Studies of grazing of crop forages by sheep

Summary Wastage associated with the grazing of rape by harnessed wethers was measured by forage sampling and by total faecal collection, to estimate intake from the consumption/excretion ratio. Blocks were grazed in accordance with Iamb fattening practice. Stubble residues wasted amounted to 18% of both the dry matter and organic matter offered. The wastage of starch equivalents was slightly lower. Grazing wastage averaged 17% of the dry matter and 20% of the organic matter. The wastage of starch equivalents was slightly higher. The mean digestion wastage was 10% of the dry matter and 7% of the organic matter of the rape offered. Only 56% of the rape dry matter offered was used for growth and maintenance. There was differential wastage of proximate constituents amounting to 95% of ether extract, 67% of crude protein and 38% of crude fibre. The wastage of nitrogen‐free extract, by far the largest fraction, was similar to that of organic matter. The results were in agreement with the hypothesis that, over the normal range of yield, a doubling of yield is accompanied by a quadrupling of grazing wastage. There appeared to be relationships between yield and other sources of wastage and between stubble wastage and grazing intensity. Further investigation of factors associated with crop and animal management is warranted if fuller utilisation of crop forages is to be achieved. It is evident from the results of this experiment that yields obtained from cutting cannot be safely used to predict animal production.