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How to reduce heat stress in dairy cows 

How to reduce heat stress in dairy cows 

Heat stress is becoming a common problem on British dairy farms with Lallemand monitor farm data from last summer showing an average estimated cost of £128 per cow. 

As heat waves become more common, it’s important farmers understand the risks of heat stress and identify ways they can mitigate its impacts.  

Cows start to show signs of being heat stressed at 21°C, but production losses can start to happen from as low as 18°C.  

Impacts of heat stress include:  

  • Drops in milk yield 
  • Poor fertility 
  • Increased health challenges, such as lameness and ketosis 

How to improve ventilation in cow housing

Providing cool, well-ventilated housing during periods of high temperature and humidity should be a priority. Badly designed sheds could be 5°C hotter than temperatures outside; however, in a good shed, the temperature should be at least 5°C cooler. 

You can reduce the temperature inside housing by: 

  • Having a good open ridge 
  • Insulating your roof  
  • Adding vertical fans and possibly sprinklers to the worst ventilated areas or spaces with the highest stocking density such as collecting yards 
  • Removing Yorkshire boarding or if annual weather permits opening some or all of the shed’s side walls  
  • Painting the outside of existing roofing white  

Providing cows with sufficient water

Cows need constant access to fresh, clean water, but during hot weather cows will drink a lot more.  

A cow producing 21 litres of milk a day will need to drink 109 litres of water when the temperature is 27°C, compared to a cow producing 45 litres of milk which will need 135 litres of water.  

If you have the correct water infrastructure, 10% of your herd should be able to drink at the same time and there should be enough flow and capacity to keep up with demand.  

Make sure that your cows have access to water at multiple points in the collecting yard as they will tend to bunch together, and temperatures can rise rapidly.  

How to optimise feed intakes during periods of heat stress

Although feed intakes will drop when it’s hot, there are ways to maximise nutrient intake and digestion.  

  • Feed a highly digestible forage  
  • Put fresh feed out twice a day, but not directly after milking, to maximise daily meals and prevent feed spoilage 
  • Add 20 billion CFU of rumen-specific live yeast Levucell SC per cow per day to the diet either via mineral pack, blend, compound feed or a ready-to-use POWERMIX such as Levucell SC Summershield. This will help maintain rumination behaviour, feed efficiency and milk production

How to manage heat stress in grazing cows

Grazing cows aren’t immune to heat stress, with Lallemand monitor farm data from last summer showing an average estimated loss in milk production of 129 litres.  

Adopting a ‘siesta’ management approach can help to reduce the impact of heat stress on grazed cows.  

The steps to ‘siesta’ management include: 

  1. Housing the cows in the late morning and keeping them in until after milking so they are indoors during the hottest part of the day 
  2. Turning them out again in the evening so they have a major grazing bout to maximise their grass use
  3. Reserving the shadiest paddocks for the hottest days and planting trees in the other paddocks to create future shaded areas

Published Aug 1, 2023 | Updated Dec 4, 2023

Dairy cowHeat StressLEVUCELL SCYeast