Hi. I am building a coop. I was going to put down a layer of sand under the deep litter base. I was also going to put down a layer of sand around it to keep the mud down. When I called my local excavating guy, he told me that all the chicken guys in my area use limestone grit. This is the dust that is left when they grind the limestone that is used for the gravel roads here in Northwestern Illinois. I have never heard of this. Anyone out there have any views on this? Thanks.