ENERGY FOR THE HORSE
The chemist recognizes the importance of feed energy and measures it in an instrument known as the bomb calorimeter, in which the feed is placed, then burned with the aid of oxygen.
Briefly stated, the procedure is this: An electric wire is attached to the material being tested, so that it can be ignited by remote control; 2,000 grams of water are poured around the bomb; 25 to 30 atmospheres of oxygen are added to the bomb; the material is ignited; the heat given off from the burned material warms the water; and the thermometer registers the change in temperature of the water. For example, if one gram of feed is burned and the temperature of the water is raised one degree centrigrade, 2,000 calories are given off. Hence, the material contains 2,000 calories per gram. A kilocalorie( kcal) is equivalent to 1,000 calories.
THE HORSEMAN MEASURES ENERGY IN PERFORMANCE
The horseman recognizes the importance of feed energy and measures it in terms of work— in speed and endurance. Additionally, feed energy is essential for normal reproduction, and for growth of young stock.
The energy needs of horses vary with the individuality and size of animals, and the kind, amount and severity of work performed. In racing, horses may use up to 100 times the energy utilized at rest.
It is common knowledge that a ration must contain proteins, fats, and carbohydrates. Although each of these has specific functions in maintaining a normal body, they can all be used to provide energy for maintenance, for work, or for fattening. From the standpoint of supplying the normal energy needs of horses, however, the carbohydrates are by far the most important, more of them being consumed than any other compound, whereas the fats are next in importance for energy purposes. Carbohydrates are usually more abundant and cheaper, and they are very easily digested, absorbed, and transformed into body fat. Also, carbohydrate feeds may be more easily stored in warm weather and for longer periods of time. Feeds high in fat content are likely to become rancid, and rancid feeds is unpalatable, if not actually injurious in some instances. Also, fats are utilized very poorly by horses.
Generally, increased energy for horses is met by increasing the grain and decreasing the roughage.
A lack of energy may cause slow and stunted growth in foals, and loss of weight, poor conditions, and excessive fatigue in mature horses.
CARBOHYDRATES
The carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen. This includes the sugars, starch, cellulose, gums, and related substances. They are formed in the plant by photosynthesis as follows:
6CO2 + 6H20- }-energy from sun = C6H1206( glucose) + 602
On the average, the carbohydrates comprise about three-fourths of all the dry matter in plants, the chief three-fourths of all the dry matter in plants, the chief source of horse feed. They form the woody frame work of plants as well as the chief reserve food stored in seeds, roots, and tubers. When consumed by horses, carbohydrates are used as a source of heat and energy, and any excess of them is stored in the body as fat, or, in part, secreted.
From a feeding standpoint, the carbohydrates consist of nitrogen-free extract( N. F. E.) and fiber. The nitrogenfree extract includes the more soluble, and, therefore, the more digestible, carbohydrates— such as the starches, sugars, hemicelluloses, and the more soluble part of the celluloses and pentosans. Also N. F. E. contains some lignin. The fiber is that woody portion of plants( or feeds) which is not dissolved out by weak acids and alkalies. Fiber, therefore, is less easily digested. It includes cellulose, hemicellulose, and lignin.
The ability of horses to utilize roughages— to digest the fiber therein— depends chiefly on bacterial action. It is a true symbiotic type of relationship, carried out chiefly by anaerobic bacteria, mostly in the cecum and colon of the horse. This bacterial digestion breaks down the cellulose and pentosans of feeds into usable organic acids( chiefly acetic, propionic and butryic acids).
The fiber of growing pasture grass, fresh or dried, is more digestible than the fiber of most hay. Likewise, the fiber of early cut hay is more digestible than that of hay cut in the late-bloom or seed stages. The difference is due to both chemical and physical structure, especially to the presence of certain encrusting substances( notably lignin) which are deposited in the cell wall with age. This is understandable when it is recognized that lignin is the principal constituent of wood; for no one would think of feeding wood to horses.
Young equines and working( or running) horses must have rations in which a large part of the carbohydrate content of the ration is low in fiber, and in the form of nitrogen-free extract.
34 VOICE of the Tennessee Walking Horse