Seasonal variation in sexual behavior, plasma testosterone and semen characteristics of Argentine Pampinta and Corriedale rams.

Five Argentine Pampinta (dairy breed) and six Corriedale (dual-purpose breed) adult rams were used to study the effect of season on sexual behavior, plasma testosterone (T) and semen characteristics for a period of 1 year. Scrotal circumference (SC) and T concentrations were determined at 2-week intervals. Each ram was exposed monthly to three ovariectomized ewes in one 20-min test and the total number of mounts and successful matings were recorded. Semen collection was attempted from each ram twice weekly for six co nsecutive weeks during each season. In both breeds, SC varied seasonally showing the lowest mean values during winter and spring and in the Corriedale rams (32.8 ± 0.3 cm) was smaller ( p 0.05) was recorded in T concentration between breeds and both breeds reached a peak in summer and autumn. Number of matings showed the maximal values in autumn in both breeds. Season had no significant effect on mass motility, sperm concentration and percentage of live sperm. Semen volume, percentage of progressive motility and total sperm per ejaculate were higher during summer and autumn than in other seasons of the year. Pampinta rams had thehighest values ( p< 0.05) of sperm concentration, total sperm per ejaculate and percentage of abnormal sperm. Results of this study show that sexual behavior, SC and T concentrations exhibit seasonal variation in Pampinta and Corriedale rams and that semen of superior quantity and quality is especially collected in both breeds during the summer and autumn.