Efficiency of conversion of food to wool. 2. Comparison of the efficiency of the same Merino ewes on two different rations

Abstract

During a 12-meek period a group of nine medium Peppin maiden ewes was fed ad libitum a ration of lucerne chaff while a similar group was fed ad libitium a mixture of oaten chaff and lucerne chaff in the ratio of 10 to 1. During a second 12-week period the rations of these two groups were reversed. Food consumed by each sheep was weighed and protein consumption obtained from food and residue analyses. Clean wool production for each sheep was recorded in each period. Two measures of efficiency used were the ratios of clean wool to air-dry food consumed (W/F) and to crude protein consumed (W/P). For W/F the interaction between sheep and ration or period was significantly greater than variation between subperiods (P < 0.001), but the between-sheep variance was in its turn much greater than the interaction (P<0.O01), giving a repeatability of 0.76 for efficiency measures on the same sheep. For W/P also the interaction was significant (P <0.05), the repeatability estimate being 0.74. The correlation coefficient between measures for the same sheep on the two rations were 0.83 for W/F and 0.84 for W/P. It is concluded that, although some significant interaction between sheep and ration was demonstrated, it was not of great importance, and, consequently, selection of sheep on efficiency with one ration of the type described u-auld also hold, with small loss of accuracy, with a second such ration.