Worked on a ranch when I was a kid and I swear the yard dogs they had hunted rattlers. They had three, one was a St. Bernard, a cocker spaniel and some mid sized mixed mutt. At least two of them would get bit a couple times a year. They would show up and be sick and swollen up for a couple days but never had any lasting effects and never went to the vet. I killed several rattlers when I heard them barking and they were baying one. Crazy! Funny thing too was the working dogs never got bit.