Studies in the wool production of grazing sheep. 1. Seasonal variation in feed intake, liveweight and wool production

Abstract

A four year experiment is described in which Merino wethers were continuously grazed on Phalaris- subterranean clover pasture containing some annual grasses, at three rates for a year and at four rates in subsequent years. For the first year of the experiment a pasture of annual grasses and subterranean clover was also studied at three stocking rates. From the time that the eco-systems that were established reached an equilibrium there was rarely less than 2500 lb of herbage dry-matter an acre available on the lowest stocking rate and rarely more than 1000 lb an acre on the highest stocking rate. There was a significant difference in wool cut per head only in the first year ; over the last three years of the experiment it was slightly lower on the highest and lowest stocking rates than on the intermediate stocking rate. Wool production per acre was proportional to stocking rate. Large seasonal fluctuations were recorded in estimated digestible organic matter intake, liveweight, and wool production. Peaks of intake, liveweight gain, and wool production occurred in autumn and spring but at different dates at different stocking rates. At all but the highest stocking rate, wool production per unit time was lower in summer than in winter. Estimated herbage intake increased with decreasing availability of pasture. Digestibility of the diet, availability of pasture, and body condition of the sheep appeared to affect intake. Despite a higher estimated herbage intake on the higher stocking rate treatments, wool production was no higher.