Recent weather patterns are trending towards hotter summers. This means dairy farmers may consider ways to modify cattle housing designs to reduce the impact of hot weather on cow performance. 

Housing could increase the incidence of heat stress as many structures are typically poorly ventilated.  

Heat stress in cattle can cause physiological changes leading to reduced milk yield and fertility, while also increasing the risk of disease and lameness.

According to new research, heat stress in cows can result in annual production losses ranging from £24,000 to £90,000, depending on herd size.

What is heat stress?

Heat stress occurs when a cow’s body temperature exceeds the normal range of 38ºC to 39ºC. Although cows can try to cool themselves down through panting and sweating, cows suffering from heat stress aren’t able to reduce their temperature enough to negate the impact of high temperatures.

While the ideal comfort zone for a dairy cow is between -15°C to +25°C, high relative humidity can make heat stress a problem even at moderate temperatures that might not initially be a cause for concern.

When humidity is higher, it reduces the amount of evaporation that can take place, which can make the temperature seem even higher. This can make for an uncomfortable environment for cattle.

Galebreaker has just launched a new website, alongside Phibro, which shows real-time THI values from dairy buildings across Europe. This means you can stay up to date with the THI in your area. Click here to find out more.

How heat stress affects dairy cow performance

A temperature-humidity index (THI) score of 57, indicating mild to moderate heat stress risk, can happen at relatively low temperatures and can impact conception rates and milk yields.

Cows generate heat internally through digestion and milk production, complicating their ability to cool down. For example, a cow yielding 18 litres of milk per day generates over a quarter more body heat than a dry cow, and a cow producing 31 litres per day generates almost 1.5 times more heat.

Read more: Could heat stress be affecting your bottom line

Preventing heat stress with ventilation

A  project conducted by Galebreaker and Smartbell , the Animal Centred Controlled Environment for Dairy (ACCED) project,  explored how dairy farmers can reduce the impact of heat stress in cattle.

The study monitored cow behaviour and productivity during a heatwave in September 2023 on two commercial dairy farms in Devon and Monmouthshire. The results were clear – high-yielding cows in poorly ventilated environments suffered significant heat stress, with milk production dropping by an average of 50 litres per cow over a 20-day period.

However, installing a mechanical ventilation system, such as the Galebreaker VentTube Cool, significantly increased a cows’ resilience to heat stress.

The cows in a ventilated environment recovered from heat stress within one or two days, minimising milk production losses. These cows also spent more time lying down, benefiting from the ‘chill effect’ of improved airflow. More time lying down is is likely to reduce lameness in the following months.

To find out more about how you can reduce the impact of heat stress on your herd,  speak to our  expert team. Contact us by clicking here.

Read more: Monitor Temperature Humidity Index to prevent cow heat stress this summer