In conclusion, under the conditions of this study, vaccination against GnRF using the specific GnRF analog-diphtheria toxoid conjugate (2 doses 4 to 6 wk apart with the second dose given 7 to 9 wk before slaughter) was shown to be effective in reducing androstenone and also, compared with physical castration, resulted in greater BW at slaughter and improved ADG and FCR from the time of first vaccination to slaughter.