
"" have just had a litter of vizslas and one of the bitches seems to have an open wound (hole) on her spine
the pup came out like this.
she is weak and her back end seems limp she cannot turn over on her own"
A Dermoid Sinus isn't a wound. It's a very, very, very small opening in the skin, barely visible even when you've shaved the coat off, to get a better look if you suspect a sinus. The sinus is a thread-like canal, feels like a thin fishing line when you feel it through the skin.
IF this is a D.S it'd definitely not a typical one. Normally the pup isn't at all affected by it until older. And it's NO wound, just a small opening in the skin, with both hairs and skin lining it, just like on the rest of the dog.. A D.S that's severe, and connected to the spine, will be leathal for the pup if not operated on. In Sweden we put pups with D.S to sleep. It's in my way of thinking the most humane way. The alternative is to let the pup live, wait until it's at least 4 months old, and then find an EXPERIENCED vet to do the operation. Then keep your fingers crossed the op is successful. Which there are no guarantees of. Not all operations succeed. You'll not know until the pup is at least nine months old, in the mean time you will of course keep the pup, it's not ethical to sell a pup that might die in a couple of months time.
To the O.P. I'd seriously think this over, and discuss it with my vet again. Newfiedreams, you'll get no flying bricks from me, I agree with you, and I think it's in the pup's best interest to let it go, it's the kindest thing to do.