Effects of testosterone injection on the semen quality in boars during high ambient temperature

Abstract

Attempts were made to inhibit the reduction in semen quality and reproductive performance by injecting testosterone into boars during the hot summer months. Testosterone enanthate (250 or 500 mg per boar) was injected into the rump muscle of boars once a month from June to September. The most remarkable effects were obtained in the incidence of abnormal spermatozoa. In the control group (no injection), the percentages of abnormal spermatozoa i.e. those with proximal cytoplasmic droplets, abnormal heads and coiled and bent tails increased to 34.3 ± 3.6% in September. In contrast, the percentages of abnormal spermatozoa in the testosterone-injected groups remained unchanged at 9.7% (250 mg per boar) and 12.9% (500 mg per boar) during this period. Furthermore, in the testosterone-injected groups, litter sizes at birth, of gilts naturally mated in August and September, were significantly higher than those of the control group. However, a decrease in the total spermatozoa per ejaculate was observed during and after treatment with a high concentration of testosterone (500 mg per boar). These results suggest that injecting suitable concentrations of testosterone into boars during the hot summer months would be effective for the maintenance of their reproductive performance.