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Animal Heath Alert – Heat Stressed Cows

December 7, 2017

Over the past two weeks environmental conditions have led to many cows in local milking herds suffering the consequences of heat stress.

Heat stressed cows seek shade and water in vast quantities, with some reported water intakes well exceeding 100 litres per cow per day in high producing herds. Often this increased demand is not met by the water supply leading to severe dehydration of cows, especially those least dominant.


Severely affected cows can become incredibly stressed and agitated showing signs of:

  • Rapid breathing
  • Drooling
  • Ketosis
  • Milk fever
  • Depression
  • Apparent sudden death


From an animal health perspective there are many associated issues relating to a combination of heat stress and dehydration such as:

  • Decreased fertility
  • Loss of electrolytes (Sodium and Potassium) through increased salivation & sweating
  • Disturbances in rumen pH and function presenting as acidosis and colic
  • Reduced Dry Matter Intake and production
  • Elevated BTSCC and clinical mastitis


In these conditions consider measures to reduce the impact of heat stress on cows by:

  • Ensuring adequate access to shade, especially in the heat of the day.
  • Ensuring adequate access to water by choosing paddocks with greater numbers of working water troughs and using temporary water troughs on the races outside the cow shed.
  • Reducing mob sizes to allow greater access to water
  • The use of high volume sprinklers in the yard (water needs to be running off the cow’s belly)
  • Provision of salt licks or the addition of salt to feed at the rate of 20–30 g per cow per day