Multiphasic analysis of embryonic mortality in chickens

Infertility and embryonic mortality are economically important for the commercial broiler industry because they are components of hatchability. Embryonic mortality in chickens is not uniformly distributed over the course of incubation; two phases of embryonic mortality are characteristic of chicken development. The objective of this paper was to develop a mathematical model to assess infertility and to characterize the distribution over time of embryonic mortality in chickens. A model was constructed based on evidence in the literature for multiple phases of embryonic mortality before and during incubation. A multiphasic model, with two phases, included parameters for the proportion of eggs that were infertile and the proportion that were fertile but the embryo died before or during incubation. For those eggs that were fertile but the embryo died, the model included the proportion of embryonic mortality during each phase, day of peak mortality, and duration of phase. Data on embryonic mortality for white Cornish chickens were used to illustrate the multiphasic model. Model parameters could be estimated easily and interpreted with clear biological meaning. Estimates of parameters, in general, were reasonably precise and consistent with the literature. With multiphasic analysis, one can assess infertility and characterize the distribution of embryonic mortality in chickens, which can lead to a useful understanding of management and genetic aspects of these components of hatchability.