One year I bought oat hay. I never saw anything so infested with mice. I put poison out in the barn and within a day I started seeing dead mice everywhere. The neighborhood cats had a hay day cleaning up the carcasses that were outside the barn. I never saw any evidence of any of the cats getting sick from eating the poisoned mice. Of course that was the good stuff that has since been banned. I don't know whether you can trust the new poisons or if they might be harmful to other critters.cat died last summer. within a week the chipmunks and voles took over the garden.
This fall the mice moved in parents old house. The teenages were sitting on the counter watching me on the computer. Easy chicken feed. Caught a few in bucket trap and a few in snap traps... When it got in the single digits, I figured they were not going outside and I put poison out.. no signs of mice now.... dog will try to kill but not eat them... of course this means even though I picked up the bait, I am not going to feed any house mice to the chickens just in case.