268 BEGINNINGS IN ANIMAL HUSBANDRY 



of which milk is .an example. On this account people who 

 feed live stock must regulate the food in amount and kind if 

 they wish to obtain the best results. 



The protein in the food during digestion is acted on by 

 what are called digestive ferments. One of these, pepsin, 

 attacks the protein in the stomach, and hydrochloric acid 

 also takes a part here. These break up the protein into 

 simpler forms, making them suitable for use in the body. 

 After the protein gets into the intestines, two other ferments 

 attack it, and make such changes in it that it is easily dis- 

 solved and absorbed, and distributed through the tissues 

 of the body. The animal cannot take the protein in the 

 plant and use it at once as body protein, but it must go 

 through these changes in the digestive organs before it can 

 be used. The protein in the food is changed to body pro- 

 tein, of which lean meat is the best example. To some 

 extent it may also be changed into fat. Animals that 

 depend entirely upon flesh for food can live on protein alone 

 if necessary. During starvation, the body loses a small but 

 rather constant amount of protein. So we consider this 

 substance especially valuable for building up the muscles, 

 the hair, wool, internal organs, blood, and similar tissues. 



The carbohydrates in the food are largely changed into 

 sugar during digestion. Thus they are more easily absorbed 

 into the body. There are different kinds of sugars, but that 

 in the food is converted into glucose. This sugar is then 

 taken up by the circulation and carried to the liver, where it 

 is again changed somewhat, and from here is distributed 

 over the body as needed. The carbohydrates are largely 

 used in the system to furnish the energy necessary in work, 

 and to make fat. Interesting experiments with animals, 

 show that more fat is stored in the body than can be sup- 

 plied by the protein and fat in the food. Dr. Jordan of the 



