The use of urea-molasses supplements for sheep grazing semi-arid tropical pastures

Abstract

The performance of unsupplemented Merino ewes grazing dry season semi-arid tropical pastures was compared with that of other sheep supplemented with either urea-molasses or molasses. Over the experimental period from September 1970 until late January 1971 mean daily intakes per head of urea and molasses respectively were: low urea group, 11.7 g and 35.1 g; high urea group, 15.2 g and 45.6 g; molasses, 38.9 g. Monthly estimates of the proportions of animals consuming the supplement over the period September to January varied from: urea-molasses-71 per cent to 97 per cent; molasses-75 per cent to 96 per cent. Unsupplemented sheep lost significantly more liveweight than did supplemented groups in the period September to February. However, during the period of greatest nutritional stress from December to February, sheep recewing molasses lost significantly more weight than did those supplemented with urea-molasses, and liveweight loss was greater in the low urea group than in the high urea group. Wool growth rates were significantly higher in groups receiving urea-molasses, with highest wool growth rates in animals on the high level of urea. Total fleece weights were unaffected by treatment as were the reproductive factors examined. Faecal nitrogen levels declined until the onset of pasture regrowth in February and were associated with low digestibility of the available forage. Compensatory liveweight gains following pasture regrowth outweighed any advantage of the dry season supplementation. It was concluded that urea-molasses supplements were of little direct benefit to sheep grazing these pastures.