A. M. Amerah

FEED PARTICLE SIZE: IMPLICATIONS ON THE DIGESTION AND PERFORMANCE OF POULTRY

This review highlights the limited amount of research conducted regarding the optimum particle size of different feeds for efficient poultry production. The current industry practice of using highly processed, pelleted diets masks the influence of particle size, but some reports suggest that the effects of feed particle size on performance may be maintained even after pelleting. There appears to be a general consensus that particle sizes of broiler diets based on maize or sorghum, optimum particle size should be between 600 and 900 μm. Available data clearly show that grain particle size is more critical in mash diets than in pelleted or crumble diets. Although it has been postulated that finer grinding increases substrate availability for enzymatic digestion, there is evidence that coarser grinding to a more uniform particle size improves the performance of birds maintained on mash diets. This counter-intuitive effect may result from the positive effect of feed particle size on gizzard development. A more developed gizzard is associated with increased grinding activity, resulting in increased gut motility and greater digestion of nutrients. Although grinding to fine particle size is thought to improve pellet quality, it will markedly increase energy consumption during milling. Systematic investigations on the relationships of feed particle size and diet uniformity with bird performance, gut health and pellet quality are warranted if efficiency is to be optimised in respect of the energy expenditure of grinding.

Influence of Feed Particle Size on the Performance, Energy Utilization, Digestive Tract Development, and Digesta Parameters of Broiler Starters Fed Wheat- and Corn-Based Diets

The influence of particle size and grain type on the performance, AME(n), and on gross morphological and histological parameters of the various segments of the digestive tract of broilers fed wheat- or corn-based diets was investigated. The experimental design was a 2 x 2 factorial arrangement of treatments evaluating 2 particle sizes (fine and coarse) and 2 grain types (wheat and corn). The 2 particle sizes were achieved by grinding the whole grains in a hammer mill to pass through 1-mm and 7-mm screen sizes. Broiler starter diets, based on wheat- or corn-soybean meal, were formulated, pelleted, and each diet was offered to 6 cages of 8 male broilers each from d 1 to 21 posthatching. The results showed that the differences in particle size distribution still existed between diets after pelleting especially in the proportion of coarse particles (1 mm and over). In corn-based diets, coarse grinding improved (P = 0.06) weight gains compared with fine grinding, but this particle size effect was not observed in wheat-based diets. In both diets, coarse grinding lowered (P < 0.001) feed per gain of broilers compared with fine grinding. In wheat-based diets, coarse grinding improved (P = 0.06) AME(n) compared with fine grinding. Heavier (P < 0.05) gizzard weights were observed in birds fed the coarse corn-based diet, but particle size had no effect on the gizzard size in birds fed wheat-based diets. Villus height, crypt depth, and epithelial thickness in the duodenum were unaffected (P > 0.05) by particle size and grain type. Overall, the present results showed that the effect of feed particle size varies depending on grain type.

Influence of insoluble fibre and whole wheat inclusion on the performance, digestive tract development and ileal microbiota profile of broiler chickens

1. An experiment of 21-d duration was conducted to examine the effects of diluting wheat-based diets with insoluble fibre sources and whole wheat inclusion on the performance, nutrient utilisation, digestive tract development and ileal microbiota profile of broiler chickens. The treatments were as follows: Treatment 1, control diet based on ground wheat; Treatment 2, where 200 g/kg whole wheat replaced the ground wheat pre-pelleting; and Treatments 3 and 4 where the control diet was diluted with fine cellulose and wood shavings, respectively, at a ratio of 6 : 100 (w/w). 2. Weight gains and apparent metabolisable energy were unaffected by dietary treatment. Gain : feed ratio was not influenced by the inclusion of whole wheat or wood shavings, but decreased with cellulose inclusion. However, when gain:feed of birds was corrected by subtracting the amount of cellulose and wood shavings from the total feed consumption, it was found that the inclusion of wood shavings increased gain : feed, while cellulose inclusion had no effect. Similarly, AMEN was unaffected by dietary treatment. However, when AMEN was corrected for energy contribution from cellulose or wood shavings, improvements in AMEN were observed in these two treatments. 3. Wood shavings increased the relative gizzard weights and improved ileal starch digestibility compared to other dietary treatments. All gut components were shorter in birds given diets containing cellulose and wood shavings compared to those receiving the control and whole wheat diets. 4. Ileal microbiota profiling, using denaturing gradient gel electrophoresis, showed that microbial composition was affected by dietary treatment and that the treatments were grouped into two main clusters. The two groupings showed similarity between birds receiving the control and cellulose diets and similarity between birds fed on the whole wheat and wood shavings diets. 5. The findings suggest that the effects of insoluble fibre on broiler performance differed depending on the fibre particle size.

Effect of calcium level and phytase addition on ileal phytate degradation and amino acid digestibility of broilers fed corn-based diets

This study investigated the effect of dietary Ca to available P (AvP) ratio and phytase supplementation on bone ash, ileal phytate degradation, and nutrient digestibility in broilers fed corn-based diets. The experimental design was a 4 × 2 factorial arrangement of treatments evaluating 4 Ca:AvP ratios (1.43, 2.14, 2.86, and 3.57) and 2 levels of phytase (0 and 1,000 phytase units/kg of feed). The 4 Ca:AvP ratios were achieved by formulating all diets to a constant AvP level of 0.28% and varying Ca levels (0.4, 0.6, 0.8, and 1.0%). Each treatment was fed to 6 cages of 8 male Ross 308 broilers from 5 to 21 d. At 21 d, digesta from the terminal ileum was collected and analyzed for energy, phytate, P, Ca, and amino acids (AA) to determine digestibility. Digesta pH was measured in each segment (crop, gizzard, duodenum, and ileum) of the digestive tract. Data were analyzed by 2-way analysis of covariance. There was a significant interaction between dietary Ca:AvP ratio and phytase supplementation for weight gain (WG), feed intake (FI), and feed conversion ratio (FCR). In diets with no phytase, Ca:AvP ratio had a greater effect on WG, FI, and FCR compared with those fed diets without phytase. The orthogonal polynomial contrasts showed that the increase in dietary Ca:AvP ratio significantly decreased WG and FI in a quadratic manner, whereas FCR increased (P < 0.05) linearly with higher dietary Ca:AvP ratio. Increasing dietary Ca:AvP ratio led to a significant quadratic decrease in phytate degradation and significant linear decreases in P digestibility and bone ash. Phytase addition increased (P < 0.05) phytate degradation and improved (P < 0.05) energy, AA, and P digestibility at all levels of Ca:AvP with no interaction (P > 0.05) between the main factors. Digestibility of AA was positively correlated (P < 0.05) with the degree of phytate degradation. Increasing dietary Ca:AvP ratio significantly increased gizzard pH in a linear manner. In conclusion, phytase (1,000 phytase units/kg of feed) improved phytate, and P and AA digestibility at all Ca:AvP ratios evaluated in this study.

Influence of whole wheat inclusion and a blend of essential oils on the performance, nutrient utilisation, digestive tract development and ileal microbiota profile of broiler chickens

1. The aim of the present experiment was to examine the influence of whole wheat inclusion and a blend of essential oils (EO; cinnamaldehyde and thymol) supplementation on the performance, nutrient utilisation, digestive tract development and ileal microbiota profile of broiler chickens. 2. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating two wheat forms (ground wheat [GW] and whole wheat [WW]; 100 and 200 g/kg WW replacing GW during starter [1 to 21 d] and finisher [22 to 35 d] diets respectively) and two levels of EO inclusion (0 or 100 g/tonne diet). All dietary treatments were supplemented with 2000 xylanase units/kg feed. Broiler starter and finisher diets based on wheat and soybean meal were formulated and each diet fed ad libitum to 6 pens of 8 male broilers. 3. During the trial period (1–35 d), wheat form had no significant effect on weight gain or feed intake. However, WW inclusion tended (P = 0.06) to improve feed per gain. Essential oil supplementation significantly improved weight gain in both diets, but the improvements were greater in the GW diet as indicated by a significant wheat form × EO interaction. 4. Main effects of wheat form and EO on the relative weight, length and digesta content of various segments of the digestive tract were not significant. Significant interactions, however, were found for relative gizzard and caecal weights. Essential oil supplementation significantly increased the relative gizzard weight and lowered relative caecal weight in birds fed on the GW based diet, but had no effect in those fed on the WW based diet. 5. Whole wheat inclusion and EO supplementation significantly improved apparent ileal nitrogen digestibility. Apparent ileal digestible energy was not significantly influenced by the dietary treatments. 6. Ileal microbiota profiling, using denaturing gradient gel electrophoresis, showed that the ileal microbiota composition was influenced by feed form. The mean numbers of bacterial species in the ileal contents of birds fed on the GW diet supplemented with EO tended (P = 0.07) to be higher than those of the ileal contents of birds fed on unsupplemented GW based diet. 7. The present data suggested that dietary addition of EO improves broiler weight gain and ileal nitrogen digestibility both in GW and WW based diets, but that the magnitude of the response to EO for weight gain was greater in GW based diet. Whole wheat feeding was found to be beneficial in terms of feed efficiency.

Influence of wheat hardness and xylanase supplementation on the performance, energy utilisation, digestive tract development and digesta parameters of broiler starters

The aim of this study was to examine the influence of wheat hardness and xylanase supplementation on the performance, energy utilisation, digestive tract development and digesta parameters of broilers fed wheat-based diets. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating wheat hardness (soft or hard) with or without xylanase supplementation. Two diets based on soft or hard wheat were formulated. Whole wheat (200 g/kg) from the same wheat batch replaced ground wheat before cold-pelleting of each diet. Each diet was fed ad libitum to six pens of eight male broilers each from day 1 to 21 posthatch. The distribution of particle size differed between diets, with the hard wheat diet having 32.7% of particles greater than 1 mm in size compared with 18.7% in the soft wheat diet. Interactions (P < 0.05) were observed between wheat hardness and enzyme supplementation for weight gain, feed intake, feed per gain and nitrogen-corrected apparent metabolisable energy (AMEn). Enzyme supplementation increased (P < 0.05) weight gain in the soft wheat-based diet but not in the hard wheat diet. Enzyme supplementation also increased (P < 0.05) feed intake in the soft wheat-based diet, but reduced (P < 0.05) intake in the hard wheat diet. Feed per gain and AMEn were improved (P < 0.05) by enzyme supplementation in the hard wheat-based diet, while no enzyme effect was observed in the soft wheat diet. Feeding the hard wheat-based diet increased (P < 0.05) the relative gizzard weight, and this was associated with a general increase in finer particles in the proximal intestinal digesta when compared with those present in the diet. These results suggest that the response of broilers to xylanase supplementation is influenced by wheat hardness and that wheat hardness may be an important criterion to consider when choosing for whole wheat inclusion in broiler diets.

Influence of feed processing on the efficacy of exogenous enzymes in broiler diets

The use of commercial exogenous enzymes in poultry diets is now a common practice. Broilers are predominantly fed pelleted diets; of the various unit operations in the production of pellets, grinding and conditioning are the components that can influence the efficacy of exogenous enzymes. The aim of this paper was to review the feed processing factors that influence the efficacy of exogenous enzymes in broiler diets. Recent studies have shown that the efficacy of exogenous enzymes is influenced by the degree of grinding. Available data suggest that enzyme responses on intestinal viscosity are more pronounced in feeds subjected to high conditioning temperatures. The issue of enzyme stability during conditioning and pelleting therefore becomes relevant and new enzyme technologies are being developed to overcome the high thermal processing issues. However, the effects of steam conditioning practices on enzyme stability have received less attention and need to be explored in future studies.

Influence of particle size and xylanase supplementation on the performance, energy utilisation, digestive tract parameters and digesta viscosity of broiler starters.

1. The aim of the present experiment was to examine the influence of particle size and xylanase supplementation on the performance, energy utilisation, and gross morphological and histological parameters of the digestive tract of broiler starters fed wheat-based diets. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating two wheat particle sizes (medium and coarse) and two levels of xylanase supplementation (without or with 1000 xylanase units/kg diet). The two particle sizes were achieved by grinding the whole wheat in a hammer mill to pass through 3 and 7 mm screens, respectively. Broiler starter diets, based on wheat and soybean meal, were formulated and each diet was fed ad libitum to 6 pens of 8 male broilers each from d 1 to 21 post-hatch. 2. Wheat particle size had no effect on the performance of broilers. Xylanase supplementation had no effect on weight gain and feed intake. However, a significant particle size × xylanase interaction was observed for feed per unit gain with xylanase lowering feed per gain only in the coarse particle size diet. Xylanase supplementation improved the nitrogen-corrected apparent metabolisable energy at both particle sizes. 3. Xylanase supplementation decreased the relative weight and relative length of all gut components. Villus height and crypt depth and total extent of the mucosal layer were unaffected by both wheat particle size and xylanase supplementation. 4. The apparent viscosity of intestinal digesta, determined over the physiological range of shear rates, was not influenced by xylanase addition or particle size. 5. The findings of this study suggest that the effectiveness of exogenous xylanase in broiler diets is influenced by wheat particle size.

Effect of coccidia challenge and natural betaine supplementation on performance, nutrient utilization, and intestinal lesion scores of broiler chickens fed suboptimal level of dietary methionine

The aim of the present experiment was to examine the effect of coccidia challenge and natural betaine supplementation on performance, nutrient utilization, and intestinal lesion scores of broiler chickens fed suboptimal level of dietary methionine. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating two levels of betaine supplementation (0 and 960 g betaine/t of feed) without or with coccidia challenge. Each treatment was fed to 8 cages of 8 male broilers (Ross 308) for 1 to 21d. On d 14, birds in the 2 challenged groups received mixed inocula of Eimeria species from a recent field isolate, containing approximately 180,000 E. acervulina, 6,000 E. maxima, and 18,000 E. tenella oocysts. At 21d, digesta from the terminal ileum was collected for the determination of dry matter, energy, nitrogen, amino acids, starch, fat, and ash digestibilities. Lesion scores in the different segments of the small intestine were also measured on d 21. Performance and nutrient digestibility data were analyzed by two-way ANOVA. Lesion score data were analyzed using Pearson chi-square test to identify significant differences between treatments. Orthogonal polynomial contrasts were used to assess the significance of linear or quadratic models to describe the response in the dependent variable to total lesion scores. Coccidia challenge reduced (P < 0.0001) the weight gain and feed intake, and increased (P < 0.0001) the feed conversion ratio. Betaine supplementation had no effect (P > 0.05) on the weight gain or feed intake, but lowered (P < 0.05) the feed conversion ratio. No interaction (P > 0.05) between coccidia challenge and betaine supplementation was observed for performance parameters. Betaine supplementation increased (P < 0.05) the digestibility of dry matter, nitrogen, energy, fat, and amino acids only in birds challenged with coccidia as indicated by the significant interaction (P < 0.0001) between betaine supplementation and coccidia challenge. The main effect of coccidia challenge reduced (P < 0.05) starch digestibility. Betaine supplementation improved (P < 0.05) starch digestibility regardless of the coccidia challenge. For each unit increase in the total lesion score, there was a linear (P < 0.001) decrease in digestibility of mean amino acids, starch, and fat by 3.8, 3.4 and 16%, respectively. Increasing total lesion scores resulted in a quadratic (P < 0.05) decrease in dry matter digestibility and ileal digestible energy. No lesions were found in the intestine or ceca of the unchallenged treatments. In the challenged treatments, betaine supplementation reduced (P < 0.01) the lesion scores at the duodenum, lower jejunum, and total lesion scores compared to the treatment without supplements. In conclusion, coccidia challenge lowered the digestibility of energy and nutrients and increased the feed conversion ratio of broilers. However, betaine supplementation reduced the impact of coccidia challenge and positively affected nutrient digestibility and the feed conversion ratio.

Influence of particle size and microbial phytase supplementation on the performance, nutrient utilisation and digestive tract parameters of broiler starters.

The aim of the present experiment was to examine the interaction between particle size and microbial phytase supplementation on the performance, nutrient utilisation and digestive tract development of broiler starters fed maize-based diets. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating two maize particle sizes (medium and coarse) and two levels of phytase supplementation (without or with 500 phytase units/kg diet). The two particle sizes were achieved by grinding the whole maize in a hammer mill to pass through 3- and 7-mm screens, respectively. Broiler starter diets, based on maize and soybean meal, were formulated to meet recommended requirements for major nutrients, except phosphorus. Each of the four diets was fed ad libitum to six pens of eight male broilers each, from day 1 to day 21 post-hatching. Phytase supplementation increased (P 0.05) on feed intake and feed per gain. No interactions (P > 0.05) between phytase supplementation and particle size were observed for any of the performance parameters. Phytase supplementation increased (P < 0.001) ileal phosphorus digestibility and toe ash content of birds fed the medium particle size diet, but had no effect in those fed the coarse particle size diet. Apparent metabolisable energy and ileal digestibility of calcium and nitrogen were not influenced by particle size or phytase supplementation. The present findings suggest that the effectiveness of supplemental phytase on broiler performance is not influenced by the particle size of maize.