Genotype by environment interactions using fast-growing, lean or fat broiler chickens, originating from The...

Male and female broiler chicks from five different broiler crosses (WI = Israeli chicks selected for body weight; LF and HF = Israeli chicks selected for low and high abdominal fat, respectively; FC = Dutch chicks selected for feed conversion; and WN = Dutch chicks selected for body weight) were raised under normal and subnormal temperatures. Weight gain, protein and fat content in the carcass, and feed and protein efficiency were determined at 4 and 6 wk of age, and at equal body weight. In addition to an overall effect of genotype, contrasts between Dutch (WN and FC) and Israeli (WI and LF) chicks and between chicks selected for body weight (WN and WI) or leanness (LF and FC) were examined. Temperature, genetic background, sex, and age affected all traits examined. Significant interactions were observed for weight gain, protein deposition, and feed and protein efficiency but were less evident for fat deposition. At low temperature, the broilers derived from Dutch strains had higher weight gain and protein deposition than those derived from Israeli strains; at the normal temperature the Israeli chicks performed better. The relations between body composition, weight gain, and efficiency are discussed to explain the interactions found.