AbstractLeaf protein concentrates were tested as sources of supplementary protein in the diets of growing chicks and growing rats. Provided that the method of drying did not involve high temperatures, products made from mixed grasses, kale, barley leaves, rye leaves, and tares were all of uniformly high value, being similar to soya‐bean meal as protein sources. When drying was carried out in a forced draught oven, the temperature zone within which there was damage to the nutritive value of the protein was 82° to 9