It is essential that horses maintain access to a clean, ample supply of drinkable water during the cold winter months, " says Dr. Bullock. "They run a real risk of impaction colic if they don't get enough to drink, either because it is frozen or because it is too cold for them to drink comfortably. Gulping down freezing cold water after a workout can make a horse pretty uncomfortable," says Dr. Bullock. "It should be at least 40 degrees. From article by Sarah Christie for Nov.2000 issue of Horse Illustrated
Dr. Julie Bullock, DMV - ,