Asymmetric hindquarter syndrome in pigs.

An outbreak of the asymmetric hindquarter syndrome was investigated in a Western Australian piggery. The condition was manifested as asymmetry of the hindquarter, particularly the semitendinosis, semimembranosis and biceps femoris muscles. The gait of affected animals was not noticeably altered, despite an obvious disparity in size between normal and affected limbs. Histologically, muscular degenerative and dystrophic changes were seen but were not present in all undersized muscles and were occasionally present in macroscopically normal muscles. All 7 affected pigs whose breeding history could be traced were sired by the same boar. The condition adversely affected conformation and resulted in down-grading of carcases.