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Battling the Heat in Dairy Herds

June 23, 2016

Summer brings heat and humidity to the I-29 Corridor region of the Upper Midwest. We need to remember that lactating dairy cattle have an ambient temperature comfort zone (thermoneutral zone) of between 40 to 68° F. Keep in mind the perceived temperature is the combined effect of the current air temperature, humidity level and air movement. When the ambient temperature goes beyond 68° F it causes the cow to elicit physiological changes to decrease the heat stress on her body. For example, dry matter intakes will decrease on average 0.17 lbs for each degree above 68° F. Producers need to be vigilant in their heat stress abatement strategies.

Heat Stress Symptoms
Even though a reduction in dry matter intake and increased water intake are indicators of heat stress, producers will see a drop in milk production and butterfat, along with increased reproductive issues such as pregnancy loss. Other heat stress indicators include: open mouth panting, increased respiration, sweating, increased amount of time standing, and changes in manure consistency.

Management Tips
What can dairy producers do to help reduce heat stress? What follows are some basic tips for dairy cattle heat stress reduction:

  • Provide shade if cattle have access to an outside lot.
  • Increase access to clean, fresh drinking water. This may involve adding extra tanks of water and checking for appropriate flow of water in drinking fountains.
  • Dairy cows in a holding pen should be cooled by a combination of air movement, water sprinkling systems, and shade.
  • Make sure to use large droplets of water when sprinkling (soaking) cows as small droplets often found in misters will not allow for heat dissipation from the cow. Intermittent cycles allow time for the water to evaporate and cool the animal before the next cycle. Sprinkle cows with low pressure sprinklers over their backs away from the feed bunks. Trying to keep the udders dry in this process will help minimize the incidence of mastitis.
  • Use large fans in combination with sprinklers to help cool cows and the air simultaneously.
  • Adjust diets accordingly as dry matter intake decreases, utilizing higher quality forages and increasing the energy density of the diet. As diet adjustments are made care should be taken to make sure that there is enough effective fiber to maximize rumination and keep acidosis and displaced abomasums to a minimum. Adding buffers such as sodium bicarbonate to energy dense diets also help aid in appropriate rumen function. Some producers may also offer sodium bicarbonate free choice to the lactating dairy cows.
  • Diets should contain at least 0.25 lbs. of white salt per cow per day, along with offering access to free choice salt and trace minerals.

The Bottom Line
Cow comfort is essential for high milk production especially during periods of heat stress. Taking the time to focus on cow comfort aids such as additional fresh clean water, air movement, shade, evaporate cooling via sprinklers, while providing energy dense, palatable diets will help minimize lost milk production and reproductive efficiencies due to heat stress.

Additional resources are available in the Dairy Heat Stress Management and Energy Use Planning Guide.

Source: Tracey Erickson, South Dakota State University