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What is Line Breeding?

A recent email from Aaron:  Paul, my long time hunting buddy is getting old and I need to get a puppy this spring.  A pointer kennel I’m looking at advertises many years of conscientious line breeding.  What is line breeding?

Your author is not a veterinarian or genetic scientist; however, I can give a layman’s answer to this question. Animal breeders typically talk about two types of breeding: in-breeding and line breeding.  Let’s look at each.

In-breeding is something we’ve all heard about at some point in our lives; it’s incestuous breeding between two immediate family members such as parent-child or between two siblings.  In-breeding prevents genetic diversity.  This means that a puppy could inherit an identical, but undesirable, gene from both parents.  If only one parent has the undesirable gene, there is much less chance of the gene becoming dominant.  The technical term for inheriting two identical genes from the same parent is homozygosis.  The result of close in-breeding could result in many diseases and health issues including hip dysplasia, poor immune system, both male and female sterility, sight problems…and much more.

Line breeding is, amongst purebreds, an acceptable form of in-breeding.  Since the initial genetic pool for purebreds was small, the probability that two copies of any given gene will be identical, within a purebred strain of dogs, will be high.  In fact, the whole concept behind line breeding is to breed good genes into a litter of pups.  Line breeding is the foundation for selective breeding which has given us chickens with large all-white-meat breasts and cows that produce more milk.

For dogs, good breeders have been striving for years, through line breeding, to produce puppies with correct standards, good temperament, and, for sporting dogs, animals that have better scenting ability, locate more birds, stay staunch on point and retrieve reliably.  Of course, harnessing all these wonderful characteristics can also mean harnessing undesirable genes.  So, how does a responsible breeder help ensure that his line breeding captures as many of the good genes as possible but avoids the undesirable genes?  The first step is to make sure the sire and dam are in very good health.  This is crucial to good line breeding; it helps avoid the unwanted health issue gene.  The second step is to breed to healthy dogs that have the trait you want to introduce or strengthen in your line of dogs.  Here is additional information for good line breeding.

The United States, with all of our sophisticated technology, has, in my opinion, lagged behind in helping breeders with smart decisions for line breeding. My father was a veterinarian.  We had a kennel full of English setters and beagles.  Beagles, however, were what we bred and raised for both brace field trials and rabbit hunting.  My father used to talk about an in-breeding coefficient; a method of determining the relationship between sire and dam.  A low coefficient meant very little relationship and a high coefficient meant a very high relationship.  However, the “in-breeding coefficient”, if I recall, was only used in Europe.  Dad said that we didn’t have the record keeping in this country to use the “in-breeding coefficient”.

Here’s the formula my father used.  He felt that there should be at least three generations of separation for line breeding.  He liked five generations or more, but felt three was satisfactory.  Dad recognized that maintaining a good line-breeding program with five generations of separation would be difficult…too many years to reach your objective.  So, my simple answer for Aaron:  check the pedigree of the sire and dam producing the litter and watch for repetitive names in those pedigrees.  If you find repetitive names within three generations, I suggest you look for another litter.

Here’s one final comment on line breeding.  Genetic research is progressing dramatically every year.  Within a few years, I’m sure that there will be a simple and inexpensive method of checking for unhealthy breeding in a sire and dam.  We’ve all seen the ads on TV that say “Show me the CarFax.” This document reportedly lists any accidents in which a used car has been involved. Someday soon you’ll say to a breeder “let me see the CanineGeneFax”.

In simple and layman’s terms, I hope this article has been helpful.  And, although he’s been gone for years, I want to thank my Dad for allowing me, as a young boy, to sit and listen to his adult conversations with fellow dog breeders.

Paul Fuller is a lifelong sportsman.  He’s been an outdoor writer since 1971. He’s the host and producer of the award winning Bird Dogs Afield TV show ( and produced the epic video Grouse, Guns & Dogs. Paul shot over his first German short-haired pointer in 1961.

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