Influence of nutrition on seasonal variations in testicular morphology and function in corriedale rams

Abstract

To test the hypothesis that seasonal variations in testicular morphology and function differ in Corriedale rams subject to different feeding levels, 24 spring-born Corriedale rams, aged 14-15 months at the beginning of the trial and raised under extensive grazing conditions in Uruguay, were allotted at random to two groups: Group H, that grazed on improved (sown) pastures, and Group L, the control, that grazed on natural pastures (range). Clinical data (live weight, scrotal circumference), semen, blood and tissue samples (testis, epididymis and seminal vesicle) were collected during each of four seasons (for one month/season) of the year. According to data measured, testicular form and function had its peak in autumn followed by a decline in winter and a subsequent recovery in spring and summer. Live weight loss during winter was significantly decreased in Group L but not in Group H. Scrotal circumference, seminiferous tubules diameter and seminal vesicle epithelial height decreased significantly during winter in both groups. Group H scrotal circumference returned earlier (spring) than Group L (summer) to autumn values. By summer, seminiferous tubules and seminal vesicle epithelial height had returned to autumn values in Group H, but not in Group L. Decrements of scrotal circumference in winter and spring were milder in Group H than in Group L animals. Group H testosterone values in autumn were higher than those from Group L in spring. In summary: 1) differences existed in seasonal variations in testicular morphology and function between Corriedale rams subjected to different feeding levels and, 2) the findings suggest that nutritional factors contributed, at least partly, to the differences in variations observed throughout the experiment.