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 suger (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 
