Use of immunocontraception in the regulation of male goat sexual activity

Abstract

This study focused on continuous monitoring of the immunocontraceptive effect of Improvac® vaccine on the sexual activity of male goats determined by measuring plasma testosterone levels, testicular biometric and ejaculate examination. The animals in the experimental group (n=12) were administered two doses of 2 ml of Improvac® at a four-week interval; the animals in the control group (n=5) received 2 ml of saline. Blood collection, semen collection and testicular measurements were performed at 14-day intervals. A total of 8 samples were collected from each animal. In 9 animals a significant decrease (p<0.05) in testosterone concentration was observed two weeks after the first dose. At the end of the experiment (16 weeks), eight goats reached a testosterone concentration below the detection limit and one goat had a concentration of 0.47nmol/L. The testicular size was significantly (p<0.01) smaller four weeks after the first dose. At the end of the experiment, the testicular size was approximately three times smaller (p<0.001). Motility was 0% in two goats at the end of the experiment, 1% in one animal and 10% in one animal. The median sperm concentration was significantly lower (p<0.01) at the end of the study. A significant (p<0.0001) shift in the percentage of morphological changes was recorded eight weeks after the first administration. At the end of the study, there were five animals with azoospermia, two with 100% morphologically altered sperm, one with 99% and one with 96% morphologically altered sperm. In the three male goats, a significant skin reaction occurred after the first application, which resulted in an inadequate response to the treatment. Our results show that Improvac had a significant effect on the sexual function and sperm production in 9 out of 12 male goats.