290 The Feeding of Animals 



weight of the animal would produce absurd conditions, 

 especially in the case of cows where production and not 

 the size of the animal is the main factor. 



However, we cannot ignore the size of the animal 

 in determining the quantity of the ration. Concern- 

 ing this Armsby says: "The function of the mainte- 

 nance ration is essentially to supply heat to the body 

 to replace the constant loss that takes place.* Now, 

 Henneberg has long ago shown that, in round num- 

 bers, over 90 per cent of this heat is removed by 

 radiation and evaporation. Consequently, we should 

 expect the demands of the organism for heat (i. e., 

 for maintenance), to be proportional to its surface 

 (including lung surface), rather than to its weight, and 

 the more recent researches of Rubner have confirmed this 

 theoretical conclusion." For the purposes of calcula- 

 tion it is assumed that animals are geometrically 

 similar figures and therefore that their surfaces are 

 proportional to the cube root of the square of their 

 weights. Several steers having weights from 1,0(JO 

 pounds 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 



approximately 1,000 Ibs. live weight 



1,000 Ibs. 100 



1,100 " 96 



1,200 " 93 



1,300 " 90 



1,400 " 88 



1,500 " 86 



1,600 " 84 



1,700 " 82 

 * The note on p. 169 should be read in this connection. 



