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In an experiment at Hamilton in western Victoria, groups of 30 Merino ewes were stocked at 11.7, 15.4 or 19.2 ewes ha-1 and joined to Merino rams each year on April 5 or May 8 for five weeks. Hay was conserved on half the number of plots and fed back to the ewes before and during joining. Observations on birth weight, survival, and growth of lambs born between 1970-73 are presented. Both the highest stocking rate and the earlier lambing were associated with a depression of about 7 per cent in the birth weight of twin lambs, but single lambs had similar birth weights on all treatments. Lamb survival was highly variable and there were few significant treatment effects. However, mortalities within 48 hours of birth were lower amongst flocks joined to lamb in October than those lambing in September (single lambs 9.2 per cent vs. 14.7 per cent-twin lambs 19.9 per cent vs. 40.2 per cent). Most of the improvement was attributed to drier conditions and lower windspeeds in October. Lamb growth rates fell with increasing stocking rate but the variation in weaning weight was less than 2 kg. Lambs born in September were about 10 per cent heavier at weaning than those born in October. Compensatory growth after weaning resulted in negligible differences in weight at 12 months between lambs from the different stocking rate treatments, but lambs born in September were still significantly heavier than those born in October.

In an experiment at Hamilton in western Victoria, groups of 30 Merino ewes born in 1967 were stocked at 11.7, 15.4 or 19.2 ewes ha-1 and joined to Merino rams each year on April 5 or May 8 for five weeks. Hay was conserved on half the number of plots and fed back to the ewes at joining. Observations at mating and lambing in each year from 1970 - 73 are presented. Seasonal conditions exerted a greater effect upon liveweight change before joining than did the applied treatments but liveweight at joining declined significantly as stocking rate increased. Oestrus activity and the number of ewes returning to service were similar on all treatments. Both the number of lambs and the proportion of twin births declined linearly as stocking rate increased. It is concluded that a similar relationship between liveweight and ovulation rate existed on all treatments. Withholding the introduction of rams from April until May did not result in any change in the number of lambs born. Hay feeding failed to increase the number of lambs born. It is suggested that the ewes substituted hay for pasture.