THE COMPOSITION OF FEEDING STUFFS 



15 



The pectin bodies occur especially in unripe fruits ; these sub- 

 stances are responsible for the jellying of fruit juices, which de- 

 pends upon pectin taking up water during the boiling of the fruit, 

 gelatinous substances being formed known as pectoses or pectic 

 acids. The mucilaginous substances of flaxseed and seeds or roots 

 of some other plants belong to this group ; these substances do not, 

 however, possess the importance that is attached to the preceding 

 three groups of compounds. 



Fiber (called crude fiber or woody fiber by some authors) 

 makes up the cell walls of the plants and is largely composed of 

 cellulose. So-called incrusting substances (lignin and cutin) are 

 always present, especially in tough, woody plant materials, like 



10 15 20 25 30 35 40 45 



COTTON-SEED HULLS 



'BUCKWHEAT HULLS 



OAT STRAW 



OAT HULLS 



CORN COBS 



TIMOTHY HAY 



CLOVER HAY 



CORN STALKS 



DRIED BREWERS' GRAINS 



QAT5 



WHEAT BRAN 



GLUTEN FEED 



WHEAT MIDDLINGS 



BARLEY 



INDIAN CORN 



50 



FIG. 4. Fiber in plant materials, in per cent. 



husk, hulls, seed-coats, overripe hay and straw, which contain con- 

 siderable proportions of these substances in the fiber. Fiber is more 

 resistant to the action of solvents and digestive fluids than other 

 groups of plant materials. It is attacked by bacteria and possibly 

 by special ferments in the intestinal tract of herbivorous animals. 

 By this decomposition marsh gas and other gases are formed, and 

 also organic acids, like acetic and butyric acids. Since straw is very 

 high in fiber, and ruminants, like steers, sheep, and goats, can sub- 

 sist for a long time on coarse straw only, we are justified in con- 

 cluding that this substance possesses a certain nutritive value, 

 although authorities differ as to how much value shall be ascribed 

 to the digestible portion of cellulose. 



Plants increase in their contents of fiber toward maturity as the 



