The productivity of breeding ewes grazing on lucerne or grass and clover pastures on the tablelands of southern Australia. II. Wool production and ewe weight.

Abstract

Spring-lambing Merino and crossbred ewes grazing on dryland lucerne pastures were generally heavier throughout the year than ewes grazing on phalaris and subterranean clover pastures, even though they experienced greater weight losses during winter. These losses were mostly eliminated by compensatory gains in spring. Annual fleece weights of the Merino ewes grazing on lucerne or phalaris and subterranean clover pastures declined linearly by 146 and 64 g respectively for each additional ewe carried over a range of stocking rates from 9 to 18 ha-1. Corresponding figures for crossbred ewes were 114 and 46 g. In each case the difference between pasture species was significant (P < 0.02). Only at the lowest stocking rates were fleeces from ewes on lucerne heavier (by c. 500 g) than those from ewes on phalaris. At the highest stocking rates, there were no advantages in terms of wool production from grazing breeding ewes on lucerne. Not only was there a greater need for supplementary feed during late pregnancy to avoid losses from pregnancy toxaemia, but the lucerne pastures at all stocking rates proved more sensitive to unfavourable physical and chemical characteristics of soils than did phalaris and subterranean clover pastures. The fleece weights of Merino and crossbred ewes declined, on average, by 70 and 50 g per year for ewes aged between 1+ and 6+ years. Pregnancy reduced fleece weights by 5-10% in Merinos and 5-21% in crossbred ewes, depending on seasonal conditions which varied from year to year. For Merinos only, dry ewes grew about 4% more wool than lactating ewes. No other effects of reproduction on fleece weights were observed.