I recently witnessed three cows that were diagnosed as being calcium deficient by a local vet. These cows had body trembling, paralysis in the back end, and would not get up again days after being treated with a calcium IV. The feeds have been tested and are more than adequate with calcium for cows in their third trimester, even post calving. No known antagonist in the water. All other responses from the cows appear to be normal. What else could this be?