Dietary Betaine Reduces the Negative Effects of Cyclic Heat Exposure on Growth Performance, Blood Gas Status and Meat Quality in Broiler Chickens

Abstract

Heat stress (HS) impairs growth performance and has a severe impact on lipid and protein metabolism, leading to serious adverse effects on meat quality. Forty-eight day-old-male Ross-308 chicks were assigned to two temperature conditions, thermoneutral or cyclical HS, and fed with either a control diet (CON) or the CON plus betaine (BET). Heat stress increased rectal temperature (p < 0.001), respiration rate (p < 0.001) and increased blood pH (p = 0.017), indicating that HS caused respiratory alkalosis. Heat stress reduced body weight during the final stage of growing period (p = 0.005), while BET improved it (p = 0.023). Heat stress tended to reduce breast muscle water content and drip loss (p = 0.089 and p = 0.082), while both were improved with BET (p = 0.008 and p = 0.001). Heat stress tended to reduce the myofibril fragmentation index (p = 0.081) whereas it increased with BET (p = 0.017). Heat stress increased thiobarbituric acid reactive substances (p = 0.017), while BET improved it (p = 0.008). Meat tenderness was not affected by HS, but was improved with BET (p < 0.001). In conclusion, BET improved growth performance over the latter stages of the growing period, and improved product quality of broiler chickens when chickens exposed to HS.