Influence of egg shell embryonic incubation temperature and broiler breeder flock age on posthatch growth performance and carcass characteristics.

A study was conducted to examine the posthatch growth performance of high-yielding broilers when eggs were incubated at 3 different embryo temperatures from 2 flocks of breeders at different ages (different egg size). Two thousand, four hundred eggs from 2 broiler breeder flocks (29 and 57 wk of age) of the same high-yielding strain (Cobb x Cobb) were incubated in the same incubator for 16 d at 37.5 degrees C. Following candling, the eggs from the 2 flocks were transferred into 3 hatcher cabinets at starting temperatures of 36.5 degrees C (low, L), 37.6 degrees C (middle, M), and 38.7 degrees C (high, H) and adjusted to achieve a shell temperature of 37.5 degrees C (L), 38.6 degrees C (M), and 39.7 degrees C (H) using an infrared thermometer. All chicks were taken off at 21 d of incubation, randomized into floor pens, and reared for 44 d. Body weights, feed intake, and feed conversion were determined at 21, 35, and 44 d of age. Body weight of birds from the H treatment was significantly less at 21, 35, and 44 d compared with the M birds. Birds in the L group weighed significantly less at 35 and 44 d compared with the M birds. Progeny from the older breeder flock had significantly greater BW at 1, 21, and 35 d of age, but had only numerically greater BW at 44 d when compared with birds from the younger flock. Feed conversion for the H birds was significantly higher from 0 to 21 d of age compared with the M and L birds. Broilers from the 29-wk-old breeder flock had lower cumulative feed conversion values than the birds from the 57-wk-old flock. No significant differences in mortality were observed. Posthatch performance appears to be affected by hatcher environment as determined by embryo shell temperature.