xt7gf18scv94 https://exploreuk.uky.edu/dips/xt7gf18scv94/data/mets.xml   Kentucky Agricultural Experiment Station. 1931 journals kaes_circulars_251 English Lexington : The Service, 1913-1958. Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Circular (Kentucky Agricultural Experiment Station) n. 251 text Circular (Kentucky Agricultural Experiment Station) n. 251 1931 2014 true xt7gf18scv94 section xt7gf18scv94 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
I
\.· ___ _ _ _ {A

 2 Kentucky Extension Circular N0. .251.
for differences to occur in the butterfat test of milk from individual
cows within a breed. It is not uncommon for the milk of one Holstein 8
cow to test 2.8 percent butterfat while that from another Holstein in 3
_ the same herd, receiving the same feed and care, may test 4.0 percent. 1:
In the same way Jersey cows in the same herd normally may produce i.
milk varying from 4.0 percent butterfat to 6.0 percent or even more. j,
This variation also exists within other breeds and is an inherited
characteristic. t
3. The stage of lactation of the cows. A cow, shortly after t
freshening, has a tendency to produce milk relatively rich in butterfat. E
As she reaches her peak of milk production usually her milk tests t
lower in butterfat. As she nears the end of her lactation period and (
gradually drops off in milk production usually her milk becomes richer X
in butterfat. Plainly this is the reason why butterfat tests on each
cow must be made at regular intervals in O1`(]B1' to measure production [
properly, in the individual cow. A cow cannot *be called a "high (
tester" or a "low tester" on the basis of one or two tests. If a con- i
siderable numiber of cows in the herd are "strippers" this contributes 1
to a relatively high test of the milk from the herd. On the other hand,
if a number of cows in the herd are in the "flush" of production, the I
average test of the milk of the herd may lbe somewhat lowered. ;
4. The conditi0n of the cows at time of freshening. 1f a cow is 1
naturally a heavy producer and is in high condition when she freshens, 1
her milk is likely to be especially rich in butterfat during a period of
one to three weeks after calving. As the flush of production approaches ,
the butterfat test of the milk drops to normal. ]
5. Variation with the season of the year. The effect of the season 1
.of the year on the percent of butterfat in milk often is disregarded by 3
dairymen. A lowering of the butterfat test often is noticed when the- .
cows go on pasture in the spring. Later, as cool weather sets in, the 1
average test of the milk of the herd rises. Often it is assumed incor-
rectly that this is due to the succulent grass consumed by the cows. 4
Much experimental evidence shows that the milk from the herd is 1
richer in butterfat in the winter than in summer, due probably to the ;
heat and high humidity during the summer. A lower test is especially
noticeable in herds when many cows freshen in the spring. Such cows
are in their low-testing stage of lactation during the warm weather.
6. Daily variation, and variation between milkings. It is known
that considerable variation in the butterfat test of milk from individual
cows occurs from day to day and even between milkings the same day.
Little is known regarding its cause. These differences are of little
importance when the test of the milk from an entire herd is taken into
consideration. They do, however, suggest the importance of con-
. tinued sampling and testing at regular intervals, in measuring the
normal fat content of milk produced by individual cows.
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Variation in the Bntterfat Content of Milk and Cream. 3
iduel 7. Length of time between milkings. When the herd is milked
Stem at irregular intervals there is a slight tendency toward a higher test
in in at the milking following the shortest interval. When the lapsed time
Cent- between milkings is exactly the same there should lbe little difference
’d“C€ in the average test of the milk produced by the herd, if everything else
nom- is normal.
*i`it€d -8. Completeness of milking. Last-drawn milk (strippings) often
tests 8 or 9 .percent butterfat as compared with first-drawn milk con-
after taining 1% to 2 percent. Cows often fail to "give down their milk" to
€l`t&t· strangers or inexperienced milkers. Unusual noise, abusive treatment,
tests the presence of dogs or extreme exposure may have the same effect.
i and The result is an incomplete milking and a low butterfat test due to
‘i€h€!` withholding the rich last-drawn milk.
each 9. The influence of exercise. The milk from cows which have
iction been kept in stanchions for several Weeks and then allowed moderate
"high exercise has been found temporarily to ·be .2 to .3 of one percent richer
i 0011- in butterfat. Such moderate exercise, however, should be free from
.butes undue excitement.
hand, 10. The effect of the feed. Contrary to the opinion of many
n, the practical dairymen, neither the kind of feed nor the method of feeding
. affects more than very temporarily the test of the milk. The use of
now iS feeds which induce a feverish, sick condition may greatly lower milk
shens, production and affect temporarily the butterfat test of the milk.
iod of 11. Miscellaneous causes of slight variation. Any illness may
>a0h€S cause a decrease in milk production and variation in butterfat test.
Milk from some cows tests higher during heat periods than at other
season times. This condition has little effect on the butterfat test of the
led by milk of the herd because so few cows are in heat at any one time.
en the- Advanced age of cows has a very slight tendency to lower the butter-
in, the fat test of milk. `
incor- 1E The condition of the milk. Milk which is slightly sour,
i cows. churned or frozen may contain fine curd particles or butter granules. A
rerd is truly representative sample for testing cannot be taken from milk i
to the such condition.
mecially
>h COWF FACT-ORS INFLUENOING THE PERCENT OF BUTTERFAT
Father- IN CREAM
known Separating cream by any other method than with a centrifugal
»ivi<1¤¤l cream separator results in a loss of from 10 to 20 percent of the
U6 day- butterfat.
’f little 1. The richness of the milk. Factors which affect the test of the
€¤ inte milk also affect the test of the cream. A separator delivers approxi-
0f C0¤‘ mately the same quantity of cream from a given quantity of milk
lng W9 regardless of the test of the milk. The difference is in the test of the
cream. A separator which is adjusted to deliver 40 percent cream

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4 Kentucky Extension Circular N0. 251.
from 5 percent milk may be expected to deliver approximately 32;
percent cream from 4 percent milk, when operated in exactly the same
manner.
2. The temperature of the milk. As milk cools it becomes in-
creasingly difficult to separate it efficiently; Cold cream does not flow
so readilyas warm cream, and is inclined to clog the cream opening.
This results in a smaller amount of richer cream and a loss of butter-
fat in the skim-milk.
3. Operation of the separator.
Adjustment. KA properly adjusted and operated cream separator
delivers skim-milk testing less than .02 of 1 percent of butterfat, which
is negligible. By adjusting a simple device in either the skini-milk or
cream opening, the operator can control the amount of cream or skiin-
milk delivered by the separator. The result may be richer cream and
more skim—milk, or vice versa, regardless of the test of the milk of the
herd.
Speed of the machine. Separators are designed to operate at a
certain speed. Slower speed results in a larger volume of thinner
cream and a loss of butterfat in the skim-milk. Higher speed causes
a smaller volume of richer cream and more skim-milk.
Rate of inflow. Usually this is regulated automatically by a float.
If for any reason the rate of inflow is too slow the result will be a
richer cream. If the separator is fed too fast the milk is forced from ,
the bowl before the centrifugal force has been sufficiently applied and  
the result will be lower-testing cream and loss of butterfat in the l
skim-milk. l
Vibration of separator bowl. \Vorn bearings, an unbalanced bowl
or failure of the separator to be properly leveled may cause the bowl to
vibrate. This results in a lower—testing cream and a loss of butterfat
in the skim-milk.
Clcanness of the separator bowl. When separators are washed so
infrequently that curd particles or separator slime partially clog the
bowl, efhcient skimming is not possible. A clogged bowl causes an
excess of Slilllklllllk to he forced thru the cream opening, which results
in a low—testing cream.
Amount of ytush-water used. If the cream spout is allowed to
drain into the cream just enough water should be used as a rinse to
cause a very small amount to emerge from the cream spout. It will
greatly reduce the chance for variation in the butterfat test of the
cream if the same amount of water is used each time.
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