I also want to point out that just because your breeder tells you they've never had a problem with liver shunt, doesn't mean they haven't. Breeders CAN lie

I have a good friend who bought a puppy from a show breeder. She specifically asked the breeder beforehand if she'd ever had any health issues in her breeding program. The breeder told her no. Well, she found out a few months later that her breeder did in fact have a liver shunt puppy and lied to her about it. Luckily, the two dogs are from completely different lines and are not related, but this just goes to show you that breeders may hide the fact that they had a liver shunt puppy. Always be sure that the parents were BATed and be sure to see PROOF of the BATs...don't only take the breeders word for it. I've seen firsthand that not all breeders are honest.
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~Magnifique Yorkies~
Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs.
Educate yourself and buy from reputable breeders or rescue.