Hot weather is tough on stock, particularly dairy cows.

Cows get heat stress at temperatures greater than 24°C and with the mercury hitting over 30°C this week, there are lots of cows under pressure.

Cows are classed as thermoneutral animals and like to be in temperatures of between -15°C and 25°C.

At higher temperatures, humidity has a big part to play. Even lower temperatures with high humidity will cause heat stress.

Humidity levels in Ireland are currently at 66%.

According to a chart developed by NADIS in the UK, at that level of humidity, temperatures over 28°C will cause severe heat stress.

Controlling temperature

This can be observed by cows panting – this is the only method they have of controlling their temperature as, similar to dogs, they can’t sweat.

There are two key elements to managing heat stress in grazing systems. The first is shade and the second is water.

On hot days with little wind, make sure cows have access to shade – such as high hedges or trees.

Given that summers are going to be hotter, farmers should really be thinking about planting shelter belts to provide shade.

Some US research shows that heat can be reduced by 20% where cows have shade.

Water is also critical, with cows drinking up to 100 litres per cow, per day, during hot weather.

If milking cows in the early afternoon under intense heat, consider cooling the herd down with sprinklers in the collecting yard.