More than 50 sperm may penetrate the outer layer of the ovum, but only one unites with the female pronucleus to form the zygote. Even though only one sperm is needed to fertilize the ovum, research has shown that when sperm penetration average is less than 30 in a breeder flock, poor fertility will be associated with that flock. Flocks with good fertility average well above 50 sperm penetrations per ovum. Normally, maximum fertility from a flock of hens will not occur until at least the second day post mating. Viability of newly produced sperm.
Fresh sperm have a fertilization advantage.
Because of their greater viability and the fact that the sperm from the most recent insemination are stored on top of older sperm in the storage ducts they have a greater chance of reaching the ova. If roosters are removed from the flock and replaced with new males on the same day, after three days practically all offspring will be sired by the new males. Fertility after removal of males from flock. Fertile eggs can be produced for up to 4 weeks after removal of males, but the number of sperm is reduced resulting in lower fertility and hatchability. With continued advancements in this area, storage of semen for later use, as in the case with mammals, could become practical in the future.