326 THE ESSENTIALS OF AGRICULTURE 



animal is growing rapidly a much larger quantity will be required 

 for the new tissue to be built as well as for old tissue to be 

 repaired. Cows in milk and laying hens require much protein, 

 because eggs and milk contain much protein. 



422. Sources of protein. All protein feeds are not of equal 

 value. Animal proteins 1 are generally more completely and 

 more easily used than are the proteins of vegetables. The 

 poultry man knows that laying hens will do better if given skim 

 milk or meat-meal along with the usual grains and green feed. 

 In fattening calves for the show, milk in abundance is used. 

 Skim milk and tankage, with grain, force pigs to the limit of 

 their capacity. 



There is a great variation in the value of different vegetable 

 proteins. A part of the protein of corn is incapable of pro- 

 ducing growth in young animals and is called an incomplete 

 protein. This probably explains why young pigs confined in a 

 dry lot and fed exclusively on corn soon become unthrifty and 

 sometimes die of starvation, although they have all the corn 

 they will eat. Most coarse feeds are low in protein, but the 

 hays made from the legumes are relatively rich in protein 

 which is of good quality. Thus colts, calves, and lambs when 

 fed on corn and wheat straw or millet or timothy or prairie 

 hay grow slowly, or cease to grow, and soon show a general 

 lack of thrift ; while those fed on corn and on hay made from 

 legumes grow rapidly. 



Wool production is stimulated somewhat by the addition of 

 protein to the ordinary farm ration. The coat of hair of horses, 

 cattle, and hogs is lustrous and silky when protein is fed liber- 

 ally and is pale and harsh when protein is deficient in the ration. 

 A larger and stronger bone is produced when plenty of protein 

 of the proper sort is combined with sufficient mineral ingredi- 

 ents. Without protein in abundance the minerals are ineffective 

 in bone building. The protein supply presents one of the prin- 

 cipal problems connected with proper feeding of animals. 



1 Proteins that have been worked over and organized as a part of the animal 

 body, such as milk, eggs, dried blood, meat, meat-meal, and tankage. 



