Visual assessment of post-mortem lesions exhibits little additive genetic variation in growing pigs

Abstract

This study tested the premise that additive genetic variation for incidence of post-mortem disease lesions visually assessed during routine carcass inspection exists in growing pigs. A total of 23 478 male growing pigs were assessed for three categories of disease lesions: any post-mortem lesion; respiratory lesions; and abscesses. Additive genetic variation for each category of lesions was estimated by fitting a categorical threshold liability model, formulated in a Bayesian context, to the incidences of the lesions (i.e. not diagnosed/diagnosed with one lesion/diagnosed with two or more different lesions). The amount of additive genetic variation detected for the incidence of any post-mortem lesion on the underlying liability scale was very low [additive genetic variance (marginal posterior mean, 95% highest posterior density region)=0.019, 0.000–0.046; heritability (marginal posterior mean, 95% highest posterior density region)=0.03, 0.00–0.06]. By comparison, the amount of additive genetic variation was negligible for respiratory lesions (0.002, 0.000–0.015; 0.00, 0.00–0.03) and low for abscesses (0.050, 0.001–0.098; 0.08, 0.00–0.15). The general lack of additive genetic variation suggests that the incidence of post-mortem lesions visually assessed during routine carcass inspection would not provide a suitable criterion by which to select pigs for resistance to clinical and sub-clinical disease.