Development of long-term, pre-finishing immunocastration protocols for male Iberian pigs: 2. carcass

Male immunocastration (IC) should be adapted to the long life cycle of Iberian (IB) pigs. We previously developed long-term, 3-dose, pre-finishing IC protocols for male Iberian pigs whose efficacy seemed to be influenced by nutritional and stress level. Study 1 aimed to improve the efficacy of protocols by a short-term increase in feeding intake. IC males (ICM; n=47) were fed commercial concentrate in an extensive system, immunized against GnRH at 11, 12 and 14 months (m) of age and slaughtered at 16 m. The treated subgroup (23 ICM) was submitted to a 15-day ad libitum feeding period starting at the 3rd vaccination, and the remaining ICM were the Control subgroup. The treated ICM group reached 100% efficacy as all its animals had 150-g testes. Study 2 aimed to adjust the protocol to suit the chronology of the acorn- feeding free-range period (montanera; MT). We tested whether improving body condition homogeneity at the start of MT would homogenize testicular atrophy. Control IB pigs (C; n=18) were immunized at 10.5, 12 and 13.5 m. Treated pigs (T; n=17 IB males) were immunized at 10.5, 11.5 and 13 m, with a 15-day ad libitum (AL) feeding period starting at the 3rd dose. Montanera started at 13.5 m, and slaughter took place at 16 m. The AdLib group (IB × Duroc; n=15) were fed AL with concentrate during growth and finishing phases in an extensive system, immunized at 8, 9 and 10 m, and slaughtered at 13 m. The Adlib and T treatments showed a 100% efficacy. Backfat androstenone and skatole levels were basal. Ham yield and backfat thickness were similar for the 3 groups. Unlike in Study 1 and our previous studies, intramuscular fat content, backfat thickness and meat texture did not seem different from those usually reported for surgically castrates. We conclude that nutritional level can be used to improve the IC efficacy. Longer finishing after the last vaccination may increase fat deposition. Funded by European Union’s H2020 RIA program (grant agreement no. 634476).