148 Effects of the Immunization Against Gonadotropin-releasing Hormone in Gilts and Boars Under Commercial Conditions

Abstract Our objective was to determine the effects of immunocastration on growth performance, carcass characteristics and reproductive tract traits of gilts and boars. A total of 1,584 gilts and boars (PIC 337 x Camborough®, 6.11±0.29 kg, 20.64±0.81 days of age) were blocked by weaning group, and the gilt pens were randomly allotted to 1 of 2 treatments, which consisted of: T1) non-immunocastrated gilts, T2) immunocastrated gilts; whereas the boar pens were alloted to: T3) immunocastrated barrows. There were a total of 12 pens per treatment for T1 and T2, and 24 pens per treatment for T3, with 33 pigs per pen. The immunization against gonadotropin-releasing hormone (administrated with Vivax®, Zoetis, São Paulo, SP, Brazil) was given at 108±1.16 and 143±1.16 days of age (21 days before harvest). Growth performance was assessed from day 143 of age until harvest. Performance data were analyzed using the GLIMMIX procedure of SAS with pen as the experimental unit, and carcass and reproductive tract data were analyzed with pig as the experimental unit. Initial (day 143) and final (day 164) body weights were greater (P < 0.05) for T3 than T1 or T2, with no evidence for differences between T1 and T2 (P > 0.05). There were no evidence for treatment differences (P > 0.05) for average daily gain and feed efficiency. Average daily feed intake was reduced (P < 0.05) for T1 compared to T2 or T3. Hot carcass weight and lean content were greater (P < 0.05) and backfat thickness was thinner (P < 0.05) for T3 compared to T1 or T2, but no evidence for treatment differences (P > 0.05) were observed for loin depth. The ovary weights and the percentage of ovulatory follicles were greater (P < 0.05) for T1 compared to T2. Results of this study show no evidence for differences for immunocastration on growth performance of gilts or barrows. However, immunocastration influenced gilts’ reproductive tract traits.