As temperatures climb, heat stress can quickly become a challenge on farm. It does not just affect how cows feel. You will often see it come through in their behaviour, health and milk yield as well. Keeping a close eye on the herd and making a few small adjustments early on can make all the difference.
Keep an eye on breathing
One of the easiest ways to gauge how cows are coping is by watching respiration rates at different points in the day. It is a simple check, but it tells you a lot.
In general:
- 20 to 40 breaths per minute is normal.
- 40 to 50 is a sign to start paying closer attention.
- Over 60 usually means the cow is struggling with heat.
It is worth checking more than once a day, especially during warmer spells, as things can change quite quickly.
What do heat-stressed cows look like?
Heat stress does not always show itself straight away. In many cases, the early signs are easy to miss.
As it develops, you might notice:
- Panting or breathing with an open mouth.
- Standing with the neck stretched out.
- Cows are looking dull or lacking energy.
- Slight unsteadiness.
Often, it is small changes like this that give the first hint that something is not quite right.
The effect on milk yield
In most herds, milk yield is one of the first things to drop when cows are under heat stress.
- Mild heat stress can mean around 1.2 kg less per cow per day.
- As it becomes more of an issue, losses of 1 to 4 litres per day are common.
- In more severe cases, this can rise to over 5 litres per cow per day.
It does not take long for those losses to add up across a group.
Signs to watch across the herd
You will usually see a mix of signs rather than just one on its own:
- Increased panting and sweating.
- Higher body temperatures.
- Cows stand more and lie less.
- A drop in feed intake.
- Reduced fertility.
- Changes in normal behaviour.
- Cows group together in shaded areas.
- More time spent around water troughs.
Looking at the herd as a whole often gives a clearer picture than focusing on one animal.
Practical ways to help cows cope
There are a number of straightforward steps that can take the edge off during hot weather:
- Keep an eye on temperature and humidity levels.
- Improve airflow where you can. Even a small increase helps.
- Feed during cooler parts of the day, such as early morning or later in the evening.
- Remove stale or rejected feed to keep intakes up.
- Keep feed fresh and push it up regularly.
- Make sure there is a constant supply of clean water.
- Adjust diets so cows are still getting enough energy.
None of these changes are complicated, but together they can have a real impact.
Supporting energy intake with fat
Adding fat to the diet can be useful in warmer conditions. It produces less heat during digestion compared to carbohydrates, which helps cows stay more comfortable. It is also a good way of keeping energy intake up when cows are not eating as much as they normally would.
Do not overlook forage quality
Forage quality becomes even more important during hot weather, particularly for higher-yielding cows. Good levels of effective fibre and Neutral Detergent Fibre help keep the rumen working properly, support intakes and reduce the risk of acidosis.
Rumen support
Yeast and rumen buffers can also play a part by helping to keep rumen pH stable. If they are already part of the ration, it may be worth reviewing how they are being used during hotter periods, especially for cows that are more at risk.
Water matters more than ever
Water intake tends to rise sharply during heat stress, often by 30 to 50 percent. As a guide, cows will usually drink 3 to 5 litres of water for every litre of milk produced.
A few practical points:
- Make sure there is enough trough space so cows are not pushed away.
- Keep troughs clean to encourage intake.
- Aim for water temperatures between 15 and 20°C where possible.
Water is sometimes overlooked, but in hot conditions, it becomes one of the most important factors.