Did you read the label on the poison container? I use sevin dust. I stir up the mounds real good, then heavily sprinkle sevin dust on them heheheh. BTW: Chickens wont mess with sevin dust. I've used it to dust chickens for lice, once they're released the chickens shake themselves off and go on about their business.
I like that sevin dust idea, will have to try it. Odds are the chickens already know to stay away from the mounds. One time is enough to figure out it's not a winning strategy to scratch a fire ant hill and peck to their heart's content. No relief for the chicken as their's no catching them after the ants start biting. Nature teaches them not to do it again.