You can get your dog a rattlesnake vaccine from your vet before hand, 2 shots a month apart to build immunities. Most dogs survive snake bites with proper care from a vet, but antivenom is a bit pricey, and a big lab may need quite a few viles. The vaccine is equivalent to 4 viles of av so even with this the dog needs to go to the vet. The best strategy for anyone regularly hunting rattler territory is to take your dog to rattlesnake avoidance class.