SUSPECTED PHOTOSENSITIZATION IN LAMBS GRAZING BIRDSFOOT-TREFOIL (LOTUS-CORNICULATUS)

Suspected photosensitisation occurred in three groups of lambs grazing birdsfoot trefoil (Lotus corniculatus c.v. Grasslands Goldie). In one group, sucking lambs aged about 10 weeks, grazing birdsfoot trefoil, developed skin lesions while lambs of a similar age and from the same flock grazing lucerne (Medicago sativa) or a mixed sward of both speci es showed no signs of photosensitisation. Affected lambs had lesions o n their backs and ears. In a few animals the tips of the ears were sho rtened by 2-3 cm. In the affected lambs, serum liver enzymes (gamma-gl utamyltransferase, glutamate dehydrogenase), bilirubin and serum Vitam in Bit levels were within the normal range. At necropsy, no significan t pathological changes were detected in the liver and histological cha nges in the skin were consistent with primary photosensitisation. In t he second group, three of 80 weaned lambs grazing the same birdsfoot t refoil at a restricted intake were affected in the same manner as the first group. In the third group, 15 animals from 28 sets of sucking tw in lambs were also affected. In only two sets of twins were both lambs affected. None of the ewes grazing with the lambs in the first or thi rd groups showed any clinical signs of photosensitisation.