Instead of trying to figure out how to enforce a price level(price fixing), breeders should endevour to price their animals at a fair to high price.
You can't make people sell at any certain price. I don't think anyone SHOULD be able to. That's why it's a 'free market'.

By the same coin... people are always bragging about what a great deal they got... "I got this bubble python for $40!!" instead of saying "That price is too low, and I'm not buying from that person."