Relative efficiencies of conversion of feed to wool at three levels of nutrition in flocks genetically different in wool production

Abstract

The efficiency of conversion of feed to wool was measured with adult ewes at three levels of nutrition. During the period at which each level was fed, changes in body weight and feed intake were minimized. These ewes were chosen as representative of the total drops of three flocks, one of which had been selected for high clean fleece weight (Fleece Plus), one for low clean fleece weight (Fleece Minus) and a control flock selected at random (Random). The intermediate and high levels of nutrition were intended to maintain 20 per cent and 44 per cent higher body weights than at the low level of nutrition. The average intakes of lucerne pellets at the low, .intermediate, and high levels of nutrition were approximately 500, 800, and 950 grams a day respectively. The average body weights at these intakes were 30, 36, and 45 kg and the average gains in body weight were -11, +7, and +16 grams a day during the 18 weeks of measurement at each level. There were no differences between the flocks in these measurements. The relative wool production of the Fleece Plus, Random, and Fleece Minus flocks changed between levels of nutrition, being 101 : 100 : 96 at the low level, 120 : 100 : 88 at the intermediate and 121 : 100 : 96 at the high level of nutrition. Part of this differential response could be attributed to different feed intakes between the flocks and part to a smaller decrease in the efficiency of the Fleece Plus flock with increasing level of nutrition. The relative net efficiencies measured at the intermediate level were 116 : 100 : 86.5 for the Fleece Plus, Random, and Fleece Minus flocks respectively.