A Cooler Barn Supports Stable Milk Production During Summer

Heat stress starts at lower temperatures than many expect

Heat stress is often associated only with extreme heat waves. However, research and expert guidance indicate that dairy cows can begin to suffer from heat stress when barn temperatures reach around 20 °C, particularly when humidity levels are high. In these conditions, cows must divert energy towards regulating body temperature instead of feed intake and milk production.

Livestock buildings typically heat up quickly as outdoor temperatures rise but cool down slowly. This means that heat stress thresholds are easily exceeded indoors, even during relatively short warm spells, and the effects may persist after outdoor temperatures fall.

For dairy cows, the optimal ambient temperature is below 18 °C. Once temperatures exceed 20 °C, cows reduce feed intake and rumination, which can quickly lead to lower milk yields – especially in high-yielding animals.

Production losses quickly affect farm profitability

The effects of heat stress are not limited to prolonged heat events. Studies show that even short periods of elevated temperature can reduce milk yield by several litres per cow per day. During extended hot conditions, losses of up to 4–5 kg of milk per cow per day have been documented.

In exceptionally warm years, the number of hot days can rise significantly even in northern regions. In Finland, for example, the summer of 2018 recorded around 40 hot days in the south and approximately 20 in Lapland, with milk yields remaining below normal levels for up to four months in many years.

Targeted cooling as a practical barn solution

The Rex Nordic HP-19 air conditioning unit offers a practical option where efficient yet flexible cooling is required without permanent installation. Designed for professional use, it is well suited to environments where heat load fluctuates throughout the day.

Cooler and drier conditions for the animals

The HP-19 produces cooled, dehumidified air that can be directed precisely where it is needed via separate air ducts. In a dairy barn, this may include milking robot waiting areas, feed table edges, or resting zones where cows spend most of their time.

Research indicates that targeted cooling in animal living areas is more effective than cooling an entire building, as it directly influences feed intake and resting time. By cooling the right locations rather than the whole structure, effective results can be achieved with lower energy demand. The solution is also easy to scale for barns of different sizes, with multiple units positioned according to heat load if required. 

Cow behaviour indicates successful cooling

Farm experience and research both show that the benefits of cooling become visible quickly in cow behaviour. Heat stress reduces resting time and feed intake, which directly impacts milk production.

When indoor conditions remain comfortable during warm weather, cows expend less energy on cooling their bodies. They eat more normally and rest longer, helping to reduce the negative effects of heat stress and maintain more consistent production levels.

A cooler barn environment also encourages cows to return indoors during warm nights, supporting a steadier milking routine and improving overall utilisation of the milking system.

Drier air supports air quality and udder health

High temperatures combined with high humidity place additional strain on animals and reduce indoor air quality. Heat stress has been linked to increased somatic cell counts, often associated with compromised udder health. Mastitis can reduce the milk yield of an affected cow by 4–10 %. Studies show somatic cell counts are typically highest in the end of summer.

The HP-19 removes moisture from the air during operation, helping maintain a fresher, more comfortable barn environment for both animals and staff. Condensed water is collected in an internal tank, with emptying being the only regular maintenance task.

Improved working conditions for staff

Working in barns during warm weather is physically demanding. Targeted cooling improves comfort in milking areas, feeding zones, and service spaces. Reduced heat load improves stamina, safety and overall working conditions.

An effective response to summer heat challenges

The Rex Nordic HP-19 provides a fast and practical way to improve barn conditions as temperatures rise. Targeted cooling, humidity control and mobility make it a versatile solution for a wide range of dairy operations.

When animals feel better, production remains more stable – and working conditions improve at the same time.