Spermatogenesis ‐ A Clinical Approach

Abstract

A well functional spermatogenesis is essential for fertilizing capacity, i.e sperm production must be satisfactory and the spermatozoa produced must have a good quality.Sperm morphology and fertility Evidence of a relationship between sperm morphology and fertility in bulls was desribed by Lagerlof, as early as in 1934. Based on the findings, he stated that the incidence of sperm abnormalities in semen was correlated to the histopathological changes found in the testes in bulls with low fertility .Several studies on fertility in domestic animals have shown that when the proportion of abnormal spermatozoa in the ejaculate increases beyond physiological limits, a decrease in fertility can be expected (Bielanski, 195 1 ; Rao, 197 1 ;Malmgren and Larsson, 1984; Chevalier-Clement et al. 1991). Soderquist and coworkers (1991) found a negative correlation beween abnormal spermatozoa assessed in fresh semen and fertility (56-day NR rate) in frozen semen, even if none of the sperm morphology categories exceeded 4%. They suggested that a correlation between sperm morphology and fertility would most likely not have been detected if the bulls had been used for natural service, as the incidence of abnormal spermatozoa was probably mainly an indication of other associated and more deliterious changes in sperm viability. In general, the results from studies trying to relate sperm morphology to fertility are conflicting, due to influence from other factors, such as difference in the number of females mated and management. Low fertility after use of semen of poor quality raises the questions whether males with a large number of of abnormal spermatozoa in their ejaculates have lowered fertility because the spermatozoa are unable to penetrate the eggs, or because the spermatozoa do not reach the site of fertilization in adequate numbers. Malmgren and Larsson (1984) inseminated gilts with semen of good and poor quality and compared the number of fertilized ova. The small number of spermatozoa attached to the zona pellucida of ova from the gilts inseminated with poor semen indicated that the concentration of fertile spermatozoa in the oviducts was low. Further, Larsson (1988; heifer) suggested that abnormal spermatozoa are unable to reach the site of fertilization in adequate numbers, caused by a slection mechanism in the UTJ (utero-tubaljunction). Sacke and coworkers (1 988) found that the proportion of spermatozoa with normal head morphology attached to the ova, was higher than for spematozoa in the inseminate. It seems as sperm motility also is of great importance in order for the spermatozoa to reach the ova. Only a small number of spermatozoa were recovered from the UTJ and the oviducts in heifers inseminated with immotile spermatozoa (Larsson,