The efficiency of conversion of feed to wool in Merino flocks selected for and against fleece weight

Abstract

The efficiency of conversion of feed to wool was measured in three jocks of Peppin Merino sheep, namely : Fleece Plus-Selected for nine years on high clean fleece weight ; Fleece Minus-Selected for nine years on low clean fleece weight ; Random-An unselected, control flock. Ten 18 month old ewes from each of these flocks were individually housed and fed ad lib on hammer-milled lucerne hay for 54 weeks. Highly significant differences between flocks were observed in feed intake, wool growth, and efficiency of conversion of feed to wool. The relative productive levels for the Fleece Plus, Random and Fleece Minus flocks were-for feed intake, 108 : 100 : 88-for clean fleece weight, 118 : 100 : 70-and for efficiency 109 : 100 : 79. The correlation between efficiency and daily feed intake was very highly significant and negative within each flock, (-0.918, -0.929 and -0.924, for Fleece Plus, Random and Fleece Minus flocks respectively), whereas the correlation between jocks was significantly positive, r = 0.997. The relative importance of the factors determining the 18 per cent increase in clean fleece weight of the Fleece Plus over the Random flock was : efficiency, 55 per cent and feed intake, 45 per cent-and comparing the Random to the Fleece Minus flock : efficiency, 60 per cent and feed intake, 40 per cent. Approximately half the difference in feed intake was independent of body weight.