Hi,
we once tried a horse rug on a cow that had done the splits in the cubicles, and had to be put outside on grass, in the middle of winter, the rug lasted 24 hours, as cows get up back end first, it stood on the front of the rug as it was getting up, and totally ripped the front of it apart. We found that an old wool sheet, with a hole cut in for it's head, so that it was high enough up on the front end so she couldn't kneel on it, and then put on an elasticated circingle ( it's a length of elasticated stuff with a clip on it, that goes right around the animal ), it worked for us, although a wool sheet may not let in enough air.
Regards
Sue