Fertility in poultry is generally measured as the “percentage fertile eggs” laid by hens during a period of time following artificial insemination or natural mating. This parameter has presented some problems for the statistical analysis of fertility and its main limitations derive from the binary classification of an egg as fertile or infertile. An alternative measurements of breeding efficiency is the number of soermatozoa that associate with eggs at fertilisation. These can be estimated in laid eggs and present a robust and fundamental measurement of the efficiency of sperm transfer into hens. In several applications they have revealed differences in the efficiency of mating or artificial insenination that were not discernible by traditional estimations of fertility.
