‘THE BABCOCK TEST

rm —
7 r 7
4 , Bt - : “
; Y P ¢; “as UY s
» 5

KHAKI UNIVERSITY OF CANADA ||
es Series 1.—Neo. 9.

1918

Testing the farmers’ milk and teaching their children.
ng ug

Reprinted, with adaptations, from “THE <BABCOCK TEST,
AND TESTING PROBLEMS,” by HC. Troy, in
“Cornell Reading Courses.”

THE BABCOCK TEST
H. Cy Trey.

THE BABCOCK TEST AND TESTING PROBLEMS.
Previous {to 1890 practically all milk was bought
and sold by weight or measure regardless of its composi-
tion. In that year Dr. 8. M. Babcock invented the milk-
fat test that bears his name. By the application of
this test it has become generally known that the percent-

Water 88.434,
water 85 472,

Walrer
G54 Li
(a

Lrerqy Ururs S80 Everqgu urits GOO
Comparative od value oO’ per qt Comparative toca ralue G.27%per Gr

Fic. 99.—Comparison of average composition and food
value of milk containing 3 and 5 » per cent. of fat.

age of fat in milk from different herds often varies
widely. This fact is important because fat is the most
valuable milk constituent, and often forms the chief
basis in fixing the price of milk. The farmer cannot
now determine whether it will be more profitable to

3

sell his milk by the hundredweight or on the milk-fat
basis, unless he first tests the milk.

It is also necessary for the farmer to know the amount
of milk produced by a cow and the percentage of fat
her milk contains when he fixes her market value or
attempts to improve his herd by removing the poorer
cows and by replacing them with better ones. The
farmer cannot intelligently select young stock for
building up his herd unless he has the milk and fat
records back of the dams and sires to direct him.

In this lesson, an attempt is made to give directions
that will assist dairymen in determining the percentage
of fat in milk and cream, and by practical problems
to point out how they may determine which are the
valuable cows in a herd or which method of marketing
a dairy product will bring the larger returns,

It is also expected that the lesson will be of use in
country and village schools, because the Babcock
test in rural schools can be of great service to the dairy-
man in the school district. It is not difficult for the
farmer to learn how to test milk, nor does the operation
require very much time; but under the pressure of
other work testing may often be neglected. If each
rural school were equipped with an outfit for testing
milk and cream, the tests for the farmers in a school
district could be made at the school. That would
reduce the expenses very much because one set of testing
apparatus would serve many dairymen. The teacher
could instruct the older pupils to make the test and
assist in the work. They would quickly learn the best
method of performing each part of the operation and
would gain confidence to continue the practice of testing
their herds. The test can also be made the basis for
problems in arithmetic that will quicken the pupils’

4

interest when the application is so readily seen. The
pupils will find real pleasure in making the test, and
they will become interested in a useful work when com-
paring the milk and fat records of different cows and
herds, and the methods of feeding and breeding that
produce the best results.

FAT VARIATIONS IN MILK.

There are several causes for the variations in the
percentage of fat in pure milk. One of the most import-
ant is the breed of the cows. Next comes the individual
of the breed. The percentage of fat in the milk of an
individual in extreme cases may average either one per
cent. above or one per cent. below the breed average.
Also, the percentage of fat is affected by the length
of time since the cow has freshened. It is a well-known
fact that toward the end of the lactation period, when
the cow is being dried off, the milk contains a higher
percentage ot fat than it did earlier in the season. It
is also fairly well established that, when the time elapsing
between milkings is not of equal length, the milk drawn
after the longer period contains the lower percentage
of fat. There are also minor influences affecting the
fat content, such as a feverish condition of the animal
or over-excitement, due to dogging or other ill treatment
that might cause the cow to hold up part of her milk,
thus giving a larger proportion of the milk thatis first
let down, which is not so rich in fat as the strippings.
It has become a well-established fact that the character
of the food of an animal has very little effect on the
percentage of fat in the milk, although it has a marked
effect on the amount of milk and fat produced.

Fat exists in milk in the form of very small globules.
With the aid of a high-power microscope they may

~

0

|
\ AY
\ \ ee

NWN

ing outfit,

ampl

Milk s

100

‘
.

Fic

be seen floating in the liquid. Since the fat globules
are lighter than the other milk constituents, most of
them rise to the surface under the influence of the force
of gravity. There, mixed with other milk substance,
these globules form a layer of cream.

Whensulphuric acidof proper strength and temperature
is added to milk, as in the Babcock fat test, the casein,
the milk sugar, and the albumen are decomposed, and
the sticky quality of the milk is destroyed. The acid
does not, however, decompose the fat, but leaves it
free to come to the surface of the mixture under the
influence of centrifugal force generated in the testing
machine.

EQUIPMENT.

The testing equipment that a dairyman should
purchase may vary according to different circumstances.
lf the farmers in a neighbourhood arrange to have their
miik tested at a central point, such as a district school,
then each would need to purchase only the sampling
outfit, which would cost between three and four dollars.
If they tested their milk at their homes, in addition
to the sampling outfit each would need the milk-testing
outfit and, for the accurate testing of cream, the addi- ©
tional cream-testing apparatus.

MILK-SAMPLING OUTFIT.

Spring scales... a2 hs ie $3.00
Record sheet .. ii ae re 05
Sampling dipper 3 oe ae 15
Six sample jars nip a i . 60

$3.80

~]

MILK-TESTING OUTFIT.

2 pipettes with capacity of 17.6 ¢.c... $0.40

12 Babcock milk test bottles .. ze 1.50
2 skimmed milk test bottles... a 1.00
2 acid measures with capacity of

Bee, ea e oe 25
1 twelve-bottle tester... ae Ee 12.00
1 tin cup with spout .. Be sk 25
1 gallon of sulphuric acid .. ~~ 75

ADDITIONAL APPARATUS FOR TESTING CREAM.

4 cream test bottles .. ae os $1.00
1 cream seales.. — i A 8.00
1 tin pail - 23 Pe ie 15
1 thermometer dg s re 00
1 pint of meniscus remover (glymol) 25
1 dropping pipette .. - of: .10
$10.00

Totaltix: _ - ae .. $29.95

When ordering Babcock milk or cream test bottles
cr 17.6 cubic centimetre milk pipettes, the buyer should
specify “‘ Standard Babcock Glassware ” that has been
tested for accuracy.

MILK SAMPLING OUTFIT.

In the sampling outfit, bottles holding between four
to eight ounces, or from one-fourth to one-half pint,
could be substituted for the sample jars. The wide
neck of the latter, however, permits the milk to be added
quickly without danger of loss and also enables the
operator to observe the condition of the sample and to
clean the jar more readily. The jar should be labelled
with the name or number of the cow producing the milk
sample. The sampling dipper should held an ounce and
should have a wire handle about a foot long. A spring
scales, permanently suspended near the location of the
receiving cans, affords the simplest method of weighing
the milk. A convenient arrangement of the sampling
apparatus is shown in Fig. 100.

If it is impossible to afford a spring scales, the weight
of the milk may be calculated. To do this, first accu-
rately measure the milk, then multiply the number of
quarts by 2.15, as one quart of average milk weighs
about 2.15 pounds. Thus if a cow yields 7.25 quarts
at a milking. the weight of the milk would be approxi-
mately 15.58 pounds.

7.25 x 2.15 =15.58 x

MILK-TESTING OUTFIT.

The number of test bottles that should be ordered
with the testing outfit depends on the amount of testing
to be done. Usually two test bottles are allowed for
each cow in the herd. Two each of pipettes, acid
measures. and acid bottles would be sufficient. Then
if one were broken, another would be ready for use.
Where hand power is used, the covered form of twelve-
bottle hand tester is safer than the four-bottle machine.
It also may be kept at a proper temperature with less

9

\ \

\

i:

‘

\

\\
\

\

\\

g outfit.

-testin

Fic. 101.—Milk

10

difficulty than the smaller machine. The four-bottle
tester might serve where only one or two cows are to
be tested.

The sulphuric acid may be bought at almost any drug
store. The buyer should state that the acid is to be
used in the Babcock test and that it should be of such
concentration that it will have a specific gravity between
1.82and 1.83. Theacidshould be kept in glass-stoppered
jugs or bottles; otherwise it will absorb moisture from
the air and become too weak to dissolve the milk solids
and free the fat. Acid that is too strong might burn the
fat. The acid is astrong poison, and if it happens to come
in contact with the flesh or the clothing, should be removed
at once by washing with large quantities of cold water.
Bicarbonate of soda (common bakimg soda), ammonia, or
a similar alkaline substance should be applied to remove
any acid not washed away.

CREAM-TESTING APPARATUS.

There are several forms and sizes of cream test bottles.
The six-inch nine-gram bottles are preferable especially
for use in hand testers. ‘This form of bottle has a scale
graduated to read from 0 to 50 per cent., the smallest
seale divisions equalling 0.5 of 1 per cent.

The balance for weighing cream test samples should
be sensitive to .1 of agram. A form of balance should
be bought that may also be used for general weighing
purposes, especially if it is for use in a school. There
it may be used in many instructive experiments that will
interest the pupils and form the basis of many problems
in arithmetic. A good form of druggist’s dispensing
balance with a set of weights in grams would serve well,
It would be the least expensive and most durable.

An ordinary four-quart pail would serve as a vat in

1]

which to bring the fat in the cream test bottle to the
proper temperature before adding the meniscus remover
and reading the test. The vat should be of such depth
that when it is nearly full of water and the cream test
bottles are placed upright in it, the upper surface of the
water and of the fat columns will be on about the same
level.

The thermometer should be of a form that registers
each temperature degree between the freezing and boiling
points of water. That would permit of its use for a
variety of purposes.

The meniscus remover is made from a purified mineral
oil that has been coloured red with alkanet root. It is
sometimes called glymol. When placed on the top of
a fat column in a cream test bottle, it flattens the curved
surface, which is known as the meniscus.

RURAL SCHOOL TESTING EQUIPMENT.

A complete testing equipment for a rural school would
include all the apparatus listed. The sampling appa-
ratus would be useful in showing dairymen what they
should have. Or the school might first obtain the milk-
testing outfit if it could not afford the complete list, and
the other apparatus could be added as the work pro-
gressed. The covered twelve bottle tester should always
be used where children are present, in preference to the
open form of smaller machine, because there would be
much less danger of accident.

TAKING TEST SAMPLES.

The milk from each cow in a herd should be weighed
and tested at regular intervals. A very good practice
is to weigh and test the milk on the first, the tenth, and
twentieth of each month. Since there is likely to bea
little difference in the percentage of fat in the night’s

12

and morning’s milk, it is preferable each time to weigh
and sample two successive milkings.

At milking time
a pail of known
weight may be
hung on the scales
and the milk from
a cow poured into
it and weighed.
When several
pails are used, it
is convenient to
make them all of
equal weight by
attaching solder
to the bottoms of
the lighter ones.
Then when a cow
is milked, the pail
may be hung on
the scales. The
weight of each
cow's milk should
be set down after
the name or num-
Fic. 102.— Correct position of the pipette ber of the cow on

and test bottle while transferring the the record sheet.
milk.

The milk should
, then be mixed by
pouring it from one pail to another or by thorough
stirring. By use of the sampling dipper two ounces
of the milk should immediately be placed in the sample
jar. The jar should be stoppered and kept in a cool
place until more milk is added or until the milk is

13

tested. It would be well to first weight and sample the
night’s milk; then a sample from the morning’s milk
taken in like manner could be added to it and the mixture
tested. Or each sample could be held and _ tested
separately. :

TESTING THE MILK.

Mix the milk by pouring, allowing it to flow down the
side of the vessels to avoid incorporating air bubbles.
Vigorous shaking should be avoided. See that all cream
is removed from the
sides of the sample
bottle and that it is
evenly distributed
throughout the milk.
Then, holding the
pipette between the »
thumb and the second
finger of the right hand,
place its tip well under
the surface and draw in
the milk by suction with
the lips on the upper
end until it is filled well tion and position of a test bottle
above the graduation. while mixing the milk and the acid.
Quickly place the fleshy
pad of the forefinger over the opening and at right
angles to the pipette. By rolling the pipette a little
between the thumb and the second finger sufficient air
will enter to allow the milk to run out slowly until the
upper surface is exactly level with the graduation. The
pipette should be held perpendicular at this time with
the graduation on a level with the eye.

Hold the milk test bottle in a slanting position and

14

Fia. 103.— Diagram showing the mo-

=

place the tip of the pipette into it about one-third of an
inch and at a slight angle (fig. 102). Allow the milk to flow
slowly down the side of the bottle neck, making certain
that none is blown out by the escaping air. Blow the
drop that remains at the tip of the pipette into the test
bottle. Measure out another test sample in the same
manner, as the test must be made in duplicate.

ADDING THE ACID.

Fill the measure to the mark with acid, and then rotate
the test bottle slowly while adding the acid so that it
will rinse down any milk remaining in the neck. Im-
mediately mix the acid and the milk thoroughly by whirl-
ing the body of the bottle in a circle five or six inches in
diameter (fig. 103), using care to keep the mixture out of
the neck of the bottle. Shake the mixture vigorously
for about one minute after all curd has disappeared, and
shake it again just before centrifuging to insure complete
solution. Avoid pointing the neck of the bottle toward
any person during the mixing operation, and so prevent
the possibility of having acid thrown into the eyes or
on the clothing. The acid unites with all of the milk
substances except the fat, thus generating much heat.
The temperature of the mixture usually rises to 225° F.

CENTRIFUGING THE BOTTLES.

First heat the centrifuge either by placing it on a stove
or by adding a few quarts of boiling water. A corked
opening in the bottom provides a means of removing
the water.

The dise of the machine must be balanced by placing
test bottles in exactly opposite pockets. Cover the
machine before turning the handle. About eighty re-
volutions of the handle per minute usually generate one

15

thousand revolutions, the required speed of the dise.
After whirling the bottles for five minutes, stop, and,
without removing the bottles from the pockets, fill them
nearly to the base of the neck with water that is nearly

boiling hot. The
pipette or a tin
cup with a slen-
der spout may be
used for this pur-
pose (fig. 104).
Whirl the bottles
again for two
minutes in order
to wash any sedi-
ment from the fat.
Again add hot
water to the test
bottles until the
top of the fat
column is a little
below the highest
graduations on
the scale. Whirl
the bottles for one
minute, and take
the readings im-

ee a SE eS ee ee

Fic. 104.—Pouwring the hot water into
the bottles.

mediately. If the tests are not read immediately, they
should be held at a temperature between 130° and
140° F. either by keeping the centrifuge hot and covered
or by placing the test bottles in water at that tempera-
ture and deep enough to surround the fat columns.

READING

THE PERCENTAGE OF FAT.

Subtract the reading on the scale at the base of the
fat column from the reading at the highest point at the

16

top of the fat

of fat in the milk.

Fria. 105—Meth-
od of reading
the percentage
of fat in milk.

The arrows indi-
cate the points on
the scale at the
ends of the fat
column at which
the readings
should be taken,

column. The difference is the percentage
Thus, if the seale at the base of
the column reads 1.7 and at the top it
reads 5.8, then 5.8 — 1.7 =4.1, the per-
centage of fatin the milk. The curved
surface called the meniscus, which always
exists at the top of the fat column,
must be included in the reading, as it is
just large enough to make up for a small
amount of fat remaining down in the
body of the bottle. The limit of error for
the test is usually less than .2 of 1 per
cent. When such a difference occurs in
a duplicate test, the average of the dupli-
cate readings should be taken.

SAMPLING CREAM.

Cream differs from milk by containing
a higher percentage of fat. Cream con-
taining 30 per cent. of fat would contain
70 per cent. of skimmed milk substance,
or milk serum. Before sampling, the
fat should be evenly distributed by
thorough mixing or pouring. If the cream
is old or lumpy or some has dried on the
container, it should be warmed to about
95° F. and the lumps should be passed
through a strainer before mixing. Then
about two ounces should be placed in the
sample bottle.

TESTING
The test

THE CREAM.

sampie must be weighed

instead of measured because:

17

\
\

N

<
G

|

\

\
i)

ting outfit.

/ream-tes

+. 106.—C

Fic

1. The percentage of fat and the specific gravity of
cream vary widely, and the weight of a definite volume
would vary accordingly.

2. Cream may contain bubbles of air or of carbon
dioxide.

3. Cream varies so widely in viscosity (sticky quality)
that the amount delivered or the amount remaining
in the pipette would be unknown.

In testing cream 9 grams is used. Balance the bottle on
the scales, and place a 9-gram weight on the opposite side.
Mix the sample thoroughly, and by means of a pipette
transfer cream to the test bottle until the scales exactly
balance. Next add about 9 cubic centimetres of water
to the test bottle. (This water may be measured with
sufficient accuracy in the acid measure by filling it
a little over halfway to the mark.) Add about 15
cubic centimetres of the acid to the test bottle, and
mix the centents thoroughly. The cream and acid
mixture should not turn black but should remain coffee
colour. About 15 cubic centimetres of acid gives the
proper concentration to dissolve the solids not fat,
since the fat forms such a large part of the mixture
and does not go into solution. Centrifuge the bottles,
and add the water exactly as in testing whole milk.

TEMPERING THE FAT AND READING THE PERCENTAGE.
When the last whirling is completed, transfer the
test bottles to the tempering vat containing water held
at a temperature of 140° F. The water should be
tempered in advance, and it should be deep enough
to surround the necks of the bottles to the top of the fat
columns. After four minutes take the bottles from the
water, and add the meniscus remover at once by
placing the tip of a dropping pipette containing some

19

of the substance against the inside of the bottle’s neck,
which is held in a slightly slanting position (fig. 107).
The red liquid is allowed to run slowly down the inside
of the neck and spread over the fat to a depth of about

one-fourth of an inch. It should not mix with the fat.
Read the test im-

mediately by
subtracting the
number on the
scale at the boi-
tom of the fat
column trom tke
number on tke
scale at the line
of division be-
tween the fat and
the meniscus
remover. Thus if
the bottom line of
the fat column
reads 12 and the
line between the
meniscus remover
and the fat at the
top reads 39, the
percentage of fat
would be 27.

In testing milk
the meniscus should be included in the reading as
it is just sufficient to make up for the fat that
is not brought up by the test. But the volume
of the meniscus on the cream test is much larger than the
one on the milk test, while the amount of impurities in

the larger volume of fat in the cream test is about suffi-

Fic. 107.— Adding the meniscus remover
to the cream test.

20

cient to make up for any fat remaining down in the

bottle.
should be removed before reading

the percentage of fat.

WASHING BABCOCK GLASSWARE.

Wash the glassware thoroughly
between each test. Any fat re-
maining in the test bottles would
increase the following test. First
empty the contents of the test
bottles on an ash heap or some
place where the mixture will not
come in contact with the food or
the feet of animals. Do not empty
the mixture into ordinary sinks or
drains because the acid solution
will destroy the sink and piping.
Then rinse out the bottles with hot
water. Add a strong hot solution
of a good washing powder until the
bottles are half full. Shake them
vigorously while emptying them, and
pass a small brush through the necks;
then rinse them again using plenty
of hot water. The bottles will then
be ready to use in another test

The pipette should be rinsed
out with water immediately after
measuring out the samples, for if
the milk is allowed to dry it will be
difficult to clean the instrument.

Therefore the meniscus on the cream test

Fie. 108. — Method

of reading the per-

centage of fat in
cream.

The arrows indicate

the points onthe scale at

the ends of the fat

column at which the
readings should be taken

It should also be

washed with the hot soap solution when the bottles
are being washed, and well rinsed afterwards.

21

A simple tray for holding test bottles (fig. 109) while
carrying or washing them is made by boring twelve
or fourteen holes, to fit the bottoms of the bottles,
nearly through a piece of plank 12 inches long, 6 inches
wide, and 1.5 inches thick. A cover half an inch thick
is made with corresponding holes. The holes in the
cover should be large enough to permit the necks of
the bottles to pass through, but not the bodies.

When several bottles are to be emptied and washed,
they may be placed in the block and the cover placed
down over them. By holding the block and cover
together at each end, several bottles may be shaken
or emptied as quickly as one.

TESTING SKIMMED MILK AND BUTTERMILK.

The skimmed milk test bottle (fig. 110)is also used in
testing buttermilk, and the operation is the same for each
substance. The graduated neck of the skimmed milk
test bottle has a very small bore in order to measure
the fat accurately. A second neck with larger bore
is attached to provide a convenient means of filling
the bottle. The smallest divisions on the scale usually
indicate .01 of 1 per cent., but on some bottles they
indicate .05 of 1 per cent.

The same care is necessary in mixing and sampling
skimmed milk and buttermilk that is required for whole
milk, and the same pipette is used in measuring out the
sample. The skimmed milk is added to the test bottle
through the larger neck. Since a little more acid is
necessary to thoroughly free the fat in skimmde milk,
the measure should be filled to about a quarter of an
inch above the mark. First add about one-half of the
acid, and shake the mixture thoroughly; then add the
remainder, and again shake it vigorously for about a

22

minute. Avoid throwing undissolved casein into the
small neck while mixing the milk with the acid. The
bottles are then centrifuged and filled in the same manner
as in testing whole milk, except that the first whirling
should be continued for ten minutes, instead of five,
in order to bring
up all the smaller
fat globules. The
percentage of fat
is read imme-
diately on com-
pleting the final
whirling.

SPECIAL
EXPLANATIONS.

While one may
be able to make
the Babcock test
successfully with-
out knowing all
the basic facts on
which it depends, Fic. 109.— Tray and cover for
a knowledge of holding test bottles.
them is often of
advantage. This appliesespecially when difficulties are
met in getting correct tests or when teachers are ex-
plaining the test and answering questions. Therefore a
few of the fundamental principles are explained here.

SPECIFIC GRAVITY.

When equal volumes of milk and water are weighed
it will be found that the milk is heavier. A vessel
that holds 1,000 grams of water will hold 1,032 grams

9
29

of average milk; or for each gram of water there would
be 1.032 grams of milk. 1,032~—1,000 = 1.032. Therefore
1.032 equals the specific gravity of milk, since it is the
existing ratio between the weights of equal volumes

milk test bottle.

of milk and the standard ‘sub-
stance water. One cubic cen-
timetre of water at the proper tem-
perature (4° C., or 15.55° F.) weighs
one gram.

THE PIPETTE.

The Babcock pipette used in
measuring milk test samples de-
livers 18 grams of milk. 18—1.032
(the specific gravity of milk) =17.44,
the cubic centimetres of milk de-
livered into the test bottle. The
pipette is made to hold 17.6 cubic
centimetres because it has been
found by experiment that the
difference between 17.6 cubic centi-
metres and 17.44 cubic centimetres,
or .16 cubie centimetre. remains
in the pipette.

THE MILK TEST BOTTLE.

When the Babcock test was first
invented, the scale on the neck of
each test bottle was graduated to
read from 0 to 10 per cent. The

smallest graduations indicated .2 of 1 per cent. In
recent years preference has been given to a test bottle
that has a scale in which the smallest divisions indicate

.l of 1 per cent.

The seale on this bottle reads from

24

0 to 8 per cent. Both forms of bottles are in use at
the present time.

The graduated portion of the neck of the 10-per-cent.
bottle holds 2 cubic centimetres. One cubic centimetre
of butterfat at a temperature of 140° F. weighs .9 of
a gram. Therefore if the graduated portion of the neck
of the miik test bottle were full of fat, it would contain
1.8 grams. That
would be 10 per
cent. of 18 grams.
1.8 + 18 = .10.
ax 100 = 10
per cent. Eigh-
teen grams is the
weight of the
milk placed in
the test bottle.
When 2 cubic
centimetres, the
volume in the

neck, is divided fie. 111.— A convenient form of scales
into ten equal for weighing creamsamples. Especially
parts, one part good for use in schools.

equals one per

cent.

APPEARANCE OF A COMPLETED TEST.

In a completed test the fat should be straw yellow in
colour; the ends of the fat column should be clearly
and sharply defined ; the fat should be free from specks
and sediment; the water in the neck just below the
fat should be clear ; and the fat should be in the graduated
part of the neck. Some of the defects and remedies are
explained in the following paragraphs.

If the fat column is too dark in colour, the acid may

25

have been too strong, or too much may have been used,
or the temperature of the milk and the acid may have
been too high just before mixing. Mixing too slowly
might also permit charring of partof the fat. The charred
or darkened condition of the fat may be corrected
to some extent by using less acid, by cooling both milk
and acid below 60° F. just before mixing, and by rapid,
vigorous mixing continued for about a minute after all
casein has been dissolved.

If the fat column is too light in colour, the acid was
either too weak or too cold. This condition may be
corrected to some extent in succeeding tests by using
more acid and by having the milk and the acid at a little
higher temperature when brought together.

If the acid is not of the correct strength (specific
gravity 1.82 to 1.83), it will be difficult to get a correct
test, but the trouble may be partially overcome by
using more acid when it is weak and less when it is too
strong.

HERD TESTING PROBLEMS.

The prices used in these problems are simply for the
purpose of illustration. As the price of milk changes,
regular market values may be substituted for the prices
here given.

i:

A farmer had four cows: Bell, Spot, Fawn and Dot.
The milk produced by each cow in two successive milk-
ings was weighed, sampled, and tested three times
during the month of April. The pounds of milk, the
percentages of fat, and the dates the samples were taken,
are recorded in Table 1 as follows :—

26

TABLE l.

April.. 1 2 10 11 20 21
Per- Per- Per-
Pounds of cent- Pounds of cent- | Pounds of — cent-
milk. age milk. age milk. age
of fat. of fat. ; of fat.
PM. | AM. Pee}. Awe Bim: |" Aes
l a
Bell... 11.0 9.0 4.1 12.0 9.8 4.2, 11.8 11.0 4.0
Spot... 16.0 15.0 Be 18.0 15.0 aall 17.5 16.0 3.1
Fawn.. 9.0 10.5 Bal 10.0 11.0 5 af 11.4 10.0 3.6
OU... « 18.0 17.0 4.4 18.5 17.0 4.5 19.0 LES 4:3
Probiems.

1. Find the average number of pounds of milk and of
fat that each cow produced per day, and the total number
of pounds of milk and of fat produced by each cow for
the month.

Solution of the problem for the cow named Bell—

Pounds of Pounds of
milk. fat.
ere Oe OAT = 820
i 6,-— S25-— 21.8. .042 — .915
hes -— LEO = 22.8" .040 = .912

3) 64.6 3) 2.647
Average per day = 21.53 .8823
30 days in April 30 30
Totalfor month = 645.90 26.4690

The cow produced on the average 21.53 pounds of milk
and .8823 pounds of fat per day, and during the month

27

she produced 645.9 pounds of milk containing 26.469
pounds of fat.

2. Compute the monthly income from each cow
valuing the milk at $1.50 per hundred pounds.
3. Assuming that each cow gave as much milk as the

best one, how much more money would the farmer
have received during the month ?

it &

A herd of cows produced on an average 350 pounds
of 3.8 per cent. milk per day during the month of June.
The milk could be sold for $1.30 per hundred pounds,
or it could be separated and the fat in the cream sold for
32 cents a pound. Assume that if the milk were
separated there would be 9,520 pounds of skimmed
milk containing 7 pounds of fat and that the skimmed
milk would be worth 30 cents per 100 pounds when
fed to farm animals.

Problems. ;
1. Which method of sale would bring the larger
returns, and how much difference would there be ?
2. What percentage of fat would the cream contain ?
3. What percentage of fat would the skimmed milk
contain ?

Solutions.
1. 350 x 30 = 10,500, number of pounds of milk for
the month.
105 x $1.30 per hundred pounds = $136. 50,
returns when sold as whole milk.

28

now

bo

10,500 x .038 = 399, number of pounds of fat
in the milk.

399 — 7 = 392, number of pounds of fat in the
cream.

392 « $.32 = $125.44, value of fat in the cream.

95.20 x $.30 per hundred pounds = $28.56, value
of the skimmed milk.

$125.44 + $28.56 = $154.00, returns when the
milk is separated.

$154.00 — $136.50 = $17.50

Therefore larger returns are obtained by separating
the milk, and the difference is $17.50. Answer.

10,500 — 9.520 = 980, number of pounds _ of
cream.

10,500 «x .038 = 399, number of pounds of fat
in the milk.

399 — 7 = 392, number of pounds of fat in the
cream.

392 + 980 = .40 x 100 = 40.0 per cent. of fat
in the cream. Answer.

3. 7 — 9,520 = .00073 «x 100 = .073, per cent. of fat

in the skimmed milk. Answer.

TIL

The first year that a farmer kept an exact record
of his herd of eight cows, he obtained the results given
in table 2.

TABLE 2.

Pounds Average Cost

Number of cow. .| of milk | percent- of feed

per year. | age of fat. | per year.

—_———————— SFM

4.1 $51.00

6,520
2 5,740 4.3 51.28
3 5,590 | 3.9 49.50
4 4900 | 4.6 45.70
5 4,625 | 3.7 43.90
6 4,150 | 4.0 43.50
7 3,960 | 3.8 42.80
8 3425 | 38 42.20
|

Three years later, after improving his herd by testing,
disposing of the poorer animals, selecting better ones,
and practising better feeding methods, the farmer
had eight cows that gave the following results (table 3).

TABLE 3.
Pounds Average | Cost
Number of cow. of milk percent- | of feed

yer year. | age of fat. | per year.
per } - 3

i 11,862 | 3.9 $73.60
2 mA a 10,143 | 3.7 70.24
3 f _ oe 8,027 | 4.1 62.50
4 is a ze 7,240 | 3.9 58.45
5 " = ae 6,354 | 4.3 56.42
6 2 a af 6,215 | 4.0 54.27
7 an i be 5,784 | 4.2 54.00
8 »- >. a 4,966 | 4.4 51.60

Problems based on the data in tables 2 and 3.

1. Compute the number of pounds of fat produced by
each cow in (a) table 2. (b) table 3.

2. Find the average number of pounds of milk and
of fat for the cows (a) in table 2, (b) in table 3.

3. What would be the value of the milk at $1.30 per
hundred pounds for each cow in (a) table 2, (b) table 3 ?

4. Find for each cow in (a) table 2, (b) table 3, the
difference between the cost of the feed and the income
when the milk is sold at $1.30 per hundred pounds.

5. Find the value of the milk from each cow in (a)
table 2, (b) table 3, computed on a basis of 52 cents
a pound for the fat.

6. Find the value of the milk for each cow in (a)
table 2, (b) table 3, allowing 30 cents a pound for the
fat and 20 cents for the skimmed milk from each 100
pounds of whole milk.

7. Find for each cow in (a) table 2, (b) table 3, the
difference between the cost of the feed and the income
when the milk is sold on a basis of 32 cents a pound for
the fat.

8. Find for each cow in (a) table 2, (b) table 3, the
difference between the cost of the feed and the value
of the milk, allowing 30 cents a pound for the fat and
20 cents for the skimmed milk from each 100 pounds
of whole milk.

9. After deducting the cost of each cow’s feed, how
many cows like No. 7 in table 2 would it take to give
the same income as that from (a) cow No. 1, table 2,
(b) cow No. 1, table 3 ?

10. Compute the total value of the milk in table 2
31

at $1.30 per 100 pounds, and find how much milk there
would have been, and how much it would have brought,
if each cow had given as much milk as cow No. 1.

11. Compute the total value of the milk in table 3
at $1.30 per 100 pounds, and find how much more it
would have brought if each cow had given as much
milk as No. 1.

12. When milk is valued at $1.30 per 100 pounds,
how much more would the owner of the cows in table
2 have received if each cow had given as much milk
as cow No. 1 in table 3?

QUESTIONS AND ANSWERS.

These questions and answers were suggested by many
inquiries received from dairymen.

1. What are the principal substances and the per-
centage of each in average milk ?

Answer.—Water, 87.37 per cent.; fat, 3.8 per cent.;
casein, 2.6 per cent.; sugar, 4.8 per cent.; albumen,
./1 per cent.; ash, .72 per cent.

2. What substances make up the milk solids ?

Answer.—All the constituents, except the water.

3. What percentage of solids is found in milk of average
composition ?

Answer.—About 12.63 per cent.

4. How are the solids of milk sometimes classified for
the purpose of comparison ?

Answer.—They are classified as fat and solids not fat.

32

5. What is the average percentage of solids not fat
in milk ? .
Answer.—About 8.83 per cent.

6. Which constituent of milk is the most variable
in amount ?
Answer.—The fat.

7. Between what limits is the percentage of fat
usually found ?
Answer.—Between 3 per cent. and 6 per cent.

8. What is meant when it is said that average milk
contains 3.8 per cent. of fat ?

Answer.—This means that 100 pounds of milk of
average composition contains 3.8 pounds of milk-fat.

9. In what condition does the fat in milk exist ?
Answer.—It is present in the form of very minute
round particles called globules.

10. What is another property that distinguishes the
fat from the other milk substances ?

Answer.—lIt is lighter in weight than the other milk
substances.

11. How does the dairyman make use of these
properties of the fat ?

Answer.—The lighter fat eben come to the top of
the milk serum (skimmed milk) when he sets the milk,
and he skims them off as cream with some of the serum ;
or he passes the milk through a separator, and draws
the cream off from the centre of the revolving bowl, while
most of the heavier milk serum is thrown to the outside
of the bowl and is drawn off through a separator spout.

4

oo

12. Are milk serum and skimmed milk the same sub-
stance ?

Answer.—Yes.

13. How does the serum after separation differ from
the cream ?

Answer.—The serum contains only traces of fat, while
the cream is made up of both milk serum and fat.

14. Does the serum of cream differ from the serum
forming skimmed milk ?

Answer.—The serum in each substance is the same.
15. What is meant when dairymen speak of 30 per
cent. cream ?

Answer.—They mean that 100 pounds of the cream
contains 30 pounds of fat and 70 pounds of the serum.

16. What is the legal requirement for milk in New
York State ?

Answer.—Milk cffered for sale in New York State must
be clean and pure, and drawn from healthy cows.
Nothing may be added to it and nothing taken from it,

and it must contain at least 3 per cent. of fat and 11.5
per cent. of solids.

17. Does the 11.5 per cent. of solids include the fat ?
Answer.—Yes.

18. Give the legal requirement for cream in New
York State.

Answer.—Cream must be made from clean pure milk,
and contain not less than 18 per cent. of fat.

o4

19. How does the skimmed milk obtained by setting
the milk differ from that obtained by passing the milk
through a good separator ?

Answer.—The skimmed milk from the separator con-
tains less fat.

20. How much difference might one expect to find in
the skimmed milk obtained by these two methods ?

Answer.—The skimmed milk from the separator should
contain less than .1 of 1 per cent. of fat, while the other
would probably contain between .25 and .5 of 1 per cent.
of fat.

21. What is buttermilk ?

Answer.—Buttermilk is the substance found in the
ehurn with the butter when the process of churning
cream is completed.

22. Which substance in cream forms the butter and
which the buttermilk ?

Answer.—The fat globules in the cream unite during
the churning process to form the butter, while the serum
of the cream remains as buttermilk.

23. Should not buttermilk, therefore, be very much
like skimmed milk, since both are the same as milk
serum ?

Answer.—Buttermilk is the same as sour skimmed milk,
and contains about thesame percentage of fat as skimmed
milk from the setting process, except that the lumps of
casein in the buttermilk have been broken into small
particles during churning.

24. Why does milk turn sour and the casein coagulate ?

Answer.—Little plants, called bacteria, change the
milk sugar into a substance known as lactic acid. The
acid gives milk a sour taste and brings about the coagu-
lation of the casein.

25. How do the bacteria usually enter the milk ?

Answer.—The bacteria fall in from the air on particles
of dust or dirt, or they may be on the milk pails or other
utensils.

26. What can a milk producer do to keep the bacteria
out, and to prevent the milk from souring ?

Answer.—Keep the stable and the cattle clean.

Wipe off the cow’s udder and surrounding
parts with a damp cloth immediately
before milking.

Use milk utensils that have been thoroughly
cleaned and then sterilized with boiling
water, or live steam for 30 minutes.

Wash the hands just before milking.

Use small-top milking pails.

Milk with dry hands.

Cool] the milk to a temperature below 50° F.
and keep it cold.

13.

14.

QUESTIONS.
Why should the farmer use some such test as the

Babcock ?

What are the causes of variation in the percentage
of butterfat in milk?

Give a list of the equipment necessary for the farmer
who tests milk.

. What precautions are to be taken in keeping the

acid for the test?
How would you take samples for testing for
individual cows?

Describe the process of filling the pipette and
transferring the milk to the test bottle.

How is acid added to and mixed with the milk?

Describe the centrifuging of the bottle—detailing
various precautions to be followed.

How does testing cream differ from testing milk ?
How is Babcock glassware washed?
Define specific gravity.

Describe the following: The pipette; the milk-
test bottle.

Describe the appearance of a complete test and
some possible variations and what they indicate.

Work out the problem of Spot. Fawn and Dot, as
outlined under 1, 2 and 3, Table 1.

Work out the problems under Tables 2 and 3.

us
~I