234 PRODUCTIVE FEEDING OF FARM ANIMALS 
feeding fat or oil, but the evidence with regard to this point fur- 
nished by different experiments is often conflicting, and in cases 
where greater differences were found as a result of a certain system 
of feeding there was a gradual return to normal after a couple of 
weeks or before, when the cows became accustomed to the feed. 
In general, both dairy farmers and scientists are now agreed that 
it is impossible to change materially the percentage of fat in a 
cow's milk by the. feed; no amount of rich feeding or supplying 
special feeds will change the milk of a Holstein to a composition 
similar to that of a Jersey, or make low-testing cows or families 
into “high testers.” The largest improvement in quality that 
can be hoped for would be within a few tenths of one per cent. 
“The quality of the milk which the cow produces is as natural to 
her as the color of her hair ”; it is a practically fixed character that 
is intimately connected with the functional activity of the mammary 
gland. 
Influence on Quantity of Milk.—The feed eaten by a cow in- 
fluences in a marked manner the quantity of milk secreted, and 
determines the production that the cow will make, up to the capacity 
of her mammary glands. The feed is, therefore, of primary im- 
portance in the management of a dairy, and the problem before 
the dairy farmer is to provide feed for his cows that will secure the 
largest production of which these are capable, at a minimum cost. 
As it is only the excess of feed eaten over and above mainten- 
ance requirements that is used for productive purposes, it follows 
that the more a cow will eat without increasing appreciably in body 
weight, the larger returns she will yield per unit eaten (see chart, 
p. 236). The old saying, “ Feed your cow and she will feed you,” 
expresses the practical experience as to the relation of feed to 
product. With cows of the dairy type that respond to a more 
liberal system of feeding by an increase in milk production and not 
by a gain in body weight, this is a safe rule to follow in the manage- 
ment of a dairy. It is the heavy eaters that produce the largest 
yields and give the most economical production.?° 
The Value of High-producing Cows.—Results obtained in 
the Wisconsin Dairy Cow Competition, 1909-1911, illustrate in a 
striking manner the value of high-producing cows. The following 
table gives some of the main data for the highest, medium, and 
lowest producers among the 398 cows in the competition for which 
complete records of production for a full year were obtained. The 
* Proc. Soc. Prom. Agr. Science, 1912, p. 23; Wisconsin Bulletin 102, 
p. 78, and Research Bulletin 26. 
