OSTEOCHONDROSIS AND LEG WEAKNESS IN PIGS SELECTED FOR LEAN TISSUE-GROWTH RATE

This study was based on Swedish Yorkshire pigs from two lines in a selection experiment. Selection was performed in four generations for high lean tissue growth rate (LTGR) on a low protein (LP, 13.1% crude protein (CP)) or a high protein (HP, 18.5% CP) diet. In total, 2817 pigs were scored for leg weakness (LWS), LTGR, lean percentage and growth rate. After being performance tested 1470 of the non-selected pigs were slaughtered. Osteochondrotic (OC) changes in their elbow and knee joints were then scored, and lean percentage was estimated by partial dissection. The LP-line had a significantly better constitution, regarding both LWS and OC-scores, than the HP-line. Females had better OC-scores than males. Generic parameters were estimated with REML using a multiple-trait animal model. The heritabilities estimated were 0.1-0.2 for LWS and 0.2-0.5 for OC. LTGR showed a weak but favourable genetic correlation with osteochondrosis in the knee in both lines. LWS did not show any genetic correlation with LTGR in the LP-line, but showed an unfavourable genetic correlation (-0.50) with LTGR in the HP-line. A significant unfavourable genetic trend was found for LWS in the HP-line. Lean percentage was unfavourably correlated genetically with LWS and OC-scores for the elbow. Genetic correlations between LWS and OC-scores were in the expected direction.