Higher levels of CO₂ during late incubation alter the hatch time of chicken embryos

Abstract

1. It has been reported that the increasing CO₂ tension triggers the embryo to pip the air cell and emerge from the egg. However, the mechanism by which higher CO₂ concentrations during the last few days of incubation affect chick physiology and the hatching process is unclear. This study investigated the effect of CO₂ concentrations up to 1% during pipping, on the onset and length of the hatch window (HW) and chick quality.

2. Four batches of Ross 308 broiler eggs (600 eggs per batch) were incubated in two small-scale custom-built incubators (Petersime NV). During the final 3 d of incubation, control eggs were exposed to a lower CO₂ concentration (0.3%), while the test eggs experienced a higher CO₂ concentration programme (peak of 1%).

3. There were no significant differences in blood values, organ weight and body weight. There was also no difference in hatchability between control and test groups. However, a small increase in the chick weight and the percentage of first class chicks was found in the test groups. Furthermore, plasma corticosterone profiles during hatching were altered in embryos exposed to higher CO_2; however, they dropped to normal levels at d 21 of incubation. Importantly, the hatching process was delayed and synchronised in the test group, resulting in a narrowed HW which was 2.7 h shorter and 5.3 h later than the control group.

4. These results showed that exposing chicks to 1% CO₂ concentration during pipping did not have negative impacts on physiological status of newly hatched chicks. In addition, it may have a significant impact on the physiological mechanisms controlling hatching and have benefits for the health and welfare of chickens by reducing the waiting time after hatching.

ACKNOWLEDGEMENT

We are grateful to Dr Yumei Chang for statistical advice and the support of Biological Services Unit at the Royal Veterinary College.

Additional information

Funding

This research is a part of the BioBusiness Project [FP7-PEOPLE-ITN-2008] which is supported by the EU Commission and Marie Curie Initial Training Network.