CHAPTER II 



THE COMPOSITION OF ANIMALS 



We find, in general, similar substances in the animal body as in 

 plants, but the relation between the different groups of components 

 differs, and some substances found in animals do not exist in plants, 

 or differ in their propertied from the corresponding plant constit- 

 uents. Animals are composed of water, protein bodies, fat and 

 mineral matter ; the protein, or protein and fat, make up the largest 

 proportions of the dry matter of animals, while carbohydrates are 

 present in only small amounts. We have seen that the dry matter of 

 plants, on the other hand, is largely composed of carbohydrates, 

 and that protein is, as a rule, present in relatively small amounts. 



The composition of different farm animals varies according 

 to age and body condition, especially the amount of fat which they 

 carry. The classic experiments of Lawes and Gilbert which were 

 conducted about 1850 at the Kothamsted Experiment Station, Eng- 

 land, furnished the first accurate information on this point; their 

 findings have been corroborated during later years by investigations 

 at the Maine and Missouri Experiment Stations and elsewhere. 

 The following summary table shows the percentage composition of 

 live animals, less contents of stomach and intestines : 



Composition of Live Animals, in Per Cent. (Lawes and Gilbert.) 



Fat calf 



Steer, well fed . 

 half fat . . . 

 fat 



Sheep, lean — 

 well fed . . . 

 half fed... 



fat 



very fat.. 



Swine, well fed 

 fat 



Ash 



4.8 



5.9 

 5.2 

 4.4 



4.0 

 3.9 

 3.8 

 3.3 

 3.1 



2.9 

 1.9 



The figures given in the table show that the fatter an animal is, 

 the less water, protein, and ash will it contain ; also, that the per- 

 centage of fat in the body of a steer may range from at least 8 to 30 

 per cent, that in a sheep from 10 to 41 per cent, and that in a hog 



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