Abstract
The development of a healthy gut during prestarter and starter phases is crucial to drive chicken's productivity. This study aimed to evaluate the effects of a thermomechanical, enzyme-facilitated, coprocessed yeast and soybean meal (pYSM) on growth performance, organ weights, leg health, and gut development in broiler chickens. A total of 576 as-hatched broiler chicks were randomly allotted to 3 dietary treatments (8 replicates/treatment, 24 chickens/replicate): a control group (C) without the pYSM, a treatment group 1 (T1), in which the pSYM was included at 20, 10, 5, 0, and 0% levels in the prestarter, starter, grower, finisher I, and finisher II feeding phases, respectively, and a treatment group 2 (T2), in which the pSYM was included at 5, 5, 5, 0, and 0% levels in each feeding phase. On d 3 and 10, 16 broilers/treatment were euthanized. The T1 broilers tended to show higher live weight (d 3 and 7) and average daily gain (prestarter and starter phases) than the other groups (P ≤ 0.10). Differently, pYSM-based diets did not influence the growth performance of the other feeding phases and the whole experimental period (P > 0.05). Relative weights of pancreas and liver were also unaffected by pYSM utilization (P > 0.05). Litter quality tended to have higher average scores in C group (P = 0.079), but no differences were observed for leg health (P > 0.05). Histomorphometry of gut, liver, and bursa of Fabricius was not affected by diet (P > 0.05). Gut immunity was driven to an anti-inflammatory pattern, with the reduction of IL-2, INF-γ, and TNF-α in the duodenum of treated birds (d 3, P < 0.05). Also, MUC-2 was greater in the duodenum of C and T2 group when compared to T1 (d 3, P = 0.016). Finally, T1-fed chickens displayed greater aminopeptidase activity in the duodenum (d 3 and 10, P < 0.05) and jejunum (d 3, P < 0.05). Feeding high levels of pYSM (10-20%) to broilers in the first 10 d tended to improve growth performance in the prestarter and starter phases. It also positively downregulated proinflammatory cytokines during the first 3 d, as well as stimulated the aminopeptidase activity in the prestarter and starter periods.