Influence of dietary energy level and corn particle size on performance, nutrient digestibility, and gut development...

This study evaluated the effects of dietary energy levels and corn particle sizes on the growth performance and nutrient digestibility of broiler chickens. The energy used in this experiment is based on nitrogen-corrected apparent metabolizable energy (AMEn): low AMEn (2,850 kcal/kg) and high AMEn (3,000 kcal/kg) were paired with three corn particle sizes: 2.5, 5.0, and 8.0 mm. Birds fed low-energy diets had significantly greater feed intake and weight gain (P < 0.01). Coarse particles had the lowest FCR when diets contained high AMEn (P < 0.05), while the lowest FCR in the low AMEn group was produced by medium particles (P < 0.05). The CAID of DM, GE, and P were increased by feeding fine particles in the low AMEn group (P < 0.05). Greater CAID of starch and N was found in birds fed low-energy diets (P < 0.05). The absolute and relative weight of breast meat was greater in the low AMEn group (P < 0.05). Energy levels or particle sizes did not significantly affect the weights and lengths of the small intestine compartments (P > 0.05). A heavier gizzard was found in birds fed coarse particles (P < 0.05), as well as the lowest gizzard pH (P < 0.05). Treatments did not affect the villi length of the jejunum and ileum, and crypt depth of the jejunum (P > 0.05), but affected the ileum crypt depth (P < 0.05). Also, no effect on jejunum and ileum epithelial thickness (P > 0.05). The findings indicate that the benefits of coarse particles on gizzard weight and function are evident, although enhancements in the AIDE and CAID of DM, GE, and P occurred only when coarse particles were combined with high-energy diets. The performance of birds was most notable on a low-energy diet, likely due to increased feed intake.