Nutrition of the Animal Body 239 



may extract from it. In comparing feeding substances 

 we should not only know the actual amount of proteids, 

 fat, carbohydrates, etc., contained, but what per cent of 

 these substances is digestible. 



In some digestion tests at the Oklahoma Experiment 

 Station with cockerels, it was found that 79.4 per cent, 

 of the whole kaffir corn was digested, i. e., retained 

 in the animal's body; in the same way 81.9 per cent of 

 corn, and 64.1 per cent of cowpeas were digested. 



332. Digestibility of the Nutrients. In the digestion 

 tests mentioned above the composition of the substance 

 fed, the nutrients digested and the waste, were as fol- 

 lows for each 100 grams consumed: 



Protein Carbohydrates and fats 



Nutrients in Kaffir corn. .. 11.88 grams 75.16 grams 



Digested and retained 6.28 grams 73.09 grams 



Undigested waste 5.60 grams 2.07 grams 



In the above case it is noted that nearly all the 

 carbohydrates were digested, though only about half 

 of the proteids were used in the cockerel's body. Similar 

 tests have been made for many kinds of feeds with 

 many kinds of animals. 



We see from this example that a chemical analysis 

 giving the quantity of the nutrients is not an exact 

 statement of the available nutrients. Appendix D gives 

 the average results of many tests of the digestibility of 

 American feeding materials. See also tables of compo- 

 sition in Appendix. 



333. Ratio of Digestible Nutrients. In feeding ani- 

 mals it is important, as will be shown, to know the ratio 

 of the digestible proteids, or flesh -forming nutrients, 

 to the effective heat -forming substances. This ratio 



