FEEDING STUFFS, the materials on which animals feed, may be (i.) grass or other growing crops eaten in the fresh con dition; (ii.) the same preserved for winter use by drying or ensiling; (iii.) seeds, or products made from seeds; (iv.) miscel laneous products of various industries dealing with plant or animal materials.
Class (i.) includes such materials as pasture grass, rotation grasses and leguminous crops, rape, mustard, cabbage, kale, tur nips, swedes and mangolds. They are characterized by a high content of water-7o to 90%. Of their dry matter, about 4o to 6o% is soluble carbohydrate, 20 to 30% fibre, 8 to 20% protein or other nitrogenous substances, and 5 to i o% ash. On account of their high water content they are known as succulents. Those which consist mainly of green leaves supply an abundance of vitamins.
Class (ii.). Permanent and temporary grass is usually pre served by air drying which converts it into hay. Grass should be cut for hay before the flowers set seed ; otherwise much of the nutritive material is removed from the leaves and stems and stored in the seeds. These are lost in haymaking and the result ing hay is fibrous and indigestible. When the seeds are allowed to ripen and removed in threshing, as is the case with the cereals and many other crops, the remaining leaves and stems are called straw. Hay and straw are bulky feeding stuffs of low nutritive value. They are commonly called roughages.
Other green crops, e.g., oats sown together with vetches, beans or peas, are often cut green and preserved by compression into a silo after being cut into short lengths in a chaff cutter. This process is known as ensilage, and the product as silage (q.v.) .
Class (iii.) includes such materials as the cereal grains and their products, the leguminous grains, and the residues which remain after the removal of oil from oil—seeds; e.g., linseed, cotton-seed, palm kernels, copra, etc. Oil-seed residues vary con siderably in value according to the method of manufacture. In some cases the husk is removed from the seeds before the oil is separated. The residue is then said to be decorticated. It con tains comparatively little indigestible fibre and its nutritive value is relatively high. When the oil is removed simply by pressure, the residue still contains from 5 to io% of oil, which raises its nutritive value. If the oil is extracted by chemical means, the residue may contain as little as 1% of oil and the nutritive value is correspondingly decreased. The feeding stuffs in this class contain, on the whole, not more than from i o to 15% of water, and not more than 7 to 8% of fibre. Their content of nutritive materials is therefore high and they are known as concentrated feeding stuffs, or simply concentrates.
Class (iv.) comprises a number of industrial residues, some derived from plants, others from animals. A typical example is fish meal, the dried and ground refuse from the fish-curing indus try. It should be made from white fish comparatively free from oil, and should not contain more than 4% of salt. Fish meal containing more than 4 or 5% of oil is liable to give a fishy taint to the flesh, milk or eggs of animals fed on it.
Dried blood, dried and ground meat and bone residues are other examples of feeding stuffs of animal origin. Separated milk, buttermilk and whey are valuable additions to the diet of growing pigs, commonly used on farms where they are pro duced. Dried yeast, a waste product of the brewing industry, dried sugar-beet pulp and molasses from the sugar factories, are examples of plant waste products used for feeding animals.
All the four classes mentioned above are commonly described as "straight" feeding stuffs, which implies that they are composed of one easily recognized article. There is, however, a very large trade in feeding stuffs manufactured by mixing together or com pounding several articles. Many of them are good, some are bad. They are, however, a stumbling-block to the progressive farmer who wishes to work out rations for his animals on a modern basis, because, their make-up being unknown and perhaps vari able, it is not possible to estimate their real nutritive value.
If production is desired, a production ration must be given in addition to the maintenance ration, and the amount of the pro duction ration must be estimated in proportion to the amount which it is desired to produce. This method of computing rations has been in general and successful use amongst progressive dairy farmers for some years. Information is now available for com puting rations for growth and fattening on a similar basis. It is obvious that the weight of a feeding stuff is not a measure of its nutritive value. Ten pounds of mangolds containing go% of water are evidently of less nutritive value than i o lb. of linseed cake containing only io% of water. A better measure of nutritive value is obtained by making a chemical analysis to de termine the percentages of nutrients—proteins, commonly known as albuminoids or flesh formers, oils or fats, and carbohydrates; and this is the method approved by the Fertilizers and Feeding Stuffs Act, which regulates the sale of feeding stuffs.
Percentages of nutrients as determined by chemical analysis do not accurately measure nutritive value, for all the nutrients found by analysis are not digestible, and only that portion of the nutrients which is digested is of value to the animal. More over, even the sum of the digestible nutrients in a feeding stuff does not measure accurately its real nutritive value. It must be discounted for the nutrients used up during the processes of digestion and absorption. Kellner first showed 4o years ago how to estimate the real net nutritive value of feeding stuffs by find ing how much starch was required to produce in the body of an ox as much fat as was produced by the consumption of i oo lb. of the feeding stuff. He called this figure the starch equivalent of the feeding stuff. Armsby has more recently arrived at simi lar results by a totally different method. He expresses his figures for net nutritive value as calories of net energy. When expressed in the same units Armsby's figures agree reasonably well with Kellner's. Kellner's starch equivalents are the generally accepted measure of nutritive value in this country. Armsby's figures for net energy are in general use in the United States.
To compute a ration for an animal it is necessary to know:— I. The live weight of the animal, because the maintenance ration depends on the live weight being proportional to the square of the cube root of the live weight.
2. The amount of growth or milk which it is desired that the animal should produce.
3. The amount of starch equivalent required to produce unit weight or volume of product ; e.g., i lb. of live-weight in crease, or i gal. of milk.
4. The maximum capacity of the animal's appetite, usually stated in lb. of dry matter per day or per week.
5. The minimum weight of protein required to keep the work ing parts of the body in repair, and to provide for growth of working parts in a young animal or for making milk in a milking animal.
Approximate data for the above so far as they have been ascer tained are tabulated below for cattle, sheep and pigs. No data are available for the relation between food consumption and work, because there is no practicable method of measuring the work done by a horse or other draught animal.
From these data the ration in terms of starch equivalent is then computed from the equation:— Ration = maintenance ration -}- gain in live weight X weight of starch equivalent required to make i lb. gain + gal. milk X weight of starch equivalent required to make i gal. milk.
Having computed the ration in lb. of starch equivalent the next step is to calculate the proportion in which the available feeding stuffs must be mixed in order to include within the limits of the animal's appetite the necessary weight of starch equiva lent. The weight of digestible protein in the mixture must then be calculated for comparison with the minimum weight shown in the table. If found too low the ration must be adjusted by sub stituting a feeding stuff rich in protein for part of it. If a little too high, no harm as a rule will result.
In the case of young growing pigs and heavy milking cows it is desirable to calculate the amount of ash in the ration, and it may be necessary to supplement the ration with a mineral mixture. If the ration contains a fair proportion of fresh green food no anxiety need be felt about the risk of deficiency in vita mins, indeed there is in general small risk of vitamin deficiency among farm animals.
The data for computing rations are as follows : Appetite, especially of heavy milkers, higher than that of other cattle of similar weight.
Maintenance ration, as for other cattle of similar weight. Minimum requirement of digestible protein, exclusive of that required for milk production, .75 lb. per day.
Production requirement per gal. of average milk, 2.5 lb. starch equivalent including .55 lb. digestible protein.
See T. B. Wood, Animal Nutrition (1924); also Rations for Live Stock and Report of Departmental Committee on Rationing of Dairy Cows, published by the Ministry of Agriculture. (T. B. W.)