Figure 1.

Animal experimental procedure. Twenty-eight male chicks were randomly allocated to two treatments (n = 14 for each treatment group) in a completely randomized design at 14 days of age. The chicks of the 4-PBA group were switched to the diet containing 4-PBA and fed for 10 days. At 24 days of age, the chicks were separated into 4 groups such that the mean weights of the groups were the same. Then, HS groups were exposed to HS (36.0 ± 0.5 °C, relative humidity 50.0 ± 5.0%) for 2 h. TN: thermoneutral group; HS: heat-stressed group; RH: relative humidity.