Embryonic development in birds has been assumed to be totally dependent on egg composition, which is in turn determined by the female (hen). However, recent research of the Adaptation Physiology group of Wageningen University in collaboration with Hendrix Genetics has demonstrated that the male (rooster) also plays a role in egg composition and embryonic development. Additionally, embryonic development is affected by the temperature during the incubation process. Consequently, for optimal embryo development, not only the mother and the incubation temperature should be considered, but also the father from which the embryo originates.
During the research on laying hens, eggs originating from the same dam line, but from two different sire lines, were incubated and egg composition and embryonic development were investigated. Eggs of the same egg size tended to differ in yolk size between the two sire lines, which suggest that the male appears to influence yolk production by the female. This might be related to the sexual attractiveness of the male, as demonstrated in more dominant behaviour. During incubation, the embryonic heat production was determined by measuring oxygen consumption and carbon dioxide production. Embryos in eggs with the larger yolk produced more heat, which might suggest that these embryo are developing faster. Chicken quality at the moment of hatching was also affected by the father line.
The research revealed that embryonic development and chicken quality at hatching is also affected by the temperature during incubation. For broiler-type chickens this has been demonstrated frequently, but the current research demonstrates that this also holds for layer-type chickens. A higher incubation temperature between day 14.5 of incubation and hatching increased the embryonic metabolism and resulted in a poorer chicken quality at hatching. This was reflected in lower utilization of the yolk, smaller heart sizes and smaller intestine sizes.
This research will be published in an upcoming issue of Poultry Science and is now available online: