Oxford Democrat., 1919-03-25

lCkrespondence on practical agricultural topic
eoncttod. Address all communications II
nnded for this department to HM1I D
s1 ah0sp. Agricultural Editor Oxford Dem
Variations In Milk and Cream Tests
prof L. N. Dorsey.)
Where milk and cream are pnrchaset
on the buttsrfat basis oftentimes th,
question arises a. to the correctness o.
the test a. found In the returns Of th,
creamery or milk-reoeiving station. Their
again through the inspection Of milk 4
ia quite often brought to the dairyma
Attention that he has been selling mill
which 10 below the standard in per cen
Of fat required by Law, " hen In all good
faith he believed the milk to be all right
in this respect. Occasionally the same
trouble occurs with cream. The inten,
OF this article IL to set forth some of ths
reasons why the fat test OF milk or cream
will vary from time to time.
There are q number Of reasons why
milk varies In test and the folio wing are
among the most important: 1st, breed oi
cows; End, stage Of lsctation; 3rd, season
Of the year; 4tb, condition of the animal
5,h, time of milking; 9th, thoroughnes'
of milking; 7tb, method of sampliDg the
milk; 9Th, condition Of the milk when
tested.
In connection with the various breeds
it Is found that in the order of the ia,
test, the Jerseys are highest, Guerpseys
second, Ayreshires third, and Holstein.
Friesians fourth. In all four of these
dairy breeds there are individual COWS
which may give higher or lower fat
test than the breed average.
In general as the lactation period ad-
vancss the milk OF COW while decreas-
ing in amount will have an increasing fat
test.
The milk of herd of cows, fresheniug
at different times of the year, will have a
lower fat test through the summer than
through the winter months. In q small
herd II number of cows fresben at about
the same time the milk of the herd will
be lowered in test.
An animal subjected to great excite
ment, such as fright, @strum, or pro-
lopged running, may give milk with an
increased test over that of normal or II
may be decreased below normal. In q
herd some animals may be affected in an
opposite manner from others SO that the
disturbances In milk secretion counter
balance each other. When the calf Is
taken away after remaining several days
with the COW, the cows milk will de-
crease in test and then after day or two
return to normal. A change of mixers
sometimes causes the COW to give milk
with lower test than normal.
The milk of herd of cows will test
higher for the night milking than for the
morning milking. The test of the milk
of the individual COW may vary from one
milking to the next, but usually she gives
the higher per cent of fst in the nights
milk. When cows are MIXED Ofteuer
than twice day considerable variation
may occur in the test from one milking
TO another.
II COW is not milked dry her milk
will test less in fat than II she had been
thoroughly milked. This Is because the
first drawn milk tests less than the last
drawn.
Milk In order to be accurately tested
should be thoroughly and uniformly
mixed when the sample for testing pur-
poses 10 taken; also when this sample is
to be tested 1t must be uniformly mixed.
Where composite samples Of milk are
kept the portions taken from each lot Of
milk should be exactly proportional by
weight IN order that an accurate average
test may be secured.
Milk which has churned slightly or has
soured 10 difficult to test and must be
carefully prepared before sample for
testing purposes Ia taken. The same is
true Of partially or wholly frozen milk.
Milk on which cream has raised must
have the cream uniformity distributed In
the rest of the milk before sampling.
Milk to which preservatives have been
added must be carefully treated, because
quite often hard layer of cream forms
which must be incorporated with the
rest of the milk. These above mentioned
conditions of milk when sampled might
be tho means of obtaining either higher
or lower test for the milk than It actually
should have.
Cream test variations are to some ex-
tent influenced by variations In the test
of the milk from which the cream 10 sep
arated. The cream separator itself 10 the
source of number of variations In tests
of cream. Factors which cause cream
test variations are a. follows: 1st, method
of separation; End, test of milk sepa-
rated; Srd, temperature Of the milk; 4th,
rate of inflow of milk; 5th, speed OF sep
arator: 9th, amount of liquid used In
flushing out bowl; 7tb, methods of sam
ming: Stb. condition of the milk whom
tested.
Cream obtained by any gravity system
of creaming will vary In fat percentage
from one time to another due to varia.
tiops in tenn perature and thoroughnesa
with which the skimming Is done. When
the centrifugal hand separator 10 used.
cream of uniform test may be obtained
II all conditions governing operation are
uniform and the milk does not vary IN
test for each run. The cream screw may
| be adjusted to deliver cream OF uniform
test from milk of uniform test.
The higher milk tests the higher will
cream test which is separated from It.
| For this reason cream from nights mill
will test higher than cream separated
| from mornings milk. This 10 because
the cream screw Of the separator 10 &C
regulated a. to deliver certain ratio Of
skimmed milk to cream; usually Ss
pounds skinned milk to 10 pounds
cream. II milk tested 8 per cent fat ano
100 pounds were separated, We wouic
obtain Is pounds of cream containing
pounds of fat, or . test OF 3 divided by
| is. multiplied by 100, equals 20 per cent
| II 100 pounds of As per cent test miii
were run through the same machine W
would have the same amount OF cream
namely, is pounds; but 1t would contain
pounds of fat which would cause th'
test to bs As divided by 10. multiplied
by 100, equals 80 per cent. :,
From these two examples IL can o.
readily understood why variations In th'
test of milk will bring about . cream tes
\ variation, no matter II oil other condi
tions of the separation are ideal. In viev
OF this factor the cream screw should D
turned in when the summer months com
around in order to keep the cream tes
uniform.
Milk should be separated ct NO les
tam perature than S5 degrees f., W de
degrees r. to 100 degrees F., being pref
srsble. The cooler the milk 10, the les
sasilv In the cream separated, and tn
higher its test will be; and the loss o
|faf In the skinned milk will be YER
large. ~ A., -.
above or below normal will cause de
crsased fst test in the cream.
M. h,oha, the speed at which the scr