22 DiREC toe's Report of the 



would be necessary for mere commercial operations. It is for 

 these reasons then that an experimental farm should be regarded 

 as a failure if it returns a financial profit, because the existence of 

 such profit would mean that little experimental work of a high 

 character is carried on. 



INVESTIGATION. 



ANIMAL NUTRITION. 



The problems pertaining to the feeding of animals are among 

 the most complex and difficult of solution with which science has 

 to deal. This is due largely to the fact that the processes of nutri- 

 tion are hidden. Direct observations are, in the main, not pos- 

 sible, and the conclusions reached must be largely inferential in 

 their nature. When a milch cow, for instance, consumes a given 

 quantity of food of a certain kind, we have as exterior results the 

 production of a certain quantity of milk and the maintenance of 

 the body of the animal at a given weight, or with a gain or loss in 

 body substance as the case may be. These measurements give 

 little clue to the function of the various constituents of which the 

 food is composed. 



The study of the problems of animal nutrition enters the field 

 of both chemistry and physiology and the patient studies carried 

 on during the past half century have revealed a great many facts 

 which we now regard as thoroughly established. We know much 

 about the functions of ash constituents, proteins, carbohj-drates 

 and fats and we have quite definite data as to the quantities of 

 nutrients necessary to support the various classes of animals under 

 given conditions. This knowledge is embodied in feeding 

 standards. 



In recent years, these standards appear to be shifting from quan- 

 tities of nutrients to energy measurements, this change having 

 been brought about by exhaustive studies of energy and heat rela- 

 tions by the aid of what is known as the respiration calorimeter. 



