FEEDS AND FEEDING 563 



mineral matter, especially if considerable corn is used in the ration. The 

 hogs should have access to a mineral mixture consisting of charcoal, air- 

 slaked lime, salt, wood-ashes and rock phosphate or "floats." 



Crude Protein includes all the compounds of the feed which contain 

 the element nitrogen. Familiar forms of protein are egg albumen (the white 

 of the egg) and casein (the curd of milk). Protein is found in all living- 

 matter and is absolutely essential to life. It is found in every plant cell, 

 but in larger amounts in the seeds. It also occurs in every animal cell and 

 makes up a large part of the solid matter of the blood, muscles and organs 

 of the body. Thus the crude protein of the ration is absolutely essential 

 to the animal for the repair and growth of the muscles, bones, organs, etc. 

 It is also essential for a pregnant animal for the formation of the foetus 

 and, later, for milk production. If there is any surplus of protein in the 

 ration above the requirements of the animal for the purposes just mentioned, 

 the surplus may be used to produce energy or to liberate heat. If there is 

 still a surplus, it may be used for the production of body fat. However, 

 protein is not an economical source of energy or body fat, as it usually 

 is the most expensive nutrient and the one which it is most often necessary 

 to buy. Hence, no more protein should be fed than needed by the animal 

 for repair, growth and milk production. Tankage, cottonseed meal, 

 linseed meal, gluten feed, distillers' grains, brewers' grains, bran, middlings 

 and soy beans are high in protein. The legume hays are also relatively 

 high in protein. Corn, timothy hay, the straws, fodder, stover and silage 

 are low in crude protein. 



Carbohydrates are the chief constituents of all plants. However, 

 they are not found to any large extent in animals. Familiar forms of the 

 carbohydrates are starch, sugar and vegetable fiber, such as hemp, paper 

 and cotton. As the carbohydrates contain such a variety of compounds 

 which differ considerably in nutritive value, they are often divided into two 

 sub-classes: "nitrogen-free extract" and "crude fiber." 



Nitrogen-free extract includes those carbohydrates which are high in 

 feeding value, as starch and sugar. In the animal body these substances 

 are used as a source of energy to do work or for heat to keep the body warm. 

 If there is any surplus, it may be used for the production of energy and the 

 formation of body fat. As carbohydrates are considerably cheaper than 

 protein, it is more economical to use them for these purposes than to use 

 protein. Feeds high in nitrogen-free extract are corn, wheat, barley, rye, 

 rice and oats. The flour by-products, the oil meals, the straws and hays 

 contain medium amounts: while the pastures, silage and packing house 

 by-products are low. 



Crude fiber includes the tough, woody, fibrous portion of the plant. 

 Owing to the fact that it is not very digestible, the nutritive value of crude 

 fiber is less than that of the other nutrients. In the animal the digested 

 crude fiber is used as a source of energy and as a source of body fat. Feeds 

 high in crude fiber are the hays, straws, fodders, stovers and roughages in 



