The phenomenon of lactation is of perennial interest to the physiologist, biologic chemist and pediatrician. Not only is the period of preparation an illustration of fine endocrine coordination and balance but the actual production of milk presents an opportunity to study metabolism taking place at an unusually rapid rate. The turnover of materials incident to the elaboration of large quantities of milk may present astounding values. Some dairy cows have made records of 100 pounds of milk a day; this yield means a large consumption of feed and water. It means the annual loss by way of the mammary glands of some 150 pounds of ash, of 25 pounds of calcium, of ten times the organic matter contained in the cow's body and of more than 1,000 pounds of protein.
The product of the mammary gland for several days post partum is unusually rich in protein. This secretion, called colostrum,
FORMATION OF MILK PROTEINS. JAMA. 1938;111(25):2305–2306. doi:10.1001/jama.1938.02790510053016