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The following is some information and a brief description of some breeding terms and procedures used in animal genetics. The single biggest misconception is when someone tries to equate animal genetics with human reproduction. Parings that humans feel are totally unacceptable are a standard, recognized, and proper practice in animal and plant genetics. This is not a moral issue. It is not a question of whether you should produce more puppies. It is simply a guide to the terminology involved in breeding programs.
INBREEDING "The interbreeding of closely related individuals especially to preserve and fix desirable characters of and to eliminate unfavorable characters from a stock." Quoted from the Merriam Webster Dictionary.
LINE BREEDING "The inbreeding of animals descended from an ancestor having some desirable characteristics which it is wished to strengthen and perpetuate." Quoted from the Merriam Webster Dictionary.
OUT BREEDING "(1) To mate (animals not closely related, selected for their qualities) so as to improve stock. (2) To get rid of an undesirable characteristic by selective breeding." Quoted from the New Lexicon Webster's Dictionary
OUT CROSSING The interbreeding of different breeds (cockapoo) or species (mule) of animals. This term is of no use to the serious breeder. (So the next time you hear someone mention a complete out-cross, ask them whether they bred to a poodle or a jack.)
As you can see from the dictionary quotes, inbreeding and line breeding are actually the same thing. The use of ancestors to perpetuate or eliminate characteristics. Out breeding is used to gain characteristics your stock lacks or to hide detrimental characteristics your stock has.
INBREEDING (LINE-BREEDING) Since all pure breeds of puppies trace back to a relatively limited number of foundation dogs, all pure breeding is by definition inbreeding. This is the use of parings in a breeding program such as father/daughter, mother/son, brother/sister, grandfather/granddaughter, grandmother/grandson.
Inbreeding is used to establish type. When an exemplary individual comes close to your 'ideal' of the perfect animal, you might inbreed to that animal to create puppies with similar type to use in your future breeding efforts. You might also use inbreeding to establish a specific color or coat pattern such as breeding a non-brown bitch to her brown father to produce brown puppies. you can also use inbreeding to check your stock for detrimental recessive genes.
What does inbreeding do? Basically, it increase the probability that the two copies of any given gene will be identical and derived from the same ancestor. Technically, the animal is homozygous for that gene. The heterozygous animal has some differences in the two copies of the gene. Remember that each animal (or plant, for that matter) has two copies of any given gene, one derived from the father and one from the mother. If the father and mother are related, there is a chance that the two genes in the offspring are both identical copies contributed by the common ancestor. This is neither good nor bad in itself. Consider, for instance, the gene for PRA (progressive retinal atrophy), which causes progressive blindness. Carriers have normal vision, but if one is mated to another carrier, one in four of the puppies will have PRA and go blind. Inbreeding will increase both the number of affected dogs (bad) and the number of genetically normal dogs (good) at the expense of carriers. Inbreeding can thus bring these undesirable recessive genes to the surface, where they can be removed from the breeding pool.
The difference between the use of the terms 'inbreeding', and 'line breeding', is that inbreeding is usually thought of as coming from one side of the pedigree, but line breeding comes from both sides. For example, in line breeding, both parents have the same dog in their background. In reality inbreeding and line breeding are the same. They are the accumulation of homozygous genes. The only thing to be concerned with inbreeding is loss of vigor.
Pure bred in its truest sense means homozygous. Animals are called purebred when they share an extensive amount of genes so as to create a pronounced similarity, and pass these similarities to the next generation.
Inbreeding can be used for many purposes such as specific traits, specific color, length of ears, size of feet, etc. To inbreed just because it is convenient and handy is never a good reason. This will bring down the quality of the animal and stamp it on succeeding generations. Inbreeding can be used to bring up the quality of your breeding stock, but line breeding will maintain it. This means that in a closed breeding group, all future breeding animals are selected from within a related group. All of these methods of breeding must be done with caution and careful selections of future breeding stock.
OUT BREEDING is the mating of unrelated individuals within the same breed. Out breeding is used to bring in traits to your gene pool to enhance what you already have. Out breeding is also used to make deleterious recessive traits in your breeding stock, such as eye and hip problems.
Out breeding is used when you need to gain specific traits in your breeding stock and you cannot find related stock. It is also used if your closed breeding program is too small in numbers and you find that loss of vitality or constant small litter size is becoming a concern. The most common use of out breeding is to hide detrimental genes such as eye, hip, or other inherited abnormalities.
If you need more information on this subject, go to your public library and ask the librarian for books on livestock breeding practices.
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