Proceedings of Seventeenth Normal Institute ITl 



TAT 



The vegetable and animal fats and oils serve as a source of 

 energy for tlie maintenance of the activities of the animal body, 

 being in this respect equal to about two and one-fourth times the 

 same weight of carbohydrates. The fats of the food may also be 

 utilized for the production of body fats, and to some extent per- 

 haps of the milk fats. 



We may consider the relative importance of these classes of in- 

 gredients in the animal economy from two •points of view, namely, 

 physiologically and commercially. Considered from the point 

 of view of physiological necessities, these ingredients are all es- 

 sential to animal growth and maintenance, and in this sence have 

 equal physiological value. While the animal must have suffi- 

 cient proteins to meet the demands for constructive and replace- 

 ment purposes, it is equally true that it must have sufficient di- 

 gestible food to supply the energy necessary for maintaining 

 internal and external activities, A lack in either case is fatal, 

 certainly to physical well-being and possibly to existence. A 

 deficiency in either direction would limit the production of a 

 milch cow or require the use of her body substance. The food of 

 a given animal should contain no less than a minimum amount of 

 protein. On the other hand, a milch cow giving thirty pounds of 

 5-per-cent milk utilizes daily sixteen pounds of digestible organic 

 matter, at least eleven pounds of which would be applied to fuel 

 purposes. If a fattening steer were eating the same kind of 

 digestible food and gained two pounds of live weight daily, at 

 least thirteen and one-half pounds of the sixteen would be 

 oxidized for energy purposes. 



Water is confessedly an essential ingredient of an animal's 

 food, and the formation of bone and of the soft tissues, as well as 

 the digestive processes, requires the presence in food of the com- 

 pounds of tho ash. It is not possible then to claim rationally 

 that any one class of the ingredients above mentioned is 

 supremely important to the growth, maintenance and welfare of 

 the animal body. 



The reasons why protein has been given such large prominence 

 in our discussions of animal nutrition are largely commercial, 



