University of Kentucky———C0llege of Agriculture
. . . EXTENSION DIVISION
THOMAS P. COOPER, Dean and Director .
Circular No. 251 December, 1931
Published in connection with the agricultural extension work carried
on by cooperation of the College oi Agriculture, University of Kentucky, _
with the U.   Department of Agriculture, and distributed in further-
ance of the work provided for in the Act of Congress of May S, 1914.
 
Variation in the Butterfat Content of Milk and Cream
By FORDYCE ELY
Milk and cream are usually bought and sold on the basis of the
percent of butter fat they contain. This is determined by the Babcock
test,'a simple routine laboratory operation which when properly con-
ducted offerswlittle opportunity for error.
It is natural for variations to occur in the butterfat content of
milk from a herd of dairy cows. Frequently dairymen fail to realize
that certain conditions normally tend to increase or decrease the
butterfat content of milk and cream. Failure to recognize these con-
- ditions often leads to a lack of confidence between buyer and seller
and sometimes an unjustiiiedrchange inpatronage. The purpose of
this circular is to explain some of the common causes of the varia-
tions in the butterfat test of milk and cream.
FACTORS INFLUENCING THE PERCENT OF BUTTERFAT
IN MILK
1. The breed of the cows in the herd. Considerable variation
exists in the percent of butterfat in the milk from cows of different
dairy breeds. Usually Jersey milk is richest in butterfat and Holstein
milk contains the least. The butterfatt coritcnt of the milk of tl1e
leading dairy breeds ranks in the following order: Jersey, Guernsey,
Ayrshire and Holstein. In the amount of milk produced usually the
ranking is exactly reversed. Therefore, little difference exists between
the breeds in butterfat production. Obviously, if a number of Jersey
cows are added to a herd the butterfat test of the milk produced will
have a tendency to rise, whereas, if Jersey cows are replaced Iby
1 Holsteins, a larger volume of milk of lower butterfat test will result.
‘ 2. The individual cow. It is the rule rather than the exception
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