Genetic relationships between measures of sexual development, boar taint, health and aggressiveness in pigs

Breeding intact boars is a promising alternative to surgical castration of piglets. Genetic selection should enable to solve problems due to boar taint and aggressiveness, while taking into account potential consequences on other traits of interest. The aim of the study was to estimate genetic relations between sexual development, boar taint, health and aggressiveness. About 1600 Pietrain (purebred) or Pietrain x Large White (crossbred) boars were raised in a testing station. Blood samples were collected at about 105 kg body weight for measuring sex hormones (testosterone, estradiol), and indicators of the inflammatory status (C-reactive protein: CRP, Pig Major Acute-Phase Protein: pigMAP, blood formula). Animals were slaughtered 9 d later, measured for boar taint compounds present in fat (androstenone, skatole) and skin lesions on carcass, an indicator of aggressiveness. For both genetic types, heritability was moderate for sex hormones (from 0.17 to 0.29) and skatole (purebred: 0.24, crossbred: 0.37), and high for androstenone (0.63 and 0.70). Genetic correlations between sex hormones and boar taint compounds were moderate to high (from 0.31 to 0.95). Heritability was moderate for CRP (0.24 and 0.46) and very low for pigMAP (0.06 and 0.05). Numbers of leucocytes had moderate to high heritabilities according to the genetic type (0.21 and 0.52). Heritability of skin lesions was moderate for both genetic types (0.31). Genetic correlations were negative between sex hormones and inflammatory measures (from -0.46 to -0.05), positive between testosterone and number of lesions (0.43 and 0.53), and low between androstenone and lesions (-0.06 and -0.17). Overall, both breeds of pigs had very similar estimations of heritabilities but estimates of genetic correlations were different for some pairs of traits. It would be possible to select boars on their plasma concentration of sex hormones to decrease boar taint and aggressiveness, without important consequences on the immune response. However, because of the strong links between boar taint and reproductive function, the possible consequences on the reproductive performance should be evaluated