Intratesticular retention of sperm and premature decline in fertility in the domestic rooster, Gallus domesticus

In domestic roosters, which were originally seasonal breeders and that are now kept under unnatural and unchanging conditions throughout the year, fertility peaks at 32 weeks of age (96%) but it subsequently declines rapidly to only 5% at 110 weeks despite the fact that roosters can live for about 10 years. Roosters exhibiting this low‐fertility syndrome have reduced levels of spermatozoa in the ejaculate. Concomitantly, however, superabundant but apparently normal spermatozoa are found attached to Sertoli cells and, in addition, the seminiferous epithelium fails to show evidence of the regression or atrophy that characterizes both aging non‐seasonal breeders and true seasonal breeders during non‐reproductive periods. This syndrome of premature low fertility appears to stem from impaired spermiation with resultant retention of spermatozoa by Sertoli cells. To examine this problem, we compared intratesticular incorporation of 3H‐thymidine between high‐fertility (32‐week‐old) and low‐fertility (82‐week‐old) roosters. Radioactivity associated with spermatozoa, 33 days post‐injection, was almost 50% higher in the low‐fertility roosters than in the high‐fertility ones. By contrast, both groups showed similar characteristics with respect to a) intratesticular incorporation of 3H‐thymidine, b) dynamics of spermatogenesis, c) intratesticular level of radioactivity just before the initiation of spermiation, and d) the duration of both spermatogenesis and the time required for sperm to pass through the genital tract. Our results confirm that intratesticular retention of sperm occurs in roosters with premature low‐fertility syndrome and suggest new possibilities for the study of the complex relationship between Sertoli cells and spermatozoa and the effects of this relationship on fertility. © 1995 Wiley‐Liss, Inc.