Mitigating heat stress in housed dairy cows

Taking steps to mitigate the impact of heat stress on dairy cows will help avoid production losses when temperatures rise.

Lallemand Animal Nutrition’s ruminant technical support manager, Nico Vreeburg, shares his top tips on how to prevent heat stress in housed dairy cows.

How much does heat stress cost farmers?

Heat stress is becoming a big problem on UK dairy farms as higher temperatures during the summer months become more frequent.

A study involving Lallemand and Chalcombe Ltd, conducted over six months between April and October 2022, found:

What impact does heat stress have on cows?

Heat stress, if left unmanaged, can cause costly production losses as the studies have shown.

Cows start to express signs of heat stress at 21°C, but production losses start to occur at temperatures as low as 18°C due to the UK’s relatively high humidity.

These production losses are down to various factors including:

How to manage heat stress in cows?

To prevent heat stress causing costly production losses, dairy farmers should focus on the following three areas:

Higher temperatures during the summer months mean heat stress needs to become a fundamental part of any cow management plan.

What needs to be considered with housing?

Housing design, and the installation of any technology to help keep cows cool, can have a positive impact on cows during periods of heat stress.

The temperature inside a badly designed shed could be 5°C hotter than the temperature outside, however inside a good shed, the temperature could be 5°C cooler than outside.

Housing measures to prevent heat stress include:

How much water do cows need?

Cows will inevitably drink more in the heat.

As an example, a cow producing 21 litres of milk per day will drink 103 litres of water when the temperature is 21°C – her daily drinking requirement increases to 109 litres of water when the temperature is 27°C.

For a cow producing 45 litres of milk a day, her daily drinking requirement is 128 litres of water – this increases to 135 litres of water when the temperature rises to 27°C.

Ensuring cows have access to a constant supply of fresh water is therefore crucial during periods of high temperatures.

How can nutrition be altered to mitigate heat stress?

Dry matter intakes will decline and cows will experience impaired rumen function and diet digestion during periods of heat stress.

This can be mitigated by ensuring everything the cows eat is of high-quality, and by including a live yeast in the ration.

Trials have shown benefits from feeding Lallemand’s rumen-specific live yeast Saccharomyces cerevisiae CNCM I-1077, known commercially as Levucell SC, to cows during periods of heat stress.

Including Levucell SC in the ration at double the standard dose has been shown to result in a 6% increase in feed efficiency and milk yields in cows suffering heat stress[1].

[1] World meat analysis, De Ondarza, 2010