When I was searchihg for Ava I found a show breeder who was selling a puppy with an underbite. She told me it was "slight". Before I drove quite a distance to see the pup, I called several vets to see what their opinion were on underbites in small breeds and I asked several other breeders and they all said a "slight" overbite" does not affect quality of life and they can eat just fine and all. A "severe" underbite however can be a very serious problem. I also researched on the internet.
It broke my heart when I went to see this puppy because I had my heart set on her from her pictures but when I opened her mouth, the underbite was very noticeable and the breeder said "it had gotten worse" so needless to say, I did not get the puppy. She did sell the puppy for $2400 to someone else.
I would say if the underbite is so severe as to be "life altering" then I would not breed her, but if it is as "slight" as you say and you can find a male without the recessive gene, and you are producing purely pet quality yorkies, and she is "perfect" in all other areas, then I think it would not be irresponsible to breed her if you have a mentor and a good vet. JMHO |