Abstract
This study aimed to investigate the interactions between corn particle size (PS) and conditioning temperature (CT) on the performance, carcass traits, intestinal morphology, and immune responses in broilers fed a corn-soybean meal-based diet. A total of 360 one-day-old male broiler chicks (Ross 308) were randomly allocated into six dietary treatments in a 2 × 3 factorial arrangement, consisting of two corn PS (finely ground with geometric mean diameter (GMD) of 357 µm (PS(F)) vs. coarsely ground corn with GMD of 737 µm (PS(C)), and three CT [unconditioned (CT(U)), conditioned at 75 °C (CT(75)) and 90 °C (CT(90))]. Birds were accommodated in 30 pens with five replicates and 12 chicks per each pen. There was no interaction between corn PS and CT on the growth performance and immune response of broilers at any growth phases. However, during the starter (0-10 days) period, the average daily weight gain (ADWG) and feed conversion ratio (FCR) of PS(F)-fed birds were significantly improved compared to those fed PS(C) (p < 0.05). During the starter (0-10 days) and grower (11-24 days) periods, increasing the conditioning temperature of corn increased the ADWG, while in the starter phase only the CT(75) caused a lower FCR (p < 0.05). Broilers fed PS(F) corn showed the lowest FCR during the finisher (25-42 days) period compared to those fed PS(C) (p < 0.05). Conditioning corn at 75 °C reduced FCR during the finisher (25-42 days) period compared to the birds fed CT(U) and CT(90) corn (p < 0.05). In whole experimental periods (1-42 days), PS(F) and CT(75) treatment increased the ADWG compared to the PS(C) and CT(U) (p < 0.05). The CT(75) treatment improved primary total anti-sheep red blood cell (SRBCs) titer (IgT) and IgM and secondary IgT and IgG responses compared to the other experimental groups (CT(U) and CT(90)) (p < 0.05). No significant PS × CT interaction was found on the Newcastle disease (ND) antibody titer of broiler chickens (p > 0.05). Feeding CT(75) corn reduced duodenum and jejunum relative lengths compared to the birds fed diets containing CT(U) corn. Significant PS × CT interactions (p < 0.05) were observed for villus height, villus height to crypt depth, crypt depth, muscle thickness, and absorption surface area of the jejunum. The highest carcass yield was observed in the PS(F)-CT(75) group (p < 0.05). In conclusion, the use of finely ground corn (PSF) conditioned at 75 °C (CT75) was beneficial to growth performance, development of the digestive tract, jejunum histomorphometry and the immune responses of broilers.