Evaluation of Gnrh Contraceptive Vaccine Using Domestic Swine as a Model for Feral Hogs

We determined the effect of a GnRH vaccine on reproductive function of sexually mature 5-month female and male domestic swine. The vaccine, GonaCon, developed at NWRC contains a GnRH peptide conjugated to KLH, combined with AdjuVac adjuvant also developed at NWRC. Four groups of ten females were given single IM immunizations either of 800μg GnRH vaccine, 1600μg GnRH vaccine, a prime and boost of 400μg GnRH vaccine and a sham dose adjuvant alone (control). At 8 months old, females were evaluated daily for estrus and bred by artificial insemination if in standing heat. Females not showing heat after 60 days were considered infertile. Farrowing data were collected for bred females ~115days later. All control gilts showed heat and became pregnant, whereas none given the dual 400μg dose showed heat or were bred. Of the 10 gilts receiving 800μg GnRH vaccine 3 were bred, but only 2 became pregnant. For gilts receiving 1600μg, 1 showed heat and became pregnant. Serum antibody titers were non-detectable in the control group, highest in gilts receiving 2×-400μg, followed by 1600μg and 800μg treatments. Titers were inversely correlated to suppression of estrus and fertility. Groups of five boars received either adjuvant only, 1×800μg or 1600μg, or 2×400μg GnRH vaccine IM. Blood and scrotal testicular measurements were taken initially and 4 and 16week post-treatment. Testicular size and serum testosterone decreased in all groups except controls and was inversely related to serum antibody titers. The authors conclude that; injectable GnRH vaccine is effective for contraception of swine.