LAUSR

This study was conducted to assess the potential interactions of different levels of hydrolyzable tannin (HT) and organic acids (OA) on the selected ileal microbiota and histology, immunological responses, and growth performance of broiler chickens. A total of 1092 one-day-old female Ross 308 broiler chickens were randomly assigned to six experimental treatments with seven replicates of 26 chicks each. Treatments consisted of a 2 × 3 factorial arrangement, consisting of 0 and 1 g HT/kg of diet (0HT, and 1HT) and 0, 1, and 2 g OA/kg of diet (0OA, 1OA, and 2OA). Dietary administration of 1HT + 2OA led to a significant enhancement (P < 0.01) in average daily weight gain (ADWG) during the finisher phase (25–42 days), as well as a notable reduction (P < 0.01) in feed conversion ratio (FCR) during both the finisher phase and the overall trial period. This treatment resulted in a significant reduction (P < 0.01) in the relative weight of abdominal fat, while concurrently enhancing (P < 0.01) the partial weight of the bursa of Fabricius, the thickness of ileal lamina propria lymphoid follicles (LLF), the ratio of ileal villi length to crypt depth, and the apparent villus surface area. The main effects of feeding either 1HT or 2OA resulted in significantly lower pH levels in the ileum and gizzard (P < 0.01), as well as the highest relative weights of the spleen, bursa of Fabricius, and thymus (P < 0.05). Additionally, the dietary inclusion of these concentrations of HT or OA led to a reduction (P < 0.05) in the ileal population of E. coli, a decrease in the relative weights of the pancreas, liver, and abdominal fat, and an enhancement (P < 0.05) in selected hematological parameters, humoral immunity, the thickness of LLF, and FCR during the starter phase (1–10 days). The main effect of 2OA resulted in significantly elevated numbers of either Lactobacillus or LLF in the ileum (P < 0.05). In general, feeding 1HT + 2OA, without an adverse effect on the microbial population, manifested positive effects on the growth performance of broiler chickens via refinement of the ileal histology, the relative weight of bursa of Fabricius, and the ileal absorptive surface area.