PRINCIPLES OF FEEDING. 137 



carbohydrates, and ether extract, but it is im- 

 portant to know the proportion of each of these 

 two kinds (tissue-forming and heat-producing) 

 of digestible nutrients in the feed required to 

 produce the best results in different animals un- 

 der various conditions of development or re- 

 quirements of work. Such a food, or combina- 

 tion of foods, for each day is called " a balanced 

 ration." 



2. How the Standards were Obtained. Many 

 feeding trials have been made for the purpose 

 of ascertaining the ratio which should exist be- 

 tween the two kinds heat and energy produ- 

 cing and tissue-forming nutrients. 



The feeding standards originally prepared by 

 Dr. Emil v. Wolff and modified by Dr. C. L. 

 Lehmann hence, called the Wolff-Lehmann 

 feeding standards are the results of such trials, 

 and while these standards (see Table IV.) are 

 not to be considered absolute, they are based 

 upon actual results obtained by repeated trials 

 of various combinations of these nutrients. 

 " The standards are arranged to meet the re- 

 quirements of farm animals under normal con- 

 ditions." 



3. TJiese Standards are Used Only as a Basis. 

 This table, while giving the actual amounts 

 digested by the animals which were fed, is only 

 approximately true for other animals under sim- 

 ilar conditions, for the amount digested depends 



