18 PRINCIPLES OF FEEDING FARM ANIMALS <. 



fiber in the feed. This method, which is known as the Weende method 

 gives pure cellulose or woody fiber, with some impurities like pentosans, 

 incrusting substances (lignin, cutin), and certain insoluble proteins. The 

 method does not give very satisfactory results, and is only used for want 

 of some better method of arriving at the amount of fiber present in feeding 

 stuffs. 



e. Ash or mineral matter is obtained by igniting at a low red heat 2 

 grams of the sample and weighing the residue after cooling in a desic- 

 cator. The crude ash thus obtained generally contains some free carbon, as 

 well as carbonates and sulfates formed by oxidation of organic components 

 of plant materials. It is sometimes purified by treatment with distilled 

 water, and the amount thus found is given as pure ash. 



f. Nitrogen-free extract is obtained by subtracting the sum of the 

 percentages of the preceding components from 100. It includes chiefly 

 starch, sugar, pentosans, and organic acids (p. 13). The amounts of the 

 first three components are also sometimes determined separately by well- 

 known methods of analysis that are of interest mainly to chemists. 2 



The example given below will show the customary form of re- 

 porting analyses of feeding stuffs. 



Chemical Analysis of Timothy Hay 



Per cent 



Moisture 13.2 



Crude protein 5.9 



Fat 2.5 



Fiber 29.0 



Nitrogen-free extract 45.0 



Ash . 4.4 



100.0 

 QUESTIONS 



1. Name the elements essential to plant growth; also some others that 



are always present in plants. 



2. What are the groups of plant components determined in ordinary chemical 



analyses ? 



3. Give the main characteristics of each one of these components. 



4. What is protein, nitrogen-free extract, carbohydrates? 



5. State the difference in the chemical composition of these substances. 



6. Give the ordinary form of reporting a chemical analysis of a feeding 



stuff. 



8 For complete directions for making chemical analyses of f eedin * 

 stuffs and other agricultural products, see Official and Provisional Methods 

 of Analysis, Association of Official Agricultural Chemists, Bureau of 

 Chemistry, U. S. Department of Agriculture, Bulletin 107 (Revised), 

 Washington, 1912. 



