242 NATURE AUGUST 30, 1941, VOL. 148 MILK PRODUCTION IN WAR-TIME BY PROF. H. D. KAY, O.B.E. NATIONAL INSTITUTE FOR RESEARCH IN DAIRYING JF from the point of view of human nutrition in on a rather arbitrary definition as between a war-time the gravest problem is that of pro­ 'dairy' cow and a 'beef' cow), the huge size of the viding sufficient calories, the next in importance is problem-that of providing some twelve million undoubtedly that of maintaining at the highest tons (dry weight) of feeding stuff per annum t,o possible level the daily inflow into the national secure adequate milk production-is apparent. larder of milk-with its unquestioned value in It is not generally realized that as much as balancing and reinforcing, either for the young or 80-85 per cent of the total food consumed by the the adult, a diet which may be short of calcium, dairy cow (estimated, of course, on a dry-matter vitamin A, riboflavin,. animal protein, and fat. basis) is, in peace-time, produced at home, from The adequate solution· of the milk problem is grazing and from other farm-produced foodstuffs dependent on many factors, agricultural, economic, such as hay, straw, roots, kale, silage, etc., these administrative, etc. It is proposed to- discuss a latter for the most part bulky foods with a few of those in the first of these categories, mainly relatively low energy and protein content and concerned with feeding and management of the containing a large proportion of indigestible fibre. dairy cow in war-time. For present purposes we may regard the essential It is believed that of all farm animals, the food requirements for efficient lactation in the modern dairy cow is the most efficient converter of dairy cow as being a sufficiency of digestible farm feeding stuffs into human food. This, how­ nutrients in a bulk which does not exceed the ever, is true only for the animal of medium or assimilatory capacity of the animal. These higher yield, say, for present purposes, for the nutrients have to provide (a) the animal's basal animal yielding not less than 500-600 gallons per metabolic needs for energy, (b) her energy require­ lactation. It is again fortunate that, as a ruminant ments for purposes of muscular movement, and by preference almost entirely a herbivore, the digestion and glandular activity, including the cow, unlike the pig and the hen, does not seriously activity of the mammary gland and the relatively compete directly with man for the kind of food­ small amount of material necessary for the day-to­ stuff he requires his own diet. In the third day repair of these tissues, and (c) the materials place it is fortunate also that as a result of past needed for the synthesis of the very considerable research, a great deal is now known about the quantities of lactose, casein and lactalbumin, and detailed nutritional needs of this highly specialized fat secreted by the udder*. The war-time signi­ animal for efficient lactation, though this know­ ficance of this statement is that the food materials ledge, particularly valuable in war-time, is effec­ required for (c) are rather different in composition tively applied on far too small a proportion of our than those needed for (a) and (b). They are richer dairy farms. in protein, and belong mainly to the type of Quantitatively, the dimensions of the problem concentrates that was extensively imported from of feeding the cow are greater in this than in the abroad in peace-time. War of 1914-18. The dairy cow population at the To obtain the necessary nutrients under (a), outbreak of the present War was more than 20 per (b) and (c) from the ordinary, bulky farm foods is cent above that of 1914, and there has, if anything, only possible if the yield of milk is small, say been an upward trend in the last two years. In t-1 gallon a day. The capacity and appetite of a tonnage, the amount of food required for the high-yielding dairy cow do not allow her to eat dairy herd is not far short of that needed for the sufficient of such bulky foods to maintain her milk entire human population. The average dairy cow yield for very long. She is, like nearly all modern weighs about half a ton, and although she will farm animals, in a state of unstable biological provide each year say 500-600 gallons of milk, equilibrium. Without adequate feeding of con­ containing a dry weight of some 6 cwt. (that is, centrated foods she may for a short time continue nearly twice her own dry weight) of first-class to secrete large amounts of milk at the expense of human food, she must have, if she is to remain a her own tissues, but this process will not continue productive unit, not far short of four tons a and she will eventually rapidly fall off in yield. year of foodstuff, estimated as dry matter. When The main problem of feeding for milk production this requirement is multiplied by well over three • The nutrients have also to provide, in most cases, for the growth of the freta! calf. The maiu demand here, however, is late iu lactation million (the exact number of 'dairy' cows depends when the milk yield is falling otf. ©1941 Nature Publishing Group No. 3748, AUGUST 30, 1941 NATURE 243 in war-time is to provide the type of concentrated for making containers to store the 130,000 tons protein-rich nutrients required for purpose (c), and or more of processed milk, probably an organization that despite the facts that importation of con­ to reconstitute the milk in numerous depots, and centrates from abroad is severely cut down, that certainly a formidable change in food habits. the by-products of flour milling will soon be both Though milk dried or "evaporated" by modern less in quantity and in nutritive value since 85 methods and properly packed for storage loses per cent instead of 73 per cent of the wheat grain very little of its nutritive value, it is very doubtful will go into flour for human consumption, that indeed whether any extensive change over to there is a shortage of skilled labour on the farm, summer milk production is either feasible in war­ and that a larger area of farm land is now being time or advisable at any time. used for the production of human foodstuffs such In present circumstances, the only means by as wheat and potatoes, the by-products of which which milk yield may be maintained in winter are not very useful for purpose (c). are : (I) the switching over to the dairy cow of Without concentrated feeding stuffs, especially sufficient concentrated feeding stuffs, both those in winter, and adequate husbandry the dairy cow produced at home and those that continue to be would fairly soon revert to a low-yielding animal imported, from less essential stock such as pigs producing most of her small output of milk from and poultry, or (2) an increase in quantity and grass in the spring and summer months, and quality of the feeding stuffs grown on dairy farms drying off completely in the winter. But alike at home, so that they not only provide all the with the good and the poor cow, feeding presents maintenance rations needed for purposes (a) and no problem at all if grass, which if of good quality (b) mentioned above, but also meet the higher will contain all the protein needed for purpose (c), protein requirements for purpose (c). is abundant. Up to four or even five gallons of Alternative (I) is the foundation of the rationing milk a day can be produced without difficulty or system that was introduced half-way through the damage to the cow, and without any supplemen­ winter of 1940-41. By this system the greater tary feeding of concentrates, if such grass is proportion of the available concentrates were available, and fields are grazed in rotation under allocated to dairy cows : farm horses and one or reasonably efficient conditions of grassland manage­ two other categories of essential animals received ment. In most parts of Great Britain, however, an a sufficient ration, beef cattle were reduced to abundant supply of grass rarely persists for more about 50 per cent of their pre-war requirements, than three or four or possibly five months of the and the small amount left was allocated to pigs twelve. For the remaining months both bulky and poultry. Alternative (2) is clearly one which farm foods and concentrates containing sufficient needs time to achieve. It means in the first place protein are essential, in addition to what the cow the improvement in quantity and quality of the can pick up from the pastures, if an average, or grass produced on the farm, an improvement better than average, yield of milk is to be main­ which had in fact begun, if only in a small way, tained. It is particularly in December, January before the War. This entails the ploughing up, and February, when natural environmental and appropriate artificial manuring, and re-seeding of war-time nutritional conditions both for the dairy worn-out or indifferent pasture, the general cow and for man are at their worst, that human improvement of grassland by adequate dressings needs for a protective food like milk are at their of lime and phosphates, the use of suitable seed greatest. mixtures and nitrogenous fertilizers on selected It has been suggested that the nationally most fields to produce grass one or two weeks earlier in satisfactory war-time plan is for the dairy farmer the season and possibly to induce grass to linger to go in for summer milk production from grass, for about the same length of time in the late and winter his cows in a practically non-lactating autumn, with a corresponding economy in con­ condition.