The experiments reported in this thesis were conducted to study sources of protein, which are available in developing countries, as supplements for ruminants fed low quality fibrous diets. Supplementation with dietary protein or non-protein nitrogen (urea) is usually suggested as a means to increase production of animals fed a low quality diet. The provision of rumen undegradable protein is suggested to supply dietary amino acids to ruminant. In the study presented here, urea and by-pass protein sources (cottonseed meal, sunflower meal, palm kernel cake, and copra meal) were used in combination as supplements for sheep fed a low quality fibrous diet. In the first experiment, the efficiency of utilization of these protein-rich supplements was compared in sheep given a low quality fibrous diet. In the second experiment, the accuracy of a technique for estimation of intake of the supplements was determined using lithium chloride as a marker. Supplementary feeding of grazing sheep during winter/spring in The Northern Tablelands of New South Wales is necessary to maintain or to support animal production. A third experiment was carried out in grazing sheep to investigate the effect of supplementary feeding during a period of low pasture growth in winter/spring in The Northern Tablelands of New South Wales. The lithium chloride technique was used to measure the intake of supplements by grazing sheep
