Meta-analysis of the effect of immunocastration on production performance, reproductive organs and boar taint compounds in pigs

Meta-analytical approach was used to quantitatively synthesize the effect of immunocastration on growth, carcass, meat quality, reproductive organs and boar taint compounds. Altogether 41 papers were collected for effect size (theta) calculation and the comparisons were made with entire males (EM) and surgical castrates (SC). The data for reproductive organs and growth performance are numerous enough to draw firm conclusions. In contrast, data for carcass and meat quality are more limited. Results of meta-analysis show efficient immunocastration with the magnitude of the response being by far the largest for reproductive organs (theta = -2.8 to -5.0) and boar taint substances (theta = -2.8 and -0.8 for androstenone and skatole, respectively). However, compared with SC, the immunocastrates exhibit larger bulbourethral glands (theta = 1.3) and slightly higher concentrations of androstenone and skatole (theta = 0.1 and theta = 0.2, respectively). The impact of immunocastration is also remarkable on performance, where the main advantage of the immunocastrates is their boar-like performance until revaccination. In the period following the second vaccination, they eat much more than EM (theta = 2.1), resulting in large effect size for growth rate compared with both EM and SC (theta = 1.1 and theta = 1.4, respectively). Considering the whole fattening period, their feed conversion ratio is higher compared with EM (theta = 0.6) and much lower than that of SC (theta = -1.3), although exhibiting moderately faster growth compared with both (theta = 0.6 and theta = 0.2, respectively). With regard to carcass quality, the immunocastrates take intermediate position between EM and SC. Besides, our analysis suggests no difference in meat quality with SC and some meat quality advantages of immunocastrates over EM because of higher intramuscular fat content (theta = 0.4) and lower shear force (theta = -0.6).