The Effect of Early Incubation Temperature and Late Incubation Conditions on Embryonic Development and Subsequent Broiler Performance.

Abstract

Six experiments were conducted to evaluate the effects of early and late incubation temperatures and hatching basket ventilation on embryonic development and early broiler performance. Eggs were exposed to a constant incubation air temperature of 37.6°C (99.7°F) from E 0-17 in Experiment 1 while Experiments 2-5 employed an incubation temperature profile that had an initial dry bulb set point of 38.1°C (100.5°F), which was gradually decreased to 37.2°C (99.0°F). Experiment 6 exposed eggs to either an Early Hot treatment (EH) that had a short initial air temperature of 38.9°C (102°F) followed by 38.1°C (100.5°F) to E 3 or an Early Cool treatment (EC) of 36.9°C (98.5°F) to E 3. Experiments 1-4 used an average air temperature of 38.1°C (100.5°F) during the late incubation period, while Experiments 5 and 6 added a late temperature treatment of approximately 35°C (95.0°F) (LC) in addition to 38.1°C (100.5°F; LH).

Hatching baskets were modified to create ventilation treatments in order to examine the effect of air flow path on embryonic development and used varyingly throughout Experiments 1-6. Two treatments were designed to restricted air flow through the hatching basket by blocking air flow through either the top half of the basket (TT) or the bottom half of the basket (BT). Other hatching baskets remained unaltered to serve as a control group (CN). Experiments 1-2 included all three types but just the TT and BT treatments were used in Experiment 3. Experiments 4-6 used the TT and CN treatments in addition to the baskets at either low density (LD) or high density (HD).

The TT treatment produced chicks with significantly less relative yolk sac in Experiment 1, but differences between ventilation treatments did not occur in other experiments. At E 15 of incubation, embryos from the EC treatment in Experiment 6 exhibited a decreased embryo weight and fluid (yolk and albumen) absorption. The LC treatment produced heavier BW and relative heart weight, as well as an increased relative yolk weight in Experiments 5 and 6. The LD treatment exhibited a lower egg temperature and greater relative weights of the heart, gizzard, and proventriculus at hatching in Experiment 4.

Experiments 3-5 also included a grow-out period to examine the effects of the incubation treatments on broiler performance as measured by feed intake (FI), body weight (BW), adjusted feed conversion (AdjFCR), and mortality. In Experiments 4 and 5, the CN treatment achieved a heavier BW than the TT treatment at 14 and 21 d of age, which coincided with a significant increase in FI, as well as an improved AdjFCR, in Experiment 4. The LD treatment exhibited a significantly increased FI, AdjFCR, and percentage mortality as compared to the HD treatment in Experiment 4, while a reduced overall mortality for the LD treatment was the only difference noted in Experiment 5. The eggs came from an older breeder flock (59-wk-old) in the case of Experiment 4 and a younger breeder flock (31-wk-old) in Experiment 5. It may be that the differences between eggs produced by different age flocks produced subtle differences during incubation that created different broilers during the grow-out period.