped with trough feeders and drinkers, and electric brooders. Water and feed were supplied ad libitum during the entire experimental period of 25 days. During the first 14 d, birds were maintained under constant incandescent light (24 h) and after this period approximately 12 h of light per day were used. Environmental temperature was maintained at 32°C on day 1 and then gradually reduced to approximately 22°C on day 25. Physical and Chemical Parameters In order to determine the amount of intact pellets, eight 500 g samples of each pelleted feed were passed through a 3.0-mm sieve, the feed remaining on top of the sieve was weighed, and its weight calculated as a percentage of the initial weight. Similarly, eight 500 g samples, with no fines, of each treatment were submitted to tumbling time of ten minutes, and a rotating speed of 50 revolutions per minute (RPM) to determine the pellet durability index (PDI). Pellet hardness was determined in a pellet-hardness tester [18] with individual pellets (eight per treatment) and expressed in kgf. The feeds and the ileal contents obtained after bird euthanasia, as described below, were ground to 1-mm particle size and analyzed for DM content by burning in a muffle at 105°C for 12 hours; for CP content (method 954.01); for acid insoluble ash (AIA) content (method 942.05), according to the AOAC [19]. Total starch content was analyzed using the method 996.11* of the AOAC adapted by Walter et al. [20]. Gross energy (GE) content was determined in a bomb calorimeter [21]. Diets were also analyzed for protein solubility in potassium hydroxide (KOH) according to Parsons et al. [22] and starch gelatinization degree according to method 27 of Compêndio Brasileiro de Nutrição Animal [23] as described in Table 2. Dietary water activity (Wa) was determined in water activity meter [24]. Table 2. Starch gelatinization degree of the experimental diets. Diet  Moisture (%)  Starch gelatinization degree (%)  Mash  13.36  30.10  P (0)  12.47  34.17  P (60)  12.59  32.47  P (80)  11.98  31.27  P (100)  12.61  33.75  P (120)  12.56  33.54  Diet  Moisture (%)  Starch gelatinization degree (%)  Mash  13.36  30.10  P (0)  12.47  34.17  P (60)  12.59  32.47  P (80)  11.98  31.27  P (100)  12.61  33.75  P (120)  12.56  33.54  View Large Performance Parameters Birds were weekly weighed per replicate to determine average weight gain (WG). Feed offer and residues per replicate were weekly weighed to determine average feed intake (FI). The FCR was calculated as the ratio between FI and WG (g/g). Birds were daily inspected for mortality, and the dead birds were removed and weighed for subsequent correction of WG for mortality. Digestibility Determination On day 25 of the experimental period, five birds per replicate were euthanized by cervical dislocation for the collection of ileal content. Ileal content samples were pooled per experimental unit, and each pool was individually homogenized, lyophilized, and ground for subsequent analyses. The content of AIA in the diets and in the ileal contents was used as internal indigestible marker for digestibility calculations, and determined according to the methodology described by Scott and Boldaji [25]. The coefficients of ileal apparent digestibility (CIAD) of the nutrients were estimated according to the equations below:   \begin{eqnarray*} \text{CIAD of diet nutrient} = \frac{\text{(nutrient in the diet)} - (\text{nutrient in the ileal digesta} \times \text{IF})}{\text{nutrient in the diet}} \end{eqnarray*} where (IF) is the ratio of dietary AIA content to the ileal digesta AIA content. Ileal digestible energy (IDE) values were calculated according to the equation:   \begin{eqnarray*} \text{IDE (Kcal/kg DM) = dietary GE level - (ileal digesta GE level } \times \text{ IF content in the ileal digesta)} \end{eqnarray*} Statistical Analysis A completely randomized experimental design, involving six treatments with eight replicates of 10 birds each, was applied. The obtained data were firstly tested for normality (Shapiro-Wilk's test) and homoscedasticity (Bartlett's test). Data complied with those assumptions, and were then submitted to analysis of variance using the GLM procedure of SAS statistical software [26]. Means were compared by the Dunnett's test at 5% probability level, using the mash diet as control treatment. Dependent treatments (pelleted diets conditioned for zero, 60, 80, 100, and 120 s) were submitted to analysis of regression. RESULTS Physical and Chemical Parameters There was a quadratic effect of conditioning time on PDI and pellet hardness (P ≤ 0.05), as shown in Table 3, with optimal values obtained at 89 and 51 s, respectively. Water activity linearly increased with conditioning time (P ≤ 0.05), whereas the amount of intact pellets was not affected (P > 0.05). Table 3. Percentage of intact pellets (IP), pellet durability index (PDI), pellet hardness, water activity (Wa), and KOH-soluble protein (PS) of pelleted diets submitted to different conditioning times.   Treatments1    P-value    P (0)  P (60)  P (80)  P (100)  P (120)  SEM  L  Q  IP (%)  95.07  95.67  96.37  95.47  96.45  0.298  0.20  0.90  PDI (%)  90.41  95.78  95.43  95.16  95.07  0.438  <0.001  <0.01  Hardness (kgf)  4.23  5.11  5.24  3.98  4.85  0.133  0.39  0.04  Wa  0.63  0.64  0.66  0.65  0.65  0.004  0.04  0.58  PS (%)  14.21  13.91  13.97  14.05  13.86  0.089  0.32  0.73    Treatments1    P-value    P (0)  P (60)  P (80)  P (100)  P (120)  SEM  L  Q  IP (%)  95.07  95.67  96.37  95.47  96.45  0.298  0.20  0.90  PDI (%)  90.41  95.78  95.43  95.16  95.07  0.438  <0.001  <0.01  Hardness (kgf)  4.23  5.11  5.24  3.98  4.85  0.133  0.39  0.04  Wa  0.63  0.64  0.66  0.65  0.65  0.004  0.04  0.58  PS (%)  14.21  13.91  13.97  14.05  13.86  0.089  0.32  0.73  1Conditioning times of the pelleted diets (0, 60, 80, 100, and 120 s) L = linear; Q = quadratic. View Large The content of KOH-soluble protein was not influenced by steam-conditioning times (Table 3). Bird Performance The pelleted diets promoted higher FI (P ≤ 0.05), except for the nonconditioned pelleted feed, and higher WG (P ≤ 0.05) compared with the control mash diet; however, FCR was not influenced (P > 0.05) by the treatments (Table 4). The diets submitted to increasing conditioning times linearly increased FI (P ≤ 0.05), but did not affect WG or FCR (P > 0.05), as shown in Table 4. Table 4. Performance of 1- to 25-d-old broilers fed mash or pelleted-crumbled diets submitted to different conditioning times.   Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  Feed intake (g)2  1269  1312  1351*  1339*  1360*  1362*  0.008  0.0027  Weight gain (g)  962  1027*  1049*  1030*  1071*  1046*  0.008  0.0014  FCR (g/g)  1.320  1.278  1.289  1.302  1.270  1.302  0.005  0.1206    Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  Feed intake (g)2  1269  1312  1351*  1339*  1360*  1362*  0.008  0.0027  Weight gain (g)  962  1027*  1049*  1030*  1071*  1046*  0.008  0.0014  FCR (g/g)  1.320  1.278  1.289  1.302  1.270  1.302  0.005  0.1206  1Mash diet (control) and pelleted diets submitted to different conditioning times (0, 60, 80, 100, and 120 s). 2Linear effect of conditioning times (P = 0.04). Y = 0.4118x + 1315.2; R² = 0.859. *Indicates difference from the control (P ≤ 0.05) by Dunnett's test. View Large Digestibility Higher CIAD of DM and CP (pelleted diets conditioned for 80 and 120 s), as well as higher IDE content, were obtained in the pelleted diets compared with the mash diet (P ≤ 0.01). However, the treatments did not affect (P > 0.05) the CIAD of starch (Table 5). Table 5. Coefficients of ileal apparent digestibility (CIAD) of dry matter (DM), starch, and crude protein (CP), and ileal digestible energy content (IDE) determined in 25-d-old broilers fed starter mash (control) or pelleted-crumbled diets submitted to different conditioning times (0, 60, 80, 100, and 120 s).   Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  CIAD of DM (%)  57.14  62.90*  65.80*  64.85*  65.59*  66.30*  0.729  <0.0001  CIAD of starch (%)  84.21  84.79  86.32  87.19  85.00  85.65  0.389  0.258  CIAD of CP (%)  71.77  71.53  74.09  74.22*  74.19  76.08*  0.549  0.011  IDE (kcal/kg DM) 2  2731  2966*  3113*  3094*  3160*  3187*  32.734  <0.0001    Treatments1        Mash  P (0)  P (60)  P (80)  P (100)  P (120)  SEM  P-value  CIAD of DM (%)  57.14  62.90*  65.80*  64.85*  65.59*  66.30*  0.729  <0.0001  CIAD of starch (%)  84.21  84.79  86.32  87.19  85.00  85.65  0.389  0.258  CIAD of CP (%)  71.77  71.53  74.09  74.22*  74.19  76.08*  0.549  0.011  IDE (kcal/kg DM) 2  2731  2966*  3113*  3094*  3160*  3187*  32.734  <0.0001  1Mash diet (control) and pelleted diets submitted to different conditioning times (0, 60, 80, 100, and 120 s). 2Quadratic effect of conditioning times (P = 0.04). Y = −0.0036x2 + 2.2155x + 2969.3 R² = 0.952. *Indicates difference from the control (P ≤ 0.05) by Dunnett's test. View Large No differences in the CIAD of DM, CP or starch were detected (P > 0.05) among pelleted diets submitted to the different conditioning times, but IDE content presented a quadratic response (P ≤ 0.05), as shown in Table 5. DISCUSSION All pelleted diets presented more than 95% intact pellets (Table 3), indicating good physical quality. Different results were obtained by Skoch et al. [5], who found higher percentage of fines in pelleted diets not submitted to conditioning (9.1%) compared with those conditioned at 65°C (3.8%) and at 80°C (3.2%); however, the percentage of fines was not affected by steam addition. Abdollahi et al. [27] reported that nonconditioned pelleted diets presented 10% less intact pellets than those submitted to heat, but not to steam-conditioning. In the present study, no pellet integrity differences were observed among pelleted diets, even at the longest conditioning time (120 s). Briggs et al. [12] found a negative correlation between the level of fines and PDI, which was not observed in the present study. Pellet durability index (PDI) presented a quadratic response to increasing conditioning time, which were more evident in the diets submitted to conditioning. The PDI of pelleted diet conditioned for 60 s was 5.9% higher compared with the nonconditioned diet. These results are in agreement with the findings of Abdollahi et al. [27], who found higher pellet durability in steam-conditioned pelleted diets than in dry-conditioned pelleted feeds. The poorer physical quality of the nonconditioned pelleted diet compared with the other pelleted diets may be explained by its low moisture, as that feed bypassed the steam conditioner. Fahrenholz [14], evaluating the influence of different conditioning times (30 and 60 s), observed that increasing mash retention time in the conditioner improved pellet durability; however, this effect was more significant when associated to other factors, such as conditioning temperature. Among the variables studied by Fahrenholz [14], conditioning time had the least influence on pellet quality. Likewise, Briggs et al. [12] observed that increasing the retention time from 5 to 15 s increased pellet durability in 4.5%. Pellet hardness responded quadratically to conditioning time up to 120 seconds. However, Fahrenholz [14] states that the PDI is a better expression of pellet physical quality than hardness, because it uses for its determination a large sample, and therefore, better represents the actual handling procedures than those used for determining pellet hardness. Thomas and Van der Poel [28] evaluated the hardness and durability of pelleted diets and found that durability results were more consistent to express pellet physical quality than hardness because they presented lower CV. There was a linear effect of conditioning time on Wa, as increasing steam exposure time during conditioning resulted in greater moisture incorporation to the feed. As all the diets were submitted to the same drying time, moisture content was similarly removed. Therefore, pelleted diets submitted to longer conditioning times presented higher Wa. However, the obtained values are close to the recommendations (nearby 0.6), and did not compromise the quality of the finished product. Protein solubility in KOH is applied especially for assessing soybean meal quality and nutrient availability, and it may be affected by inadequate heat processing of soybeans, reducing its nutritional value. The results of the present study show that even long conditioning times at 83°C did not affect protein solubility. In contrast, Muramatsu et al. [29] found that most intensive processing methods, such as expansion (110°C), reduced protein solubility in KOH from 68.6% to 64.3% during pelleting (80–82°C). The benefits of pelleting on animal performance are widely reported in the literature [3, 7, 30, 31]. These benefits were confirmed in the present study, as shown by the higher WG obtained with the pelleted diets compared with the mash diet. However, this better performance can only be achieved if the pellets produced maintain their integrity until they are consumed by the birds. Although the birds fed the steam-conditioned pelleted diets presented higher FI than those fed the mash diet, the FI values obtained with the nonconditioned pelleted diet and the mash diet were not statistically different. This probably occurred because the quality of this pelleted diet was lower (i.e., its PDI was 5% lower, on average) compared with those submitted to steam conditioning (Table 3). However, FI increased with conditioning time. Fahrenholz [14], evaluating the influence of different conditioning times (30 and 60 s), observed that longer retention times in the conditioner resulted in improved pellet durability. According to Skoch et al. [5], the addition of moisture using steam improves pellet quality by reducing the proportion of fines and increasing pellet durability. Based on these results, it is suggested that long retention times allow moisture to penetrate more efficiently into the feed particles, allowing greater adhesion among pellet components, and thereby, increasing feed intake. The pelleted diets presented better CIAD of DM, which is consistent with the findings of Zatari and Sell [32], who observed a significant increase in DM digestibility in pelleted diets compared with mash diets. Pelleted diets conditioned for 80 and 120 s presented higher protein digestibility rates than the other evaluated diets. The increase in protein digestibility may be explained by the breakdown of disulfide bridges of the protein molecule, causing its denaturation, and thereby, its easier access of proteases [9, 10]. In the present study, the steam-conditioning temperature (83°C), associated with exposure time, may have promoted these changes in the pelleted diets. The higher protein digestibility determined in those diets may also explain the higher WG obtained. Pelleting did not improve starch digestibility, as previously observed by Abdollahi et al. [31], working with corn-based diets. According to Svihus et al. [33], pelleting has marginal effects on starch availability, whereas more intensive processes such as extrusion, which includes water addition and applies higher temperatures than pelleting, result in greater starch gelatinization. Several studies have shown that only a small amount of starch is gelatinized during pelleting [5, 7, 34, 35] and that its effect on starch digestibility seems to be negligible [36]. Pelleted diets contained higher ileal digestible energy levels (IDE) compared with the mash diet. Jimenez-Moreno et al. [37] reported higher AMEn levels in broilers fed steam-cooked corn relative to raw corn. In the present study, the IDE level of the nonconditioned pelleted diet was 235 kcal/kg of DM higher compared with the mash diet. This may be attributed to the mechanical action of the feed inside the pellet mill, because the temperature measured at the exit of the due was 58.7°C. According to Abdollahi et al. [38], part of the starch gelatinization occurs after conditioning at pelleting press due to an increase in temperature and friction. This mechanical action may also be responsible for the greater availability of the other dietary fractions. Moreover, pelleted diets submitted to 60 s of steam-conditioning contained more 146 kcal/kg DM of IDE relative to the nonconditioned pelleted diet. The combination of moisture, temperature and time during conditioning may have improved the digestibility of the different dietary fractions, resulting in an increase in IDE value. The ileal digestibility of DM, CP, or starch of the pelleted diets was not influenced by conditioning times. Kokić et al. [39], evaluating different types of corn processing, determined lower degrees of starch gelatinization for flocculation (21.33%) and pelleting (25.47%), while more intensive processes, such as micronization and extrusion, yielded higher degrees of gelatinization, of 63.58 and 100%, respectively. The results obtained in the present study suggest that the steam-conditioning times employed before pelleting may not have been sufficiently to change the structures of the feedstuffs, leading to an increase in the digestibility of the diet fractions. Ileal digestible energy level presented a quadratic response to conditioning time. The behavior of IDE was similar to that of the PDI, suggesting a possible association between pellet durability and digestible energy values. McKinney and Teeter [3], feeding broilers with diets with different proportions of intact and fine pellets (with 100%, 80%, 60%, 40%, and 20% pellets, and mash), found an increase in the effective caloric value and in the resting frequency of broilers, because the birds spent less energy and time to consume pelleted feeds. Energy digestibility is influenced by many processing factors, such as temperature, time, pressure, and moisture and their interaction. In addition, it is affected by the feedstuffs included in diet and their energy contents, making it difficult to evaluate the effects of individual factors. For instance, according to Skoch et al. [5] and Voragen et al. [6], the heat treatment of starch causes granules to “swell”, and after continued heating, they disintegrate, solubilizing the individual starch molecules. Zelenka [2] mentions that one of the benefits of feeding pelleted feeds to broilers is the increase in dietary metabolizable energy value due to higher digestibility of dietary fractions. Furthermore, in the present study, FI increased as steam-conditioning time increased, which may have affected the obtained IDE values. CONCLUSIONS AND APPLICATIONS Feeding pelleted diets resulted in broilers with superior feed intake and weight gain, as well as greater ileal digestibility of dry matter, crude protein and energy compared with those fed the mash diet. Increasing conditioning time of pelleted diets improved feed intake, but weight gain and feed conversion ratio were not affected. Dry matter, starch, and crude protein ileal digestibility were not influenced by conditioning times, but the ileal digestible energy quadratically increased. It may be possible to improve pellet quality increasing steam-conditioning times. The combined effects of time, temperature, and moisture during conditioning should be further evaluated. Footnotes Primary Audience: Feed Mill Managers, Nutritionists, Broiler Producers, Researchers REFERENCES AND NOTES 1. Meinerz C., Ribeiro A. M. L., Penz A. M. Jr, Kessler A. M.. 2001. Níveis de energia e peletização no desempenho e rendimento de carcaça de frangos de corte com oferta alimentar equalizada. Rev. Bras. de Zootec.  30: 2026– 2032. Google Scholar CrossRef Search ADS   2. Zelenka J. 2003. Effect of pelleting on digestibility and metabolizable energy values of poultry diets. Czech J. Anim. Sci.  48: 239– 242. 3. Mckinney L. J., Teeter R. G.. 2004. Predicting effective caloric value of nonnutritive factors: I. Pellet quality and II. Prediction of consequential formulation dead zones. Poult. Sci.  83: 1165– 1174. Google Scholar CrossRef Search ADS PubMed  4. Reimer L.. 1992. Conditioning. Proc. Northern Crops Institute Feed Mill Management and Feed Manufacturing Technol. Short Course . p. 7. California Pellet Mill Co. Crawfordsville. 5. Skoch E. R., Behnke K. C., Deyoe C. W., Binder S. F.. 1981. The effect of steam-conditioning rate on the pelleting process. Anim. Feed Sci. Technol.  6: 83– 90. Google Scholar CrossRef Search ADS   6. Voragen A. G. J., Gruppen H., Marsmanl G. J. P., Mul A. J.. 1995. Effect of some manufacturing technologies on chemical, physical and nutritional properties of feed. Pages 93– 126 in Recent Advances in Animal Nutrition . Garnsworthy P. C., Cole D. J. A., eds. Nottingham University Press, Nottingham, UK. 7. Svihus B., Kløvstad K. H., Perez V., Zimonja O., Sahlström S., Schüller R. B., Jeksrud W. K., Prestløkken E.. 2004. Nutritional effects of pelleting of broiler chicken diets made from wheat ground to different coarsenesses by the use of roller mill and hammer mill. Anim. Feed Sci. Technol.  117: 281– 293. Google Scholar CrossRef Search ADS   8. Moran E. T. Jr. 1987. Pelleting: affects feed and its consumption. Poult. Sci.  5: 30– 31. 9. Scott T. A., Swift M. L., Bedford M. R.. 1997. The influence of feed milling, enzyme supplementation, and nutrient regimen on broiler chick performance. J. Appl. Poult. Res.  6: 391– 398. Google Scholar CrossRef Search ADS   10. Dozier W. A. 2001. Pelet de calidad para obtener carne de ave más economica. Alim. Balanc. Anim.  8: 16– 19. 11. Svihus B., Hetland H.. 2001. Ileal starch digestibility in growing broiler chickens fed on a wheat-based diet is improved by mash feeding, dilution with cellulose or whole wheat inclusion. Br. Poult. Sci.  42: 633– 637. Google Scholar CrossRef Search ADS PubMed  12. Briggs J. L., Maier D. E., Watkins B. A., Behnke K. C.. 1999. Effect of ingredients and processing parameters on pellet quality. Poult. Sci.  78: 1464– 1471. Google Scholar CrossRef Search ADS PubMed  13. Gilpin A. S., Herrman T. J., Behnke K. C., Fairchild F. J.. 2002. Feed moisture, retention time, and steam as quality and energy utilization determinants in the pelleting process. App. Eng. in Ag.  18: 331– 338. 14. Fahrenholz A. C. 2012. Evaluating factors affecting pellet durability and energy consumption in a pilot feed mill and comparing methods for evaluating pellet durability . PhD Diss. Kansas State University, Kansas. 15. Cobb. 2013. Cobb 500 Broiler: Broiler performance and nutrition supplement , Cobb-Vantress Inc., Siloam Springs, AR. 16. Van Aarsen LTV1200 Conditioner, Van Aarsen International B.V, Panheel, the Netherlands. 17. Van Aarsen C900 Standard Pellet Mill, Van Aarsen International B.V, Panheel, the Netherlands. 18. Nova Ética 298DGP Hardness Tester, Ethiktechnology, São Paulo, Brazil. 19. AOAC International. 1995. Official and tentative methods of analysis . 16th ed. Arlington, Virginia. 20. Walter M., Silva L. P., Perdomo D. M. X.. 2005. Amido disponível e resistente em alimentos: adaptação do método da AOAC 996.11*. Alimentos e Nutrição. 16: 39– 43. 21. Ika Werke C 2000. Control Oxygen Bomb Calorimeter , Ika-Werke GmbH&Co, Staufen, Germany. 22. Parsons C. M., Hashimoto K., Wedekind K. J., Baker D. H.. 1991. Soybean protein solubility in potassium hydroxide: an in vitro test of in vivo protein quality. J. Anim. Sci.  69: 2918– 2924. Google Scholar CrossRef Search ADS PubMed  23. Sindirações. 2009. Brazilian Compendium in Animal Nutrition. 24. Aqualab S3TE Water Activity Meter, Decagon Devices Inc., Washington, USA. 25. Scott T. A., Boldaji F.. 1997. Comparison of inert markers [chromic oxide or insoluble ash (CeliteTM)] for determining apparent metabolizable energy of wheat- or barley- based broiler diets with or without enzymes. Poult. Sci.  76: 594– 598. Google Scholar CrossRef Search ADS PubMed  26. SAS User's Guide. 2004. Version 9.0. ed  SAS Inst. Inc., Cary, NC. 27. Abdollahi M. R., Ravindran V., Wester T. J., Ravindran G., Thomas D. V.. 2011. Influence of feed form and conditioning temperature on performance, apparent metabolisable energy and ileal digestibility of starch and nitrogen in broiler starters fed wheat-based diet. Anim. Feed Sci. Technol.  168: 88– 99. Google Scholar CrossRef Search ADS   28. Thomas M., Van der Poel A. F. B.. 1996. Physical quality of pelleted animal feed. Anim. Feed Sci. Technol.  61: 89– 112. Google Scholar CrossRef Search ADS   29. Muramatsu K., Maiorka A., Vaccari I. C. M., Reis R. N., Dahlke F., Pinto A. A., Orlando U. A. D., Bueno M., Imagawa M.. 2013. Impact of particle size, thermal processing, fat inclusion and moisture addition on pellet quality and protein solubility of broiler feeds. J. Agric. Sci. Technol. A.  3: 1017– 1028. 30. Oliveira A. A., Gomes A. V. C., Oliveira G. R., Lima M. F., Dias G. E. A., Agostinho T. S. P., Sousa F. D. R., Lima C. A. R.. 2011. Desempenho e características da carcaça de frangos de corte alimentados com rações de diferentes formas físicas. Rev. Bras. de Zootec. 40: 2450– 2455. 31. Abdollahi M. R., Ravindran V., Svihus B.. 2013. Influence of grain type and feed form on performance, apparent metabolisable energy and ileal digestibility of nitrogen, starch, fat, calcium and phosphorus in broiler starters. Anim. Feed Sci. Technol.  186: 193– 203. Google Scholar CrossRef Search ADS   32. Zatari I. M., Sell J. L.. 1990. Effects of pelleting diets containing sunflower meal on performance of broiler chickens. Anim. Feed Sci. Technol.  30: 121– 129. Google Scholar CrossRef Search ADS   33. Svihus B., Uhlen A. K., Harstad O. M.. 2005. Effect of starch granule structure, associated components and processing on nutritive value of cereal starch: A review. Animal Feed Science and Technology . 122: 303– 320. Google Scholar CrossRef Search ADS   34. Moritz J. S., Wilson K. J., Cramer K. R., Beyer R. S., Mckinney L. J., Cavalcanti B., Mo X.. 2002. Effect of formulation density, moisture, and surfactant on feed manufacturing, pellet quality and broiler performance. J. Appl. Poult. Res.  11: 155– 163. Google Scholar CrossRef Search ADS   35. Moritz J. S., Cramer K. R., Wilson K. J., Beyer R. S.. 2003. Feed manufacture and feeding of rations with graded levels of added moisture formulated to different energy densities. J. Appl. Poult. Res.  12: 371– 381. Google Scholar CrossRef Search ADS   36. Zimonja O., Hetland H., Lazarevic N., Edvardsen D. H., Svihus B.. 2008. Effects of fiber content in pelleted wheat and oat diets on technical pellet quality and nutritional value for broiler chickens. Can. J. Anim. Sci.  88: 613– 622. Google Scholar CrossRef Search ADS   37. Jimenez-Moreno E., Gonzalez-Alvarado J. M., Lazaro R., Mateos G. G.. 2009. Effects of type of cereal, heat processing of the cereal, and fibre inclusion in the diet on gizzard pH and nutrient utilisation in broilers at different ages. Poult. Sci.  88: 1925– 1933. Google Scholar CrossRef Search ADS PubMed  38. Abdollahi M. R., Ravindran V., Wester T. J., Ravindran G., Thomas D. V.. 2010. Influence of conditioning temperature on performance, apparent metabolisable energy, ileal digestibility of starch and nitrogen and the quality of pellets, in broiler starters fed maize and sorghum-based diets. Anim. Feed Sci. Technol.  162: 106– 115. Google Scholar CrossRef Search ADS   39. Kokić B. M., Lević J. D., Chrenková M., Formelová Z., Poláĉiková M., Rajský M., Jovanović R. D.. 2013. Influence of thermal treatments on starch gelatinization and in vitro organic matter digestibility of corn. Food and Feed Research . 40: 93– 99. © 2017 Poultry Science Association Inc.

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Journal of Applied Poultry ResearchOxford University Press

Published: Mar 1, 2018

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