Abstract

Heat stress is one of the key factors affecting broiler production. This study aimed to investigate the protective effects and underlying mechanisms of chromium propionate (CrP) against heat stress in broilers. A total of 180 yellow-feathered broilers were randomly divided into 3 groups, with 6 replicates per group and 10 broilers per replicate. The CON and HS groups were fed with a basic diet, while the PAC group was supplemented with 0.2 mg/kg CrP. Following pre-feeding for 7 days, HS and PAC groups were exposed to cyclic HS (8 h at 30, 32, and 34 °C, respectively) for two weeks, while the control group was maintained at 26 ℃ ± 1 ℃. The experiment was designed in accordance with a randomized block design, and data were analyzed by one-way ANOVA. The results demonstrated that dietary supplementation with CrP eased heat stress–induced reductions in BW and ADG as well as increased the feed conversion ratio. Heat stress considerably decreased gut length and V/C across all intestinal segments. Moreover, CrP suppressed heat stress–induced increases in serum corticosterone and lipopolysaccharide levels while enhancing intestinal glutathione peroxidase activity. Gene expression analysis of jejunal mucosa revealed that CrP downregulated heat stress-induced upregulation of heat shock proteins and inflammation-related genes COX2 and NLRP3 while enhancing the expression of Mucin2, Occludin and ZO-1. Analysis of 16S rRNA sequencing revealed distinct differences in microbial composition and potential functional shifts among groups. At the genus level, heat stress decreased Alistipes relative abundance along with marked increases in Lactobacillus count; conversely, CrP reversed these trends. LEfSe identified Lactobacillus and Parabacteroides as the predominant bacteria in the HS group, while Gemmatimonas and Cetobacterium predominated the PAC group.