158 FIBST PRINCIPLES OF AGRICULTURE. 



mal, too, a large portion of the nutriment is used in 

 making muscle, tissue, and bone; while in a mature ani- 

 mal the amount of the food constituents that go to form 

 new products is comparatively small, the larger portion 

 being used in maintaining animal heat. 



The proportion of the three general classes of ^ood 

 compounds should therefore be different for the various 

 purposes of feeding. 



The Proportion of the Food Constituents Re- 

 quired for the Different Purposes of Feeding. — 

 Experiments in feeding animals have been conducted 

 in which all variable conditions have as far as possible 

 been controlled, in order to secure exact data as to the 

 proper proportions in a ration, as well as the amounts of 

 the nitrogenous and non-nitrogenous substances required 

 for the various purposes of feeding. The results of these 

 experiments have led to the fixing of what are termed 

 " feeding standards ; " that is, statements of the amounts 

 of digestible protein, or albuminoids, fat and carbohy- 

 drates, which appear to be, and are perhaps under aver- 

 age conditions, best adapted to the various conditions of 

 the animal and the numerous purposes of feeding. 



Feeding Standards. — The " feeding standards " in 

 most common use are those of the German experimenter 

 Wolff, which are given in the Appendix. For example, 

 his standard ration per day for a milch cow of one thou- 

 sand pounds live weight, in full flow, requires twenty-five 

 pounds of organic substance, which shall contain 0.40 

 (i.e., four-tenths) pounds of digestible fat, 2.60 pounds of 

 digestible protein, and 12.50 pounds of digestible car- 

 bohydrates. A ration for dairy cows showing these 



