I would say offhand that it would be a day or maybe less. Cold does more to drain you of water than heat: if you feel muscles knotting up then you are low on salt and it can kill you. Snow is mostly air. There is surprisingly little water in it and it is cold enough to induce hypothermia.
Your cattle need warm water. If you have a cattle tank, use a pick or sledge to break open a place for them to drink and keep it open.
If possible keep a heater in the tank so that the water won't freeze.
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