The effect of five different supplements on the degradation of straw in sheep given untreated barley straw

Five experiments were conducted to investigate the dietary factors within the rumen environment which could contribute to changes in the degradation of barley straw. Degradation was measured by recording the losses of dry matter (DM) from samples of straw incubated in nylon bags in the rumen for various periods of time. Three sources of supplementary energy (sugar-beet pulp, citrus pulp and dried grass) and two sources of protein (soya-bean meal and fish meal) were investigated for their ability to increase degradation of straw when given as supplements to untreated straw. The untreated straw used in these experiments was adequately supplemented with rumen-degradable nitrogen, sulphur, vitamins and minerals. Unmolassed sugar-beet pulp and dried grass, when given at a level of 150 g kg−1 straw DM, increased both the rate and extent of degradation of straw DM. Citrus pulp and soya-bean meal had no effect on the degradation of straw, while fish meal appeared to have a small effect. It was concluded that in particular digestible cellulose and/or hemicellulose improved the conditions in the rumen for straw fibre degradation in animals given straw diets.