f' 



28 PRINCIPLES OF FEEDING FARM ANIMALS 



act on the starch. In the lining of the right side, on the other 

 hand, there are numerous glands which secrete gastric juice, as in 

 the case of the fourth stomach of ruminants. From this point on, 

 the digestion of the feed takes place in essentially the same manner 

 in non-ruminants as in ruminants. 



The Digestion of Feed. The various digestive fluids which 

 act on the feed during its passage through the body are (1) saliva, 

 (2) gastric juice, (3) pancreatic juice and the bile, and (4) 

 intestinal juice. 



Saliva. The first step in the digestion of feed occurs in the 

 mouth. When an animal is eating, the feed is crushed and ground 

 by the teeth, and at the same time mixed with saliva. This is a 

 digestive fluid secreted by several glands located beneath or at the 

 base of the tongue. The secretion of saliva is stimulated by the 

 presence of feed in the mouth, and the saliva is intimately mixed 

 with the feed in the process of mastication, especially in the case 

 of coarse and dry feeds. 



This insalivation of the feed serves two purposes: First, it 

 moistens and softens the feed so that it may be readily swallowed. 

 Second, saliva contains a digestive ferment, called ptyalin, which 

 acts upon the starch of the feed, changing it to sugar (maltose, 

 the same sugar as is found in malted barley) . Saliva is an alkaline, 

 viscous fluid which is secreted in immense quantities in the case of 

 the large farm animals. A horse fed on hay has been found to 

 secrete over 10 pounds of saliva per hour. Oats require a little 

 more than their own weight of saliva, and dry, coarse feed requires 

 four times its weight. As a horse or cow will consume at least 24 

 pounds of dry feed in a day, it follows that the quantity of saliva 

 secreted daily by these animals may reach or even go beyond 100 

 pounds (over 12 gallons). 



The Gastric Juice. The digestion of the protein substances of 

 the feed is commenced in the true stomach (abomasum) of the 

 ruminants, or in the single stomach of the non-ruminants, where 

 the feed comes into contact with the gastric juice, which is 

 secreted here. This digestive fluid contains two ferments, pepsin 

 and rennin, and also an appreciable quantity of free hydrochloric 

 acid (about 0.5 per cent). Both rennin and pepsin have the 

 faculty of coagulating the casein of milk, a wonderful provision of 

 nature which insures that milk will remain in the stomach long 

 enough to be acted upon by the stomach ferments, and its nutrients 

 thus fully utilized by the animal. In young calves and other young 

 ruminants the first three stomachs are not much developed, and 



