N(i. li. 



IJEPAK'IMENT Ui' ACiUlCULTUKL: 



tfjX 



il couve^is the idea that a paiticular loud •'agrtH-s" wilh the ii«er, 

 i. t\, that it does uot cause distress \viu,'ii eateu. The term is also 

 very couimouly uuderstood to mean the ease or rapidity of digestion, 

 and cue food is often said to be more digestible than another because 

 it is digested in less time. However, the term digestibility is most 

 commonly understood in scientific treatises on the subject to mean 

 thoroughness of digestion. The digestibility of any food may be 

 learned most satisfactorily by experiments with man, although ex- 

 periments are also made by methods of artificial digestion. In the 

 experiments with man both food and feces are analyzed. Deducting 

 the amounts of the several nutrients in the feces from the total 

 amounts of each nutrient consumed shows how much of each was 

 digested. The results are usually expressed in percentages and 

 spoken of coeflicients of digestibility. Fi'om a large number of 

 experiments w ith man it has been calculated that on an average the 

 different groups into which foods may for convenience be divided 

 have the following coefficients of digestibility: 



Coefficients of Digestibility of Different Groups of Foods. 



a; c 

 c o 



Animal foods, i 98 



Cereals and sugars | 85 



Vegetables and fruits 80 



97 

 90 

 90 



100 

 98 

 95 



75 

 75 

 75 



Maliing use of these figures, the digestible nutrients furnished by 

 any food may be readily calculated. Thus, as shown by the table 

 on composition above, sirloin steak contains 16.5 per cent, protein. 

 One and one-half pounds would therefore contain 0.2475 pound pro- 

 tein, or in round numbers, 0.25 pound (1.5 ^ 16.5 = 0.2475). As 

 shown by the coefficients of digestibility quoted above, 98 per cent, 

 of the protein of animal food is digestible. Therefore, 1.5 pounds 

 sirloin f^teak would furnish 0.245 pound digestible protein (0.25 x 

 0.98 = 0.245). The digestibility of the several nutrients in a given 

 quantity of any food may be calculated in a similar way. 



