This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Cow's milk differs much in quality according to the breed and condition of the animal, quality of its food, and care bestowed upon feeding and hygienic surroundings. The chief variation concerns the quantity of cream produced.
The milk of Alderney, Jersey, and Guernsey cows has more pro-teid than that of ordinary animals, and Alderneys give more fat than longhorns. Individual cows are liable to vary among themselves and from day to day in the quantity of their milk, and therefore, notwithstanding general belief, it is a disadvantage to feed an infant always upon the milk of the same cow. More uniformity will, on the average, be secured by feeding the mixed milk of several animals, the variations in the components neutralising each other.
"Strippings" is the name given to residual milk which may be drawn off shortly after the ordinary milking has been completed.
Contrary to popular belief, it possesses no advantage as food over the rest of the milk, and what little difference in composition exists can be artificially produced. It is richer in fat but poorer in casein than the milk first drawn. For infant use it should be diluted with two parts of water.
Human milk differs from cow's milk in several important particulars. For this reason it becomes necessary when infants are fed upon the latter to so modify it as to render it more digestible for them.
The important differences between human milk and cow's milk are that woman's milk is sweeter by one third and contains little less than half as much casein. The analyses of the United States Department of Agriculture give the percentage of casein in cow's milk as varying between 3.43 and 3.91, whereas that of mother's milk averages 1.5, hence the importance of diluting cow's milk in the early months of infant feeding. As Leeds says, the calf grows faster and has to manufacture more muscle than the baby - it needs more albumin for tissue building. The casein of mother's milk, moreover, forms smaller coagulae both with rennet and in the stomach, which are more easily dissolved. The normal reaction of human milk is alkaline. Cow's milk varies from faintly alkaline to neutral, and it often becomes acid, especially when the animals are not pasture-fed. There is nearly one half per cent more fat, and the globules exist in a finer emulsion in woman's than in cow's milk. Cow's milk appears richer, whiter, and more opaque than human milk.
These differences are emphasised by the following comparative analyses by Leeds of average cow's milk and human milk:
Sound dairy milk.
3.75 per cent.
4.13 per cent.