The Interactive Impacts of Corn Particle Size and Conditioning Temperature on Performance, Carcass Traits, and Intestinal Morphology of Broiler Chickens

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 (CT₇₅) and 90 °C (CT₉₀)]. 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 (<i>p</i> < 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 CT₇₅ caused a lower FCR (<i>p</i> < 0.05). Broilers fed PS_F corn showed the lowest FCR during the finisher (25–42 days) period compared to those fed PS_C (<i>p</i> < 0.05). Conditioning corn at 75 °C reduced FCR during the finisher (25–42 days) period compared to the birds fed CT_U and CT₉₀ corn (<i>p</i> < 0.05). In whole experimental periods (1–42 days), PS_F and CT₇₅ treatment increased the ADWG compared to the PS_C and CT_U (<i>p</i> < 0.05). The CT₇₅ 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 CT₉₀) (<i>p</i> < 0.05). No significant PS × CT interaction was found on the Newcastle disease (ND) antibody titer of broiler chickens (<i>p</i> > 0.05). Feeding CT₇₅ corn reduced duodenum and jejunum relative lengths compared to the birds fed diets containing CT_U corn. Significant PS × CT interactions (<i>p</i> < 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-CT₇₅ group (<i>p</i> < 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.