LAUSR

ABSTRACT Three experiments were conducted to determine the effects of increased CO2 concentration during the first 3 d of incubation on albumen height and pH, embryonic mortality, and hatchability of broiler hatching eggs. Hatching eggs were obtained from commercial broiler breeder flocks of Ross 308 at 39 and 37 wk of age in Experiments 1 and 2, respectively. In Experiment 3, eggs were collected at 28 and 35 wk of age. Eggs were incubated under either standard conditions (Control‐CO2) for the entire incubation or increased CO2 concentrations during the first 3 d of incubation (High‐CO2) in 3 experiments. In Experiments 1 and 2, the CO2 concentration was gradually increased from the beginning of incubation onwards to reach 0.80% at 72 h by manual injection of CO2 into airtight laboratory incubators. In the control incubators, the CO2 concentration remained below 0.10% during the same period. Prior to setting, and at 3 d of incubation, the eggs were opened for albumen height and pH measurements in Experiments 1 and 2. In Experiment 3, the eggs were set in commercial incubators. During the first 3 d of incubation, the CO2 concentration was gradually increased to reach 0.70% at 72 h naturally (High‐CO2). In the Control‐CO2 incubator, the CO2 concentration remained below 0.10%. After 3 d, incubation was continued with the control incubator conditions for all eggs from both groups in the 3 experiments. The albumen height was not affected by CO2 treatment, but the treatment significantly decreased albumen pH at 3 d in Experiments 1 and 2 (P < 0.05). A greater CO2 concentration during early incubation reduced fertile hatchability due to increased early embryonic mortality by 2% in the 3 experiments (P ≤ 0.05). The differences in pH might provide one explanation why increased CO2 concentration during early incubation resulted in increased early embryonic mortality. These data indicated that at the beginning of the incubation, ventilation was necessary to prevent increases in CO2 concentration for optimum hatchability results.