Effects of layer breeder age and reduced incubator oxygen concentrations on embryo development, hatching events, chick quality, embryonic mortality and hatchability of fertile eggs.

The combined effects of breeder age and oxygen (O) concentrations on embryo development, hatching events, chick quality, embryonic mortality and hatchability were investigated. A total of 900 hatching eggs of average weight of 53.85 ± 2.40 g and 60.42 ± 2.02 g from 33 to 50 wks ISA layer breeders were incubated for six days at 37.7 °C temperature and 56 % relative humidity before exposure to hypoxic stimulation of 15 % and 17 % O (experimental groups) and 21 % O (control group). In a 2 x 3 factorial experiment, air-N flushing to reduce O was 1 h daily from embryonic day (ED)7-9. The study investigated fresh egg weight before setting, egg weight loss and embryonic parameters at ED11, hatching events, chick quality, embryonic mortality and hatchability. Results showed that regardless of breeder age, early mild hypoxia reduces (P < 0.001) embryonic growth rate immediately after exposure and 50 wks breeders were more susceptible because of higher (P < 0.001) egg weight loss. There was an interaction effect (P < 0.05) on hatching durations, hatch time, hatch window, chick weight, yolk-free chick weight and pipping muscle. Results also showed a combined effect (P < 0.05) on high early and pipping embryonic mortality while causing a decrease in the hatch of fertile eggs. Early hypoxic stimulation decreased (P = 0.05) yolk sac weight at hatch due to the catch-up growth mechanism during embryogenesis. Conclusively, an early mild hypoxic stimulation can potentially improve chick quality in both young and old layer breeders if an optimal condition can be achieved.