I am on the second time doing this, but I still worry. This summer, I used two seed heating mats in my outside brooder pen with 24 Cornish Cross chicks. My sister had built a rack for the mats to lay on and the chicks to go under. I think it worked fine since all my chicks were fine. About three weeks ago I got ten more meat chicks and three regular chicks. The regular chicks were on the older side when I bought them. I would guess one to two weeks old. I thought that would work better for them to brood with the fast-growing other chicks. We had some freezing nights 30 F and cool days the 40s. This time I used a Thermo-Peep heat pad and one seeding mat. I've worried about them, but they are growing and doing well. My question is, one of my challenges has been how dirty the mats get with poo. I have tried covering them with pine shavings, but they just kick them off. Does anyone have any thoughts on this?