Genotype-by-Environment Interaction with Broiler Genotypes Differing in Growth Rate. 4. Association Between Responses to Heat Stress and to Cold-Induced Ascites

ABSTRACT Males and females, selected from a com-mercial line to represent its phenotypic variation for BW, were mated with similarly ranked mates to produce sire families representing a wide genetic variation in potential growth rate (GR). Following 5 wk of rearing at normal ambient temperatures, birds representing all sire families were exposed to cold (Days 37 to 47, Trial 1) or hot (Days 43 to 48, Trial 2) environments. Birds exhibiting ascites syndrome (AS) in the cold environment (Trial 1) were counted, and the incidence of AS (%AS) per family was calculated. Sire families ’ least-square means of BW at 37 d of age in Trial 1 and BW at 43 d of age in Trial 2 represented the families ’ potential GR (i.e., GR under normal conditions). A significant positive correlation was found between potential GR and %AS (r = 0.479, Trial 1), indicating tha