Studies on the supplementary feeding of sheep consuming mulga (Acacia aneura). 2. Comparative levels of molasses and urea supplements fed under pen conditions

Abstract

Sheep maintained on a mulga (Acacia aneura) diet plus 2 g phosphorus (P) day-1 were supplemented with molasses at levels of 0, 50, 100 or 200 g DM day-1 with or without 8 g urea day-1. The supplements were offered for a period of 18 weeks and were then withdrawn and animals maintained on the basal mulga diet plus P for a further eight weeks. Provision of urea had no effect on mulga dry matter (DM) intakes or on any of the production measurements made. Daily DM intakes of mulga were significantly increased by molasses supplementation, intakes being 41 per cent, 57 per cent and 62 per cent higher than controls at levels of 50, 100 or 200 g DM molasses day-1 respectively. Liveweight gain followed a similar pattern, and at the end of the supplementation period liveweights for the 50, 100 and 200 g DM molasses day-1 were respectively 29 per cent, 42 per cent and 48 per cent heavier than the controls. Wool growth rates were significantly higher in all groups receiving molasses, the response being linear with increasing levels of molasses supplementation. Fleece yields also showed a linear trend with increasing levels of supplementation, the major response being attributable to the provision of the first 50 g molasses. Cessation of supplementation resulted in a rapid decline in mulga DM intake to levels approximately that of the controls. Liveweights of supplemented animals also declined during the post-supplementation period although in groups receiving either 100 or 200 g DM molasses day-1, they only declined to pre-experimental levels.