The Essential Amino Acid Content of the Proteins Isolated from Milk of the Cow, Ewe, Sow, and Mare

Abstract

Summary Mixed proteins isolated from the milk of the cow, ewe, sow, and mare have been assayed for the essential amino acids by microbiological methods. In general, the concentration of the amino acids in the proteins from the different species is similar, although higher concentrations of arginine and lower concentrations of tryptophan may be present in the milk proteins of the sow and mare than are present in the proteins of the cow and ewe. There appeared to be no difference between the amino acid content of the proteins isolated from the milk of the Shropshire, Rambouillet, and Hampshire breeds of ewes. Species difference in the amino acid components of mammalian milk proteins is not as spectacular as it is in the fatty acids components of milk fat, although the protein molecules are more complex than fat molecules.