In this recent peer reviewed publication Dr. Nora Khaldi and co-authors undertake a comparative genomic study of milk proteins between 13 mammalian species spanning 200 million years of evolution. The set of species include Human, Chimp, Monkey, Mouse, Rat, Guinea pig, Rabbit, Cat, Dog, Horse, Cow, Opossum, and Platypus. Although high levels of particular amino acids appear to be consistently maintained between all 13 species, Nuritas founder shows some significant differences in the composition of certain amino acids between mammals. The authors discuss that these observations indicate that milk proteins may have adapted to the different needs of the offspring of the different species that we consider.
You can obtain the paper at the Journal of Dairy Science following this link .