SEASONAL-VARIATIONS IN TESTICULAR MORPHOLOGY IN URUGUAYAN CORRIEDALE RAMS

The fine structure of the testes from young Corriedale rams raised und er extensive grazing conditions in Uruguay was studied in the four sea sons of a year and related to clinical, morphometric, seminal and endo crine parameters. Scrotal circumference varied significantly throughou t the year, with lowest values in winter. Spermatogenic activity was p resent throughout the year, with minor non-significant variations in s emen morphology. Structural variations could be seen in the seminifero us epithelium, particularly during winter, with the presence of affect ed Sertoli cells. This picture appeared similar during spring but norm al morphology was restored by summer. Similar temporal changes were al so detected in the Leydig cells, Plasma levels of testosterone were hi ghest in autumn, decreased significantly by winter and were low during spring and summer, Seminiferous tubule diameter was significantly cor related with scrotal circumference and with testosterone levels. It is concluded that testicular morphology and function in Corriedale rams under extensive rearing conditions on natural pasture in Uruguay are m ildly affected by the season of the year. Possible explanations are di scussed.