It stinks to lose calves, especially when you have been anticipating them, monitor the calving and assume they are doing fine. Now what to do? I agree with Dun, assuming these are some heifers that you are otherwise proud of. If you have the time, I would recommend getting a calf (from a dairy or the sale barn) and grafting it on the heifer. It takes some effort, but is worth it, in my opinion. I have done it several times and every time, about the 2nd or 3rd day into it I'm wondering "Why the heck am I doing this again?" But when she finally claims the calf and chases the dog out of the corral and softly and sweetly bellers to the calf, it is rewarding. Plus, it teaches her how to raise a calf, so she'll do well with the next one. With a calf on her, it increases your options. You can sell her as a pair, which will bring much more through the ring than an open heifer. You can breed her back and sell the calf separately, and sell her as a bred cow, which will usually also bring more through the ring than an open heifer. Or, you can breed her back and keep her, and sell the grafted calf after it is weaned.