Sperm-egg interaction and fertility of Japanese breeder quails from 10 to 61 weeks.

The influence of the age of Japanese breeder quails was studied by the analysis of fertility and sperm-egg interactions on the perivitelline layer of fertile eggs along the reproductive lifetime. Thus, 10 quail couples were observed every 30 d from 70 to 430 d. In each analyzed period, the males remained with the females for 24 h, and the oviposited eggs were analyzed up to the laying of 3 consecutive infertile eggs. The eggs were examined, and their fertility and the number of sperm (sptz)adhering to the outer perivitelline layer over the germinal disc were determined and expressed as sptz/mm(2). The age of the males had no effect (P > 0.05) on the maintenance of fertility after mating and on the number of sperm in the fertile eggs. The age of the females influenced (P < 0.05) the sptz/mm(2), which decreased 8 d after copulation. The probability of the eggs being fertile diminished with the age of the females combined with the time after copulation, and this probability became lower than 20% after 9 d. The number of sperm trapped in the perivitelline layer overlaying the germinal disc was reduced as a function of the age of the females and the time after copulation. From 3 sptz/mm(2) and on, the quails presented a 95% probability of having their eggs fertilized in females up to 55 wk of age. For breeder Japanese quails, the age of the females represents an important factor for fertility maintenance.