Today I decided to use fine grinded natural rock as the first layer in the chicken house, then I laid a semi thick spread of wood shavings over it. When it was time for the chickens to go in their house, some of them won't go in. They seem to be afraid of the natural rock. I lift them up and put them in and they seem to be ok.? Does anyone know why they would be afraid or hesitant to go in. Is the bedding I just mention ok for chicken layers?