THE COMPOSITION OF FEEDING STUFFS 13 



Fat contains more carbon and less hydrogen than the group 

 known as carbohydrates, viz., on the average, 



Carbon, 76 per cent 



Hydrogen, 12 per cent 



Oxygen, : 11.5 per cent 



They, therefore, furnish more energy on combustion and are 

 more valuable as heat-producing substances than are the carbo- 

 hydrates (for which see below). 



Nitrogen-free extract is a general name for all non-nitrogenous 

 organic substances in plants and plant materials besides fat and 

 fiber. It includes a large number of substances of different proper- 

 ties and value for feeding purposes, such as starch, sugar, pentosans, 

 pectin, organic acids, and other compounds that are present in 

 plants in small amounts and are of minor importance. The name 

 " nitrogen-free extract " is in reality a misnomer, as but few of the 

 substances included under this group name are soluble in water or 

 other liquids ; it has come into general use, however, since the early 

 days of agricultural chemical analysis, and no better name for this 

 group of substances has so far been suggested. 



Carbohydrates. — The nitrogen-free extract and fiber form the 

 group called carbohydrates. These include substances widely dis- 

 tributed in plants and of the greatest importance to the feeder. 

 They are, in general, characterized by the fact that they contain the 

 elements carbon, oxygen, and hydrogen, the latter two being present 

 in the same ratio as in water, one molecule of which contains two. 

 atoms of hydrogen and one atom of oxygen (H 2 0). The more im-^ 

 portant substances of this group are briefly considered below.' 



Starch is one of the first organic substances formed in the living 

 plant from the carbon-dioxide of the air and water. It is changed to 

 sugar in the transfer of carbohydrates from one part of the plant 

 to another, and accumulates as such in large quantities as reserve 

 material in some plants, as the beet root and sugar cane. In others 

 it is changed into oil or fat, as in the so-called oil-bearing seeds, 

 flax, sunflower, castor bean, etc. In still others, which most fre- 

 quently happens, there is an accumulation of starch in the seeds, 

 as in the case of the cereals and legumes. 



On boiling with dilute acid or through the action of diastatic 

 ferments (diastase, ptyalin, etc.), starch is changed to sugar. This 

 process forms the basis for the manufacture of corn or glucose syrup 

 from Indian corn. 



