I am building my chicken coop and pen inside a fenced garden area. My chicks will have to stay in locked in the pen most of the time except when I am at home on weekends because of problems we have with loose dogs and other predators. We have already lost one pet rabbit and a cat. I now keep hot-wire around my rabbit hutch. ANYWAY, can I put a base of grit and/or oyster shell in the pen to keep it from getting muddy? Will they just sit around and eat it? I could also put down a base of sand if this would be better. Any suggestions are welcome.