Effect of selection for body weight on reproduction in broiler lines

This study was carried out to evaluate the response of selection for body weight on genetic gain for fertility (FERT) and hatchability (ECLO). Four experimental (LL, ZZ, PP and KK), two commercial (LC1 and LC2) and two control lines (LLc and PPc) were evaluated. The male lines (LP)-LL, ZZ and LC1 were selected for body weight (PC), and the female lines (LM)-PP, KK and LC2, were selected for PC and egg production for seven generations. The selection for fertility and hatchability was done through independent culling levels. The regression coefficients of the deviation between selected and control lines on the generation number for fertility were -1.01+/-0.34 (LL), -0.62+/-0.22 (ZZ), 0.58+/-0.21 (PP) and -0.50+/-0.11% (KK). For hatchability such coefficients were -0.37+/-0.16 (LL), 0.28+/-0.12 (ZZ), 0.79+/-0.27 (PP) and 1.70+/-0.45% (KK). These values indicated that, except for hatchability in LM, there were significant genetic changes for fertility and hatchability, and mainly reduction in fertility, in LP. The use of independent culling levels was not efficient to maintain high levels of fertility in LP. In general, the negative correlated response of selection for PC on fertility was greater in LP. The depressive effect on hatchability in LP was smaller than for fertility.