I purchases some year old corriente heifers from a local breeder. All were current on worming and vaccinations. However, all were generally unthrifty although they had good appetites. One heifer got pretty thin and then I found her down about a week ago. Flat out on her side. She wouldn't get up, so I moved her into a stall using the tractor. Since then I have got her to eat and drink and she is laying with her legs under her, but I can't get her up. I have slung her daily, but she won't stand. Any ideas what could be wrong or what I should do. Thanks.