Heat Stress in Dairy Herds: Get the Facts



As we move into the summer months and temperatures start rising, it is time to consider how you can manage heat stress in your herd. Optimal management leads to improved on-farm performance in relation to targets and KPIs.



What is heat stress?


Heat stress occurs when a dairy cow cannot shed heat quickly enough to protect optimal metabolism functioning. As a cow moves around or digests food, for instance, heat is produced. Excessive heating from the environment adds to this heat, so on particularly hot and/or humid days, conditions can push the cow into heat stress.



When do cows experience heat stress?


Mild heat stress begins to set in at temperatures above 22°C and become severe when temperatures reach 28°C in high humidity conditions. In low humidity conditions, mild heat stress will set in above 25°C and will become severe at 36°C.



What are the negative impacts of heat stress in dairy cows?


Even mild heat stress can have significant negative impacts on your productivity and profit.

Mildly heat stressed cows will spend more time seeking water and shade and less time grazing, leading to reduced feed intakes. This directly impacts production, causing the steep summer decline typically seen on dairy farms. In addition, mild heat stress reduces in-calf rates.


High heat stress compounds the above issues, with sharp drops in production (by up to 25%) and milk protein percentages. Cows require greater energy for maintenance as nutrient levels become depleted. pH in the rumen also drops.


Severely heat stressed cows have further problems as their systems struggle to cope, leading to an increase is somatic cell counts, mastitis and lameness. Production can be reduced by up to 40% in such cases.





Management strategies for heat stress


Important strategies that may help with managing heat stress are:

- Access to drinking water

- Sprinklers in holding areas

- Shade in paddocks

- Shifting stock optimally

- Support rumen health with yeast and probiotics


Access to drinking water


Check troughs regularly to ensure your herd has access to clean drinking water at all times. Water intakes will increase significantly in hot conditions.


Remember to keep up your pump maintenance and check that flow volumes are sufficient for the number of cows in the paddock.


Sprinklers and fans in sheds and holding areas


When cows are bunched together or in areas with reduced ventilation, heat stress can escalate quickly. Providing sprinklers and fans at these times can keep temperatures bearable so that cows are better able to cope.


Shade in paddocks


While not a quick fix, trees in the paddock can provide an important refuge from the heat. Re-consider the need to remove trees from the paddock for this reason, only doing so if there is a clear benefit.


Shifting stock optimally


Avoid shifting stock during the hottest hours of the day, unless absolutely necessary. Select the shortest route and provide opportunities for shade or water along the way if possible.


Support rumen health with yeast and probiotics


Active live yeast has powerful rumen stabilising benefits. Multiple studies have shown yeast fed to dairy cows during heat stress increases feed intakes and milk production, slowing the steep drop-off in production typically experienced. It does this by stabilising rumen pH and improving feed breakdown – cows are less prone to acidosis. When production does drop temporarily, recovery is quicker when it is included in the ration.


BioPro DFM is an all-natural Direct Fed Microbial that utilises the powerful benefits of 11 key ingredients - including active live yeast and the highest number of probiotic strains and Colony Forming Units (CFUs) per gram on the market - to assist in supporting all measurable parameters of your milking herd.


Supplementing with BioPro DFM is an easy and cost-effective way to support herd health and performance during the summer months. Click here to get started



Heat stress can significantly reduce herd health and farm income during the summer months. These impacts can be reduced with careful management, including internal and external support for your herd.