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Monitor and control to mitigate heat stress

Taking steps to improve cow-house ventilation, using AI and the latest environmental control equipment, can help to mitigate the impact of heat stress on UK dairy herds, as a recent collaborative study has shown.


Heat stress poses a significant threat to cow welfare and productivity, and managing the housing environment has a key role to play in mitigating the impact of rising temperatures in the UK. The interaction between temperature and humidity exacerbate heat stress, so both need to be addressed on dairy units.

“We are all familiar with how the discomfort of a hot day intensifies when it is also humid, and for a cow it is no different,” says Galebreaker’s Andrew Gardner. The temperature humidity index (THI) serves as a vital metric for this issue, with sustained high THI levels proving particularly detrimental. For housed herds, the internal climate and its subsequent impact on cows is directly influenced by building ventilation. Buildings with poor ventilation suffer from two main problems – increased humidity and inadequate airflow.

Moisture from cows’ respiration, as well as evaporation from water troughs and slurry, leads to a higher relative humidity of the air inside the shed compared to outside, which increases the THI.

Inadequate airflow means that air inside the shed is not refreshed by natural or mechanical ventilation, meaning there’s little, if any, convective cooling for cows. In a bid to tackle both issues, Galebreaker and Smartbell have successfully completed the Animal Centred Controlled Environment for Dairy.

Funded by Innovate UK, the study assessed how cow behaviour and production was affected on two commercial dairy units, based in Devon and Monmouthshire, during September 2023’s heatwave.

Invaluable insights

The work involved the use of Smartbell’s ear-tag technology, in combination with Galebreaker’s expertise in environmental control solutions, and provided invaluable insights into the impact of heat stress on dairy herds.

“We were able to create ‘heat maps’ with THI data collected from sensors on the test units, which showed the proportion of time a building spent in each THI threshold per day, for a given time period.

“Overlaying these with other data, such as behaviour and milk yields, the correlations between heat stress and cow welfare and productivity became obvious,” says Mr Gardner.

Temperature and humidity sensors were installed in several areas of each building on both units in the study, which highlighted poorly ventilated areas. “By monitoring THI in several areas of the cow shed, we were not only able to visualise variation between buildings, but also detect subtle differences between specific areas within the buildings,” he says.

“During heat ‘events’, cows are often found to congregate in certain areas of the shed – areas that almost always record lower THI levels, even if only by one or two points. Cows can obviously can feel the difference.”

This was observed on the Monmouthshire-based unit, where one side of the shed was blocked from prevailing wind. CCTV showed cows bunching in the opposite end of the shed, and THI data collected by internal sensors showed that the preferred cubicles were 1°C cooler. This variation underlines the impact of factors such as building orientation and openness on the effectiveness of natural ventilation.

THI levels were more uniform across the shed on the Devon-based unit. But, in this building, sunlight was found to be a more significant factor in cubicle preference. Galebreaker Bayscreens were installed to create more shade in lying areas.

So how does high THI impact cow behaviour? Activity data collected from the Smartbell ear tags enabled the development of behaviour models, which were validated by in-person observations. The results showed how some cows altered their behaviour more than others during the heat event, indicating varying levels of resilience between groups.

A stark contrast was observed in lying behaviour between cows exposed to mechanical cooling with positive pressure tube ventilation (PPTV), and those which were not cooled during the heat event.

“Following the period of high temperatures, cows with access to a Galebreaker VentTube Cool were back up to typical lying times within just two days, whereas cows which were not cooled took almost 15 times as long (29 days) to return to ‘normal’ lying behaviour,” says Mr Gardner.

“Feed intakes also dropped significantly in all cows during the heat event. On the hottest day of the study, time spent feeding fell by 95% or more in all cows, which has severe implications for health and productivity.” The impact of heat stress on milk production was also monitored during the study. While cows under the PPTV system did not experience significant reductions in milk yield during heat events those without cooling mechanisms experienced considerable losses, resulting in an average loss of 50 litres per cow, with substantial financial costs.

Heat stress

“High-yielding cows producing more than 40 litres milk per day, and in peak lactation during the heat event suffered most from heat stress. They experienced, on average, a 20% drop in milk production, and also had the most significantly impacted lying times, which were reduced by 79%,” says Mr Gardner.

Following the heat event, daily milk yields began to return to normal, but this took around 20 days, demonstrating that even a relatively short heatwave can have a prolonged impact on production.

The project showed how installing an effective ventilation system can deliver a worthwhile return on investment, helping to safeguard cow health, welfare and productivity in the event of hot weather. But, crucially, the study demonstrates how cow-monitoring technology that uses artificial intelligence (AI) to flag when animals are exhibiting early signs of heat stress, can work well in connection with ventilation systems.

“This project has opened the door to potential follow-up studies that use behaviour as a control for optimising the environment – taking automated environmental control systems to the next level,” says Mr Gardner.

“I see a future where AI-driven cow-monitoring technology seamlessly integrates with advanced environmental control systems.

“Money can always be saved where precision is applied to dairy-management techniques, and smart cooling systems will help producers to maintain herd productivity and reduce costs,” he adds.

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