The outcome of line breeding depends on the quality of the common ancester. If the grandparent that the dogs share in common is not an excellent representation of the breed of excellent health than you would be going backward. Doubling up will only produce as good as the dog that you are doubling. If the common ancester has LP for example your pups will now be twice as likely to have LP even if neither of it's parents have it.
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Tami |