Heritability of All-or-None Traits: Hatchability and Resistance to Death to Ten Weeks of Age

THE economic loss resulting from poor hatchability of eggs amounts to several million dollars annually in the United States. A much greater loss results from mortality. In broilers, the loss from mortality includes the cost of raising birds to the age of death plus the potential income that the producer would have received if the birds had lived to market age. The development of new drugs, vaccines, and better feeds have done much to decrease the death loss among domestic birds. Improved management practices, refrigeration and better incubators have improved the percentage hatch of fertile eggs. However, there is still a need to improve these conditions in commercial flocks. There is some evidence that both hatchability and viability are inherited; thus, some improvement can be made by selecting for these two characteristics in breeding programs. Present evidence indicates that the heritabilities of hatchability and viability are low; hence, the rate …