1 8 COMPOSITION 



the feed passes on through the stomach and is stored in a 

 large receptacle located between the small intestine and 

 the large intestine known as the csecum. In this organ 

 a great deal of absorption takes place. The hog con- 

 sumes less roughage than the horse or the cow and has 

 no such provision for the storing and softening of coarse 

 roughage. 



Now what changes take place in the feeds as they pass 

 through the digestive tract ? 



Protein. — The protein material is first acted upon in the 

 stomach by pepsin, a ferment of the gastric juice, secreted 

 from the walls of the stomach. The gastric juice contains 

 another ferment known as rennin which curdles milk so 

 that it cannot pass through the stomach before being acted 

 upon by the secretions of the stomach. The pepsin breaks 

 the protein material down into simpler substances which 

 are then passed on to the small intestine where they are 

 acted upon by trypsin, an enzyme contained in the pan- 

 creatic juice (secreted by the pancreas, a gland located near 

 the stomach), and by the erepsin, a juice secreted by the 

 walls of the small intestine. 



After having undergone all this action the protein material 

 is changed finally into simple substances called amino acids. 

 In this form it is absorbed from the digestive tract. 



In the circulation of the blood these protein substances 

 are carried to different parts of the animal's body and used 

 to build up new tissues such as muscular fibers, ligaments, 

 nerves, hair, hoof, horn, and skin, and to repair tissues 

 broken down in work. What is left, over and above these 

 requirements, goes to furnish heat for the body and energy 

 for work. Some of the excess is used to furnish protein 

 for the milk of female animals. 



