PRINCIPLES OF LIVESTOCK BREEDING. 43 



the methods which give the greatest control are not necessarily 

 those which lead to most rapid improvement. 



UNIFORMITY OF TYPE. 



The method of obtaining such uniformity of type as is possible, 

 is, as already indicated, close breeding, accompanied by selection. 

 This method was one of the foundations of Robert Bakewell's success 

 in improving the Longhorn cattle and Leicestershire sheep of the 

 eighteenth century. His example was followed in the foundation 

 period of most of the British breeds of livestock. Injurious effects of 

 inbreeding became apparent later in certain lines, as in the low 

 fertility of the Bates Shorthorns. There are to-day breeders who 

 have reached great success through inbreeding and others who have 

 met disaster. 



The degree of inbreeding which should be followed depends to a 

 large extent on the purpose. Type, color, and utility have already 

 been fixed to some extent in most of the pure breeds, and merely the 

 consistent use of males of the same pure breed may be sufficiently 

 close breeding in many cases. To fix a superior type within a breed, 

 however, requires closer breeding. The closer the breeding, the 

 more readily will characteristics become fixed. 



The expression "line breeding" is often used for various mild 

 forms of close breeding. Thus, continued breeding within a herd or 

 within a few related herds, with the avoidance of close inbreeding, 

 is a kind of line breeding. The term is perhaps most frequently 

 used when there is an effort to concentrate the blood of an especially 

 worthy animal by mating together animals descended from him. In 

 either case characters are fixed more slowly than with close inbreed- 

 ing. There is, in consequence, less danger of fixing undesirable 

 qualities in the stock by accident. It may be well to add that in 

 line breeding, as in any form of inbreeding, animals should be mated 

 primarily on their merits, regardless of the exact degree of relation- 

 ship. The attempt- to follow a rigid system of mating, such as is 

 sometimes represented on charts, usually interferes too much with 

 selection to be a success. 



The degree of inbreeding which a man can afford to follow depends 

 in part on the size of his herd, in part on his ability in selecting the 

 best for breeding stock, and in part on the extent to which he can 

 take a chance. As already noted, most valuable characteristics of 

 livestock are affected to such a large extent by feed and management 

 and also by uncontrollable conditions, that the selection of the best 

 individuals does not always mean selection of the best heredity. 

 Hereditary differences can often be recognized clearly only when 

 different inbred lines are compared with each other. Thus, among 

 a number of inbred lines started from the same stock and maintained 



