A suspected inherited neuromuscular disease in dorset down sheep

Extract

Madam:– This is the first report in New Zealand of what appears to be an inherited neuromuscular disease in Dorset Down sheep. During two successive breeding seasons approximately 20% of ewes in a stud flock comprising 54 ewes and one ram gave birth to lambs showing pronounced weakness of either both hind or all four limbs. Over 20 male or female single, twin, or one of a pair of twin lambs were affected. From birth these animals were alert and could raise their heads but they were unable to stand. Characteristically they lay with hindlimbs tucked under their bodies and forelimbs splayed sideways. Most affected lambs were slaughtered but those which were hand reared made a partial recovery. One such animal examined at five weeks of age showed pronounced flexion of the tarsal joints so that it walked on its hocks. The forelimbs were held unusually straight and the carpal joints occasionally knuckled over when the lamb walked. The limb joints were fully mobile upon manipulation and the hindlimbs were able to bear weight for short periods of time.