Vaccination of boars with a GnRH vaccine (Improvac) eliminates boar taint and increases growth performance

Peri- and postpubertal boars accumulate substances (e.g., androstenone and skatole) in their fatty tissue that are responsible for boar taint in pork. The objective of this study was to assess the efficacy of a GnRH vaccine, Improvac, in eliminating boar taint. Three hundred male (200 intact boars, 100 barrows) crossbred (Large White x Landrace) pigs were used in a 2 x 3 f actorially arranged experiment. The respective factors were sex group (barr ows, boars treated with placebo, or boars treated with Improvac) and slaugh ter age (23 or 26 wk). Vaccines were administered 8 and 4 wk before slaught er. All Improvac-treated pigs exhibited anti-GnRH titers. Testes and bulbo- urethral gland weights in treated pigs were reduced by approximately 50% (P < 0.001) and serum testosterone levels were below 2 ng/mL in the majority of treated boars (94 and 92% across both age groups at 2 and 4 wk, respecti vely). Boar taint, as assessed by the concentration of androstenone and ska tole in s.c. fat, was suppressed to low or undetectable levels in 100% of I mprovac-treated boars. No Improvac-treated pigs had significant concentrati ons of either androstenone (> 1.0 pg/g) or skatole (> 0.20 pg/g). In contra st, 49.5% of placebo-treated controls had significant androstenone and 10.8 % had significant skatole levels, resulting in 10% of the control boars wit h high concentrations of both compounds. The mean concentrations of taint c ompounds in the Improvac-treated pigs were not significantly different from those in barrows. Improvac-treated boars grew more rapidly (P = 0.051 and < 0.001 for pigs slaughtered at 23 and 26 wk of age, respectively) than con trol boars over the 4 wk after the secondary vaccination, possibly because of reduced sexual and aggressive activities. Compared with barrows, Improva c-treated boars were leaner and had superior feed conversion efficiency. Th e vaccine was well tolerated by the pigs, and no observable site reactions could be detected at the time of slaughter. Vaccination of boars with Impro vac allows production of heavy boars with improved meat quality through pre vention and control of boar taint.