58. Milk and Its Products 
mal, carefully kept, should retain his breeding powers 
up to eight or nine years of age, or even beyond. 
Grading up the herd.—The successful and pro- 
gressive dairyman will not only give his best efforts 
toward securing a herd that will make a satisfactory 
production, but will look to the future, and secure 
still further improvement by breeding from his herd 
succeeding generations that shall be even larger pro- 
ducers than their ancestors. Such a dairyman may, 
if he chooses, secure as the foundation herd pure-bred 
animals that may be depended upon to transmit their 
qualities to their descendants. But with even the 
highest-bred animals there will be the necessity for 
selection, if the original standards of production are 
to be maintained, to say nothing of being increased. 
On the other hand, the large majority of dairymen 
seeking to improve their herds must depend, more or 
less, upon the individual animals they have already 
on hand as the basis from which to start the im- 
provement. In either case, careful selection must be 
practiced, and a knowledge of at least the elementary 
principles of selection is necessary for progress along 
this line. It is proposed, then, briefly to indicate the 
lines along which an attempt to breed up, or improve, 
a herd of common, native or mixed cattle is most 
likely to prove successful. 
In the improvement of a herd of cows it has beet 
very common to recommend that the practice should 
be to use a pure-bred bull, and to raise the heifer 
calves from the best cows in the herd. Whether or 
not this practice is correct will depend, to a great 
