CHAPTER X. 

 PRINCIPLES THAT GOVERN FEEDING. 



The discussion in Chapter X relates to the principles 

 that govern the feeding of animals with reference to the 

 chemical constituents which feeds possess, as adapted to the 

 class and age of animals to which they are to be fed and the 

 precise objects for which they are maintained. It differs 

 from the discussion in Part I in that it is specific while the 

 former is general. The principles in this chapter relate 10 

 furnishing feeds that will contain the nutrients which they 

 must have in due proportion if the end sought is to be 

 reached. 



In theory, these principles have all the strength of law, 

 but in practice it is very frequently not possible to apply 

 them so that the results sought or that should be expected 

 from such feeding, will follow, owing to the subtle influ- 

 ences that frequently result from environment, from inter- 

 nal causes that cannot always be discerned, and from varia- 

 tions resulting from the physiological influence of feeds 

 apart from the nutrients they contain as given by chemical 

 analysis. 



The elementary substances necessary to the growth 

 of plants are essentially the same as the chemical elements 

 of the animal body. These are carbon, hydrogen, oxygen, 

 nitrogen, sulphur, phosphorus, potassium, calcium, magne- 

 sium and iron. In addition to these are chlorine and so- 

 dium, the elements of common salt. These elements do not 

 exist simply but are united into numberless compounds, 

 both organic and inorganic. For convenience of reference, 

 they are classified as nitrogenous or non-nitrogenous, ac- 

 cording as the chemical compounds of which they are com- 

 posed contain nitrogen or do not contain nitrogen. The 

 water in foods must also be considered, but this is not so 



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