Potential daily sperm production, Sertoli cell number, and seminiferous tubule characteristics in beef bulls fed conventional or gossypol-enriched diets.

The objective of this study was to determine the amount of germ cell degeneration throughout spermatogenesis in the bull and to determine if gossypol-enriched diets enhance that degeneration. Twenty-six adult beef bulls in two different sets of treatment groups were chosen for the study. The first set of bulls were broken into three groups, receiving soybean meal (<0.03 g gossypol per bull, per day), cottonseed meal (1.8 g gossypol per bull, per day), or whole cottonseed (16 g gossypol per bull per day). The second set of bulls were fed 4 g of gossypol per day for 180 days and then were placed in their respective treatment groups of 0 g or 4 g of gossypol per day for 72 days to evaluate the effect of continued gossypol treatment versus stopping treatment. Hence, one group received gossypol for 180 days, followed by withdrawal for 72 days. The treated group received gossypol up to castration at 250 days. In both sets of bulls, significant germ cell degeneration occurred between B spermatogonia and primary spermatocytes (i.e., at the end of mitosis and into the beginning of meiosis), with no subsequent degeneration throughout the rest of spermatogenesis. For both sets of bulls, the gossypol-enriched diet fed had no effect on the nuclear volume or number per gram parenchyma of any germ cell or Sertoli cell. Therefore, gossypol did not augment the amount of germ cell degeneration that occurred between B spermatogonia and homogenate-resistant (mature) spermatids in either set of bulls. Gossypol-enriched diets also had no effect on volume density, diameter, luminal diameter, or basement membrane thickness of seminiferous tubules for the first set of bulls. The second set of bulls, with continued diets enriched with gossypol, had a larger number of B spermatogonia per gram than did bulls removed from the gossypol-enriched diet. In conclusion, the bull did experience significant degeneration of germ cells between B spermatogonia and pachytene primary spermatocytes, with no subsequent loss throughout the rest of spermatogenesis, and the gossypol-enriched diet did not further enhance germ cell degeneration.