72 NUTRITION OF FARM ANIMALS 



but as a rule the nitrogen-free extract consists to a considerable 

 extent of carbohydrates of one sort or another. Indeed, it has 

 sometimes been designated by the latter name, but the use of 

 the word in this sense is misleading and undesirable. 



The nitrogen-free extract includes not only hexose but also 

 pentose carbohydrates, these latter substances being, therefore, 

 by the ordinary method of feeding stuffs analysis, divided be- 

 tween the crude fiber and nitrogen-free extract. Some of 

 these various carbohydrates can be determined separately with 

 a reasonable degree of accuracy, while others, including unfor- 

 tunately starch, can be determined only more or less approxi- 

 mately. That the nitrogen-free extract is far from consisting 

 exclusively of carbohydrates has been strikingly shown, by 

 Stone. 1 He determined the content of the various classes of 

 carbohydrates in samples of wheat and maize as accurately as 

 possible and found that the sum in both cases was considerably 

 less than the amount of nitrogen-free extract as determined 

 by the conventional method. Much greater differences in this 

 respect have been shown to exist in roughages. 



111. Classes of feeding stuffs. The composition and char- 

 acteristics of the principal classes of feeding stuffs are considered 

 in Chapter XV, but it seems desirable to anticipate that dis- 

 cussion here to the extent of indicating the three major classes 

 into which the feeding stuffs are commonly divided. This 

 classification is based primarily on botanical characteristics 

 with which, however, are associated corresponding differences 

 in chemical composition. 



Concentrates or concentrated feeds. As the name implies, 

 these are feeding stuffs which contain much nutriment in a 

 small bulk. They include primarily the grains and other seeds 

 and, secondarily, a wide range of technical by-products de- 

 rived from them as well as certain by-products of animal origin. 

 Chemically, they are characterized by their relatively low con- 

 tent of crude fiber, ranging from practically zero in certain by- 

 products to perhaps 10 or 12 per cent in grains having a con- 

 siderable proportion of hulls, like oats or buckwheat, and in 

 certain by-products. 



Coarse fodders or roughage. Botanically, these consist of 

 the vegetative organs of the plant, i. e., substantially of stalks 



1 Jour. Amer. Chem. Soc., 19 (1897), 183. 



