Mitigating heat stress

Rachel Rose

| Cattle & Dairy

| May 28, 2024

Mitigating heat stress

High temperatures throughout summer can bring on heat stress in cows which consequently has effects on intakes, lameness, milk yield and fertility. Heat stress occurs between early-May and mid-September.  

Dairy cows are homoeothermic, which means they need to maintain a constant body temperature of around 38.8°C +/- 0.5°C. This makes them sensitive to factors that impact their heat exchange for instance, air temperature, air velocity and humidity.

Grazing cows are naturally at greater risk of heat stress as they are exposed to direct sunlight with limited access to shade. Heat stress is most likely to occur when there is short bursts of hot weather, as this doesn’t allow the cow to adapt to the rising temperatures.

Symptoms of heat stress:
  • Lethargy.
  • Reduced activity.
  • Reduced dry matter intake, leading to digestive disorders like acidiosis or displaced abomasums.
  • Stand with head held low (bowed).
  • Pant.
  • Increased respiration.
  • Cows suffering from heat stress often move closer together and stand in tightly packed groups.
  • Reduced milk yield.
  • Reduction in fertility.
  • Risk of mastitis.
  • Increased risk of lameness.
  • Death.
Managing heat stress:
  • Ensure adequate supply of water in field – cows are unlikely to walk more than 250 metres to drink.
  • Ensure water source is close to shade and a source of feed. In hot weather a cows water intake can increase by 10-20%.
  • Provide adequate shade (house cattle between 10am and 2pm when its hottest in the day) / graze pastures with natural shade.
  • If feed intake decreases, ensure high quality forage is provided (faster digestion means less heat produced).
  • Change feeding times – feed 60% of ration between 8pm and 8am when its cooler.
  • Ensure good ventilation in sheds – which may include fans / water sprinklers.
  • Reduce walking distance.
  • Alter milking times.
Milk Insights by Herdwatch

Herdwatch allows you to identify your cows individual performance through the milk performance module. This module allows you to identify any potential health problems within your herd on a case by case basis from your pocket. Reduced milk yield, quality and increased somatic cell counts (SCC), are all potential warning signs of heat stress.   

> Tap on Performance.

> Tap on Milk Recordings.

> Tap on Per Cow.

‘Per Cow’ breaks down the information on an individual basis for each animal. All relevant headings from your milk recording are covered. This section also can be filtered down if you want to search for specific animals milk recording . Using the magnifying glass in top right hand corner it also gives you the option to filter:

  • The date of the milk recording.
  • Lactation.
  • Calving date.
  • Days in milk.
  • SCC.
  • Milk KG.
  • Fat.
  • Protein.
  • Milk Solids.
  • EBI.

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