Effects of Bile Acids on Growth Performance and Lipid Metabolism during Chronic Heat Stress in Broiler Chickens

SIMPLE SUMMARY: The negative impacts of heat stress (HS) on growth performance and lipid metabolism have been reported, but there are still no effective nutritional strategies to alleviate heat stress. Bile acids are new for their antioxidative properties and regulatory effect on lipid metabolism. This study was carried out to evaluate the growth performance and lipid metabolism in chickens under heat stress when fed with bile acid supplements in their diet. The results showed that mild heat stress (32 °C) induced hepatic lipogenic gene (hepatic SREBP-1c) expressions and lipid deposition, without obvious tissue damage in broilers. Dietary supplementation of bile acid could decrease hepatic lipid deposition without affecting endogenous bile acid biosynthesis. Therefore, bile acid supplements can benefit broiler chickens during high ambient temperatures, serving as a new nutritional strategy against heat stress. ABSTRACT: This study aimed to investigate whether dietary bile acid (BA) supplements can improve growth performance and lipid metabolism in heat-stressed broiler chickens. A total of 288 Arbor Acres broilers were blocked by BW and then randomly allocated into 4 treatments at 21 days of age. Birds reared under 32 °C had a higher cloacal temperature (p = 0.01), faster respiratory rate (p < 0.001), and a greatly reduced average daily feed intake (ADFI, p = 0.016), average daily gain (ADG, p = 0.006), final body weight (FBW, p = 0.008), and feed conversion rate (FCR, p = 0.004). In heat stress (HS) birds, the breast muscle rate (p = 0.006) and pH 24 h postmortem (p = 0.065) were lower, and the shear force was higher (p = 0.027). Dietary BA supplements tended to increase the breast muscle rate (p = 0.075) without affecting the growth performance and serum lipids (p > 0.05). Serum total bile acid (TBA) was roughly duplicated after BA supplements (p = 0.001). In the liver, total cholesterol was lower (p = 0.046), and triglycerides were higher (p = 0.04) in the HS birds, whereas the expression of SREBP-1c showed an increasing trend (p = 0.06). In contrast, dietary BA decreased triglycerides and the expressions of hepatic SREBP-1c and FAS in the liver (p < 0.05). In summary, mild HS causes hepatic lipid accumulation without obvious tissue damages, whereas BA has positive effects on relieving abnormal lipid metabolism, indicating that BA as a nutritional strategy has a certain potential in alleviating HS.