Heat stress results in milk production, reproductive performance, and health losses for not only milking cows, but also dry cows, heifers, and calves. These effects may not be seen until after a heat stress event and can have long lasting effects. Drops in milk production may lag 24 to 48 hours from a heat stress event. Reproductive effects may last for 6 weeks or more. In dry cows, negative effects are seen in their calves and the calves of their calves when they become milking cows!

  1. Check that all fans are working and are correctly angled for maximum air flow over cows. Fans should be serviced such that fan blades are cleaned of accumulated dust and fan belts replaced for more efficient energy use.
  2. Fans in eating and resting areas as well as the holding pen should come on automatically when temperatures are greater than 65°F. Sprinklers or soakers should be used and placed on a timer, come on when temperatures are greater than 68°F, and run for approx. 2 minutes and off for 10 to 12 minutes with fans running continuously. Soaker time should increase with increasing temperatures. Wetting the cows using soakers helps dissipate heat and is needed along with fans for reducing heat loads even though soakers adds water to barn alleys.
  3. Ensure that adequate amounts of cool, clean water are always available— remember those calves! Check temperature of water in waterers of pastured heifers and cows; open water troughs in the sun heat quickly when not refreshed often!!!
  4. Mix feed twice a day with more fed during the cooler hours of the day.
  5. Ensure adequate amounts of potassium and sodium are included in the milking cow diets to replace those lost as a result of heat stress.
  6. Remember to provide heat abatement to dry cows as heat stress reduces future milk production and calf survivability.
  7. Calf hutches should also be shaded to reduce heat stress on baby calves and improve their immunity. Often times, temperatures in hutches are way above ambient temperatures and can reach >100º F on hot days.