Computing Rations for Farm Animals 1569 



of protein in the ration. The discussion of the necessary amount 

 of protein for different uses will be taken up later under " Feeding 

 standards." 



The amount of digestible protein in the food varies within somewhat 

 wide limits. The percentage varies from 1 per cent in succulent foods, 

 such as mangels, through 7.1 per cent for red clover hay and 8.5 per cent 

 among the cereals, to as high as 37.6 per cent for cottonseed meal. Thus 

 it is seen that there is a large list from which to choose in regulating the 

 amount of protein in a ration. 



Carbohydrates. — The carbohydrates are divided by the chemists into 

 what are called "crude fiber" and " nitrogen- free extract," because the 

 crude fiber is less digestible than the other carbohydrate material. In a 

 fodder analysis the ash, protein, fat, and fiber are first determined. Their 

 sum is then subtracted from the total dry matter, and the result is called 

 "nitrogen-free extract." This term includes all the carbohydrates except 

 the fiber. The digestible nitrogen-free extract and digestible fiber have 

 the same food value for all practical purposes and perform the same work 

 in the nutrition of the animal. This work consists mainly in furnishing 

 energy for whatever use the animal may need it. If there is more energy 

 provided in the ration than is needed at that particular time, the excess 

 energy may be stored in the body as fat. 



The amount of fiber and nitrogen-free extract in the foods, taken to- 

 gether, varies as much as does the protein, but there is always a relatively 

 larger amount of carbohydrates than of protein. In every case, when 

 there is a low percentage of protein there is a high percentage of carbo- 

 hydrates. 



Fats. — The food fats are used by the animal in about the same way 

 as are the carbohydrates. They provide energy to be used in any way 

 that the animal needs, and if the animal has more energy than is needed 

 it may be stored in the form of fat. The fat, however, has an energy 

 value equal to about 2\ times the energy value of the same weight of 

 carbohydrates. 



The amount of digestible fat in the different foods varies without re- 

 spect to the other constituents. It is low in the coarse fodders, running 

 up to 1 1.6 per cent in distillers' dried grains. 



Summary of the requirements of the body and the relation of the constituents 



of the food to these requirements 



The animal body may be likened to a steam engine. The engine must 

 have three things to keep it going: First, it must have repair material; 

 if any part of the engine or boiler gives out it must be repaired at once. 



