FOOD AND MILK PRODUCTION.]
DAIRY-FARMING
of lactation, should not yield an average of less than 8 quarts, or 2 gallons, and would seldom exceed 10 quarts, or 2^ gallons, per head per day the year round. Table Y. Comparison of the Constituents of Food carried off in Milk, and in the Fattening Increase of Oxen. NonNitroNitrogenous genous Fat. Sub- Mineral Total [1 Gallon=10-33 lb.] Solid Substance Matter. Matter. stance. not Fat (Sugar). In Milk per Week. If:— 4 quarts per head per day 6 „
lb lb lb 223334556-66 6687-92 799-24 811-65 1010T2 1311111413-20 1216-65
lb 0-54 0-81
lb 9-04 13-56 18-08 22-60 27-12 31-64 36-16 40-68 45-20
347
foods consumed per 1000 ft) 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 nonnitrogenous (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 ft), whilst Wolff’s 1 estimated requirement, as stated at the foot of the table, is 24 ft). But his ration would doubtless consist 64 53 3 to a96 greater extent of hay and straw-chaff, containing a 80 9 larger proportion06 of indigestible and efi'ete woody fibre. 28 The 60 figures show, indeed, that the Bothamsted ration 33 3 supplied, though59 nearly the 9 same, even a somewhat less 86 amount of total digestible constituents than Wolff’s. 56 3 88 39 9 Table VI. Constituents consumed per 1000 lb Live-Weight per 65 Day, for Sustenance and for Milk-Production. The Rothamsted Herd of 30 Cows, Spring 1884.
In Increase in Live- Weight per Week.—Oxen. If 10 It) increase If 15 lt> increase
0-75 1-13
6-35 9-53
0-15 0-22
Digestible. 7-25 10-88
For the sake of illustration, an average yield of milk of 10 quarts, equal 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 Eb per 1000 lb live-weight, or 1 "5 per cent, 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 Id3 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 ft), the milk would contain only 6'33 ft), or only about twothirds as much. On the other hand, whilst the fattening increase contains no other non-nitrogenous substance than fat, the milk would carry off 8-3 2 ft) in the form of milksugar. 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. 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 ft) live-weight per day in the case of the Itothamsted herd of 30 cows in the spring of 1884. On the left hand are shown the actual amounts of the different
3-1 lb Cotton cake . 2 "7 lb Bran 2 "8 lb Hay-chaff 5 "6 lb Oat-straw-chaff 62 8 lb Mangel . Total Required for sustenance Available for milk In 23 "3 lb milk . Excess in food
Wolff .
Total Total NitroDry Nitro- Non-Nitro- genous Sub- genous genous Nonstance. Sub- Substance and Nitrostance. (as Starch). genous Substance. lb lb lb lb 2-76 1-07 1-50 2-57 2-33 0-33 11-42 2-34 0-15 11-18 4-64 0-08 227'85 1-01 5-73 619-92
2-64 0-57
11-71 * 7-40
14-35 7-
J
2-07 0-85
4-31 3-02
6-38 3-87
1-22
1-29
2-51
Per 1000 lb Live- Weight. lb lb 24 2-5
lb 12-5f
lb 15-4
- Albuminoid ratio, 1-4"4.
t Exclusive of 0-4 fat; albuminoid ratio, 1-5-4. Of digestible nitrogen substance, the food supplied 2'64 ft) per day, whilst the amount estimated to be required for sustenance merely is 0'57 ft); leaving, therefore, 2'07 ft) available for milk-production. The 2 3'3 ft) of milk yielded per 1000 ft) live-weight per day would, however, contain only 0'85 ft); and there would thus remain an apparent excess of 1'22 ft) of digestible nitrogenous substance in the food supplied. But against the amount of 2'64 ft) actually consumed, Wolff’s estimate of the amount required for sustenance and for milk-production is 2'5 ft), or but little less than the amount actually consumed at Bothamsted. 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 Landw. Fiitterungslehre, 5te Aufl., 1888, p. 249.
