Sale price is always negotiable especially if issues come up. It may be negotiable, however, it is not a requirement for the seller to negotiate...they may negotiate, they may not.
Have your vet write up his "official" findings in an official manner..ie, typed letter with his company logo (if he has one), contact information and signature. Present that to the seller(s) when you approach them about negotiating price.
Verbal hearsay, which would be you just passing on the vet's thoughts won't have as much impact as an official write-up.
I edited this as I had originally read farrier for vet as I had "feet" in my head. On that note, however, I would have your farrier also take a look after consulting with your vet and if he/she agrees to the problems identified by the vet, have them also write up their findings. This gives more weight to the idea of negotiation.
Last edited by tlkng1; 07-27-2013 at 09:11 AM.