principles of horse feeding 327 



Uses of the Matter 'and the Energy of the Food 



[ a. To maintain body temperature 



I b. To repair waste tissue 



1 . To support life ^ 



I c. To form new tissue 



[ d. To supply muscular activity of the vital processes 



2. To reproduce life. 



(a. Stored up as fat or flesh in the tissue 



b. Secreted in the form of milk or wool 

 4. To perform labor. 



Digestibility of food.— The value of a food depends, not 

 alone upon its composition, but upon the digestibility of 

 the various materials of which it is composed. To aid 

 in an understanding of the digestibility of food, we will 

 review briefly the process of digestion, in which the food 

 materials pass on their wa}' from the food as such to the 

 flesh and energy of the animal body. 



Digestion. — This is largely a process of solution, aided 

 by chemical changes that take place through the action 

 of ferments. The digestive organs form a canal through 

 the body and the food in its passage through this canal is 

 acted upon by these ferments. Each ferment has a 

 special work to do in the process of digestion. The food 

 is first taken into the mouth, where it is masticated and 

 reduced to fine particles, in order that the digestive juices 

 may better do their work. This also puts the food in 

 condition to be swallowed. During this mastication 

 there is a digestive fluid, called saliva, poured upon the 

 food, which moistens it and changes a part of the starch. 



This material now enters the stomach, where it comes in 

 contact with a digestive fluid, called gastric juice, which 

 changes a part of the protein. It next enters the small 

 intestines, where it comes in contact with two digestive 

 fluids — the bile from the liver and the pancreatic juice 

 from the pancreas. The former prepares the material 

 for the action of the latter, which has a complex function, 

 acting upon the proteids, starches and fats. Digestive 

 juices secreted by the walls of the intestines as the ma- 



