VARIATION IN MILK TESTS
G. W. Shaw in Hoard’s Dairyman of March 10, 1916 says:
“It is a well-known fact that the percentage of butter fat in the
milk of cows increases very materially toward the end of a period of
lactation. There are also other slight changes in that period. During
the first month the fat generally averages higher than during the
second month. Under normal conditions of feed, etc., the fat increases
from the third or fourth month to the end of lactation.
“Although it is a fact that cows cannot be fed to give beyond a certain
percentage of butterfat, yet it has been proven many times that if
poorly fed for a considerable length of time, the average test will
decrease. This is especially true if cows become thin and poor in
flesh. Many times this will account for a farmer’s average herd test
dropping from one period to the next. It is also noticeable that the
quantity of water taken, whether as water or succulent feed, affects
the herd. This is particularly noticeable when cows are changed from a
diet of dry hay to green feed or vice versa.
“It has been noted that the change of weather affects the test. A
sudden cold period coming will usually decrease the quantity of milk,
but increase the percentage of fat. If the cold period continues,
this change will tend to right itself. It would seem that there is a
connection between the question of heat and cold and the amount of
water taken.
“It is a well-known fact that the first milk drawn from a cow’s udder
is very low in butterfat, not over 1%, whereas the last drawn is quite
high, sometimes reaching 10%. The importance of exhaustive milking is
evident. By carefully milking to the fullest extent each time, the test
will undoubtedly be higher than if milking were not exhaustive. This,
continued over a period of time, would have its effect on the 15-day
test.
“Another very important point we wish to make is this, unless a man who
does his testing at home understands how to do it thoroughly and is
very careful in taking his sample, he will not check with the factory
test. There are several reasons for differences between tests made
on samples taken at the farm and those made on samples taken at the
factory.
“Many farmers have a habit of taking a little cream or top milk for
family use, and think that it will not materially affect the average
test. As a matter of fact it will affect materially. For instance, if a
farmer were producing 100 pounds of milk testing 3.5% and he used one
quart of top milk, testing 10%, his average test would be reduced .2 of
1%; that is, instead of delivering milk testing 3.5% it would actually
test 3.3%.
“Some farmers adopt another method; they use, for family purposes the
milk from a cow which gives the richest milk, so that the result is
always the same, the average test being lower.
“Another cause of difference in tests, and we think this is a very
important one, is found in the condition of the milk when received
at the factory. Some farmer’s milk, when brought in, is smooth and
homogeneous; some bring in milk which is slightly churned; that is,
there are small particles of butter, which is separated butterfat
floating on the surface. This latter milk is very hard to sample; the
sampler is plunged into the milk and is likely to miss a due proportion
of these floating particles. In addition, some of the separated
butterfat is sure to be left behind, both on the sides of can and on
the cover. Butterfat adheres to any surface much more rapidly than
any other of the milk solids. It is quite evident that milk which is
partially churned will get a lower test at the factory than it did at
the farm before it became churned.
“In order to prevent this churning, it is most important that the milk
be quickly and thoroughly cooled after milking. If milk is poured into
cans and stirred and handled in a half warm condition, it is sure to
separate to some extent. While the particles of butterfat are not large
enough to be particularly noticeable, they are there and adhere to the
surfaces as described.
“Another condition which causes trouble in sampling, is found where
some of the cream is firm and floats around in hard lumps but is not
churned. This kind of cream is also hard to sample and these lumps are
liable to be left behind on the sides of the can and cover. We believe
this condition is caused by allowing milk to cool spontaneously. That
is, instead of cooling quickly, the farmer fills up his milk can and
lets it stand to cool slowly. This is liable to give a hard cream on
the surface which does not break up readily. The farmer, therefore,
will get a better test by =cooling his milk quickly and thoroughly and
refraining from using the top milk for family use=.
“We have come to this conclusion, namely, that certain conditions
affect cows and their work, the same as that of human beings. As
someone has said: ‘Put yourself in a cow’s place and try to get
her point of view. Could you do good work if a swarm of flies were
bothering you all the time? What effect does an extremely warm day or
two have on your capacity for work? If you were out in a cold, rain,
and wind storm, how would it affect your work? Suppose you were thirsty
and had to wait two or three hours before you could get a drink and
then got foul and stagnant water? Or, suppose that someone stronger
than yourself would chase you away from the shade or sheltered spot or
forced you to move when you were resting or eating? Suppose you were
forced to eat food that you did not like or enjoy? How long would it be
before these things would show in your work? Any or all of them would
impair your efficiency and lessen your ability.’”