Published online by Cambridge University Press: 27 February 2018
Broiler breeders conduct their breeding programs only in optimal environments, claiming that because farmers are instructed to provide the broilers with optimal management, genotype by environment interactions (GxE) are not important for the broiler industry. However, with the rapid development of the poultry industry worldwide, high-performance broiler stocks are now being imported to developing countries where environmental control, mainly the mitigation of hot climates, is not feasible. Moreover, results from several studies suggest that due to the increase in genetic potential for rapid growth rate, resulting from successful breeding programs, broilers are becoming more sensitive to rather small environmental deviations from optimal conditions (Leenstra and Cahaner, 1991; Cahaner and Leenstra, 1992; Cahaner et al., 1993; Settar et al., 1999; Yunis et al, 1999). Hence, also in developed countries, many broilers will be, or are already being reared under suboptimal hot environments.