I don't have any suggestions but I just wanted to say I know what it is like to have a Sheltie who outs everything in their mouth. Shelby did pick up a toad once, of course she spit it out and was foaming at the mouth shaking her head. Fortunately they are not poisioness here. After that incident she never put one in her mouth again. Now she just gives them the stink eye and stays away. DH had to carry her in the house one night b/c there was one sitting by the door and she would not come near it.
Her new thing is finding the slugs at night She doesn't eat the, just gives them a nudge with her nose. But she has had her share of rabbits, mice, and snakes.