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 measurement of breeding efficiency is
the number of spermatozoa 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 insemination that
were not discernible by traditional estimations of fertility.