Heritabilities of osteochondral lesions and genetic correlations with production and exterior traits in station-tested pigs.

Osteochondrosis might reduce the performance of slaughter pigs, longevity of sows and animal welfare. The aim of the present work was to describe the prevalence in Swiss breeds and to analyse the genetic background of osteochondral lesions. Between January 2002 and December 2005, about 9500 station-tested pigs were examined for several exterior traits before slaughtering at the Swiss pig performance testing station using the Swiss linear description system with a scale from 1 to 7 per trait. The animals belonged to three breeds: Large White dam line, Swiss Landrace and Large White sire line. Additionally, a random sample of these pigs (n = 2622) was examined for osteochondral lesions at seven positions of the carcass after dissection. At first, the surface and shape of the femur, humerus, radius and ulna at the joints were evaluated by a trained person. Afterwards these bones were sawed and the state of the cartilage and the distal epiphyseal cartilage of the ulna was examined at the cutting surface. Osteochondral lesions were scored on a scale from 1 to 6. The prevalence of osteochondral lesions was low at head of humerus, condylus lateralis humeri, radius and ulna proximal and head of femur. Osteochondral lesions at condylus medialis humeri (CMH), distal epiphyseal cartilage of ulna (DEU) and condylus lateralis femoris (CMF) exhibited phenotypic and genetic variance. Their heritabilities ranged from 0.16 to 0.18 using linear mixed animal models. Therefore, it is possible to reduce the prevalence of osteochondral lesions by selection in principle. Exterior traits showed low heritabilities (0.10 to 0.26) but several favourable genetic correlations with osteochondral lesions at CMH, DEU and CMF with low to moderate magnitude. Genetic correlations between osteochondral lesions and production traits were low.