Genetics of Leg Weakness in Boars at the Danish Pig Breeding Stations

Genetic relationships among leg and performance traits were estimated for 2495 Landrace and 1778 Yorkshire boars kept at the Danish breeding test stations between 1981 and 1983. The pigs were fed ad libitum from 25 to 90 kg. Each boar was clinically scored for 14 different leg traits on a scale from 1 (normal) to 4 (very severe changes) at a weight of approx. 90 kg. The estimated heritabilities were significantly higher than 0 for 5 of the traits in Landrace varying from 0.27 to 0.61, but in Yorkshire only “buck-kneed fore legs” had a heritability higher than 0 (h2=0.24). The heritability estimate for the overall leg score was 0.45 in Landrace but only 0.04 in Yorkshire boars. Unfavorable genetic correlations between meat percentage and several leg weakness traits were found for Landrace boars, whereas the correlations between daily gain and leg weakness characters in some cases were favourable. It was found that a long body predisposes the animal to leg weakness. The mutual genetic correlations are, on average, small and negative for some symptoms, indicating that leg weakness may be several diseases with various etiologic background.