Dr. Reuben Moore, dairy specialist with Mississippi State University's Extension Service, said the ideal temperature for dairy cattle is 55 degrees. Recent temperatures in the 90s have stressed some herds. If temperatures don't drop at night, cows have difficulty recovering from the day's high heat.
Cows produce heat when they digest food, a result of fermentation in their stomachs.
When temperatures rise, cows eat less to prevent themselves from getting too hot. They produce less milk as a result. Fans, sprinklers and shades help many herds reduce heat stress. Summer diets should include less fiber to reduce the heat produced in digestion. Even five degrees makes a significant difference in milk production.