The Effect of Immunization Against Gonadotropin-releasing Factor on Growth Performance, Carcass Characteristics and Boar Taint Relevant to Pig Producers and the Pork Packing Industry: A Meta-analysis

Meta-analysis was used to compare pigs immunocastrated (IC) with Improvac® versus physically castrated (PC) or entire male (EM) pigs. Performance and carcass data as most relevant for producers and packers were analyzed and the risk of boar taint was assessed by comparing the number of pigs exceeding the consumer thresholds of detection (ToD) for skatole and androstenone. A total of 78 articles fulfilled pre-defined inclusion criteria. Compared to PC pigs, IC pigs have a higher average daily gain (ADG; +32.54 g/day, P < 0.0001) and more favorable feed conversion ratio (FCR; -0.234 kg/kg, P < 0.0001), higher live weight and percentage lean, and lower hot carcass weight (HCW) and dressing percentage. Compared to EM pigs, IC pigs have a higher ADG (+65.04 g/day, P < 0.0001), FCR (+0.075 kg/kg, P < 0.0001), live weight and HCW, and a similar dressing percentage. Conventionally raised IC pigs yield more valuable meat compared to PC (+0.628 kg) and EM (+1.385 kg) pigs. Heavy IC pigs (HCW > 97.7 kg) destined for the production of high-quality cured products gain approximately 0.3 kg more ham than their PC counterparts, with backfat and intramuscular fat still fulfilling the requirements for high-quality cured products. The risk of exceeding the ToD for skatole and androstenone is similar in IC and PC pigs, but significantly higher in EM pigs. Results from our meta-analyses confirm growth performance advantages of IC pigs compared with PC or EM pigs, and reveal a higher gain of valuable meat and a similar risk of boar taint as estimated for PC pigs.