My concern would not be "is this a line-breeding" but what is it a line-breeding to or of. If it is a dog with many more defects than advantages, or a dog with a disease or medical condition that is hereditary, I'd want to avoid it and would certainly not want to concentrate its potential genetic influence. But if it is a dog whose benefits far outweigh any negatives and it is healthy and has produced healthy offspring, I'd like to see it appearing in multiples in a pedigree. When you line-breed you are concentrating the genetic influence of an ancestor, so the question is whether that is a pro or a con. Also the mode of heritability is also important, especially when talking about health conditions. Unfortunately there are very few diseases for which we have a good understanding of how they are actually inherited-- is a dominant trait, or recessive, is it polygenic or even familial? Add into this that diseases present in several breeds often have different modes of inheritance, like PRA for example. Outcrossing without having knowledge as to the health of the ancestors of the dog to whom you are outcrossing to can be far more dangerous than line-breeding (if you have good information on those ancestors) because along with the good things you are bringing in to your line you might be opening the door to some very bad things as well.
So really the question is more one of who that grandsire of the pom is, and what he has produced... not linebreeding is bad versus outcrosses are good. Myself, I would not operate a breeding program primarily based on outcrosses, I'd never know what ingredients I was throwing into the soup with that method. |