316 PRINCIPLES OP BREEDING. 



when the conditions for retrogression are present. Thus, we 

 can easily understand the necessity for the stockman to 

 have a full understanding of this law in its action and the 

 causes which render it most influential. 



In this connection we will discuss in a very brief manner 

 some of the causes of variation and the influences of the 

 same in animal breeding. The causes of variation in animals 

 are numerous, but in this connection we will mention a few 

 of the most striking examples, such as changed conditions of 

 life due to climatic influences, food, general care, selection 

 and so on. Thus we can readily see that variation in a cer- 

 tain degree can be controlled by the man in charge. Food is 

 a most influential factor. The high type of beef animal 

 which we have at the present time is the result of liberal 

 feeding and judicious selection. The kind of feed fed will 

 have a marked influence on the conformation of the animal. 

 For instance: Liberal feeding of roughage will develop the 

 digestive organs, thus expand the body. In this way the large 

 barrel and capacity of the daily cow has been produced. On 

 the other hand, by the use of concentrates in feeding swine 

 the length and capacity of the intestines of swine has been 

 materially increased over that of the wild hog, which had to 

 secure a considerable portion of his food by grazing. 



The size of the animal can be materially increased or 

 decreased by the amount and nature of the rations fed. 

 Swine, for instance, when fed on a ration of corn alone for a 

 number of generations will dwindle in size of body and boney 

 framework. When fed on feed stuffs rich in ash and pro- 

 tein the opposite results will be obtained. 



Selection is also an important factor and is one of the 

 most important points in accomplishing variation of a de- 

 sirable and useful kind. The fine wooled breeds of sheep are 

 a good illustration in this respect. By good care and proper 

 selection they have been developed up to their present state 

 of perfection. 



Selection always plays an important part in all desirable 

 variation, whether it be in sheep, horses, cattle or swine. The 

 climate also has its influence. Its influence, however, is not 

 so marked in the case of our domestic animals, as in those 

 in their wild state. This is due to the artificial influences 

 which man has introduced in animal management by im- 

 proved buildings, thus better shelter from climatic changes. 

 The Shetland pony and the Galloway breed of cattle are both 



