The influence of feed form and particle size on the performance, coefficient of apparent ileal digestibility (CAID) of nutrients, apparent metabolisable energy (AME) and intestinal morphology in broiler starters fed maize-based diets was examined in this study. Two feed forms (mash and pellet) and three particle sizes (fine, medium and coarse) were evaluated in a 2 × 3 factorial arrangement of treatments. Birds fed pelleted diets had higher (P < 0.05) weight gain and feed intake than those fed mash diets. In mash diets, fine grinding resulted in lower (P < 0.05) feed per unit gain compared to medium and coarse grinding, whereas, in pelleted diets, there was no effect (P > 0.05) of particle size. Gizzard pH was not influenced (P > 0.05) by particle size in mash diets, but fine grinding increased (P < 0.05) gizzard pH compared to medium and coarse grinding in pelleted diets. Pelleting reduced (P < 0.05) the CAID of nitrogen but increased (P < 0.05) the ileal fat digestibility. Particle size had no effect (P > 0.05) on CAID of starch and AME in mash diets, but in pelleted diets, pellets made from medium and coarsely ground maize showed higher (P < 0.05) starch digestibility. Coarse grinding resulted in higher (P < 0.05) AME in pelleted diets. Feeding pelleted diets reduced (P < 0.05) the CAID of calcium and phosphorus, but increased (P < 0.05) that of sodium. Medium and coarse grindings resulted in higher (P < 0.05) calcium digestibility than fine grinding. Feeding pelleted diets reduced (P < 0.05 to 0.001) the relative length of all small intestinal segments and the relative weight of pancreas, proventriculus, and gizzard. Medium and coarse grinding increased (P < 0.05) the gizzard weight compared to fine grinding. In both the duodenum and jejunum, birds fed pelleted diets had greater (P < 0.05) villus height than those fed mash diets. Goblet cell number in duodenum was higher (P < 0.05) in birds fed diets containing fine particles compared to those fed medium and coarse particle sizes. The crypt depth in jejunum was greater (P < 0.05) in birds fed pelleted diets. Overall, the present data showed that coarse grinding of maize, through enhanced gizzard development and functionality, is beneficial to nutrient and energy utilisation and growth performance in broilers fed pelleted diets.
Key words: Feed form, Particle size, Broilers, Performance, Nutrient utilization.
Abstract published in Animal Feed Science and Technology, Volume 215, May 2016, Pages 92-104. https://doi.org/10.1016/j.anifeedsci.2016.02.012.