Some rabbit raisers years ago put the mineral Limestone in their rabbit's water for when their rabbits had diarrhea for 3-4 days. More than that was not suggested as it upset the balance of calcium and phosphorus creating poor growth. I wouldn't suggest it now that there are other remedies to use.
In a rabbit magazine just last year I read one of the oldest wive's tales around. The woman quoted as saying that she gave her does raw meat (bacon or hamburger) around kindling time so the doe would not eat her young. In my opinion that is one of the biggest myths ever. Occasionally a doe will "remove" a kit in this manner. Almost always the reason goes back to her wild rabbit survival instincts. When a kit is born dead, a wild mother rabbit would never want the smell to attract predators to her nesting area. That is why they may do it. She isn't turning mean, she is trying to protect the surviving kits.
Another wive's tale we would hear about at fair displays was someone saying that their neighbor's friend or some other "friend of a friend" had a Cabbit....... a cross between a cat and a rabbit. We'd explain that it is not possible for these two species to conceive. They'd insist that the animal looked like a cat but had a very short tail and would hop. Of course they'd not seen it themselves, it was always a" friend of a friend" kind of story. Yup! I was tempted to try to sell them a Jackalope.