Characterization of gossypol-induced sperm abnormalities in bulls

To characterize sperm abnormalities induced by gossypol in cattle, young Br ahman bulls (n=8) received either cottonseed meal delivering 8.2 g free gos sypol/bull/d (treatment, n=4) or isonitrogenous soybean meal (control, n=4) for 11 wk. At slaughter, semen was collected from the following extragonad al sites: mediastinum/rete testis (Site 1), caput (Site 2), corpus (Site 3) and cauda epididymis (Site 4), and ductus deferens (Site 5). At least 200 fixed spermatozoa per site were examined via differential-interference-phas e contrast (DIC) microscopy, with electron microscopy (EM) being employed w ith select samples. Sperm midpiece abnormalities were categorized as aplast ic, fragile or asymmetric, with detached sperm heads being tabulated separa tely. Of these, aplastic defects were considered most likely to occur durin g spermatogenesis. Bull sperm midpiece lesions induced by gossypol were ult rastructurally similar to those observed in other, nonruminant, species. Co mbined midpiece abnormalities generally increased with extragonadal passage (EGP) in the treated bulls, as did fragile and asymmetric but not aplastic midpieces, or detached sperm heads. This pattern of EGP changes in bull sp erm morphology following gossypol spermatoxicity suggests that structural w eakness induced during spermatogenesis leads to secondary spermatozoal chan ges during EGP, possibly due to the imposition of motility stressors upon p rior weakened structures. (C) 2000 by Elsevier Science Inc.