Xinlei Wang, Peijie Du, Chong Xi, Yunhe Cao, Chunlin Wang
The study aimed to investigate the effects of Bacillus amyloliquefaciens TL106 (TL106) on growth performance, antioxidant capacity, immune function, and intestinal microbiota in Danzhou chickens. A total of 384 healthy female Danzhou chicks were randomly assigned to a control group (CON) and three experimental groups (Ba1, Ba2, Ba3), receiving basal diets supplemented with TL106 at 5 × 107, 5 × 108, and 5 × 109 CFU/kg, respectively, for 55 d (divided into early [1-35 d] and later [36-55 d] phases). While no significant growth improvement was observed in the early phase, average daily feed intake (ADFI) and final body weight (BW) increased, and the feed-to-gain ratio (F/G) was significantly reduced (p < 0.05) during the later phase in Ba2 and Ba3, especially in Ba3. At d 55, TL106 supplementation significantly elevated serum IgM content (p < 0.001) and total superoxide dismutase (T-SOD) activity (p < 0.05), reduced malondialdehyde (MDA) content (p < 0.01), and enhanced albumin (ALB) levels (p < 0.05). The Ba3 group also improved the villus height-to-crypt depth ratios (VH/CD) of the ileum and duodenum (p < 0.05). Microbial analysis indicated that abundances of Bacteroidota and Firmicutes increased while Proteobacteria and butyrate-producing Faecalibacterium were enriched in the TL106 groups compared to CON. Cecal butyrate concentrations rose dose-dependently (p < 0.05), with most of the key parameters-including final BW, ADFI, F/G, serum ALB, IgM, T-SOD, GSH-Px, MDA (d 55), duodenal and ileal VH/CD, and cecal butyric, propionic, and valeric acids-showing significant quadratic responses (p < 0.05). The results demonstrated that TL106 in diets enhanced growth performance and intestinal health in Danzhou chickens by modulating immunity, antioxidant responses, and microbiota, with 5.0 × 108 CFU/kg appearing to be the most effective dose among those tested under the conditions of this study.