Effects of cyclic heat stress on the phenotypic response, meat quality and muscle glycolysis of breasts and thighs of yellow-feather broilers

An experiment was conducted to evaluate the effects of cyclic heat stress on phenotypic response, meat quality and muscle glycolysis of broiler. One hundred and eighty 35-day-old male Xueshan broilers with similar BW were randomly selected and exposed to either thermal neutral (TN; 23 degrees C, 55-60% RH, n = 6) or heat stress conditions (CHS; cyclic temperatures of 35 degrees C from 10:00 to 18:00, 32 degrees C from 18:00 to 20:00, 28 degrees C from 20:00 to 08:00, and 32 degrees C from 08:00 to 10:00 at 40-45% RH, n = 6) for 7 days. Relative to broilers under thermoneutral conditions, broilers subjected to cyclic heat stress had an overall increase in rectal temperature and respiration rate (p < .001, p < .001, respectively), and a reduced body weight, average daily gain, average feed intake and feed conversion ratio (p = .001, p < .001, p < .001, p = .002, respectively). A higher L* value was obtained from both the breast and thigh muscle of broilers under high temperatures (p = .022 and p = .009, respectively). Furthermore, the thigh muscle of broilers exposed to high temperatures showed a higher hexokinase activity than that of broilers exposed to thermal neutral conditions (p = .014). The results indicate that cyclic heat stress significantly lowers Xueshan broiler production performance and meat quality but has no significant effect on the chemical composition and glycolytic process of the meat.