Interaction between ascites susceptibility and CO during the second half of incubation of two broiler lines. Effect on embryonic development and hatching process

1. Because CO2 during the second half of incubation is known to influence air cell and blood gases, and embryo development, it is postulated that post-hatch development and ascites sensitivity could also be influenced. 2. An ascites susceptible (A) and an ascites resistant (E) broiler line were incubated under standard incubation or high CO2 conditions (up to 4%) from embryonic day (ED) 10 onwards. The embryonic development and the hatching process of these two lines were compared when incubated under standard or high CO2 conditions from over the second half of incubation. 3. The A line, selected for high post-hatch growth rate, exhibited a higher relative embryo weight from ED10 until ED16, which was supported by a higher air cell pCO2, lower air cell pO2, higher corticosterone and thyroid hormones and earlier hatching time. 4. Incubation under high CO2 increased air cell pCO2, retarded yolk consumption, and decreased glycogen concentration in the liver at hatch. Hatchability decreased in both lines when incubated under high CO2, due to an increased late mortality of embryos that died before IP. 5. These results suggest that the development and metabolism of CO2-incubated embryos differ from control incubated embryos.status: publishe