THE SELECTION OF FOODS 47 



measure of value in the same food for the different 

 classes of animals is very different. Oats for instance, are 

 more valuable relatively to the horse at work than to the 

 cow in milk, since they are unexcelled in producing 

 energy and in sustaining muscle so much needed by the 

 horse. The cow is not so much in need of sustenance of 

 the kinds named. She wants foods that will produce 

 milk freely at moderate cost. Other foods will do this 

 which usually cost less, but oats are more valuable rela- 

 tively for cows than for swine, since the large amount 

 of hull renders them less well adapted to the digestion of 

 swine than to that of cows. 



The necessity for changing the equilibrium or balance 

 in the foods fed with the age of the animal within the 

 class is equally apparent. It is so whether considered 

 with reference to digestibility, bulk or concentration, or 

 the character of the nutrients. The young calf is sus- 

 tained for a time solely on food taken in the liquid form 

 and easily digestible. Later meal is given nearly all of 

 which is digestible; as time goes on the young animal 

 becomes gradually more capable of digesting food with- 

 out harm which contains relatively more crude fiber. 

 With increasing age the calf becomes more capable of 

 digesting more and more bulky foods. In fact these are 

 necessary to its proper development. If they are with- 

 held unduly, the want of distention in the stomach and 

 digestive system generally will be proportionate, and 

 just in proportion to that want of distension will be the 

 lack of capacity to take enough food to result in high 

 performance. 



The necessity for such variation is usually recognized. 

 The same cannot always be said with reference to modi- 

 fication in the nutrients given, notwithstanding that the 

 latter is in some respects as essential as the former. The 

 young animal will not develop a frame equal to the 

 average in its class unless it is given enough of ash in the 

 food to accomplish such an end. When matured, ash 



