The Utilization of Urea-supplemented Roughages

In many parts of the world, poor quality roughages low in nitrogen are the only food available to the grazing ruminant. Experiments have shown that under some conditions, still not clearly defined, urea can improve both the digestion and intake of these roughages, and also the nitrogen status of the animal. However, there are reports from both the laboratory and the field, which indicate that urea supplements are not always successful e.g. Minson and Pigden (1961), Hemsley and Moir (1963), Lloyd Davies (1964, personal communication), Moir (unpublished data). The reasons for this anomalous situation are far from clear. This paper is a resume of some experiments carried out to determine the possible role of factors such as protein, production of higher volatile fatty acids (V.F.A.), energy availability, and minerals upon roughage digestion, particularly cellulose digestion, and upon microbial-protein synthesis when various urea-supplemented roughages are offered to sheep.