Immunological castration of boars temporarily reduces testosterone concentration, testis size and function, without long term effects on libido and sperm quality

The objective was to determine the effects of immunocastration (Improvest) on reproductive characteristics in boars. Seventy-two boars were used in a randomized design with three treatments: single injection (SI) or double injection (DI) of Improvest, and intact controls (no Improvest; CNT) (n = 24/group). At wk 10, 15, 20, 25, and 40, blood was collected and serum harvested to evaluate testosterone concentrations via RIA. At wk 25, 18 pigs (n = 6/ group) were sacrificed and testes were removed, weighed, and measured. Libido was assessed at 32, 36, 47, 60, and 63+ wk of age (1 to 5; 1 = no libido; 5 = high libido) and semen collected beyond 60 wk of age. Testosterone concentrations were less for DI boars compared to CNT boars and SI boars at 20 and 25 wk of age (P < 0.001), but not different at 40 wk of age. All testicular measurements and weight were less for DI boars compared to SI and CNT boars (P < 0.001). There was no treatment effect on libido between 32 to 63+ wk of age. Semen volume, gel weight and total number of sperm cells were not different among treatments. Sperm concentration was greater for DI than SI (P = 0.011), and tended to be greater for DI compared to CNT (P = 0.102). Sperm motility tended to be greater for DI boars compared to CNT boars (P = 0.066). The results show that there are no permanent effects of immunocastration on reproductive characteristics in boars.