In fact, cystine levels were higher, the further up the primates were on the evolutionary tree. And there seems to be a connection between amino acid content and a species' particular needs. For example, both tiger and house cat milks have a high arginine content. It's an important amino acid for all felines, because kittens and cubs can't synthesize it. In fact, cat parents must get all the arginine they need from food, while other mammals synthesize it.
Milk Is Milk . . .
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