9 



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 

 desirable 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 be 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 

 abundant 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 mam A brief discussion of the properties of food 

 and the o-eneral laws of nutrition follows. 



The study of foods and feeding stufl's has shown that although they 

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

 of a small number of chemical constituents, namely, protein, fat, car- 

 bohydrates, and ash, together with a larger or smaller amount of 

 water. The latter can be often seen, as in the juice of fresh plants. 

 In dry hay no water or juice is visible. A small amount is, however, 

 contained in minute particles in the plant tissues. 



Protein is a name given to the total group of nitrogenous materials 

 present. The group is made up mainly of the true proteids and 

 albumens, such as the gluten of wheat, and of nitrogenous materials 

 such as amids, which are believed to have a lower feeding value than 

 the albumens. 



The group "fat" includes the true vegetable fats and oils, like the oil 

 in cotton seed or corn, as well as vegetable wax, some chlorophyl (the 

 green coloring matter in leaves, etc.), and other coloring matters; in 

 brief, all the materials which are extracted by ether in the usual labo- 

 ratory method of estimating fat. The name "ether extract" is often 

 and very properly applied to this group. Chemically considered, the 

 true fats are glycerids of the fatty acids, chiefly oleic, stearic, and 

 palmitic. 



The group "carbohydrates" includes starches, sugars, crude fiber, 

 cellulose, pentosans, and other bodies of a similar chemical struc- 

 ture. This group is usually subdivided, according to the analytical 

 methods followed in estimating it, into "nitrogen-free extract" and 

 "crude fiber;" the former subdivision including principally sugar, 

 starches, and most of the pentosans, and the latter cellulose, lignin, 

 and other woody substances which very largely make up the rigid struc- 

 ture of plants. 



The proteids contain nitrogen in addition to carbon, oxygen, hj^dro- 

 gen, and a little phosphorus and sulphur. The fats consist of carbon, 



