. 1984. The growth performance and carcass composition of ram and ewe lambs fed on pasture or in confinement and slaughtered at similar fatness. Can. J. Anim. Sci. 64: 631_640.Forty-nine crossbred ram lambs and 62 crossbred ewe lambs were allotted at weaning (average weight 30.6 kg) to pasture (P) or concentrate (C) feeding. The number of lambs per treatment was as follows '. rams, 24 P fed and 25 C fed; ewes, 3 I P fed and 3l C fed. The lambs were slaughtered after 56, 72, 100 andl2l days on feed.Offal components were weighed, and the alimentary tract was emptied of digesta.One side ofeach carcass was broken into four cuts (leg, loin, rib, shoulder) which were further separated into fat, muscle and bone. C-fed lambs were 4.\Vo heavier live than P-fed lambs (P<0.05) and ram lambs were 9.0Voheavier live than ewe lambs (P<0.05) when evaluated at a constant depth of subcutaneous fat (4.5 mm).However, P-fed lambs required an extra 2l days (P<0.05) to reach the same fat depth as C-fed lambs. C-fed lambs had greater rib eye areas than P-fed lambs, but carcasses from all treatments had similar proportions of dissected muscle, bone and fat when evaluated at a constant proportion of subcutaneous fat. P-fed lambs had a greater proportion of their empty bodies as head and reticulo-rumen, and a lower proportion as liver and large intestine than C-fed lambs. Ram lambs had a greater proportion of their empty bodies as head, and a lower proportion as caul fat, mesenteric fat, omasum and small intestine than ewe lambs. Distribution of muscle and bone among each of the four meat cuts which were evaluated was similar for all carcasses. Sex and feeding system had only a minor effect on the distribution of the fat depots. In this study, lambs fed on pasture required 21 days longer on feed to reach the same external fatness as concentrate-fed lambs, but produced carcasses of similar composition at slightly lighter iiveweights (45.3

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