Resveratrol relieves chronic heat stress-induced liver oxidative damage in broilers by activating the Nrf2-Keap1 signaling pathway

Heat stress (HS) affects poultry production and welfare, causing enormous damage to poultry. Resveratrol, an antioxidant and anti-inflammatory natural plant polyphenol, is widely used in agriculture for the prevention of oxidative stress-related diseases. This study aimed to explore the effects and potential mechanism of resveratrol on liver oxidative damage in heat-stressed broilers. Sixty SPF chickens were randomly divided into control, heat stress (HS) and HS+ resveratrol (resveratrol) groups. Broilers were exposed to 35 +/- 2 degrees C (8 h/d) for 7 consec-utive days to induce HS, and the other 16 h/d were kept at 23 +/- 2 degrees C, similar to the control group. Broilers received 400 mg/kg resveratrol in the basic diet 2 days before exposure to HS and for the following 7 days. The results showed that resveratrol improved growth performance by increasing the average daily gain (ADG) and reducing the feed conversion ratio (FCR), compared with the HS group. Heat stress reduced liver weight and index, increased inflammatory cell infiltration in the liver, enhanced serum AST levels, and decreased TP and ALB II levels, which resulted in liver injury in broilers, and resveratrol effectively alleviated liver injury. Moreover, supplementation with resveratrol enhanced the activities of liver antioxidant enzymes resulting in higher GPX and SOD levels than those in the heat-stressed broilers, and decreased MDA levels. Furthermore, resveratrol alleviated liver oxidative stress by activating the gene and protein levels of Nrf2 and HO-1, enhancing NQO1 and SOD1 gene levels, and decreasing protein levels of HSP70, p62, and Keap1, and thereby alleviated the liver injury of heat-stressed broilers. Compared with the HS group, Nrf2 immunofluorescence was significantly up-regulated in the livers of resveratrol group. These results suggest that resveratrol can enhance the liver antioxidant function by activating the Nrf2-Keap1 signaling pathway to promote growth performance in broilers under HS.