The present experiment confirms the negative effect of high ambient temperature on growth performance.
Whatever the breed, our results show an improved tolerance to heat stress with duration of exposure, indicating an acclimation to heat. It is suggested that decrease in heat production might play a part in the observed acclimation. Finally, this study also demonstrates that physiological reactions during heat acclimation are affected by breed. However, further studies are needed to understand the mechanisms underlying the effect of breed on the onset of acclimation responses following an increase in ambient temperature.