200 



ELEMENTS OF AGRICULTURE 



the health of the animal, and all animal food should 

 contain some of these compounds. 



196. Composition of Foods. — We have already learned 

 that plants are made up of water and dry matter, and 

 that the dry matter is made up of mineral matter, pro- 

 tein, and non-nitrogenous matter- In order to deter- 

 mine the value of plants for cattle foods, the amounts 

 of the different substances they contain have been 

 determined. In determining the amounts of the com- 

 pounds,- the plant is analyzed, which means that it is 

 broken up into some of the substances* that form it. 

 When cattle foods are analyzed, they are divided up 

 into six classes of substances as follows: 



1. Water is determined by drying in an oven a 

 weighed portion of the finely ground substance until it 

 is perfectly dry. The dried portion is then weighed, 

 and the loss in weight gives the amount of water, or 

 moisture as it is often called. 



2. Ash is determined by burning at a low heat a 

 weighed portion of the ground substance. The weight 

 of the ashes gives the amount of mineral matter or ash, 

 usually called crude ash. 



3. Nitrogen is determined by a process that is too 

 complicated for us to describe here, but which is known 

 to be accurate. Protein is known to contain about 16 

 per cent of nitrogen, so if we multiply the nitrogen 

 found by 6J we get the amount of protein in the sub- 

 stance. The protein is usually called crude protein-. 



4. Fats and oils are dissolved from a weighed por- 



