SELECTION OF RATIONS 301 



This ration is still below the standard in quantity, 

 but as the relation of the nutrients is approximately 

 what is called for, it is only necessary to increase the 

 quantities of each component about one-fifteenth in 

 order to furnish the animal sixteen pounds of digestible 

 organic matter. It is, however, a good ration for cows 

 of the smaller breeds weighing from 800 to 900 pounds. 



398. Relation of ration to size of animal. — ^There are 

 several points to be considered in this connection. First 

 of all, the standard rations are the quantities to be fed 

 a day and for 1,000 pounds live weight. This is ordi- 

 narily taken to mean that if a 1,000-pound cow requires 

 16 poimds of digestible nutrients, an 800-pound cow should 

 be supplied with only four-fifths as much, or 12.8 pounds, 

 or that a 1,200-pound horse needs 50 per cent more food 

 than one weighing 800 pounds. Unfortunately this sim- 

 ple mathematical way of calculating rations does not meet 

 the plain requirements of practice. The needs of a pro- 

 ducing or working animal are not directly proportional 

 to its size, 'for the work done or the quantity of pro- 

 duction is the dominating factor. It is certain that feeding 

 milch cows or working horses in proportion to weight 

 alone contravenes known facts. 



However, we cannot ignore the size of the animal 

 in determining the quantity of the ration. Concerning 

 this, Armsby says: "The function of the maintenance 

 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 numbers, over 90 per 

 cent of this heat is removed by radiation and evapora- 

 tion. .Consequently, we should expect the demands of 

 the'lorlknism for heat (i. e., for maintenance), to be pro- 

 por^nal to its surface (including lung surface), rather 



