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FOOD AND MILK

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Originally appearing in Volume V07, Page 744 of the 1911 Encyclopedia Britannica.
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FOOD AND MILK PRODUCTION 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 Milk, and in the Fattening Increase of Oxen. Nitro- Non- Min- Total Nitro- genous genous eral solid GallonIO 1b~ Sub- Fat. Sub- Mat- Mat- [I 33 stance. stance ter. ter. not Fat (Sugar). In Milk per Week. If :- lb lb lb lb ib 4 quarts per head per day 2.64 2'53 3'33 0.54 9.04 6 „ „ ,, 3.96 3.80 4.99 o•81 13.56 8 5.28 5.06 6.66 1•o8 ,8•o8 Io „ „ „ 6.6o 6.33 8.32 1.35 22.60 12 „ „ „ 7.92 7.59 9'99 I.62 27.12 14 ,, 9'24 8.86 11.65 1.89 31'64 16 „ „ „ 10.56 Io•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 to lb increase . . . 0.75 6.35 •. 0.15 7.25 If 15 lb increase . . . 1.13 9'53 .. 0.22 Io•88 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, lo, 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 moo lb-on the assumption of a weekly increase, first, of ro 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, 4.6o sugar and o•75 of mineral matter. The estimates of the constituents in the fattening increase of oxen are founded on determinations made at Rothamsted. 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 30. 31. 32. Weigh and record the milk given by each cow, and take a sample morning and night, at least once a week, for testing by the fat test. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 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 to quarts, or 21 gallons, per head per day the year round. For the sake of illustration, an average yield of milk of 10 quarts, equal 22 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 i000 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 ib, 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. 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 i000 lb live-weight Digestible. Total Nitro- Non-Nitrq- Total Dry genous genous Nitro- Sub- Sub- Substance genous stance. stance. (as Starch). and Non- Nitro- genous Substance. 3-1 lb Cotton cake lb lb lb lb 2.7 lb Bran . 2.76 1.07 1.50 2.57 2.8 lb Hay-chaff . 2.33 0.33 1.09 1'42 2.34 0.15 1.18 1 33 4.64 0.68 2.21 2.29 7.85_ , •o1 5',73 6.74 5.6 lb Oat-straw- chaff . . 62.8 lb Mangel . sus- Total. 19.92 2.64* 11.71 * 14'35 Required for .. 0.57 7'40 7'97 tenance . 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 P29 2.51.,. Per woo lb Live-Weight. Wolff lb i lb I lb lb 24 2.5 i2.5t 15'4 *Albuminoid ratio, i 4'4 t Exclusive of o.4 fat; abuminoid ratio,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 moo 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 pro-portion 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 loon lb live-weight per day, was scarcely 20 lb, whilst Wolff's 1 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 o•57 lb; leaving, therefore, 2•o7 lb available for milk production. The 23.3 lb of milk yielded per loco lb live-weight per day would, however, contain only o•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 Rothamstbd. 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 sup-posing 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 ' Landw. Futterungslehre, 5te Aufl., 1888, p. 249• Average Composition of Milk each Rothamsted Dairy. Month, 1884• Estimated Quantity (Dr Vieth-14,235 analyses.) Average of Constituents in Solids Yield of Milk Milk per Head per Dayeadh Month. Specific Butter- not Total Per Head Solids Gravity. Fat. Fat. Solids. Per Day; 6 Years. Butter- Fat. not Fat. Total Solids. % 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 0.8$ 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 I•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 0.91 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 I•0324 4.26 9.27 13'53 21.00 0.89 1.95 2.84 " November . 1.0324 4'.36 9'29 13'45 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 LL 2.24 3.14 ".~ in excess of the direct requirement for milk-production than the It should be stated that the Rothamsted cows had , cake figures in the table would indicate, if, indeed, in excess at all. throughout the year; at first 4 lb •per. head per day, but after- The figures in the column of Table VI. relating to the estimated wards graduated according to the yield of milk, on the basis amount of digestible non-nitrogenous substance reckoned as of 4 lb for a yield of 28 lb of milk, the result being that then starch show that the quantity actually consumed was 11-71 lb, the amount given averaged more' per head per day during the whilst the amount estimated by Wolff to be required was 12.5 lb, grazing period, but less earlier and later in the year. Bran, besides o'4 lb of fat. The figures further show that, deducting hay and straw-chaff, and roots (generally mangel), were' also 7.4 lb for sustenance from the quantity actually consumed, there given when the animals were not turned out to grass. The would remain 4.31 lb available for milk-production, whilst only general plan was, therefore, to give cake alone in addition when about 3.02 lb would be required supposing that both the fat the cows were turned out to grass, but some other dry food, of the milk and the sugar. had been derived from the carbo- and roots, when entirely in the shed during the -winter and early hydrates of the food; and, according to this calculation, there spring months. would still be an excess in the daily food of 1.•29 lb. It is to be Referring to the column showing the average yield of milk borne. in mind, however, that estimates of the requirement for per head per day each month over the six years, it will be seen mere sustenance are mainly founded on the results of experiments that during the six months January,. February, September, in which the- animals are allowed only such a limited amount October, November and December the average yield was of food as will maintain them without either loss or gain when at sometimes below 20 lb, and on the- average only about 21 lb rest. But physiological considerations point to the conclusion of milk per head per day; whilst over the other six. months that the expenditure, independently of loss or gain, will be the it averaged 27.63 lb, and over May and June more than 31 . lb greater the more liberal the ration, and hence it is probable per head per day. - That is to say; the quantity of milk yielded that the real excess, if any, over that required for sustenance was considerably greater during the grazing period than when and milk-production would be less than that indicated in the the animals had more dry food, and roots instead of grass. table, which is calculated on the assumption of a fixed require- • •Next, referring to the particulars of composition, according ment for sustenance for a given live-weight of the animal. to Dr Vieth's results, which may well be considered as typical Supposing that there really was any material excess of either for the different periods of. the year, it is seen that the specific the nitrogenous or the non-nitrogenous constituents supplied gravity of the milk was only average, or lower than average, over the requirement for sustenance and milk-production, during the grazing period, but rather higher in the earlier and the question arises-Whether, or to what extent, it conduced later months of the year.- The percentage of total solids was to increase in live-weight of the animals, or whether it was in rather lower than the average at the beginning of the year, part, or wholly, voided, and so wasted. lowest during the chief grazing months, but -considerably higher As regards the influence of the period of the year, with its in the later months of the year, when the animals were kept in characteristic changes of food, on the quantity and composition the shed and received more dry food. The percentage of butter- of the milk, the first column of the second division of Table VII. - fat follows very closely that of the total solids, being the lowest shows the average yield of milk per head per day of the Rotham- during the best grazing months, but considerably higher than sted herd, averaging about 42 cows, almost exclusively Short- the average; during the last four or five months of the year, when horns, in each month of the year, over six years, 1884 to 1889 more dry food was given. The percentage of=solids not fat was Milk, and of Constituents, per Head per Days-each Month, according to Rotharsted Dairy months of the grazing period, but average, Records. 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 dining 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 over five years only, as the records did not commence until February 1884. average, from April to August indttsive: From the foregoing results it is evident inclusive; and the succeeding columns show that amounts of that the quantity of milk yielded per head is very much the butter-fat, of solids not fat, and of total solids in the average greater during the grazing months- of the year, but that the yield per head per day in each month of the year; talculatedy percentage composition of'the milk is lower during that period not according to direct analytical determinations made' at of higher yield, and considerably higher during the months of Rothamsted, but according to the results of more than 14;000 more exclusively dry-food, feeding. Nevertheless, owing to the analyses made, under the superintendence of Dr Vieth, in the much greater quantity of milk yielded- during the grazing laboratory of the Aylesbury Dairy Company in 1884;1 the months, the actual quantity of constituents yielded per cow is samples analysed representing the milk from a great many greater during those months than during the months of higher different farms in each month. percentage composition. but lower yield of milk per head. It 1 Theflnalyst, April 1885, vol. x: p. 67. 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.l 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. 1 The evidence on this point taken by the Committee on Milk and Cream Regulations in 1900 is somewhat conflicting. The report states that an impression commonly prevails that the quality of milk is more or less determined by the nature and composition of the food which the cow receives. One witness said that farmers who produce milk for sale feed differently from what they do if they are producing for butter. Another stated that most of the statistics which go to show that food has no effect on milk fail, because the experiments are not carried far enough to counterbalance that peculiarity of the animal first to utilize the food for itself before utilizing it for the milk. A witness who kept a herd of ioo milking cows expressed the opinion that improvement in the quality of milk can be effected by feeding, though not to any large extent. On the other hand, it was maintained that the fat percentage in the milk of a cow cannot be raised by any manner or method of feeding. It is possible that in the case of cows very poorly fed the addition of rich food would alter the composition of their milk, but if the cows are well-fed to begin with, this would not be so. The proprietor of a herd of 500 milking cows did not think that feeding affected the quality of milk from ordinarily well-kept animals. An experimenter found that the result of resorting to rather poor feeding was that the first effect was produced upon the weight of the cow and not upon the milk; the animal began to get thin, losing its weight, though there was not very much effect upon the quality of the milk.
End of Article: FOOD AND MILK
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