Temperature and CO2 during the hatching phase. II. Effects on chicken embryo physiology

The objective of this study was to investigate the effect of eggshell temperature (EST) and carbon dioxide concentration during only the hatching phase on physiological characteristics of embryos and chicks. Three groups of eggs were incubated at an EST of 37.8 degrees C until d 19 of incubation (E19). From E19, embryos were incubated at a low (36.7 degrees C), normal (37.8 degrees C), or high (38.9 degrees C) EST and at a low (0.2%) or high (1.0%) CO2 concentration. For E19, internal pipping (IP), hatch, and 12 h after hatch, blood parameters were analyzed and hepatic glycogen was determined. At IP, hatch, and 12 h after hatch, interactions were found between EST and CO2, but all these interactions were temporary and in most cases weak. High EST resulted in a lower hepatic glycogen concentration compared with low (Delta = 21.1) and normal EST (Delta = 14.43) at IP, and a lower hepatic glycogen concentration compared with low EST (Delta = 6.24) at hatch. At hatch, high EST resulted in lower hematocrit value (Delta = 2.4) and higher potassium (Delta = 0.5) compared with low EST. At 12 h after hatch, high EST resulted in a higher lactate concentration compared with low (Delta = 0.77) and normal EST (Delta = 0.65). And high EST resulted in higher potassium compared with low (Delta = 0.4) and normal EST (Delta = 0.3). An effect of CO2 solely was only found at IP, at which high CO2 resulted in a lower pH (Delta = 0.03) and a lower hepatic glycogen concentration (Delta = 7.27) compared with low CO2. High EST during only the hatching phase affected embryo and chick physiology, indicated by the lower hepatic glycogen levels at IP and hatch. High CO2 affected pH and hepatic glycogen at IP. Effects of CO2 were only found at low EST, which emphasizes the large effect of EST during the hatching phase.