228 PRODUCTIVE FEEDING OF FARM ANIMALS 
While it does not lie within the scope of this book to discuss the 
various factors that have a bearing on this production, it seems de- 
sirable to state briefly the main influences that affect the value of 
a cow in the herd in order that we may see more clearly what part 
the feeding plays in the successful management of a dairy (Fig. 43). 
Fic. 43.—Dairy cows of good breeding and well kept and cared for make excellent returns 
at the pail.’’ 
Composition of Milk.—Cows’ milk is composed of the follow- 
ing constituents: Water, butter fat, proteins (casein and albumen), 
milk-sugar, and ash. The amounts of these components present in 
milk of different origin, or even in milk from the same cow at 
different times, vary widely. The limits of variation for normal 
milk from American cows are about as follows: ? 
Composition of Cows’ Milk, with Variations, in Per Cent 
Minimum | Maximum] Average 
Casein and albumen... 
Milk-sugar............ 
Mineral matter.. ..... 
* Farrington-Woll, “ Testing Milk and its Products,’ 22nd edition, p 
18; see also Wisconsin Research Bulletin 26, p. 62. 
