Spot the Warning Signs of Heat Stress in Cows and Chickens



Temperature spikes in June and July saw us respond to reports of heat surges in dairy sheds and broilers, to the point at which heat stress had begun to have a negative impact on livestock.

Overheating in both chickens and cows is not only linked to a loss of productivity, but in extreme cases, death. With unpredictable weather patterns expected to continue for the foreseeable future the following brief guide outlines the risks of heat stress on animals, early signs of its onset, and how it can be treated.

Heat stress in broiler chickens and cattle
Productivity can decline at temperatures from 25°C upwards in the average cow and even lower in high yielding animals, so it’s essential that careful monitoring of heat levels takes place regularly.

For chickens, an increase in body temperature of just 4°C can result in fatalities, with birds requiring approximately five days to acclimatise to high temperatures, according to the Department for Environment Food and Rural Affairs (DEFRA).

Common signs of heat stress
To help identify the beginnings of heat stress in both cows and chickens we have outlined the following signs and symptoms of heat stress in animals:


  • Increased water consumption, in extreme cases cows can drink in excess of 50% more than their usual intake
  • Excessive panting or drooling, used to increase subcutaneous blood flow
  • Reduced food intake to lessen the impact of metabolic processes


  • Avoidance of other birds
  • Raised wings, used to increase the exposure of skin
  • Panting, which increases as the heat rises
  • Reduced feed intake
  • Increased water consumption

How to reduce heat stress in cows and chickens

Effective ventilation has been identified as key to mitigating extreme heat in cows and chickens by both DEFRA and a number of in-depth studies. Out-dated, or underperforming equipment can have a significant impact on effectiveness, so it’s vital that ventilation systems are operating at their optimum performance.

For cattle and poultry HTS Turbulator Recirculation fans or HV Belt Drive fans can be used to recirculate cool air and lower temperatures – thus creating a more productive environment for livestock.

Fans alone will only reduce shed temperatures to that of the outside environment. On hot days where the temperature is 25°C or above, evaporative cooling systems have been shown to reduce temperatures by up to 6°C compared to ambient air temperatures, potentially reducing mortality rates by up to 25%. The improved indoor climate also promotes increased feed intake resulting in higher growth rates.

The system works by introducing very small water droplets into the hot air, rapidly cooling the air inside the shed as it evaporates, while ensuring it does not dampen any surfaces or livestock.

Heat stress can have a significant impact on the welfare of both cattle and poultry. Spotting the warning signs early can help offset reduced productivity and yield, ensuring healthier livestock. By installing a modern ventilation system, broiler and dairy farmers can prevent the onset of heat stress.

Duncan Burl, Managing Director at Hydor Ltd

To support farmers Hydor has opened up its 24 hour support service, Hydor ASSIST, to those trying to tackle extreme heat during the summer months. Anyone who has concerns about heat effects on their livestock can call 01725 511422, or email at any time day or night to seek advice.


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