THE EFFECTS OF IMMUNIZATION AGAINST LUTEINIZING-HORMONE-RELEASING HORMONE OF PERFORMANCE, SEXUAL DEVELOPMENT, AND LEVELS OF BOAR TAINT-RELATED COMPOUNDS IN INTACT MALE PIGS

The effect of a newly developed anti-LH-RH vaccine on the performance, sexual development, and incidence of boar taint-related compounds was investigated in young intact male pigs. At 29 kg BW, 40 crossbred intact males and 20 castrates were allocated to three groups. Castrates and half of the intact males mere untreated. The remaining intact males were immunized against LH-RH;at 29 kg and again at 89 kg BW. All pigs were slaughtered at 105 kg BW Compared with control intact males, feed efficiency in castrates was decreased by 10%, muscle content was reduced by 5%, and carcass fat content was increased by 26%. Growth performance and carcass traits did not differ significantly between immunized and control intact males. Genital tract weight, measured at slaughter, was decreased (P less than or equal to .002) by immunization. Plasma testosterone concentrations were not significantly affected at 89 kg BW, whereas they were sevenfold lower (P < .001) in immunized than in control intact males at 105 kg BW. Fat androstenone levels, measured at slaughter, were substantially reduced (P < .001) from .66 +/- .07 mu g/g in control to .21 +/- .01 mu g/g in immunized intact males. Rates of testicular steroid biosynthesis, measured in vitro, were decreased by immunocastration. Fat skatole levels were very low and did not differ significantly between the three groups. The present results demonstrate that anti-LHRH immunization was effective in reducing the level of androstenone, a boar taint-related compound, although having a limited effect on the performance of the animals.