It really depends upon your layer feed. I've used some brands that had 4 percent calcium in the mix and the bags said not to feed additional calcium. Other brands of layer feed I've used specifically stated on the bag that additional calcium supplements such as lime or oyster shell are needed.
There are 4 different feedstores in my area and I'll just drop by any one of them for a bag of layer feed and it seems I end up with something different each time. I always assumed that "layer feed" had calcium in it, isn't that what makes it layer feed? Then I brought home a bag of Naturewise Layer Feed and right on the front of the bag it said you had to give additional calcium with their feed. I was wondering why it was a little cheaper than what I had been paying for other brands...