12 THE SCIENTIFIC FEEDING OF ANIMALS 



are easily differentiated from the latter by a number of reactions. The 

 amount of pentosanes in crude fiber is on the average from 5 to 10 per 

 cent, in meadow hay 5.2 per cent, rye straw 11.0 per cent, clover hay and 

 lupine straw 6.2 per cent. 



The total crude fiber content of straw is from 20 to 55 per cent, meadow 

 hay and young forage plants 16 to 40 per cent, grains 0.5 to 17 per cent, 

 root crops slightly above 1 per cent. 



The function of crude fiber may be regarded primarily as that of non- 

 nutrient ballast, and in the calculation of rations crude fiber is recognized 

 as an important part of the dry matter. It is important because it imparts 

 volume and texture to the feeding stuff and thus serves to fill the volumi- 

 nous spaces of the digestive canal. It also exerts a mechanical effect on 

 the mucous membranes of the digestive canal and, in a reflex manner, 

 excites the secretion of the digestive fluids and the movements of the 

 bowels. However, care must be observed in the use of feeding stuffs rich 

 in crude fiber, because on the one hand they are deficient in nutrient sub- 

 stances and on the other hand require undue effort in mastication and 

 digestion. 



As far as the nutrient value or nutrient action of crude fiber is con- 

 cerned, experiments have shown that the actual digestion of 57 per cent 

 of the crude fiber results in neither gain nor loss to the animal. If less 

 than 57 per cent is digested, there is an actual loss at the expense of the 

 other nutrients. This loss is due to undue effort on the part of the organs 

 of digestion (mastication muscular effort in moving the contents of the 

 intestinal canal, secretion of the necessary digestive fluids, etc.). On the 

 other hand, if an excess over 57 per cent of the raw fiber administered is 

 digested, there is a proportionate gain, the value of the excess digested 

 being the same as that of starch, in equal amount, 

 2. Nitrogen-Free Extracts 



The group of nitrogen-free extracts includes all nitrogen-free organic 

 substances which are not classified with the crude fat nor crude fiber. 

 They consist, therefore, of those nitrogen-free substances which are dis- 

 solved in the determination of the crude fiber. Their amount is deter- 

 mined mathematically by deducting or substracting the total percentage 

 of water, crude protein, crude fiber, crude fat and mineral matter from 

 100. This gives the percentage of nitrogen-free extract. 



The digestibility of nitrogen-free extract varies with the species of ani- 

 mal and according to the plant or feeding stuff from which it is obtained, 

 as indicated in the following table : 

 Nitrogen-free Ruminants Horses Swine 



Extract In — Digest — Digest— Digest- 



Percent Percent Percent 



Green forage, hay 43—85 40—77 57—71 



Straw, chaff 28—73 17—30 



Grains 39—95 51—98 80—99 



Roots and tubers 83—99 94—99 96—99 



Bran, etc 70—88 64 75—78 



Oil cake 46—99 80—90 



