ABSTRACT
The proteins in milk are divided into two categories: caseins and whey proteins.[1] The caseins are organized into large micelles suspended in milk and serve to transport much of the calcium and phosphorus that the young need. Upon ingestion and exposure to gastric secretions, the caseins precipitate in the stomach forming semisolid curds that are gradually digested. It is thought that species that nurse infrequently may have higher casein levels to retain milk constituents in the stomach for longer periods. Cow’s milk is higher in casein and forms a more solid curd than does the milk of humans or pigs, which suckle frequently, but few species have been compared in this light.
