of the heart, respiratory movements, etc.), or the work which is per- 

 formed outside the body (hauling a load, etc.). The body temperature 

 must also be maintained at the expense of the fuel ingredients, but 

 whether material is burned in the body primarily for this purpose, or 

 whether the necessary heat is a resultant of the internal muscular work, 

 is not known with certainty., 



The problem of successfully feeding horses differs somewhat from 

 that encountered in feeding most domestic animals. Cattle, sheep, 

 and pigs are fed to induce gains in weight, i. e. , to fatten them, or in 

 the case of milch cows to produce gains in the form of a body secretion 

 (milk) rather than as fat in the body. In a similar way sheep are fed 

 for the production of wool, and poultry for the production of eggs. 

 Sometimes cattle are also fed as beasts of burden. Horses are fed 

 almost universally as beasts of burden, whether the work consists in 

 carrying a rider or drawing a load. 



Mares with foal require food for the development of their young, 

 and after birth the colt needs it for the growth and development of 

 the body as well as for maintenance. Such demands for nutritive 

 material are common to all classes of animals. Sometimes horses are 

 fed to increase their weight; that is, to improve their condition. For 

 instance, animals are often fattened by horse dealers before they are 

 sold. However, generally speaking, the problem in horse feeding is 

 to supply sufficient nutritive material for the production of the work 

 required and at the same time to maintain the body weight. The 

 almost universal experience of practical horse feeders, and the results 

 of many carefully planned experiments, agree that there is no surer 

 test of the fitness of any given ration than that it enables the horse fed 

 to maintain a constant weight. If the animal loses weight it is evident 

 that the ration is insufficient, while if gains in weight are made and 

 the animal becomes fat it is evident that more feed is given than is 

 necessary. Provided the horse is in good condition, it is seldom desir- 

 able to induce any considerable gain in weight. Reference is not 

 made to the small daily fluctuations in weight, but to gains or losses 

 which extend over a considerable period. The most satisfactory ration 

 must necessarily bo made up of materials which are wholesome and are 

 relished by the horse. It should also be reasonable in cost. It must 

 be abundant enough to meet all body requirements, but not so abun 

 dant that the horse lays on an undesirable amount of flesh. 



PRINCIPLES OF NUTRITION. 



The foundation principles of nutrition are the same in the case of all 

 animals, including man. A brief discussion of the properties of food 

 and the general laws of nutrition follows. 



The study of foods and feeding stuffs has shown tluit although they 

 differ so much in texture and appearance they are in reality made up 



170 



