LAMB MORTALITY DUE TO INADEQUATE CARE OF TWINS BY MERINO EWES

Stevens, D., Alexander, G. and Lynch, J.J., 1982. Lamb mortality due to inadequate care of twins by Merino ewes. Appl. Anim. Ethol., 8: 243–252. One hundred and three fine-woolled Merino ewes and their twin lambs in four 12-ha paddocks, carrying 12.5 sheep per ha, were observed during daylight for 2—4 days immediately following parturition. Fifty-one ewes became permanently separated from one twin due to the ewe moving and leaving the lamb behind, mostly on the day of birth; the ewes appeared unconcerned if followed by only one lamb. Only two ewes became separated from both lambs. Human interference appeared to play only a minor role in these separations. Low vigour of one twin, as assessed within several hours of birth, usually resulted in its early separation from the ewe, but more than half of the lambs separated from the ewes were vigorous and mobile. Regardless of separation, all lambs of low vigour died. In this flock, the inability of the ewes to keep twins together, and maintain contact with both, contributed largely to the higher mortality in the twin lambs than in singles in the same birth-weight ranges; overall, 37.4% of twins died compared with 9.6% of singles. These figures indicate there could be a problem of high mortality in twin lambs from fine-wool Merino flocks under commercial conditions where lambing takes place in paddocks that are usually well in excess of 12 ha.