Dietary Lonicerae flos extract ameliorates small intestine damage via activating the Nrf-2 signaling pathway and suppressing endoplasmic reticulum stress in heat stressed broilers

The objective of this study is investigating the effects of Lonicerae flos extract (LFE) on antioxidant status, intestinal development, and jejunum barrier function in heat-stressed broilers. Two hundred and forty male broilers (28-day-old) were assigned to normal control group (NOR, 22°C, basal diet), heat stress group (HS, 32°C, basal diet) and Lonicerae flos extract supplementation group (LFE, 32°C, basal diet with 400 mg/kg, 800 mg/kg, 1200 mg/kg LFE). Results indicated that Heat stress significantly impaired growth performance, increased serum aspartate aminotransferase (AST) and d-lactate levels, decreased jejunal mucosal total antioxidant capacity (T-AOC) and jejunal villus height (P < 0.05) throughout the entire experimental period. Although not statistically significant for growth performance, Lonicerae flos extract numerically reduced the feed-to-gain ratio by 8.5 % after 14 days. Lonicerae flos extract, particularly at 800 mg/kg, significantly mitigated the heat stress-induced elevation in serum AST and d-lactate levels and enhanced jejunal T-AOC and superoxide dismutase (SOD) activity and jejunal villus height (P < 0.05). Lonicerae flos extract activated Nrf-2 pathway, downregulated the mRNA expressions of endoplasmic reticulum stress (ERS) and apoptosis-related genes, and enhanced the mRNA expressions of tight junction proteins in jejunum mucosa of heat stressed-broilers. The 800 mg/kg dose was identified as the most effective. In conclusion, dietary LFE effectively improved intestinal integrity and antioxidant capacity in heat-stressed broiler through activating Nrf-2 pathway, alleviating ERS-dependent apoptosis and improving jejunum barrier function.