Quercetin alleviates thiram induced tibial dyschondroplasia in broiler chicken through modulating oxidative stress and cecal microbiota.

Tibial dyschondroplasia (TD) is characterized by unmineralized cartilage plugs in the proximal tibial growth plate and is clinically associated with lameness and impaired growth performance in broilers. This study investigated the protective effects of quercetin, a natural flavonoid compound, against thiram-induced TD in broilers. A total of 180 one-day-old broilers were randomly assigned to a control group, a TD group, and a quercetin (QUE) group. TD was induced in the TD and QUE groups by feeding a diet containing 100 mg/kg thiram from days 4 to 7. The QUE group additionally received 600 mg/kg quercetin from the end of the adaptation period until the end of the trial. Growth performance, clinical signs, oxidative stress parameters, growth plate vascularization, cartilage-related gene expression, and gut microbiota composition were evaluated. Compared with the control group, the TD group showed significant lameness, reduced growth performance, decreased serum ALP activity, T-AOC, and SOD levels, increased MDA levels, and reduced vascularization in the growth plate. qRT-PCR analysis demonstrated that the expression of antioxidant- and cartilage-related genes, including Nrf2, HO-1, Col2a1, and ACAN, was downregulated in the TD group, whereas quercetin supplementation upregulated the expression of these genes. Gut microbiota analysis further showed an increased relative abundance of Firmicutes and a decreased abundance of Proteobacteria in TD birds. Quercetin supplementation attenuated these negative changes, modulated the composition of the gut microbiota, and increased the abundance of beneficial bacteria, thereby improving intestinal health via the gut-bone axis and exerting a positive effect on the growth plate. These findings indicate that quercetin alleviates thiram-induced TD in broilers, possibly by reducing oxidative stress, regulating cartilage-related gene expression, and improving gut microbiota homeostasis. Quercetin may therefore have potential as a feed additive for the prevention of TD, although the precise mechanisms require further investigation.