EFFECT OF IMMUNOCASTRATION (IMPROVAC®) IN FATTENING pIGS I: GROwTH pERFORMANCE, reproductive ORGANS AND MALODOROUS COMpOUNDS

The effect of the immunocastration (vaccination against gonadotropin releasing hormone using Improvac® vaccine) on growth performance, size of reproductive organs and levels of fat androstenone and skatole was studied in Slovenian pig fatteners. The pigs (50% crosses of Duroc), selected from 35 litters (2 castrates and 3-4 boars per litter) farrowed within two weeks period, were assigned to three experimental groups: boars (n=25), immunocastrated males (n=24) and surgically castrated males (n=25). The vaccinations with Improvac® were performed at the age of 10 and 19 weeks. The trial started when pigs were 12 weeks old, and lasted until 24 weeks of age, when pigs were slaughtered. During the trial, pigs were lodged individually and their daily feed intake (ad libidum) and weight (at 12, 19 and 24 weeks of age) were recorded. At the slaughter line, the testes and accessory reproductive glands were removed and weighed. Subcutaneous fat samples were taken for the determination of androstenone and skatole concentration. Results on androstenone and skatole showed that the immunisation was 100% successful. The levels of androstenone were below a detection limit of the laboratory method in all pigs. For skatole, the concentrations were at comparably low level in surgically and immunocastrated males, whereas higher levels were observed in boars. Vaccination strongly reduced the weight of testes and accessory reproductive glands. Regarding growth performance, the immunocastrated males showed comparable feed intake, feed efficiency and growth rate as boars in the period from the start of the experiment until the revaccination; thereafter they were closer to the surgical castrates. In the present study, the beneficial impact of the immunocastration on pig productivity and on the reduction of substances responsible for boar taint was confirmed in Slovenian local conditions.