Impact of corn particle size on nutrient digestibility varies depending on bird type.

The interaction between bird type (broilers and layers) and corn particle size (fine, medium, and coarse) on the coefficient of apparent ileal digestibility (CAID) of DM, nitrogen (N), starch, fat, gross energy (GE), calcium (Ca) and phosphorus (P), and AMEn was investigated in a 2 by 3 factorial study of 6 dietary treatments. Whole corn was ground in a hammer mill to pass through screen sizes of 2.0, 5.0, and 8.0 mm for fine, medium, and coarse grades, respectively. A corn-soybean meal diet, mixed using the same batch of ingredients, was fed to both bird types. Titanium dioxide was included in all diets for digestibility measurements. 35-day-old Ross 308 male broilers and 59-wk-old Hy-Line Brown layers were used in this study. For each bird type, 108 birds of uniform body weights were accommodated in 18 replicates (6 replicates per particle size and 6 birds per replicate). The treatment diets were offered ad libitum for 7 d prior to the collection of ileal digesta. A bird type by particle size interaction was observed (P < 0.001) for the CAID of DM, starch and GE. In broilers, CAID of DM, starch and GE was unaffected by particle size, whilst in layers, increasing the corn particle size to medium and coarse resulted in a greater (P < 0.05) CAID for DM, starch and GE compared to fine particles. The CAID of N and fat was greater (P < 0.05) in broilers than layers and the opposite was observed (P < 0.05) for Ca and P. Regardless of bird type, coarse and medium-ground corn resulted in a greater (P < 0.05) Ca digestibility compared to finely-ground corn. Overall, broilers had a greater digestibility of nutrients than layers, except for Ca and P. Feeding medium and coarse corn particles benefited the CAID of DM, starch and GE in layers, suggesting that digestive system in these birds is probably more sensitive to feed particle size than broilers.

Dietary inclusion of fibrous ingredients and bird type influence apparent ileal digestibility of nutrients and energy utilization.

The interaction between inclusion of fibrous ingredients and bird type on the coefficient of apparent ileal digestibility (CAID) of nutrients and energy utilization was investigated in the current study. A 2 × 3 factorial arrangement of treatments was utilized with 2 fiber contents (10.3 and 19.3 g/kg neutral detergent fiber) and 3 bird types (broilers, pullets and layers). The low-fiber diet was based on corn and soybean meal, and the high-fiber diet was developed by the inclusion of palm kernel meal, canola meal, and oat hulls. Titanium dioxide was used as an inert marker to calculate the CAID. The digesta were collected from the terminal ileum following the feeding of experimental diets for 7 d. Significant interactions (P < 0.05) between dietary fiber content and bird type were observed for the CAID of DM, starch, fat, neutral detergent fiber and energy, and AMEn. In general, the CAID coefficients were higher in broilers, intermediate in pullets, and lowest in layers at both fiber contents. The CAID of nutrients in the 3 bird types was higher (P < 0.05) in the high-fiber diet than in the low-fiber diet, but the magnitude of responses differed. Layers showed markedly higher digestibility responses to increased dietary fiber content compared to broilers and pullets. There were interactions (P < 0.05 to 0.001) between the dietary fiber content and bird type for the CAID of nitrogen and all amino acids, except for Asp and Lys. The CAID of Asp and Lys was highest (P < 0.05) in broilers, intermediate in pullets, and lowest digestibility in layers. The CAID coefficients of nitrogen and amino acid increased with increased fiber content, with distinctly greater responses in layers compared to broilers and pullets. Overall, layers showed greater digestibility of nutrients in response to the increased fiber content, suggesting that layers require high-dietary fiber contents to efficiently utilize nutrients compared to broilers and pullets.