4io 



PRINCIPLES OF AGRICULTURAL CHEMISTRY 



fiber and the quantity excreted, is calculated from the known 

 amounts of crude fiber fed and excreted. The quantity of crude 

 fiber digested, and the quantity of carbon, hydrogen, and oxygen 

 digested, are calculated from the data. From these figures we 

 can calculate the composition of the digested crude fiber. 



The crude fiber and the nitrogen-free extract in the excrement 

 contain more carbon and hydrogen than that digested, and have 

 a higher heat value. Digested crude fiber and digested nitrogen- 

 free extract have been found to have the composition and heat 

 value of a carbohydrate. For this reason, the digested crude 

 fiber and nitrogen-free extract are often referred to as carbo- 

 hydrates. The lignin is not digested. 



The composition of digested ether extract, protein, etc., can 

 be determined in the same way. The heat value of the digested 

 nutrients is estimated by a procedure somewhat similar. 



Ether extract of hays, grasses, and other coarse feeding-stuffs 

 contain waxes, etc., as we have seen, which are not digested so 

 well as fats. They accumulate in the excrement and change its 

 composition. The composition and heat value of the digested 

 ether extract is about the same as pure fat, while the ether ex- 

 tract in the excrement has a much higher heat value. 



Proteids have a heat value of 5,479 to 5,990 cal. per gram. The 

 digested proteids have practically the same value. The average 

 is 5,711 calories. 



HEAT VALUE OF CONSTITUENTS OF MEADOW HAY. 



