302 THE FEEDING OF ANIMALS 



than to its weight, and the more recent researches of 

 Rubner have confirmed this theoretical conclusion." 

 For the piu-poses of calculation, it is assumed that ani- 

 mals are geometrically similar figures and therefore that 

 their sm-faces are proportional to the cube root of the 

 square of their weights. Several steers having weights 

 from 1,000 up to 1,700 pounds would need, on this basis, 

 amounts of digestible food for maintenance propor- 

 tional to figures given in the table below: 



Weight of the animal Proportion of food per 1,000 



approximately i pounds live weight 



1,000 pounds 100 



1,100 pounds .... .96 



1,200 pounds .... . . 93 



1,300 pounds . . .... 90 



1,400 pounds .88 



1,500 pounds .... .... 86 



1,600 pounds 84 



1,700 pounds . 82 



For adjusting a maintenance ration to the weight of a 

 steer or horse, this method seems to have a plausible 

 basis, but it is evidently less applicable to dairy cows or 

 rapidly growing or fattening animals, for in these cases 

 production and not size must be chiefly considered. 



399. The protein-supply. — ^The matter of the protein- 

 supply is important. If we are trying to supply the needs 

 of a cow giving twenty-five pounds of inilk, or of a steer' 

 gaining two pounds of body substance daily, there is 

 without question a minimum quantity of food protein 

 absolutely necessary in each case. These necessary 

 quantities are certainly not the same for all individuals, 

 but they are not likely to differ widely between single 

 animals of the same class and productive capacity. It is 

 safe to assert that the earlier protein standards are those 

 which it is practicable to feed and which unquestionably 



