Quantitative estimation of spermatogenesis in bulls (Bos indicus) in a tropical environment of Nigeria.

Spermatogenesis in bulls (Bos indicus) indigenous to Nigeria, and the significance of Sertoli cell index (SCI) as a measure of testicular degeneration were studied. The mean testicular weights and dimensions were lower than reported for Bos taurus breeds. The diameters of the seminiferous tubules were lower than reported for Bos taurus, although within the same range. Inter-month and intra-month variations were highly significant (P less than 0.01). A mean annual spermatogenesis of 77.60% was reported. Active spermatogenesis was observed throughout the year, with a peak during the rainy season and extending toward the pre-dry season. This was consistent with previous reports. Severe testicular degeneration was found to influence spermatogenesis. This was reflected in the decrease in SCI. Mild degeneration had no significant effect on spermatogenesis, and did not significantly change the SCI. The SCI was defined as the ratio of the number of germinal cells to the number of Sertoli cells in the same cross sections of tubules.