Adaptation of immunocastration treatment to montanera system for male Iberian pigs: effects on reproductive organs and carcass traits

Voluntary end of male pig castration is expected in the EU in the near future, but standard immunocastration (IC) protocols need to be adapted for Iberian (IB) pig males due to their long life cycle. Our team developed a 3-dose protocol that needs a further adjustment to suit montanera (MT; free-range acorn feeding) chronology. Our hypothesis is that improving homogeneity of body condition at the start of MT will enhance and homogenize testicular atrophy. Pure IB males (n=35) reared in extensive system were feed-restricted during the growth phase (pre-montanera) as usual. Of these animals, Control pigs (C; n=18) were immunized against GnRH at 10.5, 12 and 13.5 months (m)of age. Treated pigs (T; n=17) were immunized at 10.5, 11.5 and 13 m, with a 15-day ad libitum (AL) feeding period starting at the 3rd dose. Both groups started the MT period at 13.5 m, coinciding with the 3rd dose of C and the end of the AL period of T, and both were slaughtered at 16 m. To further validate the effect of nutritional level, an additional group was fed ad libitum during growth and finishing phases with commercial feedstuff in a regular outdoor rearing system (Adlib; n=15 IB x Duroc males), with the vaccinations taking place at 8, 9 and 11 m and slaughter at 13 m (earlier, due to genotype and unrestricted feeding). Testes and epidydimides were significantly smaller in Adlib and T than C pigs. Similarly, bulbourethral glands were significantly smaller in T than C pigs. Testes parenchyme color "a" (green to red) was highly correlated (r=0.87) with testes weight. Backfat androstenone and skatole were below detection limits for all the animals. Foreleg, loin and prime-cut yields were significantly greater for Adlib than for C and T pigs. In conclusion, nutritional level can be used to improve the efficacy of male IC, and testes colorimetry can be used to monitor this efficacy. El fin voluntario de la castración de machos porcinos se prevé próximamente en la UE. Pero los protocolos habituales de inmunocastración (IC) necesitan ser modificados para los machos Ibéricos (IB) debido a su largo ciclo vital. Nuestro grupo desarrolló un protocolo de 3 dosis que pretendemos ajustar a la cronología de la montanera, basándonos en la hipótesis de que la uniformidad de la condición corporal al inicio de la montanera intensificará y homogeneizará la atrofia testicular. Machos IB puros (n=35) fueron alimentados de forma restringida durante la pre-montanera como es habitual. De ellos, los machos