Effect of ivermectin on the reproductive potential of breeding rams

Ivermectin was administered orally 6 times at 21d intervals at 400 micrograms/kg (double the recommended dosage) to 10 Merino rams. Ten other rams served as untreated controls. Semen samples were collected serially before and after each treatment, and evaluated for volume, density, colour, motility, pH, percentage live sperm and sperm morphology. One testis was removed from each ram 9d after the last treatment, and histological examinations were performed on testicular sections. The semen of the 2 groups was similar before the first and after the last treatments. The seminal pH of treated rams was lower during the periods following the first 5 treatments. The volume of ejaculates of treated rams was generally higher during the periods following the first 5 treatments, but not consistently so. No histological differences were observed in the testicular tissue of treated and control animals 9 days after the sixth treatment. It was concluded that repeated treatment with ivermectin at the recommended dosage of 200 micrograms/kg will not impair the reproductive potential of rams.