The paper discusses the nutrition of the grazing animal in general. It specifically discusses about the use and abuse of the protein component of the diet of ruminants, in particular of sheep and cattle. The paper reports experiments that have shown that ruminants efficiently use protein and amino acids when there are fed by a tube into the abomasums, thereby avoiding their destruction by microbes in the rumen. Substantial increases of wool growth have been obtained by this artificial means. Practical procedures are therefore being developed to enable feed proteins and amino acids to pass through the rumen unchanged by microbial activity. The most attractive procedures so far discovered are the coating of proteins and amino acids with protective polymers, and the chemical treatment of proteins with formalin chemically treated milk protein, when fed to sheep in a modest amount of a poor quality ration, increase wool grown by 70 percent and also resulted in an appreciable increase in body growth. These increases were obtained without any increase in the total amount of food consumed. The findings therefore offer scope for increasing the efficiency of production and the amount of wool, meat and milk from ruminants.