Effects of Environment, Feed Form, and Caloric Density on Energy Partitioning, Subsequent Performance and immune response

Past literature lacks studies that compare diets containing an improved feed form vs. an increased energy. The objective of the study was to assess the effect of variations of feed form and dietary caloric density on broilers reared on clean shavings and built-up litter. Treatments were arranged in a 2 × 2 factorial randomized block design within a split plot. Whole plot treatments considered one room (11 × 7.32 m) of either clean shavings or built-up litter; divided into 16 treatment replications of either standard (30%) or improved (80% feed form), and 16 replications of either commercial or increased (+110 kcal/kg) dietary caloric density comprising the 2 × 2 factorial arrangement. Broilers consuming an improved feed form demonstrated an improved feed intake, live weight gain, feed conversion ratio, breast weight and breast yield (P < 0.05). Providing an improved feed form demonstrated an upregulation in IgG (P < 0.05). An environment × energy interaction (P < 0.05) demonstrated upregulation of IgG in broilers fed a commercial energy reared in a built-up litter environment, whereas broilers maintained a similar regulation of IgG when fed an increased energy regardless of environment. Linear contrasts demonstrated that broilers provided improved feed form at commercial energy increased feed intake and live weight gain (P ≤ 0.05), while maintaining feed conversion ratio (P > 0.05) compared to broilers provided standard feed form at increased energy regardless of environment. These data suggest feed form improvements may partition energy towards growth more than feeding an increased energy diet.