CHAPTER XIII 



LAWS OF NUTRITION 



The preceding pages have been devoted to a discus- 

 sion of the origin of cattle foods, what they are in 

 substance, how their nutrients are made available and 

 how used. So far no attempt has been made to 

 gather together in a systematic relation what may be 

 called the fundamental principles or laws of nutrition, 

 some of which we have not yet directly stated, but 

 which are inferences from the facts presented. It is 

 desirable to do this, however, before passing to the 

 consideration of the practice of cattle feeding. 



1. All energy and building material applied to the 

 maintenance and growth of the animal body come 

 from the food, water and oxygen being included in 

 this term. The animal originates neither force nor 

 matter. 



2. Only that portion of the food which is digested, 

 i. e., that which is dissolved by the digestive fluids 

 and rendered soluble and diffusible so that it passes 

 into the blood, is available for any use whatever. This 

 fac{, is especially important in view of the greatly 

 varying digestibility of different feeding stuffs. 



3. The unutilized food and the wastes pass from the 

 body in some direction. The undigested part mainly 



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