THE FEEDING OF ANIMALS 171 



hay about CO io 65 per cent., in potatoes and carrots less than 

 50 per cent., in mangolds, turnips, and swedes about 25 per 

 cent., while in some specimens of maize silage it may be as 

 little as 12 per cent. 



Albuminoid Ratio. — It is found in practice that the food 

 of an animal may be varied considerably without any detri- 

 ment to the well being of the animal, providing the ratio of 

 albuminoids to non-albuminoids in the food be kept within 

 certain limits. 



In order to get this ratio it is necessary that some definite 

 carbohydrate be taken in which to express the non-albuminoids. 

 Starch is the substance always chosen, and it becomes necessary, 

 in order to express the fat and the other carbohydrates in terms 

 of starch, to obtain the equivalents in heat-producing power 

 of these other food constituents. This has been done (1) by 

 burning weighed portions of the various materials in calori- 

 meters and (2) by direct experiments upon animals placed in 

 large respiration calorimeters and fed with known weights of 

 the various food-stufi's. 



As the mean of several experiments it may be taken that 

 100 parts of fat evolve as much heat as 230 parts of sugar, 

 starch, or cellulose, or of protein. 



To express the percentage of total non -albuminoids of a 

 food, therefore, in terms of starch it is necessary to multiply 

 the percentage of fat by 2-3 and add the product to the per- 

 centage of soluble carbohydrates. The albuminoid ratio thus 



albuminoids 

 '^«<^°'"«' carbohydrates + (fat x 2-8)' ^^« digestihle comti- 

 tuents being taken in all cases. Suppose, for example, it is 

 desired to calculate the albuminoid ratio, or nutritive ratio, as 

 it is sometimes called, of red clover hay. From the table it 

 appears that the digestible constituents are as follows : 



Per cent. 



Protein 6-8 



Carbohydrates . . . 35 8 



Fat . . . . . 1-7 



