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An experiment was performed to determine the proportion of roughage required by pregnant and lactating ewes fed wheat-based diets under drought conditions. Five dietary treatments ranging from wheat alone to lucerne hay alone were fed to pregnant and lactating Merino ewes, at levels estimated to give a similar net energy intake per ewe per day. The energy levels fed were altered during the experiment in an attempt to maintain ewe liveweight at a constant level. Wheat alone was unsuitable for lactating ewes, while a diet of 54% hay and 46% wheat (54:46) gave the best milk yields, lamb growth and lamb survival. The mean milk yields of the ewes ranged from 26.5 (SD) 2.5 ml hour-1 for wheat alone to 38.1 2.2 ml hour-1 for the 54:46 diet. Lamb liveweight gains between birth and weaning (at seven weeks) were related to ewe milk yields, with lambs on the wheat alone diet gaining 3.17 kg and those on the 54:46 diet gaining 5.10 kg. Only half of the lambs born to ewes fed wheat alone survived to weaning, compared with 89% of lambs on the 54:46 diet. Analysis of the responses indicated that, for milk yield, the 54:46 diet was near optimum and that lamb growth and survival would be maximized at 60-67% hay.

Body condition scores of approximately 400 Merino ewes and the carcase composition of a sub-sample of ewes were determined by inexperienced operators at the tenth and twentieth weeks of pregnancy. Although the repeatability of estimating condition scores was low on both a within and between operator basis, subjectively assessed condition scores, when averaged for three operators, were positively correlated with the per cent of fat plus muscle in the carcase at both the tenth and twentieth weeks of pregnancy. Ewe liveweight was positively correlated with the per cent fat plus muscle in the carcase at the tenth but not at the twentieth week of pregnancy.