We purchased TomCat Ray bait, in a red block (I can’t remeber the exact number/type, but it’s the only red block in this brand), and it cleared out all rats. Some people worry about their chickens getting ahold of it, but, we stuffed it far in the hole, then poured water down it, and filled in the hole, forcing the rats to try and re dig, and find the poison, but preventing the chickens from getting it. At one point, We accidentally dropped a block, and a piece broke off, and a nearby hen snatched it up. After days being watched, this poison had no affect on her, confirming that it is most likely safe for chickens, if they happen to find it after being buried.