Effect of Immunocastration on Culled Sows—A Preliminary Study on Reproductive Tract, Carcass Traits, and Meat Quality

SIMPLE SUMMARY: This study focuses on the Bísaro breed and the need to prevent unwanted pregnancies and boar taint in cull sows of this breed. Three immunocastration protocols using Improvac(®) were tested and compared to a control group under the same conditions. The immunocastrated sows had significantly lighter reproductive tracts compared to the intact sows, indicating a regression in reproductive activity due to GnRH immunization. However, there were no significant differences in meat quality traits. Therefore, immunocastration can effectively suppress ovarian activity in culling sows without negatively impacting pork quality. This research offers a practical solution to manage reproductive issues, ensuring both animal welfare and meat quality. ABSTRACT: The Bísaro pig is a Portuguese autochthonous breed greatly appreciated for its meat quality and is mainly reared outdoors. Immunocastration could be a solution to avoid undesirable pregnancies and boar taint in cull sows. The present study tested three immunocastration protocols (with Improvac(®)) according to their reproductive cycle. The first inoculation was performed two weeks after farrowing (IM1, n = 5), at the beginning of estrus (IM2, n = 5), and one week after the end of estrus (IM3, n = 5), followed by a second administration four weeks apart. A control group (C, n = 5) was also included in the same housing conditions. The sample collection included the reproductive tract for morphometric evaluation, neck fat for the quantification of boar taint compounds, and a portion of the Longissimus thoracis et lumborum for meat quality trait assessment. The reproductive tracts from intact sows (C) were significantly heavier compared to the immunocastrated groups (p < 0.05) (1.403 kg C to 0.508 kg IM1, 0.590 kg IM2, and 0.599 kg IM3), suggesting the regression of the reproductive tract to nonstimulated conditions due to immunization against GnRH. The IM1 group exhibited significantly smaller reproductive tract measurements compared to group C for most of the evaluated segments (p < 0.05). No marked differences were observed in the meat quality traits. Therefore, immunocastration can be used in culling sows to avoid ovarian activity, and it is not detrimental to pork quality traits.