The objective of this study was to evaluate the effect of the season of the year on the spermprogressive motility (PM), vigor, volume of semen and sperm concentration of rams from the Bergamacia, Corriedale and Hampshire Down (Hd) breeds, with three-four years of age, from March/96 to March/97. Twenty-four rams nine Bergamacia (Be), eight Corriedale (Co) and seven Hampshire Down (Hd) were used. The semen collection and the climatic variables: wind speed (ws), air temperature (Ta), globe temperature (GT) and air relative humidity (RH) were taken monthly. For PM, the Be and Co breeds showed higher values during the summer, decreasing in the autumn and in the winter and increase again in the spring. The Hd breed presented higher values during the summer, decreasing in other seasons. For spermatic vigor, Be and Co breeds showed higher values during the summer, decreased in the autumn and in the winter, and increased again in spring. There was no effect of season on the spermatic vigor of Hd breed. For semen volume, Co and Hd showed higher values during summer, falling in autumn and in winter, and rising in spring. The spermatic concentration was not affected by the season, maintaining constant for the three studied breeds. The ws was the climatic variable that showed the highest influence on semen characteristics, followed by Ta, GT and RH. The Be and Hd breeds showed better results than Co breed for the semen characteristics, resisting better to the environment.
ram; season; semen
