CHAPTER XIII 



SYSTEMS OF BREEDING 



Inbreeding. This is one of the surest ways known to establish 

 permanent type in animals, and has been from the time of the 

 early history of improved herds of swine, as well as all other 

 domestic animals. It might be said it is nature's way of repro- 

 duction among animals and all living things, except the. human 

 family, but it must be carried on with great caution when handled 

 by man. Of course in the matter of wild animals, birds, etc., it 

 is simply a matter of the survival of the fittest, so that weaklings 

 would never probably be reproducers of their kind. For instance, 

 take game birds; there seems to be no degeneration of their 

 species, as there would be in animals of the domestic kind if they 

 were allowed to take nature's course unlimited, but a man of 

 wise judgment can inbreed even to a great degree, by being ex- 

 tremely careful in his matings and always seeing that no female 

 with a marked weak point in her make-up is ever mated with a 

 sire with the same weakness. In other words, the mating should 

 be of two animals of similar blood lines, both strong and well 

 developed in their general make-up. In this latter case the produce 

 should be an improvement on either sire or dam, and yet there 

 will occasionally crop out an inferior animal or two in the off- 

 spring which should immediately be discarded as a future repro- 

 ducer of its kind. Herds would be improved to a great degree if 

 this rule was practiced intelligently, but woe be unto the practice 

 of indiscriminate inbreeding. 



Line-Breeding. This is somewhat similar to inbreeding, but 

 not carried to as great an extent. It is the mating of animals 

 along similar blood lines on the part of both sire and dam with 

 occasional out-crosses, that is, a cross of different blood lines, but 

 of the same type, a little further back in the pedigree, as illustrated 

 in this chapter where a sample pedigree of a closely inbred animal 

 is shown and also another pedigree of a strongly line-bred animal. 



Cross-Breeding. Strictly speaking, this is understood to mean 

 the mating of two animals that are of pure breeding but of 

 different breeds, as crossing a Berkshire boar on a Poland-China 

 sow, or any other of the pure breeds bred together. Cross-breeding 

 from the feeders' and farmers' standpoint produces in the first 

 cross a very superior feeding animal, often the produce being 

 better for pork purposes than the pure-bred but it must stop at 

 the first cross; by further crossing, the animals deteriorate and 

 the result is the reversion to the scrub. It is not generally cus- 

 tomary to do any cross breeding except for experiments or special 

 results in the first cross. 



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