 More than a day or so in the backyard with food and water before I checked on them again? A cow maybe could survive maybe two days without no water. Maybe. It depends on the dew and stuff. But, yeah, I remember a story with my grandpa. We had four cows on the back 40, and he was overchecked on them. And we went over, and one of them was already on the ground. Another one wasn't acting right.