Heat Stress in Dairy Cows

Posted by Gary Walker on

An optimal living environment for cattle requires a good climate says Gary Walker of Dalton Engineering, UK Distributor of Vostermans Multifans. For dairy cows, the optimum ambient temperature is between -5 and 18 °C.

At a temperature of 19°C in combination with a high humidity, as often seen in the U.K. a cow can already suffer from heat stress.

Most noticeably cows start drinking more when heat stressed. They sweat and pant and produce more saliva, all of which causes moisture loss. This can lead to reduced rumen pH. Heat stressed cows stand for up to two hours more per day in an attempt to lose heat.

During periods of heat stress, feed intake is reduced by 8 to 12 percent or more. This reduction in feed intake reduces the production of volatile fatty acids in the rumen, resulting in reduced milk production. Decreased fertility, an increase in embryonic loss, an increase in lameness due to increased standing times and more cases of clinical mastitis are also often seen.


  • Increase the amount of water available for your herd.
  • Provide shade to reduce heat gain from solar radiation.
  • Provide cooling to the outside of the cow using fans and possibly soakers.

Ventilation is Key

  • Move high speed fresh air over the cows to aid heat loss through convection.
  • Target the collecting yard due to a high density of cows and heat.
  • Target the resting area. The goal is to decrease standing times and increase lying times.
  • Fans at the feed barrier also help to dissipate heat.

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