Broiler growth and efficiency in response to relaxed maternal feed restriction

Broiler growth performance can be influenced by maternal BW, maternal age, and sex. The present study evaluated broiler growth and efficiency in response to increased maternal BW (relaxed level of maternal feed restriction). It was hypothesized that BW and fatness would increase, and efficiency would be reduced as maternal BW increased. Ten BW trajectories were applied to precision-fed Ross 708 female broiler breeders (n = 30) from 2 to 42 wk of age. Trajectories varied in prepubertal and pubertal growth phases from 2.5 to 22.5% above the recommended BW target. Additional unrestricted breeders (n = 6) were not limited to a maximum BW (fed ad libitum). Two 35 d experiments were conducted with precision-fed broilers from these breeders at 35 and 42 wk of age. Two analyses (full and restricted analysis scopes) were performed to evaluate broiler BW, feed conversion ratio (FCR) and carcass traits with maternal BW at photostimulation (22 wk of age) as a continuous effect, and maternal age and sex as discrete effects. The full scope included broilers from all hens (feed restricted and unrestricted). The restricted scope excluded broilers from unrestricted hens. Differences were reported at P ≤ 0.05. For every kilogram increase in maternal BW, cumulative FCR increased by 0.235 and 0.471 g:g for broilers from all and feed restricted hens, respectively. Proportional gut weight of broilers from feed restricted hens decreased by 0.8244% per kilogram increase in maternal BW. Males were heavier than females on day 28 and 35, and broilers from 42-wk-old breeders were heavier than broilers from 35-wk-old breeders on day 0 and 35. Males from all hens were more feed efficient (1.318 g:g) than females (1.335 g:g) from day 29 to 35. Females from all and feed restricted hens had a greater proportional fat pad and breast muscle weight than males, and proportional breast muscle yield of broilers from 42-wk-old breeders was on average 1.04 times greater than that of broilers from 35-wk-old breeders. Maternal BW did not affect offspring BW, reduced cumulative FCR, and reduced gut weight in the restricted analysis scope.