Overheating cattle: more and more dangerous heat is coming for northern Australia’s herds

Résumé détaillé

Cattle can only cope with so much heat – and more is coming. Graziers will have to install shade – and muster at dawn.

The Sunday roast and the backyard barbecue have long been Australian rituals. The country is one of the world’s biggest consumers of red meat. The average Australian ate about 22 kilos of beef in 2024.

Australia is already about 1.5°C warmer than it was in 1910, when national records began. About half of the country’s 30.8 million cows graze the rangelands and paddocks of the tropical and semi-arid north, where they spend every day outdoors.

Cattle are built to make heat, not lose it. As they ferment grass in their complicated stomachs, cows produce a steady stream of internal warmth. They also sweat less effectively than humans can. To offload heat, they pant, seek shade or wait for cool nights. British breeds from cool European climates are especially bad at shedding heat.

Heat stress is already a problem for cattle in Australia’s north. In our new research, we found dangerous levels of heat will arrive more often. That will pose particular problems for British cattle breeds from the Bos taurus subspecies. Tropical breeds such as Brahmans from the Bos indicus subspecies will be more resilient, but not immune.

Building more shade structures could protect cattle from much of the extra heat.

We used climate models to compare the 1990–2010 period with the heat levels expected by the 2050s and 2090s under both a low- and high-emissions futures. We mapped these conditions over the whole of northern Australia for both Bos indicus and Bos taurus breeds.

We used the Heat Load Index – which combines temperature, humidity, wind and sunshine – to estimate how much heat cattle are actually accumulating.

This index makes clear how much the breed of cattle matters. British breeds such as Angus and Hereford get into trouble at a heat load index value of 86.

But tropical breeds such as the Brahman can tolerate up to 96 without accumulating more heat than they can shed. Most northern graziers already rely on Brahman or Brahman-cross breeds.

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