Heat stress Q&A

With much of the UK experiencing back-to-back heatwaves this summer, dairy producers are facing prolonged challenges around cow comfort. With THI (Temperature-Humidity Index) readings consistently reaching critical levels, ventilation is a valuable tool in reducing the impact of heat stress. Our animal welfare specialist, Chloe Rodriguez, answers your questions.

Q. Why has this summer been particularly challenging for cow comfort?

A. Since June we’ve repeatedly seen THI levels above 65 (when heat stress starts to impact cows) across the Midlands and southern England. Peaks above 80 have been recorded in parts of Wales – a clear indicator of severe heat stress.

These aren’t just uncomfortable conditions; they directly impact cow health, fertility, and milk production. The real challenge is that many of these knock-on effects only become apparent weeks later. It’s why proactive management is key to minimising heat stress

Q. Why is ventilation so important during hot weather?

A. During warm periods, the temperature inside livestock buildings can be 2–6°C hotter than outside.

Inadequate airflow creates a build-up of heat and stale, moisture-laden air. Ventilation systems like Galebreaker’s VentTube Cool help introduce fresh, cooler air at cow level, improving airflow. This reduces humidity, removes excess heat, and encourages cows to lie down, feed, and behave normally.

When ventilation is optimised, it helps maintain more stable in-shed temperatures even during external peaks, helping prevent heat stress from taking hold.

Q. What other benefits does good ventilation bring?

A. Alongside heat removal, and consistent air movement, adequate ventilation can:

• Reduce moisture accumulation and associated respiratory challenges.
• Lower the pathogen load in sheds, especially when combined with natural or mechanical extraction.
• Help prevent the ‘hot spots’ that develop in stagnant air areas, where THI can spike.

Q. What practical steps do you recommend during extreme conditions?

A. Alongside investing in or upgrading ventilation, farmers should:

• Adjust feed times to early morning or late evening to align with cooler periods.
• Ensure continuous access to clean, fresh water and check flow rates.
• Open curtains or ridge vents to promote passive airflow where possible.
• Consider a ventilation assessment to identify stagnant areas or underperforming inlets and outlets.

Q. How can farmers monitor and respond to heat stress risk more effectively?

A. With extreme heat forecast to continue into late summer, staying informed is essential to protecting herd health, welfare, and productivity.

Galebreaker’s THI-Live platform, developed with Phibro Health, gives free access to real-time insight into heat stress risk. Dairy farms can sign up to receive weekly heat map summaries.

This insight allows farmers to make adjustments – from turning on fans earlier to opening inlets, or increasing the speed of ventilation systems. Remember, monitoring only works when paired with responsive ventilation strategies.

Our animal welfare advisory team also offers tailored support – from heat stress audits and smoke testing to complete building ventilation redesigns. With tools like THI sensors, milk data overlays, and fertility benchmarking, we help farms understand where their challenges lie and how ventilation fits into the solution.

For a building assessment or to join the THI-Live monitoring service, contact Galebreaker’s animal welfare team on 01531 637900.