Evaluation of sperm and hormonal assessments in Wagyu, Nellore, and Angus bulls.

Wagyu bulls are known to have a highly exacerbated libido, as shown by the intense sexual interest of young calves. Therefore we believe that Wagyu male animals have specialized Sertoli and Leydig cells that are directly involved with the sexual precocity in this breed as mature bulls have a small scrotal circumference. This study aimed to evaluate whether there were differences in the hormone and sperm characteristics of Wagyu bulls compared with the same characteristics of subspecies Bos indicus and Bos taurus sires. Frozen-thawed semen from Wagyu, Nellore, and Angus sires were analyzed for sperm kinetics (computer-assisted sperm analysis), plasma membrane integrity, chromatin integrity, acrosome status, mitochondrial activity, lipid peroxidation and hormone [luteinizing hormone (LH) and testosterone] serum concentration. The results showed that Wagyu had lower total motility and an increased number of sperm with no motility when compared with Nellore and Angus bulls. Wagyu breed did not differ from those breeds when considering plasma and acrosome membranes integrity, mitochondrial potential, chromatin resistance, sperm lipid peroxidation or hormone (LH and testosterone) concentrations. We concluded that Wagyu sires had lower total motility when compared with Nellore and Angus bulls. Wagyu breed did not differ from these breeds when considering plasma and acrosome membranes integrity, mitochondrial potential, chromatin resistance, sperm lipid peroxidation, or hormone (LH and testosterone) concentrations.

Endocrine regulation of the establishment of spermatogenesis in pigs.

Somatic and germ cell maturation precedes the start of spermatogenesis and is coordinated, so efficient spermatogenesis will occur in the adults. The present study was conducted to evaluate endocrine regulation of germ and somatic cell homeostasis in the neonatal boar testis associated with the establishment of spermatogenesis. Testis tissue obtained from 3-, 5-, 7- and 14-day-old piglets were ectopically xenografted onto castrated, immunodeficient nude mice. Grafts were removed 22 weeks later and evaluated for growth and the establishment of spermatogenesis. Recipient mouse testosterone biosynthesis and follicle-stimulating hormone (FSH) concentrations were also assayed. Testis tissue graft growth was significantly greater in testis grafts from 3-day donor tissue when compared to all other ages; 5-, 7- and 14-day-old donor tissue weights were not significantly different at removal. Follicle-stimulating hormone concentrations in recipient mice supporting testis grafts from 5-, 7- and 14-day-old donor tissues did not differ and were similar to normal physiological levels in age-matched, intact nude mice. Serum FSH levels were significantly lower in recipient mice supporting testis grafts from 3-day-old donor tissue. Radioimmunoassay and biological assay indicated no differences in testosterone production by testis tissue grafts of varying donor age. Porcine testis tissue obtained from 3-, 5-, 7- and 14-day-old neonatal boars were all capable of producing round and elongate spermatids after 22 weeks of grafting, but testis grafts from 14-day-old donors had a significantly greater (eightfold) percentage of seminiferous tubules with spermatids compared to all other donor ages (p < 0.05). Cryopreservation did not affect the ability of testis tissue grafts to grow, produce testosterone or establish spermatogenesis when compared to controls (p < 0.05). Collectively, these data demonstrate intrinsic differences in the biological activity of germ and somatic cell populations during neonatal boar testis development associated with the establishment of spermatogenesis.