 Cattle will drink out of a muddy pond if they have to, but it's better to have cool, fresh water. It's been said that 40 degrees is considered t-shirt weather for cows, so on these hot days, watch for signs of heat stress. They can include labored breathing, open mouth breathing, and restlessness. Dr. Brian Lubbers is an associate professor of food animal therapeutics at Kansas State University. He says along with noting daytime high temperatures, you should also monitor the nighttime low temperatures.