Immunokastrering av hangrisar
Abstract: Active immunization against gonadotropin-releasing hormone (GnRH) is an alternative to surgical castration of male pigs to avoid boar taint. The aim of this study, including 128 pigs, was to evaluate the effect of a GnRH-vaccine Improvac® on performance and on social and sexual behaviour. Male pigs were assigned to three treatments; surgical castration at four days of age, immunization against GnRH and no castration. Vaccination was performed eight and four weeks before slaughter. Surgically castrated male pigs had significantly lower daily weight gain during the suckling period than entire male pigs (235 vs. 268 g). Daily weight gain from start of the experiment (at 69 days of age) to the second injection (at 139 days of age) did not differ between the groups. Immunization against GnRH resulted in significantly higher daily weight gain (160 g) compared to the other groups after the second dose of Improvac®. Immunocastrated males had 0.5 kg higher daily feed intake in this period than entire male pigs, but similar to castrated pigs. Immunized pigs had 1.5%-units lower lean meat content in carcass than entire male pigs, but 2.2%-units higher than surgically castrated pigs. They had significantly lower dressing percentage. After the second dose of Improvac®, the immunized pigs had less skin damage than the entire male pigs (21% vs. 33% of the pigs), but the same frequency as the surgically castrated. The frequencies of aggressive and social behaviours were lower for the immunized pigs than for the entire male pigs and they performed no mounting behaviour at all. Testes weight and length of Gl. Bulbourethralis at slaughter were significantly lower for the immunized pigs.
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