Milk the best animal food
Milk and the various products made therefrom constitute one of the most important groups of food in the modern bill of fare. Milk and eggs are interdicted by some vegetarians, but aside from the sentimental feeling against the taking of any food of animal origin, there are no scientific reasons for such exclusion. Dairy products are free from many of the objections assessed against the use of flesh, and they supply a number of readily soluble, digestible, and assimilable nutrients that, in many respects (curative and remedial feeding), excel anything that can be secured from the vegetable kingdom.
Results of special feeding
The composition of cow's milk varies widely. Dairy cows, by long domestication, breeding and feeding, have been brought to a high state of specialization. Some breeds have been so trained, fed, and bred as to produce large quantities of milk. Some Holsteins have been known to produce one hundred pounds of milk per day each, which of course is many times the quantity required for the nourishment of their young. Some Jersey stock have been so bred, raised, and fed as to produce large quantities of butter; in some cases the butter-fat of especially fed Jerseys has been known to run as high as 8 or 10 per cent, whereas the normal fat content of milk is not more than 3.5 or 4 per cent.
The average composition of mixed milk from many cows runs about as follows: Water, 87 per cent; lactose or milk-sugar, 4.5 per cent; butter-fat, 3.5 per cent; ash, .7 per cent; proteids, 3.3 per cent, of which about 2.5 per cent are casein, and .8 per cent albumin.
Value of milk depends upon its nitrogenous content
The commercial value of milk is measured almost entirely by its content of butter-fat. This is because the public knows practically nothing about the food value, or the chemistry of milk, therefore its value is estimated upon that which can be seen, and upon that which tastes best. The chief value of milk as a food lies in the nitrogenous element it contains. Fat can be secured from many other sources.
The nutritive elements of milk from various animals vary according to the natural requirements of the young of various species.
Cow's milk contains too large a proportion of casein, and not enough milk-sugar to meet the natural requirements of the human infant. This subject, however, will be discussed at length in Lesson XVI on "Infant Feeding," Vol. V, p. 1154.
Coagulation of casein in milk