Modulation of the fertilizing ability of spermatozoa from roosters carrying the Sd (sperm degeneration) allele.

Roosters carrying the Sd (sperm degeneration) allele produce spermatozoa that die prematurely in vivo. Consequently, these mutants are subfertile. The objective of the present study was to determine whether or not subfertility could be modulated. A previous study found that the proximal efferent ducts of mutants were characterized by a reduced surface-to-volume ratio. We hypothesized that if subfertility was exacerbated by hemicastration of chicks, which increases daily sperm production in adults, then a relationship between efferent duct function and sperm longevity would be likely. In experiment 1, hemicastration of chicks exacerbated the subfertility of adults (p < 0.001). As inferred from SDS-PAGE in previous research, mutants lack at least one non-albumin seminal plasma protein. Therefore, it was hypothesized that protein supplementation would ameliorate subfertility. In experiment 2, fertility increased (p < 0.001) when spermatozoa from mutants were mixed with albumin-depleted seminal plasma protein from fertile roosters before insemination. In contrast, supplementation with BSA had no effect (p > 0.05). In summary, the subfertile status of Sd roosters was dynamic and appeared to depend upon the interaction of testicular output, efferent duct structure, and seminal plasma protein. Thus the study of this dysfunction may help to identify factors responsible for sperm maturation in the domestic fowl.