I live on a mountaintop made mostly of limestone, granite and shale, and I have a limestone gravel driveway. Do I need to give my mixed flock of geese chickens and guineas additional calcium for laying? Theyre on a quality all flock layer feed. They free range at least 12 hrs a day. I read that limestone is a quick form that leaves the body quickly, but if they have a constant supply do you think thatll be enough for them? Tia