I have the same problem. And I have no real solution to it. My goats are oblivious to anything but food while hiking. They will walk right over snakes. The only thing that would protect them would be if they walked behind me so I can watch out for snakes. I let them go ahead a lot of the time unless it's a narrow trail. But on open country they go ahead or behind, whatever they want.
So far no problems, but I just hope for the best. Maybe if a snake were coiled up and rattling it would get their attention. But snakes don't always do that.