Leucine improves thiram-induced tibial dyschondroplasia and gut microbiota dysbiosis in broilers

Thiram, a commonly used agricultural insecticide and fungicide, has been found to cause tibial dyschondroplasia (TD) in broilers, leading to substantial economic losses in the poultry industry. In this study, we aimed to investigate the mechanism of action of leucine in mitigating thiram-induced TD and leucine effects on gut microbial diversity. Broiler chickens were randomly divided into five equal groups: control group (standard diet), thiram-induced group (thiram 80 mg/kg from day 3 to day 7), and different concentrations of leucine groups (0.3%, 0.6%, 0.9% leucine from day 8 to day 18). Performance indicator analysis and tibial parameter analysis showed that leucine positively affected thiram-induced TD broilers. Additionally, mRNA expressions and protein levels of HIF-1α/VEGFA and Ihh/PTHrP genes were determined via quantitative real-time polymerase chain reaction and western blot. The results showed that leucine recovered lameness disorder by downregulating the expression of HIF-1α, VEGFA, and PTHrP while upregulating the expression of Ihh. Moreover, the 16 S rRNA sequencing revealed that the leucine group demonstrated a decrease in the abundance of harmful bacteria compared to the TD group, with an enrichment of beneficial bacteria responsible for producing short-chain fatty acids, including Alistipes, Paludicola, CHKCI002, Lactobacillus, and Erysipelatoclostridium. In summary, the current study suggests that leucine could improve the symptoms of thiram-induced TD and maintain gut microbiota homeostasis.