Performance and carcass characteristics of immunocastrated and surgically castrated Iberian pigs fed diets of different protein concentration. Preliminary results

Immunocastration has proved to be an effective strategy to prevent sexual development and boar taint in pigs. Previous results indicate that immunocastrated (IC) pigs exhibit better performance than surgically castrated (SC) pigs. In addition to animal welfare benefits, this fact could be of interest for Iberian pigs, as their growth capacity rapidly diminishes as animal ages. The purpose of this study was to examine the effects of immunocastration on Iberian pig performance, protein utilization, and carcass traits under different dietary protein concentrations. Pure Iberian pigs (n=27) were used as follows: 3 sexes (IC males, IC females, SC males); 3 isoenergetic diets (160, 140 and 120 g CP/kg DM); 3 pigs/group. Pigs were vaccinated against Gonadotropin Releasing Hormone at 4.3 months (40 kg) and 6 months (70-80 kg) of age. Experimental diets were offered to individually-housed pigs from 40 to 100 kg BW. Digestibility and N-balance assays were performed at 50 and 90 kg BW, respectively. Pigs were slaughtered at 100 kg BW. Preliminary results indicate greater growth rate for IC males (803 vs 706 and 696 g/d, for IC males, SC males and IC females, respectively; P < 0.001). Feed efficiency (G:F) was greater for IC males (0.289 vs 0.260 and 0.263; P < 0.01). Moreover, IC males exhibited increased carcass length and greater relative weights for most lean cuts, but they also had smaller carcass yield and belly proportions than the rest of groups. No relevant differences related to dietary treatments were detected. Further research would help to elucidate possible effects of immunocastration on Iberian pig lean growth.