5. What does the term spread or margin mean, as used by cattle men ? 6. Give the main factors on which the spread depends. 7. Give the factors that determine the length of feeding period. 8. How much grain and roughage does it take, on the average, to produce

100 pounds gain in fattening steers ? 9. Why is pasture feeding for steers cheaper than feeding during the

winter months? 10. Discuss briefly the value of silage for steer feeding. 11. What is baby beef ? 12. Give the conditions under which it may be successfully produced. 13. Describe briefly the methods followed in the feeding of (a) yearling

steers, (6) two-year-olds, (c) range steers. 14. Describe the method of keeping hogs with fattening steers. 15. Where are the main cattle markets located in the United States ? 16. What do you understand by shrinkage of cattle, how is it influenced,

and what are the average figures under different conditions ? 17. What is a self-feeder? Under what conditions is its use advisable in

beef production ?

References: Farmers' Bul. 612, " Breeds of Beef Cattle.” 811, “ Pro. duction of Baby Beef.” 580, Beef Production in the South.” 588, “ Economical Cattle Feeding in the Corn Belt.” 183, “ Butchering.” 1055,

Country Hides and Skins, Skinning, Curing and Marketing."

66

66

CHAPTER XXIV

FEEDING HORSES AND MULES

Feeding Standards for Horses.—The Wolff-Lehmann and the Kellner-Armsby standards are here given, to be followed in determining the best rations for horses.

The Wolff-Lehmann Standards for Horses, per 1000 Pounds Live Weight

Work Done by the Horse (Fig. 68).-The horse is kept for the production of work; this may be pulling a load or carrying a rider; in either case, the energy in the feed eaten over and above that necessary for the maintenance of the body is used for performing the work required, in addition to moving his own body forward. The work is done by the contraction of his muscles, and the material stored up in these from the digested and assimilated feed is oxidized in this process. If the oxidation of the materials in the muscles goes on faster than the repair of muscles from the feed supplied, the horse will lose weight. This frequently happens when a horse is working hard for a considerable period of time and does not receive a sufficient quantity of easily digestible feed (concentrates).

Character of Feed Required. As the muscles are largely composed of proteins, it might be supposed that the decomposition of protein in the body would increase with the amount of labor performed; such is not the case, however. The oxidation of nonnitrogenous materials in the body, on the other hand, increases rapidly when hard work is done. A part of the energy thus set free appears as heat, and another part as mechanical work. The oxygen required for the oxidation processes going on in the body is

Fig. 68.—Draft horses that give a good account of themselves in the show ring, as breeding

animals and for doing heavy work. (Pacific Rural Press.)

supplied by the blood, and the oxidation products formed, carbondioxide and water, are exhaled through the lungs and in the perspiration. The result of heavy work is, therefore, seen in an increased consumption of oxygen and an increasing excretion of carbon-dioxide and water. This is also what takes place when mature fattening animals are gaining weight. The carbohydrates or fat, or both, are the main sources of energy supply both in the production of body fat and muscular energy, and it is not necessary to furnish more protein to working animals than in the case of fattening animals, viz., sufficient to insure a complete digestion of the feed. For this purpose a nutritive ratio of 1:8 or 1:10 will suffice.

A growing animal that is performing work requires a special supply of protein, and the same appears to be the case with race horses or driving horses which perform heavy work within a short

time; but for horses working at ordinary pace only a relatively small protein supply is required. The amounts of non-nitrogenous components of the ration, on the other hand, must be increased with the amount of work done. The standards for work horses, therefore, call for a relatively wide nutritive ratio of 1:6 or 1:7; even this ratio is narrower than that of rations ordinarily fed in this country, unless alfalfa or clover hay is fed, in which case a considerably narrower ratio is fed. Horses in the eastern and northern States are frequently given no other feeds than timothy hay and either oats or corn and oats. The nutritive ratios of these feeds are as follows: Timothy hay, 1:16; corn, 1:9.5, and oats, 1:5.5. It is evident, therefore, that rations composed of these feeds will be likely to have nutritive ratios of 1:9 or wider. American horses (outside of alfalfa sections) are rarely fed appreciable quantities of high-protein feeds, showing that they require but relatively small amounts of protein in their feed, and that they receive wide nutritive ratios even when at hard work.

Measurement of Work.—The amount of work done by a horse may be measured by one of the usual units of mechanical energy, a foot-pound or a foot-ton. A foot-pound is the amount of energy expended in raising one pound one foot high; a foot-ton is that expended in raising one ton one foot high. The horse-power is another common unit of energy, and is equivalent to 550 footpounds per second, or nearly 2,000,000 foot-pounds per hour. A horse's capacity for continuous work is, however, considerably smaller than this amount, and may be put at about 1,000,000 foot-pounds per hour per 1000 pounds weight. Light work done by horses, as commonly understood, will mean from 500,000 to 1,000,000 footpounds per hour, medium work from 1,000,000 to 1,500,000, and heavy work from 1,500,000 to 2,000,000 foot-pounds. Instead of measuring the amount of work done by units of mechanical energy, this may be measured in the same way as the potential energy of feeds, by the unit of heat, a Calorie or a therm (p. 45); this is a convenient method, because these unit values are now often used in feed analyses and in statements of feeding standards. One Calorie corresponds very closely to 1.54 foot-tons or 3087 foot-pounds.

The relation of the nutrients required for the production of a certain work by the horse under varying conditions has been studied in extensive investigations by German and French scientists, especially among the former, by Wolff, Zuntz, and Kellner. These

* Murray, “ Chemistry of Cattle Feeding,” p. 153.

studies have been of fundamental importance and through them we are able to determine approximately the net energy that must be supplied in the feed for the production of different kinds of work at varying speed, on the level, or ascending certain grades, etc. Zuntz found that nearly one-third (31.3 per cent) of the total energy of feed can be converted by the horse into useful work. This is at least three times greater economy than that obtained in a modern

steam engine. The energy required to masticate and digest feed by horses was also determined by Zuntz in an elaborate series of experiments; this energy was found to vary greatly with feeding stuffs of different character. In the case of hay, oats, and corn, for instance, the matter stands as follows:

Hay Pound total digestible matter in one pound

.391 .615

.785 Labor expended in chewing and digestion (in terms of nutrients)

.209 .219 .082 In per cent

53

Oats

Corn

35

10

In the case of coarse feeds a considerable proportion of the potential energy is consumed in the processes of mastication and digestion, and hence lost for productive purposes, while with cereals, grain feeds, and roots these processes require a smaller proportion of the energy, and more remains for production. With some kinds of straw a negative nutritive value was obtained, showing that while a certain amount of heat was liberated in the digestion of the straw which was ordinarily of benefit to the animal, there would be no excess of energy available for production; in fact, a larger portion of nutrients than found in the straw would be required to supply the energy called for by the increased internal muscular work.

Energy Requirements of the Horse. Through the result of investigations along this line that have been conducted especially by German scientists we are able to calculate the energy requirements of horses for a certain piece of work. Armsby gives the following example:

case

We will suppose that a horse weighing 1100 pounds is required to haul a load of one ton 20 miles a day on the level road. at a rate of 2.88 miles per hour, the draft averaging 100 pounds. The useful work will be in this

5280 (feet per mile) X 20 X 100 equals 10,566,000 foot-pounds, or 3,421 Calories.

Since 31.3 per cent of the energy liberated in the body is utilized in draft, It will require, to perform 3421 Calories of work, 3421 divided by .313, which equals 10,929,000 Calories of energy in the body. It has been found that it calls for an expenditure of energy equivalent to 264 Calories for a 1100-pound

* Cyclopedia American Agriculture, vol. iii, p. 88.