54 PRINCIPLES OF FEEDING FARM ANIMALS 



the principal digestion of crude fiber occurs in the rumen or 

 paunch, due to bacterial fermentation. This fermentation 

 produces acetic and butyric acids, which may serve as 

 nutrients to the animal body, and large quantities of carbon 

 dioxide and methane gases, which in part are absorbed by 

 the blood and excreted through the lungs, and in part are 

 excreted directly by way of the alimentary tract. 



Further fermentation of the crude fiber takes place in 

 the large intestine, especially of the hog and of the horse, 

 practically the same products being formed as in the paunch 

 fermentation of the ruminants. 



The acids thus formed unite with alkahes present to form 

 salts, in which form they probably are absorbed into the 

 capillaries of the small and large intestines. The undigested 

 portions of the crude fiber pass from the body in the feces. 



Fats. — Emulsified fats are acted upon in the stomach by 

 the gastric lipase, which spHts them up into glycerin and 

 fatty acids. However, the unemulsified fats undergo little 

 or no digestion until they reach the small intestine, where 

 they are acted upon by the enzyme, lipase, of the pancreatic 

 juice. This enzyme, in alkaline solution, sphts up the fats 

 into glycerin and fatty acids. The latter unite ^vith the 

 alkahes of the pancreatic juice and bile to form soaps. 

 The solution of the soaps thus formed causes an emulsion 

 to be formed with the remaining fats, enabling the lipase to 

 come in closer contact with them. The bile aids in the 

 digestion and absorption of fats by assisting in the solution 

 of the fats, fatty acids, and soaps. Tlie ])resenee of ])ile 

 also increases the activity of the pancreatic li])ase. 



The soaps, fatty acids, and glycerin are absorbed through 

 the walls of the villi of the small intestine. In passing 



