Can we improve carcass and meat quality of immunocastrates by elongation of the time post second injection

Immunocastration can be used as an alternative for surgical castration of male piglets to avoid boar taint. The vaccine is administrated twice, once around 10 weeks of age and a second time about 4 to 6 weeks before slaughter. Before this second vaccination, pigs behave and perform like entire male pigs. Afterwards, feed intake increases which may result in a lower lean meat percentage. It can be expected that the timing of the second vaccination is crucial to optimise results. In total, 180 animals (hybrid sow × Piétrain): 60 gilts, 60 early vaccinated male pigs (IM-E, 79±6 kg live weight) and 60 late vaccinated male pigs (IM-L, 87±10 kg live weight) were slaughtered at an average pen weight of 119 kg. Second vaccination was performed 42±5 and 31±3 days prior to slaughter, for IM-E and IM-L respectively. Daily feed intake (DFI), daily gain (DG) and feed conversion ratio (FCR) did not differ significantly between IM-E and IM-L, while gilts had a lower DFI and DG compared to both IM groups. FCR of gilts was higher compared to IM-L, but not compared to IM-E. Gilts showed a higher lean meat content compared to both IM groups. Earlier vaccination increased dressing which could partly be explained by the lower weight of the gastrointestinal tract, but not by testes weight. For meat quality traits, intramuscular fat content (IMF) tended to increase and redness and yellowness values tended to decrease with earlier vaccination. Within the studied time frame of second injection before slaughtering, earlier vaccination improved dressing percentage and tended to increase IMF, while maintaining performances and carcass characteristics.