Effect of probiotic supplementation on the expression of tight junction proteins, innate immunity‐associated genes, and microbiota composition of broilers subjected to cyclic heat stress

Abstract This study investigated the effects of probiotic on intestinal innate immunity‐associated gene expression and cecal microbiota in heat‐stressed broilers. A total of 180 21‐day‐old male broilers were randomly assigned to three treatment groups with four replicates per group. The thermoneutral group (TN) (23 ± 1°C) received a basal diet, and another two heat‐stressed groups (28–35–28°C for 12 h daily) were fed the basal diet (HS) or the basal diet supplemented with probiotic at a dose of 1.5 × 10 8 CFU/kg (HS_Pro) for 21 consecutive days. Compared with the TN group, the abundance of beneficial bacteria was decreased ( p < 0.05) in the caecum of heat‐stressed broilers. Heat stress downregulated ( p < 0.05) the expression of Toll‐like receptor (TLR)2 and upregulated ( p < 0.05) the expressions of TLR5, TLR15, avian β‐defensin (AvBD)4, AvBD8, and AvBD14 in the ileum as compared with the TN group. Dietary supplementation of probiotic upregulated ( p < 0.05) the occludin expression in the ileum, improved the microbiota balance in the caecum, and decreased ( p < 0.05) the gene expressions of TLR5 and TLR15 in the ileum of heat‐stressed broilers. Collectively, dietary probiotic supplementation could promote intestinal barrier function via improving gut microbiota community and regulating innate immunity‐associated gene expressions in heat‐stressed broilers.