Since most dogs can survive a snake bite I’m guessing that it was a rattler. They can be the most deadly on a dog according to a doctor friend that had a lot of bird dogs in his long life of hunting. He told me one time that the only dogs he lost to snake bite were bitten by rattlers.

To the OP, I'm sure sorry that you lost your pet. That’s never easy. My vet had a sign one times out snake bite vaccines for hunting dogs. I’d look into that by talking to your vet. I would assume it is like small doses of anti venom to build it up in their system.