Timing associated with oviductal sperm storage and release after artificial insemination in domestic hens

Female birds store sperm in sperm storage tubules (SSTs) in the uterovaginal junction of their reproductive tract for days or weeks (depending on species) before fertilization. Sperm are transported from the SSTs to the infundibulum where fertilization occurs immediately after ovulation of each ovum. The timing of sperm release from the SSTs relative to ovulation is unknown for any bird. Here, we show that, after artificial insemination of domestic fowl Gallus domesticus, sperm are not accepted into any region of the oviduct before sexual maturity. Once hens reach maturity, there is a temporal shift in the distribution of sperm throughout the oviduct. Sperm are first accepted into and accumulate in the SSTs 6 to 8 days before ovulation but are at this point significantly less numerous in the infundibulum. From 1 to 6 days before ovulation, approximately 10-fold more sperm (235 × 103 sperm) populate the infundibulum than at 6 to 8 days before ovulation (26 × 103 sperm; P < 0.001). Our results suggest that the mechanisms underlying sperm acceptance and release in the oviduct are under fine temporal control, most likely mediated by female hormones.