Reproductive physiology of the stallion. I. Spermatogenesis and testis composition.

The research explores the reproductive physiology of stallions, focusing on spermatogenesis and testis composition. The study determined the cycle of the seminiferous epithelium, the duration of spermatocytes, and provided critical information on testicular components.

Division of Seminiferous Epithelium Cycle

• The research divided the seminiferous epithelium cycle in a stallion’s testis into eight stages. The specific criteria for the division includes the presence of meiotic divisions, shapes of spermatid nuclei, and locations of spermatids with elongated nuclei in the tubule.
• The study provided the mean frequencies of each of these eight stages, indicating how often these stages occurred in the stallions’ reproductive system.

Duration of Spermatocytes and Spermatids

• The study determined the lifespan or active period of various cells involved in spermatogenesis. This period was calculated by injecting a dose of [3H]thymidine into the spermatic artery of the stallions, and then removing the testes at different intervals to measure the radioactivity.
• Primary spermatocytes had a lifespan of approximately 19 days, secondary spermatocytes had 0.7 days, spermatids with round nuclei had 8.7 days, and spermatids with elongated nuclei had 10.1 days. These figures help understand the time involved in the sperm production process.

Composition of the Testis

• The researchers presented a detailed composition of a stallion’s testicular components in terms of volumetric percentages.
• The study found that the seminiferous tubules, which carry sperm from the testicles to the urethra, made up about 61.3% of the testicular volume. Other components included spermatogonial nuclei, primary and secondary spermatocyte nuclei, Sertoli cell nuclei, tubular cytoplasm, and more.

Measurements of Seminiferous Tubules

• The research found that the diameters of the seminiferous tubules varied significantly among the stallions. However, the variation was not significant among different stages of the spermatogenesis process.
• The study provided the average length of the seminiferous tubules in each testis, which ranged from 1667 meters to 3726 meters. This measure gives valuable data about the reproductive capacity of stallions.