First, you cannot sue for the value of possible or potential puppies--that would be considered too speculative (since there's no way to prove how many would have been borne, how healthy, that they would have sold or for how much, etc.). You could potentially recover, in a lawsuit, the value of the dog you bought. To recover it, you'd need to show that either the breeder knew or should have known that the dog was sterile, or that he had given you some sort of warranty or guaranty for the dog (e.g. guaranteed that it would be capable of breeding). If he neither knew the dog was sterile nor guaranteed it, it is unlikely that you could prevail in a lawsuit; in that case, the breeder did nothing wrong, and you took the risk of breeding problems when you bought the dog.