FOOD AND MILK PRODUCTION_Encyclopaedia Britannica, 11th Edition, "Dagupan" to "David" Volume 7, Slice 9

In their comprehensive paper relating to the feeding of animals

published in 1895, Lawes and Gilbert discussed amongst other questions

that of milk production, and directed attention to the great difference

in the demands made on the food--on the one hand for the production of

meat (that is, of animal increase), and on the other for the production

of milk. Not only, however, do cows of different breeds yield different

quantities of milk, and milk of characteristically different

composition, but individual animals of the same breed have very

different milk-yielding capacity; and whatever the capacity of a cow may

be, she has a maximum yield at one period of her lactation, which is

followed by a gradual decline. Hence, in comparing the amounts of

constituents stored up in the fattening increase of an ox with the

amounts of the same constituents removed in the milk of a cow, it is

necessary to assume a wide range of difference in the yield of milk.

Accordingly, Table V. shows the amounts of nitrogenous substance, of

fat, of non-nitrogenous substance not fat, of mineral matter, and of

total solid matter, carried off in the weekly yield of milk of a cow, on

the alternative assumptions of a production of 4, 6, 8, 10, 12, 14, 16,

18 or 20 quarts per head per day. For comparison, there are given at the

foot of the table the amounts of nitrogenous substance, of fat, of

mineral matter, and of total solid matter, in the weekly increase in

live-weight of a fattening ox of an average weight of 1000 lb.--on the

assumption of a weekly increase, first, of 10 lb., and, secondly, of 15

lb. The estimates of the amounts of constituents in the milk are based

on the assumption that it will contain 12.5% of total solids--consisting

of 3.65 albuminoids, 3.50 butter-fat, 4.60 sugar and 0.75 of mineral

matter. The estimates of the constituents in the fattening increase of

oxen are founded on determinations made at Rothamsted.

TABLE V.--_Comparison of the Constituents of Food carried off in Milk,

and in the Fattening Increase of Oxen._

+---------------------------+---------+-------+---------+--------+--------+

| | | | Non- | | |

| [1 Gallon = 10.33 lb.] | Sub- | Fat. | Sub- | Matter.| Solid |

+---------------------------+---------+-------+---------+--------+--------+

| _In Milk per Week._ |

+---------------------------+---------+-------+---------+--------+--------+ | | | | |

| If:-- | lb. | lb. | lb. | lb. | lb. |

| 4 quarts per head per day | 2.64 | 2.53 | 3.33 | 0.54 | 9.04 |

| 6 " " " | 3.96 | 3.80 | 4.99 | 0.81 | 13.56 |

| 8 " " " | 5.28 | 5.06 | 6.66 | 1.08 | 18.08 |

|10 " " " | 6.60 | 6.33 | 8.32 | 1.35 | 22.60 |

|12 " " " | 7.92 | 7.59 | 9.99 | 1.62 | 27.12 |

|14 " " " | 9.24 | 8.86 | 11.65 | 1.89 | 31.64 |

|16 " " " | 10.56 | 10.12 | 13.32 | 2.16 | 36.16 |

|18 " " " | 11.88 | 11.39 | 14.98 | 2.43 | 40.68 |

|20 " " " | 13.20 | 12.65 | 16.65 | 2.70 | 45.20 |

+---------------------------+---------+-------+---------+--------+--------+

| _In Increase in Live-Weight per Week.--Oxen._ |

+---------------------------+---------+-------+---------+--------+--------+

|If 10 lb. increase | 0.75 | 6.35 | .. | 0.15 | 7.25 |

|If 15 lb. increase | 1.13 | 9.53 | .. | 0.22 | 10.88 |

+---------------------------+---------+-------+---------+--------+--------+

With regard to the very wide range of yield of milk per head per day

which the figures in the following table assume, it may be remarked that

it is by no means impossible that the same animal might yield the

largest amount, namely, 20 quarts, or 5 gallons, per day near the

beginning, and only 4 quarts, or 1 gallon, or even less, towards the end

of her period of lactation. At the same time, an entire herd of, for

example, Shorthorns or Ayrshires, of fairly average quality, well fed,

and including animals at various periods of lactation, should not yield

an average of less than 8 quarts, or 2 gallons, and would seldom exceed

10 quarts, or 2(1/2) gallons, per head per day the year round.

For the sake of illustration, an average yield of milk of 10 quarts,

equal 2(1/2) gallons, or between 25 and 26 lb. per head per day, may be

assumed, and the amount of constituents in the weekly yield at this rate

may be compared with that in the weekly increase of the fattening ox at

the higher rate assumed in the table, namely, 15 lb. per 1000 lb.

live-weight, or 1.5% per week. It is seen that whilst of the nitrogenous

substance of the food the amount stored up in the fattening increase of

an ox would be only 1.13 lb., the amount carried off as such in the milk

would be 6.6 lb., or nearly six times as much. Of mineral matter, again,

whilst the fattening increase would only require about 0.22 lb., the

milk would Carry off 1.35 lb., or again about six times as much. Of fat,

however, whilst the fattening increase would contain 9.53 lb., the milk

would contain only 6.33 lb., or only about two-thirds as much. On the

other hand, whilst the fattening increase contains no other

non-nitrogenous substance than fat, the milk would carry off 8.32 lb. in

the form of milk-sugar. This amount of milk-sugar, reckoned as fat,

would correspond approximately to the difference between the fat in the

milk and that in the fattening increase.

It is evident, then, that the drain upon the food is very much greater

for the production of milk than for that of meat. This is especially the

case in the important item of nitrogenous substance; and if, as is

frequently assumed, the butter-fat of the milk is at any rate largely

derived from the nitrogenous substance of the food, so far as it is so

at least about two parts of such substance would be required to produce

one of fat. On such an assumption, therefore, the drain upon the

nitrogenous substance of the food would be very much greater than that

indicated in the table as existing as nitrogenous substance in the milk.

To this point further reference will be made presently.

TABLE VI.--_Constituents consumed per 1000lb. Live-Weight per Day, for

Sustenance and for Milk-Production. The Rothamsted Herd of 30 Cows,

Spring 1884._

+---------------------+---------+----------------------------------+

| | | Digestible. |

| | +----------+------------+----------+

+---------------------+---------+----------+------------+----------+

| | lb. | lb. | lb. | lb. |

| 3.1 lb. Cotton cake | 2.76 | 1.07 | 1.50 | 2.57 |

| 2.7 lb. Bran | 2.33 | 0.33 | 1.09 | 1.42 |

| 2.8 lb. Hay-chaff | 2.34 | 0.15 | 1.18 | 1.33 |

| chaff | 4.64 | 0.08 | 2.21 | 2.29 |

|62.8 lb. Mangel | 7.85 | 1.01 | 5.73 | 6.74 |

| +---------+----------+------------+----------+

| Total | 19.92 | 2.64* | 11.71* | 14.35 |

| tenance | | 0.57 | 7.40 | 7.97 |

| +---------+----------+------------+----------+

| Available for milk | | 2.07 | 4.31 | 6.38 |

| In 23.3 lb. milk | | 0.85 | 3.02 | 3.87 |

| +---------+----------+------------+----------+

| Excess in food | | 1.22 | 1.29 | 2.51 |

+---------------------+---------+----------+------------+----------+

| _Per 1000 lb. Live-Weight._ |

+---------------------+---------+----------+------------+----------+

| Wolff | lb. | lb. | lb. | lb. |

| | 24 | 2.5 | 12.5** | 15.4 |

+---------------------+---------+----------+------------+----------+

* Albuminoid ratio, 1-4.4.

** Exclusive of 0.4 fat; albuminoid ratio, 1-5.4.

Attention may next be directed to the amounts of food, and of certain of

its constituents, consumed for the production of a given amount of milk.

This point is illustrated in Table VI., which shows the constituents

consumed per 1000 lb. live-weight per day in the case of the Rothamsted

herd of 30 cows in the spring of 1884. On the left hand are shown the

actual amounts of the different foods consumed per 1000 lb. live-weight

per day; and in the respective columns are recorded--first the amounts

of total dry substance which the foods contained, and then the amounts

of digestible nitrogenous, digestible non-nitrogenous (reckoned as

starch), and digestible total organic substance which the different

foods would supply; these being calculated according to Lawes and

Gilbert's own estimates of the percentage composition of the foods, and

to Wolff's estimates of the proportion of the several constituents which

would be digestible.

The first column shows that the amount of total dry substance of food

actually consumed by the herd, per 1000 lb. live-weight per day, was

scarcely 20 lb. whilst Wolff's[3] estimated requirement, as stated at

the foot of the table, is 24 lb. But his ration would doubtless consist

to a greater extent of hay and straw-chaff, containing a larger

proportion of indigestible and effete woody fibre. The figures show,

indeed that the Rothamsted ration supplied, though nearly the same, even

a somewhat less amount of total digestible constituents than Wolff's.

Of digestible nitrogen substance the food supplied 2.64 lb. per day,

whilst the amount estimated to be required for sustenance merely is 0.57

lb.; leaving, therefore, 2.07 lb. available for milk production. The

23.3 lb. of milk yielded per 1000 lb. live-weight per day would,

however, contain only 0.85 lb.; and there would thus remain an apparent

excess of 1.22 lb. of digestible nitrogenous substance in the food

supplied. But against the amount of 2.64 lb. actually consumed, Wolff's

estimate of the amount required for sustenance and for milk-production

is 2.5 lb., or but little less than the amount actually consumed at

Rothamsted. On the assumption that the expenditure of nitrogenous

substance in the production of milk is only in the formation of the

nitrogenous substances of the milk, there would appear to have been a

considerable excess given in the food. But Wolff's estimate assumes no

excess of supply, and that the whole is utilized; the fact being that he

supposes the butter-fat of the milk to have been derived largely, if not

wholly, from the albuminoids of the food.

It has been shown that although it is possible that some of the fat of a

fattening animal may be produced from the albuminoids of the food,

certainly the greater part of it, if not the whole, is derived from the

carbohydrates. But the physiological conditions of the production of

milk are so different from those for the production of fattening

increase, that it is not admissible to judge of the sources of the fat

of the one from what may be established in regard to the other. It has

been assumed, however, by those who maintain that the fat of the

fattening animal is formed from albuminoids, that the fat of milk must

be formed in the same way. Disallowing the legitimacy of such a

deduction, there do, nevertheless, seem to be reasons for supposing that

the fat of milk may, at any rate in large proportion, be derived from

albuminoids.

Thus, as compared with fattening increase, which may in a sense be said

to be little more than an accumulation of reserve material from excess

of food, milk is a special product, of a special gland, for a special

normal exigency of the animal. Further, whilst common experience shows

that the herbivorous animal becomes the more fat the more, within

certain limits, its food is rich in carbohydrates, it points to the

conclusion that both the yield of milk and its richness in butter are

more connected with a liberal supply of the nitrogenous constituents in

the food. Obviously, so far as this is the case, it may be only that

thereby more active change in the system, and therefore greater activity

of the special function, is maintained. The evidence at command is, at

any rate, not inconsistent with the supposition that a good deal of the

fat of milk may have its source in the breaking up of albuminoids, but

direct evidence on the point is still wanting; and supposing such

breaking up to take place in the gland, the question arises--What

becomes of the by-products? Assuming, however, that such change does

take place, the amount of nitrogenous substance supplied to the

Rothamsted cows would be less in excess of the direct requirement for

milk-production than the figures in the table would indicate, if,

indeed, in excess at all.

The figures in the column of Table VI. relating to the estimated amount

of digestible non-nitrogenous substance reckoned as starch show that the

quantity actually consumed was 11.71 lb., whilst the amount estimated by

Wolff to be required was 12.5 lb., besides 0.4 lb. of fat. The figures

further show that, deducting 7.4 lb. for sustenance from the quantity

actually consumed, there would remain 4.31 lb. available for

milk-production, whilst only about 3.02 lb. would be required supposing

that both the fat of the milk and the sugar had been derived from the

carbohydrates of the food; and, according to this calculation, there

would still be an excess in the daily food of 1.29 lb. It is to be borne

in mind, however, that estimates of the requirement for mere sustenance

are mainly founded on the results of experiments in which the animals

are allowed only such a limited amount of food as will maintain them

without either loss or gain when at rest. But physiological

considerations point to the conclusion that the expenditure,

independently of loss or gain, will be the greater the more liberal the

ration, and hence it is probable that the real excess, if any, over that

required for sustenance and milk-production would be less than that

indicated in the table, which is calculated on the assumption of a fixed

requirement for sustenance for a given live-weight of the animal.

Supposing that there really was any material excess of either the

nitrogenous or the non-nitrogenous constituents supplied over the

requirement for sustenance and milk-production, the question

arises--Whether, or to what extent, it conduced to increase in

live-weight of the animals, or whether it was in part, or wholly,

voided, and so wasted.

Table VII.--Percentage Composition of Milk each Month of the Year;

also Average Yield of Milk, and of Constituents, per Head per Day each

Month, according to Rothamsted Dairy Records.

+-----------+--------------------------------+---------------------------------+

| |Average Composition of Milk each| Rothamsted Diary. |

| | Month, 1884. +----------+----------------------+

| +--------+-------+------+--------+ Yield | Milk per Head per |

| | | | Fat. | | 6 Years. | Fat. | not |Solids.|

| | | | | | | | Fat. | |

+-----------+--------+-------+------+--------+----------+-------+------+-------+

| | | % | % | % | lb | lb | lb | lb |

| January | 1.0325 | 3.55 | 9.34 | 12.89 | 20.31* | 0.72 | 1.90 | 2.62 |

| February | 1.0325 | 3.53 | 9.24 | 12.77 | 22.81 | 0.80 | 2.11 | 2.91 |

| March | 1.0323 | 3.50 | 9.22 | 12.72 | 24.19 | 0.85 | 2.23 | 3.08 |

| April | 1.0323 | 3.43 | 9.22 | 12.65 | 26.50 | 0.91 | 2.44 | 3.35 |

| May | 1.0324 | 3.34 | 9.30 | 12.64 | 31.31 | 1.05 | 2.91 | 3.96 |

| June | 1.0323 | 3.31 | 9.19 | 12.50 | 30.81 | 1.02 | 2.83 | 3.85 |

| July. | 1.0319 | 3.47 | 9.13 | 12.60 | 28.00 | 0.97 | 2.56 | 3.53 |

| August | 1.0318 | 3.87 | 9.08 | 12.95 | 25.00 | 0.97 | 2.27 | 3.24 |

| September | 1.0321 | 4.11 | 9.17 | 13.28 | 22.94 | 0.94 | 2.11 | 3.05 |

| October | 1.0324 | 4.26 | 9.27 | 13.53 | 21.00 | 0.89 | 1.95 | 2.84 |

| November | 1.0324 | 4.36 | 9.29 | 13.65 | 19.19 | 0.84 | 1.78 | 2.62 |

| December | 1.0326 | 4.10 | 9.29 | 13.39 | 19.31 | 0.79 | 1.79 | 2.58 |

| +--------+-------+------+--------+----------+-------+------+-------+

| Mean | 1.0323 | 3.74 | 9.22 | 12.96 | 24.28 | 0.90 | 2.24 | 3.14 |

+-----------+--------+-------+------+--------+----------+-------+------+-------+

* Average over five years only, as the records did not commence until

February 1884.

As regards the influence of the period of the year, with its

characteristic changes of food, on the quantity and composition of the

milk, the first column of the second division of Table VII. shows the

average yield of milk per head per day of the Rothamsted herd, averaging

about 42 cows, almost exclusively Shorthorns, in each month of the year,

over six years, 1884 to 1889 inclusive; and the succeeding columns show

that amounts of butter-fat, of solids not fat, and of total solids in

the average yield per head per day in each month of the year,

calculated, not according to direct analytical determinations made at

Rothamsted, but according to the results of more than 14,000 analyses

made, under the superintendence of Dr Vieth, in the laboratory of the

Aylesbury Dairy Company in 1884;[4] the samples analysed representing

the milk from a great many different farms in each month.

It should be stated that the Rothamsted cows had cake throughout the

year; at first 4 lb. per head per day, but afterwards graduated

according to the yield of milk, on the basis of 4 lb. for a yield of 28

lb. of milk, the result being that then the amount given averaged more

per head per day during the grazing period, but less earlier and later

in the year. Bran, hay and straw-chaff, and roots (generally mangel),

were also given when the animals were not turned out to grass. The

general plan was, therefore, to give cake alone in addition when the

cows were turned out to grass, but some other dry food, and roots, when

entirely in the shed during the winter and early spring months.

Referring to the column showing the average yield of milk per head per

day each month over the six years, it will be seen that during the six

months January, February, September, October, November and December the

average yield was sometimes below 20 lb. and on the average only about

21 lb. of milk per head per day; whilst over the other six months it

averaged 27.63 lb., and over May and June more than 31 lb. per head per

day. That is to say, the quantity of milk yielded was considerably

greater during the grazing period than when the animals had more dry

food, and roots instead of grass.

Next, referring to the particulars of composition, according to Dr

Vieth's results, which may well be considered as typical for the

different periods of the year, it is seen that the specific gravity of

the milk was only average, or lower than average, during the grazing

period, but rather higher in the earlier and later months of the year.

The percentage of total solids was rather lower than the average at the

beginning of the year, lowest during the chief grazing months, but

considerably higher in the later months of the year, when the animals

were kept in the shed and received more dry food. The percentage of

butter-fat follows very closely that of the total solids, being the

lowest during the best grazing months, but considerably higher than the

average during the last four or five months of the year, when more dry

food was given. The percentage of solids not fat was considerably the

lowest during the later months of the grazing period, but average, or

higher than average, during the earlier and later months of the year. It

may be observed that, according to the average percentages given in the

table, a gallon of milk will contain more of both total solids and of

butter-fat in the later months of the year; that is, when there is less

grass and more dry food given.

Turning to the last three columns of the table, it is seen that

although, as has been shown, the percentage of the several constituents

in the milk is lower during the grazing months, the actual amounts

contained in the quantity of milk yielded per head are distinctly

greater during those months. Thus, the amount of butter-fat yielded _per

head per day_ is above the average of the year from April to September

inclusive; the amounts of solids not fat are over average from April to

August inclusive; and the amounts of total solids yielded are average,

or over average, from April to August inclusive.

From the foregoing results it is evident that the quantity of milk

yielded per head is very much the greater during the grazing months of

the year, but that the percentage composition of the milk is lower

during that period of higher yield, and considerably higher during the

months of more exclusively dry-food feeding. Nevertheless, owing to the

much greater quantity of milk yielded during the grazing months, the

actual quantity of constituents yielded per Cow is greater during those

months than during the months of higher percentage composition but lower

yield of milk per head. It may be added that a careful consideration of

the number of newly-calved cows brought into the herd each month shows

that the results as above stated were perfectly distinct, independently

of any influence of the period of lactation of the different individuals

of the herd.

The few results which have been brought forward in relation to

_milk-production_ are admittedly quite insufficient adequately to

illustrate the influence of variation in the quantity and composition of

the food on the quantity and composition of the milk yielded. Indeed,

owing to the intrinsic difficulties of experimenting on such a subject,

involving so many elements of variation, any results obtained have to be

interpreted with much care and reservation. Nevertheless, it may be

taken as clearly indicated that, within certain limits, high feeding,

and especially high nitrogenous feeding, does increase both the yield

and the richness of the milk.[5] But it is evident that when high

feeding is pushed beyond a comparatively limited range, the tendency is

to increase the weight of the animal--that is, to favour the development

of the individual, rather than to enhance the activity of the functions

connected with the reproductive system. This is, of course, a

disadvantage when the object is to maintain the milk-yielding condition

of the animal; but when a cow is to be fattened off it will be

otherwise.

It has been stated that, early in the period of six years in which the

Rothamsted results that have been quoted were obtained, the amount of

oil-cake given was graduated according to the yield of milk of each

individual cow; as it seemed unreasonable that an animal yielding, say,

only 4 quarts per day, should receive, beside the home foods, as much

cake as one yielding several times the quantity. The obvious inference

is, that any excess of food beyond that required for sustenance and

milk-production would tend to increase the weight of the animal, which,

according to the circumstances, may or may not be desirable.

It may be observed that direct experiments at Rothamsted confirm the

view, arrived at by common experience, that roots, and especially

mangel, have a favourable effect on the flow of milk. Further, the

Rothamsted experiments have shown that a higher percentage of

butter-fat, of other solids, and of total solids, was obtained with

mangel than with silage as the succulent food. The yield of milk was,

however, in a much greater degree increased by grazing than by any other

change in the food; and at Rothamsted the influence of roots comes next

in order to that of grass, though far behind it, in this respect. But

with grazing, as has been shown, the percentage composition of the milk

is considerably reduced; though, owing to the greatly increased quantity

yielded, the amount of soil-constituents removed in the milk when cows

are grazing may nevertheless be greater per head per day than under any

other conditions. Lastly, it has been clearly illustrated how very much

greater is the demand upon the food, especially for nitrogenous and for

mineral constituents, in the production of milk than in that of

fattening increase.

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