The Influence of Food on the Quantity and Quality of Milk.

By F. J. LLOYD, F.C.S.,

Consulting Chemist to the British Dairy Farmers' Association.

In 1887 I first turned my attention to the above subject, and as a result thereof published two articles in which I attempted to impress upon farmers two main facts. The first was that the fat of milk, instead of being produced, as was commonly believed, from the fat of the food, was produced from the albuminoids or nitrogenous constituents. The second contention was that an excessive amount of food might be given to dairy cows without any adequate return either in the quantity or the quality of the milk, and that profitable feeding could only be looked for when careful attention was paid to both the quantity of food given and its suitability to the object in view, whether meat or milk production.

The first contention brought down upon me showers of abuse from Scotland. Yet to-day there is probably no doctrine concerning the feeding of cattle which Scotchmen more fully believe in than this one of the influence of albuminoids in producing rich milk. My second proposition attracted at once the attention of Lord Vernon, whose interest in dairy matters is well known. He placed his herd of dairy cattle at the disposal of this Association for experiments to test the influence of an excess of food upon the milk yield. The results were most conclusive, and proved that such an excess of food was neither productive of an increase in the quantity nor in the quality of the milk yielded. These articles and experiments caused the subject to be very fully ventilated in the agricultural Press, while the question as to the effect of the nitrogenous constituents was also made the subject of many experiments abroad and at Home. The results of the experiments have been so conflicting that the question whether food has any influence on the quantity or quality of milk is still considered a debatable one. I have been a careful student of the results of all experiments which have come to my notice, and am as firmly convinced to-day as I was years ago that the food of a cow may materially influence both the quantity and the quality of her milk.

How is it, then, that the result of experiments have been so conflicting? I venture to think it is owing to the experimenters having neglected to take into account the inevitable limitations and conditions with which Nature has hemmed in this subject. As time will not permit me to review the experiments one by one, I will attempt to indicate what are these natural limitations, and to point out, in a general way, some of the causes which have detracted from the value of many experiments. In every milking cow two tendencies are at

work. The one is to convert the nourishment which is supplied by the food to the blood into milk; the second is to store up that nourishment in the body. The relative strength of these two tendencies varies greatly in different breeds of cattle. Thus, speaking generally, the Shorthorns, especially when pure-bred, have a stronger tendency to store up the nourishment in their bodies than to convert it into milk; while in Jersey cattle the stronger tendency is towards milk production. This peculiarity is even more marked among individuals than it is in the various breeds. Hence in every milking animal there is a constant struggle between the two tendencies. Sometimes a comparatively slight or simple cause may upset the balance. Take as an example the effect of cold. An exceptionally cold night will cause a marked decline in the milk yield of a large herd. The tendency of the animals to produce milk from the nourishment of the blood has been checked; the materials have been utilised for maintenance, the demand for animal heat for the time being having exercised a more powerful influence than that of milk production. In a similar manner the character of the food supplied to an animal may affect either tendency. Thus, if the food provide an excess of some particular constituent, this will ultimately strengthen the tendency for which this constituent is most adapted. For example, a cow fed with an excess of starchy food, having used all that it requires for milk production, will still be left with a surplus of nutriment in the blood. This will be utilised by the tendency of the cow to fatten. In a similar manner an excess of nitrogenous food-which, however, is far more rare-will produce a tendency to make flesh. The invariable result of an excess of nutriment is to increase the live weight of the animal. It may be well to here follow out this effect on a milk cow to its final result. The udder, like every other tissue of the animal, is capable of fattening, but in doing this its secretory power is diminished. Hence the ultimate result of a food excessively rich in nutriment is not to increase the milk yield, but to diminish it.

Let us next consider the food of an opposite character-which is deficient in nutriment. The tendency to produce milk, following the general law of Nature, whereby the maintenance of offspring is a more powerful influence than self-preservation, is, as a rule, stronger than the tendency to preserve the food stored up in the body; hence the effect on the milk of a deficiency of nutriment in the food is for some time very slight, but it will tell on the body of the animal, and there will be a gradual loss of weight. She will at first strive to make up for any want of nutriment in her food by calling upon the reserve material previously stored up in her body. How long this will hold out will depend greatly upon circumstances-mainly on the quantity of reserve nutriment stored up, but also on the daily call which is made on this nutriment. For some time only the scales would show the effect of this insufficient food, and not the milk. Hence no experiments: on the effect of food on milk supply are conclusive which do not take into consideration the effect on live weight, for the two are inseparable. The absence of any record of live weight is one of the chief failings of many of the feeding experiments which have been conducted.

Most experimenters upon this difficult subject have been content to record the volume of the milk yielded, and the composition or quality of that milk. I shall point out later on the unsatisfactory side of this method, but it will be well to first study separately the natural conditions which affect both quantity and quality. There is for every individual cow a maximum quantity of milk which she can yield at any one milking. This depends up the capacity of her udder. The udder is not always capable of holding the maximum quantity which a cow can secrete, but in such case, as most farmers know, the secretion runs away from the udder naturally. Such instances are probably not numerous, but they exist. The late Mr. E. C. Tisdall, who had devoted years of study to the milking capacity of cows, accumulated a number of measurements of the udder, and informed me that by a careful measurement of the udder it was possible to form a very approximate estimate of the quantity of milk a cow could yield, provided the feeding was so regulated as to prevent any fattening of the tissues of the udder. Now, the size of the udder bears some relation, speaking generally, to the size of the animal; hence the heavier breeds are capable of yielding more milk than the lighter ones. This is well seen by the following table, compiled from the Report on the Milking Trials for 1897, and published in Vol. XII of the B.D.F.A. Journal :

It will be noticed that the milk yield is not invariably in exact relation to the live weight. But the reason is evident. In those breeds where the tendency to fatten is strong, the yield is slightly less in proportion to live weight than in those breeds where this fattening tendency is weak. Now, it is perfectly evident that if a cow is receiving an ample supply of food containing the necessary constituents for the production of milk, she will make the maximum quantity her udder will hold. Some experimenters, starting with cows in such condition, and finding that an increase in the quantity of food, or variations in that increase (which did not diminish its nutritive value), produced, as was natural, no increase in the quantity yielded, have jumped to the conclusion that food has no effect. This is one of the most striking sources of error which experimenters have been led into. In fact, the result of such feeding has generally been to diminish the milk supply, for the reasons which have already been set forth.

Let me take two typical illustrations. I do so purposely from the very exhaustive series of experiments which have been conducted by Mr. John Speir, for I consider that the results of these experiments ought to be in the hands of every dairy farmer. The first (Period 6) experiment commenced 6th October, and ended 9th November, 1895. The cows yielded during the first week 109.4 lb. per head, but the

yield fell off each week, and during the 5th week amounted to only 80 lb. of milk per head. The other experiment (Period 15) began 16th August, and ended 19th September, 1896. The animals during the second week yielded each 154.9 lb. of milk, which during the fifth week had fallen to 98.4 lb. Now what had happened? The food was ample—in fact, more than sufficient. It supplied more nutriment than could be utilised for milk production; hence the fattening tendency of the animals was brought into play, which soon outstripped the tendency for milk production, and the animals put on no less than 90.5 lb. of flesh in the five weeks. Lastly, the volume or quantity of milk which a cow will secrete depends largely upon the quantity of water she consumes. This is most strikingly seen when the water must be taken by the animal in her endeavour to obtain sufficient solid nutriment. Examples of this may be seen when cows are feeding upon succulent grass, on brewers' grains, or on mangels, &c. One of Mr. Spier's experiments strikingly illustrates this influence (Period 21). Cows were fed on brewers' grains (wet) from 28th February, 1897. During the first week they produced 158 lb. of milk per cow per week, which rose to 177 lb., the second week, 189 the third and fourth, and fell to 180 lb. the fifth week. Now the food during this period contained only about half the nutriment that was present in the food during Period 15, just referred to. What, then, was the result on the live weight? The animals lost during this period of five weeks no less than 42 lb. per cow in live weight.

We will now pass to a consideration of the quality of milk. The quality of milk is dependent on certain factors, quite irrespective of feeding. Primarily, any influence which diminishes the quantity tends to increase the quality. This is probably one principal cause of the richness of the milk of small breeds. Thus, heifers whose udders are not fully developed yield richer milk than they will produce subsequently as cows, but the quantity of this milk is small. Again, cows, as they advance in the period of lactation, yield milk constantly decreasing in quantity, while constantly improving in quality. One other influence is the time which elapses between the milking periods. The shorter the time the smaller the quantity of milk, but the richer the quality. Hence in some places, where butter-making is the chief consideration, the system of milking three times daily, at intervals of eight hours, has, wherever practicable, been adopted.

Milk is a secretion of ever varying composition, and in a shed of fifty cows, all fed alike, and all subject to the same conditions, probably no two standing side by side would yield milk of exactly similar composition. A consideration of the preceding facts will clearly show how very difficult it is to experiment on the influence of food upon milk production. I venture to think that some experimenters have not fully realised how far the results depended upon natural considerations, how far upon food, with the inevitable result that they have drawn erroneous conclusions from the facts obtained. My experience leads me to believe that we can only get at the truth by, instead of considering quantity and quality separately, combining the two. We can thus determine the actual amount of solid matter,

whether fat or non-fatty solids, which the animal has produced as milk, together with any gain or loss in live weight which has taken place simultaneoutly; for the old saying, "Out of nothing, nothing comes," indutiably holds good in feeding. Hence the quality of milk must ever depend upon the stock of nutriment in the blood, whether that nutriment be supplied by the food or from the animal's body. This is well seen in the experiment on brewers' grains (Period 21), before referred to. Thus, while in the first week, the animals produced 6.8 lb. of fat, in the fifth week they only produced 5.4 lb. whereas under normal conditions of feeding the weight in the fifth week would have been as great as in the first, if not greater.

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In my opinion, the present state of our knowledge as regards the effect of food on milk production may be briefly summed up as follows: When properly fed, a dairy cow will neither gain nor lose in live weight, and under such conditions will produce the maximum quantity of milk which her physical conformation permits, and that milk will have its maximum quality—i.e., there will be a maximum epithelial growth. The food which produces such results is an ideal milk ration, and the nearest approach to it which man possesses is a good pasture. The moment artificial feeding commences the conditions are altered. If an excess of nutriment is given, the tendency to fatten will gradually outstrip the tendency for milk production. If a deficiency of nutriment be given, the body will suffer first, subsequently the quality of the milk, and lastly the quantity. These results will be most marked when there is simultaneously an abundant supply of water. If now the food be changed, there will be a corresponding change in the quantity and quality of the milk, but it will not be immediate. Experiments have been made for me under the latter conditions. The result was that the animals first utilised the food to

replenish their emaciated bodies. The milk remained practically unaffected for from four to six weeks. Then the food told. This fact emphasises one source of error in feeding experiments; they are not conducted for a sufficiently long period.

Some years ago I carried out a feeding experiment by placing a herd of milch cows in various pastures of different character. The milk varied, both in quantity and quality, according to the pasture the animals were on. This, I think, will be the universal experience of every observant farmer here present. And I, though a scientific man, agree with practice, and have yet to find evidence which can shake my conviction that food has a marked effect on both the quantity and quality of milk.

THE above paper was read before a meeting of the British Dairy Farmers' Association. From The Dairy we reproduce the following report of a discussion which ensued :—

Professor Nuttall, remarked that some cranks said feeding had no effect on milk. He could not think that such men had any real observation, for food had a very great influence on quantity and quality.