152 



PRINCIPLES OF FEEDING FARM ANIMALS 



A ration consisting of 7J pounds of ground corn, 3 pounds of 

 linseed oil meal, 10 pounds of clover hay, and 30 pounds of 

 corn silage would contain the following amount of digestible 

 protein and feed units : 



This ration satisfies the requirements of the standard. 



The feed unit system is especially valuable as a means 

 of comparing the efficiency of production by different cows, 

 as it is quite easy to calculate the amount of milk produced 

 per feed unit. It is the official standard of many cow-testing 

 associations in Europe. 



Self-feeders. — Any study of feeding standards and bal- 

 anced rations is incomplete without a discussion of the 

 *' cafeteria system " of balancing rations. By the cafeteria 

 system the animals are given free access to different feeds 

 and allowed to eat as much or as little of each feed as they 

 choose. This is done usually by means of a self-feeder, 

 which is a feed box so built as to hold a considerable quantity 

 of concentrated feed, a portion of which is accessible to the 

 animals at all times, and at the same time protect the large 

 bulk of the feed from the weather and keep the animals 

 from mussing over it. 



