The feeding of cattle, once a subordinate part of the operations of the farm, has now become one of its most important departments, and a large number of minute and elaborate experiments have been made by chemists and physiologists with the view of determining the principles on which its successful and economical practice depends. These investigations, while they have thrown much light on the matter, have by no means exhausted it, and it will be readily understood that the complete elucidation of a subject of such complexity, touching on so many of the most abstruse and difficult problems of chemistry and physiology, and in which the experiments are liable to be affected by disturbing causes, dependent on peculiarities of constitution of different animals, cannot be otherwise than a slow process.

In considering the principles of feeding, it is necessary to point out, in the first instance, that the plant and animal are composed of the same chemical elements, hence the food supplied to the latter invariably contains all the substances it requires for the maintenance of its functions. And not only is this the case, but these elements are to a great extent combined together in a similar manner,—the fibrine, caseine, albumen, and fatty matters contained in animals corresponding in all respects with the compounds extracted from plants under the same name; and though the starchy and saccharine substances do not form any part of the animal body, they are represented in the milk, the food which nature has provided for the young animal. It has been frequently assumed that the nitrogenous and fatty matters are simply absorbed into the animal system, and deposited unchanged in its tissues; but it is probable that the course of events is not quite so simple, although, doubtless, the decomposition which occurs is comparatively trifling. The starchy matters, on the other hand, are completely changed, and devoted to purposes which will be immediately explained.

It is a matter of familiar experience, that if the food be properly proportioned to the requirements of the animal, its weight remains unchanged; and the inference to be drawn from this fact obviously is, that the food does not remain permanently in the system, but must be again got rid of. It escapes partly through the lungs, and partly by the excretions, which do not consist merely of the part which has not been digested, but also of that portion which has been absorbed, and after performing its allotted functions within the system, has become effete and useless. When the weights of the excretions, the carbon contained in the carbonic acid expired by the lungs and the small quantity of matter which escapes in the form of perspiration, are added together, they are found in such a case to be exactly equal to the food. If the animal be deprived of nutriment, it immediately begins to lose weight, because its functions must continue—carbon must still be converted into carbonic acid to maintain respiration—and the excretions be eliminated, although diminished in quantity, because they no longer contain the undigested portion of the daily food, and the substances already stored up in the body are consumed to maintain the functions of life. Universal experience has shewn that, under such circumstances, the fat which has accumulated in various parts of the body disappears, and the animal becomes lean; but it is less generally recognised that the muscular flesh, that is the lean part of the body, also diminishes, although it is sufficiently indicated by the fact that nitrogen still continues to be found in the urine, and that the animal becomes feeble and incapable of muscular exertion. Respiration and secretion, in fact, proceed quite irrespective of the food, which is only required to repair the loss they occasion. When the course of events within the animal body is traced, it is found to be somewhat as follows: The food consumed is digested and absorbed into the blood, where it undergoes a series of complicated changes, as a consequence of which part of it is converted into carbonic acid, and eliminated by the lungs, and part is deposited in the tissues as fat and flesh. After the lapse of a certain period, longer or shorter according to circumstances, a new set of actions comes into play, by which the complex constituents of the tissues are resolved into simpler substances, and excreted chiefly by the lungs and kidneys. The changes thus produced are, to a great extent, identical with those which would take place if the fat and flesh were consumed in a fire; and the animal frame may, in a certain sense, be compared to a furnace, in which, by the daily consumption of a certain quantity of fuel and air inhaled in the process of respiration, its temperature is maintained above that of the surrounding atmosphere. If the daily supply of fuel, that is of food, be properly adjusted to the loss by combustion, the weight of the animal remains constant; if it be reduced below this quantity, it diminishes; but if it be increased, the stomach either refuses to digest and assimilate the excess, or it is absorbed and stored up in the body, increasing both the fat and flesh.

When an animal is fed in such a manner that its weight remains constant, a balance is produced between the supply of nutriment contained in the food and the waste of the tissues, the gain from the former exactly counterpoising the loss occasioned by the latter. If in this state of matters an additional supply of food be given, this balance is deranged, and the nutriment being in excess of the loss, the animal gains weight, and it continues to do this for some time, until it reaches a point at which a new balance is established, and its weight again becomes constant; and this is due to the fact that the animal becomes subject to an additional waste, consequent on the increased weight of matter accumulated in its tissues. If, after the animal has attained its new constant weight, the food be a second time increased, a further gain is obtained, and so on, with every addition to the supply of nutriment, until at length a certain point is reached, beyond which its weight cannot be forced. In fact, each successive increase of weight is obtained at a greater expenditure of food. If, for example, a lean animal is taken, and its food increased by a given quantity, it will rapidly attain a certain additional weight, but if another extra supply of food be given, the increase due to it will be much more slowly attained, and so on until at length an additional increase can only be secured by the long-continued consumption of a very large quantity of food. The great object of the feeder is to obtain the greatest possible increase with the smallest expenditure of food, and to know the point beyond which it is no longer economical to attempt to force the process of fattening. To do this it is necessary first to consider the composition of the animal itself, then that of its food, and lastly, the mode in which it may be most economically used.

It has been already observed that the animal tissues are composed of albuminous or nitrogenous compounds, fat, mineral matters, and water; but the proportions of these substances have, until lately, been very imperfectly known. Water is well known to be by far the largest constituent, and amounts in general to about two-thirds of the entire weight, and it has been generally supposed that the nitrogenous matters stood next in point of abundance, but a most important and elaborate series of experiments by Messrs. Lawes and Gilbert have shewn that they are greatly exceeded by the fatty matters. The following table contains a summary of the composition of ten different animals in different stages of fattening. The first division gives the composition of the carcass, that is, the portion of the animal usually consumed as human food; the second that of the offal, consisting of the parts not usually employed as food; and the third that of the entire animals, including the contents of the stomach and intestines:—

[Transcriber's note: Column titles are printed vertical, which is not possible to do here. Therefore they are replaced with a 2-3 character code, explained here]

Column titles:
MM = Mineral Matter
NC = Nitrogenous Compounds
TDS = Total Dry Substance
CSI = Contents of Stomachs and Intestine in moist state.
Wat = Water

From this table it appears that, in the carcass, the proportion of fat is, in general, even in lean animals, much greater than that of nitrogenous compounds. In one case only, that of the fat calf, are they equal. But in the lean sheep there is more than one and a half times as much fat as nitrogenous matters, in the half fat sheep twice, in the fat sheep four times, and in the very fat sheep about six times as much. As a general result of the analyses it may be stated, that in the carcass of an ox in good condition, the quantity of fat will be from two to nearly three times as great as that of the so called albuminous compounds; in a sheep three or four times, and in the pig four or five times as great. In the offal, including the hide, intestines, and other parts not usually consumed as food, the proportion is very different,—the quantity of fat being much smaller, and that of nitrogenous compounds considerably larger.

Taking a general average of the whole, the following may be assumed as representing approximately the general composition of a lean and a fat animal:—

The data given in the preceding table, coupled with a knowledge of the relative weights of the lean and fat animals, enable us to ascertain the composition of the increase during the fattening process. It is obvious, from the material diminution of the per centage of water, that the matters deposited in the tissues must contain a much larger proportion of dry matters than the whole body; and the reduced per centage of nitrogenous matters shews that the fat must also greatly preponderate. This is still more distinctly illustrated by the following table, giving the per centage composition of the increase in fattening oxen, sheep, and pigs:—

Hence it may be stated in round numbers, that for every pound of nitrogenous matters added to the weight of a fattening animal, it will gain ten pounds of fat, and three of water. These are the proportions over the whole period of fattening, but it is probable that during the last few weeks of the process the ratio of fat to nitrogenous matters is still higher.

In considering the composition of the food of animals, it will be readily admitted that the milk, the nutriment supplied by nature for the maintenance of the young animal, must afford special instruction as to its requirements during the early stages of existence, and indicate, at least, some of the points to be attended to under the altered conditions of mature life. The following table gives the average composition of the milk of the most important farm animals:—

In examining these, and all other analyses of food, it is necessary to draw a distinction between the flesh-forming and the respiratory elements; the former including the nitrogenous compounds which are used in the production of flesh, the latter, the non-nitrogenous substances which produce fat and support the process of respiration. The former, however much they may differ in name, are nearly or altogether identical in chemical composition, the latter embracing two great classes—the fats which exist in the body and the saccharine compounds, including the different kinds of sugar and starch which are not found in the animal tissues. It was at one time supposed that these substances were entirely consumed in the respiratory process, and eliminated by the lungs in the form of carbonic acid and water, but it has been clearly shewn that they may be and often are converted into fat, and accumulated in the system. Careful experiments on bees have demonstrated that when fed on sugar they continue to produce wax, which is a species of fat, and animals retain their health and become fat, even when their food contains scarcely any oil. There is, however, an important difference between these two classes of substances as regards their fat-producing effect. A pound of fat contained in the food is capable of producing the same quantity within the animal; but the case is different with starch and sugar, the most trustworthy experiments shewing that two and a half pounds of these substances are necessary for that purpose. Hence we talk of the fat equivalent of sugar, by which is meant the amount of fat it is capable of producing, and which is obtained by dividing its quantity by 2·5. Applying this principle to the analyses of the milk, it appears that the relative proportions of the two great classes of nutritive substances stand thus:—

Taking the general average, it may be stated, that for every pound of flesh-forming elements contained in the food of the sucking animal, it consumes respiratory compounds capable of producing one and a half pounds of fat, and this does not differ materially from the ratio subsisting between these substances in the lean animal. When the young animal is weaned, it obtains a food in which the ratio of nitrogenous to respiratory elements is maintained nearly unchanged; but the latter, in place of containing a large amount of fatty matters, is in many cases nearly devoid of these substances, and consists almost exclusively of starch and sugar, mixed most commonly with a considerable quantity of woody fibre.

A very large number of analyses of different kinds of cattle food have been made by chemists, but our information regarding them is still in some respects imperfect. The quantity of nitrogenous compounds and of oil has been accurately ascertained in almost all, but the amount of starch, sugar, and woody fibre is still imperfectly determined in many substances. This is due partly to the fact that the nitrogenous and fatty matters were formerly believed to be of the highest importance, and might be used as the measure of the nutritive value of food to the exclusion of its other constituents, and partly also to the imperfect nature of the processes in use for obtaining the amounts of woody fibre, starch, and sugar. These difficulties have now, to a certain extent, been overcome, and the quantity of fibre and of respiratory elements has been ascertained, and is introduced, so far as is known, in the subjoined table:—

Table giving the Composition of the Principal Varieties of Cattle Food.

Note.—Where a blank occurs in the oil column, the quantity of that substance is so small as to be unimportant. When the respiratory elements and fibre have not been separated, the sum of the two is given.

It is at once obvious that in many of these descriptions of food the ratio of the flesh to the fat-forming constituents differ very widely from that existing in the milk, and this becomes still more apparent when the latter are represented in their fat equivalent, as is done for a few of them in the following table:—

It is especially note-worthy that those varieties of food, which common experience has shewn to promote the fattening of stock to the greatest extent, contain in many instances the smallest quantity of respiratory or fat-forming elements relatively to their nitrogenous compounds. This is especially the case with the different kinds of oil cake, the leguminous seeds, clover, hay, and turnips. On the other hand, in the grains the ratio is nearly that of one to three, or similar to that found in fat cattle; while in the straw, the excess of the respiratory elements is extremely great.

These facts appear at first sight to be completely at variance with the composition of the increase of fattening animals, as ascertained by Messrs. Lawes and Gilbert already referred to, and which have shewn that for every pound of nitrogenous compounds, nearly ten pounds of fat are stored within the animal; and it might be supposed that those kinds of food which contain the largest relative amount of respiratory elements ought to fatten most rapidly, and should be selected by the farmer in preference to oil-cakes and similar substances. But there are other matters to be considered, dependent on the complex nature of the changes attending the absorption and assimilation of the food. It must be particularly borne in mind that only a small proportion of the food consumed is stored up within the body, and goes to increase the weight of the animal. Even in the case of the milk, in which economy in the supply of nutritive matters has been most clearly attended to by nature, a considerable proportion escapes assimilation, and in the adult animal a large amount of the food passes off with the excretions. The justice of this position is apparent when it is remembered that an ox will go on day after day consuming from a hundred weight to a hundred weight and a half of turnips, three or four pounds of bean-meal or oil-cake, and a considerable quantity of straw, although its daily increase in live weight may not exceed a couple of pounds. And in this direction a very fertile field of inquiry lies open to the agricultural experimenter; for it would be most important to determine whether there are not some substances from which the nutritive matters may not be more easily assimilated than from others, and what proportion of each is absorbable under ordinary circumstances. On this point no information has yet been obtained applicable to individual feeding substances, but the experiments of Messrs. Lawes and Gilbert have shewn the quantity of the total food, and of each of its constituents, stored up in the fattening animal, and a summary of their results is contained in the following Table:—

TABLE shewing the Amount of each Class of Constituents, stored in the increase, for 100 consumed in the Food.

Hence it appears that the pig makes a better use of its food than the sheep, retaining twice as much of its solid constituents within the body, from which may be deduced the important practical conclusion, that the former must be fattened at a much smaller cost than the latter. Looking at the individual constituents, it appears that, in the sheep, less than one-twentieth of the nitrogenous compounds, and one-tenth of the non-nitrogenous substances contained in the food, remain in the body; and a knowledge of these facts tends to modify the conclusions which might be drawn from the composition of the increase in the fattening animal. Its influence may be best illustrated by a particular example. If, for instance, the increase in a sheep contained its nitrogenous and respiratory elements in the ratio of 1 to 10, it would be totally incorrect to supply these substances in the food in the same proportions. On the contrary, it would be necessary at the very least to double the proportion of the former, because one-tenth of the fat-forming elements are absorbed, and only one-twentieth of the nitrogenous.

On further consideration, also, it seems unquestionable that the quantity of the nutritive elements stored up must depend to a large extent on the nature of the food and the particular state in which they exist in it. It is probable, or at least possible, that some kinds of food may contain their nitrogenous constituents in an easily assimilable state, and their respiratory elements in a nearly indigestible condition, or vice versa, and under these circumstances their nutritive value would be below that indicated by analysis; but these points can only be determined by elaborate and long continued feeding experiments. It is well known, however, that the mechanical state of the food has a most important influence on its nutritive value. Thus, for example, the presence of a large quantity of woody fibre protects the nutritive substances from assimilation, and seeds with hard husks pass unchanged through the animal, although, so far as their composition alone is concerned, they may be highly nutritive; and the loss of a certain quantity of many varieties of food in this way is familiar to every one.

The proper adjustment of the relative quantities of the great groups of nutritive elements in the food is a matter the importance of which cannot be over-rated, for it is in fact the foundation of successful and economical feeding; and this will be readily understood if we consider what would be the result of giving to an animal a supply of food containing a large quantity of nitrogenous and a deficiency of fat-forming compounds. In such circumstances, the animal must either languish for want of the latter, or it is forced to supply the defect by an increased consumption of food, in doing which it must take into the system a larger quantity of nitrogenous compounds than would otherwise have been requisite, and in this way the other elements, which are present in abundance, are wasted, and the theoretical and practical value of a food so constituted may be very different, and it is only when the proportions of the different groups are properly attended to that the most economical result can be obtained. It can scarcely be said that the experiments yet made by feeders enable us to fix the most suitable proportion in which those substances can be employed, although experience has led them to the use of mixtures which are in most cases theoretically correct; thus they combine oil-cakes or turnips with straw, which is poor nitrogenous, and rich in fat-forming elements; and in general it will be found that where different kinds of food are mixed, the deficiencies of the one are counterbalanced by the other, and though this has hitherto been done empirically, it cannot be doubted that as our knowledge advances it will more and more be determined by reference to the composition of the food.

Although the presence of a sufficient quantity of nutritive compounds in the food is necessarily the fundamental matter for consideration, its bulk is scarcely less important. The function of digestion requires that the food shall properly fill the stomach, and however large the supply of nutritive matters may be, their effect is imperfectly brought out if the food is too small in bulk, and it actually may become more valuable if diluted with woody fibre, or some other inert substance. At first sight this may appear at variance with the observations already made as to the effects of woody fibre in protecting the nutritive matters from absorption; but practically there are two opposite evils to be contended against, a food having too small a bulk, or one containing so large a proportion of inert substances as to become disadvantageously voluminous. The most favourable condition lies between the two extremes, and the natural food of all herbivorous animals is diluted with a certain amount of woody fibre. When these are replaced by substances containing a large quantity of nutritive matters in a small bulk, the result is that the natural instinct of the animal causes it to continue feeding until the stomach is properly distended, and it consequently consumes a much larger quantity of food than it is capable of digesting, and a more or less considerable quantity passes unchanged through the intestines, and is lost. On the other hand, if the food be too bulky, the sense of repletion causes the animal to cease eating long before it has obtained a sufficient supply of nutritive matter. It is most necessary, therefore, to study the mixture of different kinds of food, so as to obtain a proper relation between the bulk and the nutritive matters contained in the mixture; and on examining the nature of the mixed foods most in vogue among feeders, it will be found that a very bulky food is usually conjoined with another of opposite qualities. Hence it is that turnips, the most voluminous of all foods, are used along with oil-cake and bean-meal, and if from any circumstances it becomes necessary to replace a large amount of the former by either of the latter substances, the deficient bulk must be replaced by hay or straw.

It has been already remarked that there are three great purposes to which the food consumed is appropriated; the increase of weight of the animal—the object the feeder has in view and desires to promote—the supplying the waste of the tissues, and the process of respiration, both of which are sources of loss of food, and which it must necessarily be his aim to diminish as much as possible. The circumstances which must be attended to in order to do this are sufficiently well understood. It has been clearly established that the natural heat of the animal is sustained by the consumption of a certain quantity of its food in the respiratory process, during which it undergoes exactly the same changes as those which occur during combustion. It has further been observed, that the temperature of the body remains unchanged, whatever be that of the surrounding air; and it is obvious that if it is to continue the same in winter as in summer, a larger quantity of fuel (i. e. food) must be consumed for this purpose, just as a room requires more fire to keep it warm in winter than in summer, and hence it naturally follows, that if the animal be kept in a warm locality the food is economized. It may also be inferred that, if it were possible, consistently with the health of the animal, to keep it in a room artificially heated to the temperature of its own body, this source of waste of food would be entirely removed. It is not possible, however, to do this, because a limit is set to it by physiological laws, which cannot be infringed with impunity; but the housing of cattle, so as to diminish this waste as far as possible, is a point in regard to the propriety of which theory and practice are at one.

The old feeders kept their cattle in large open courts, where they were exposed to every vicissitude of the weather, but as intelligence advanced, we find them substituting, first hammels, and then stalls, in which the animals are kept during the whole time of fattening at an equable temperature. The effect of this is necessarily to introduce a considerable economy of the food required to sustain the animal heat; but it also produces a saving in another way, for it diminishes the waste of the tissues.

It has been ascertained by accurate experiments made chiefly on man, that muscular exertion is one of the most important causes of the waste of the tissues, and of increased respiratory activity. We cannot move a limb without producing a corresponding consumption of matters already laid up within the body; and it has also been found, that the difference in the quantity of carbonic acid expired during rest and active exertion, is very large. The inference to be drawn from this is, that when it is sought to fatten an animal rapidly, every effort must be made to restrain muscular motion so far as compatible with health. Hence, the peculiar advantage of stall-feeding, in which the animal is confined to one spot, and the more thoroughly it can be kept still, the greater will be the economy of food. This is gained by darkening the house, and excluding all persons, except when their presence is indispensable.

An extension of the same principle has led to the use of food artificially heated, but it is doubtful whether the advantages derived from it are commensurate to the increased expense of the process; at least opinions differ among the best informed practical men on this subject.

Many other matters, besides these mentioned, exercise an important influence on the feeding of stock, such as the general health of the animal, the breed, etc. These are subjects, however, which bear more directly on practical agriculture, and need not be discussed here.

The judicious feeder will not only give due weight to the principles already discussed in all he does, but he must take into consideration the extent to which they are liable to be modified in particular cases. He must also attend to the cost of different kinds of food, and the value of the manure produced by them, subjects of much importance in a practical point of view, and which must influence him greatly in choice of the particular substances he supplies to his cattle.