Time of year and nutritional plan: its influence on the sperm morphology in grazing Corriedale rams

Abstract

The effect of month of semen collection and nutritional level on spermatic morphology of 20 Corriedale rams 18 months old, half of them grazing on native, and the other half grazing on improved pasture were studied. Nutritional levels determined differences in ram weight and scrotal circumference, but evolution of both variables was similar among the two groups. Nutritional levels affected only percentage of spermatozoa with abaxial mid-piece, whereas month of collection affected percentages of spermatozoa with acrosome damage, abnormal contour and variable size, abnormal and abaxial mid-piece, simple and double bent tails and distal droplet. Percentages of pearshaped, narrow at the base, normal and abnormal free heads, terminally coiled tail and proximal droplet spermatozoa were not affected by month of collection. Spermatic abnormalities increased during spring and reached higher levels in summer. Most frequently abnormalities observed were tail-related, distal droplet and head abnormalities, which together represented 75% of total abnormal spermatozoa found. Most frequent specific anomalies were distal droplet and simple bent tail; together these made up almost 50% of total observed anomalies