Article Summary: Despite Australian dairy cows evolving over time to become more heat-tolerant than their ancestors, heat stress in dairy cattle is still a big issue and needs to be managed properly. Cows handling the heat will have a better chance of reproducing and passing their genes to future generations. Thankfully, New Zealand's dairy industry has been working on breeding cows that can tolerate heat for some time through the discovery of the ‘slick’ gene. We report on its progress and when you can expect to introduce heat-tolerant cows to your herd.

We’ve recently covered the breeding of climate-friendly cows, and now there’s more happening in the breeding-to-improve-farming world. This time, it’s the breeding of heat-tolerant dairy cows. Once again led by dairy innovators in New Zealand, they are using research and genomics to benefit farmers in dry, arid areas soon so that they have cattle that can withstand extreme heat and little water when necessary.

Which cows are the most heat tolerant?

Brangus cattle, 5/8 Angus and 3/8 Brahman, are good at dealing with hot weather conditions. They also have calm temperaments, good weight gain, are resilient and resistant to disease, and make good mothers.

But they are not dairy cows. Jersey cows are typically the most tolerant and yield high levels of the richest milk. Still, they aren’t adapted to withstand soaring temperatures that are especially prevalent in central and northern Australia (and New Zealand).

What makes a cow heat-tolerant?

Typically, there are several physical attributes that might make a specific cow breed averse to extreme heat. These might be:

  • Smaller body size and lighter coats to help them dissipate heat more easily

  • Greater sweat production and respiration rates to help them cool down faster

  • Higher milk production even in hot weather

How dairy cows in Australia have adapted to heat over time

Did you know that dairy cattle belong to a species called Bos taurus? This species is one of the two types of cattle found in Australia. Bos taurus cows are better suited to colder climates, while Bos indicus (like Brahman cows with loose skin) are better for hot and humid areas like Northern Australia and Asia.

Due to natural selection, Australian dairy cows have evolved over time to become more heat-tolerant than their ancestors. This means that cows that can handle the heat will have a better chance of reproducing and passing their genes to future generations.

Despite this adaptation, heat stress in dairy cattle is still a big issue and needs to be managed properly. It can affect milk production, fertility, and even the health of unborn calves. Dairy Australia has a program called 'Cool Cows' to educate farmers on managing heat stress in their herds. The program provides up-to-date scientific information and advice on how to keep cows cool during the warm months using methods like sprinklers, misters, and shading. It also sends farmers alerts via email or SMS about high-risk times of the year.

But what about right now? 

The good news is that animals are being purposely bred to withstand higher temperatures and changes in climate, and they may be available to help grow and optimise your herd soon.

New Zealand is leading the way in breeding heat-tolerant cows

Did you know that New Zealand is leading the way in breeding heat-tolerant cows? With climate change bringing more weather events to NZ, like drought and heatwaves, it's important for farmers to have cows that can handle the heat and produce high-quality milk. 

Breeding cows for heat tolerance

New Zealand's dairy industry has been working on breeding cows that can tolerate heat for some time through the discovery of the ‘slick’ gene. First discovered in a beef breed called Senepol from the Caribbean, NZ breeding company LIC has been selecting cows with this gene that makes them better at coping with heat stress over the past seven years.

With an 18-strong dairy herd for testing purposes, LIC has been monitoring cows within the herd with the slick gene and those without (nine in each group). Originally discovered due to a gene that makes cows ‘hairy’, the slick gene to keep cows cool results in a lower rumen temperature of between 05.-1.0C when the Temperature Humidity Index (THI) reaches 73, or approx 26C ambient temperature and 60% humidity. 

Less energy to break feed down means cooler animals.

While the results are promising, there are still issues to iron out with this programme, as cows with the gene are producing around 18% less milk than their non-slick gene counterparts in the test group. While it is expected to change over time, it is agreed that genetics is a long game and that with advances in genomics and further research, milk yield will catch up to ensure that heat-tolerant cows find their way to your farm by 2029.

How heat-tolerant cows can help farmers

Heat-tolerant cows can provide many benefits for farmers, such as:

  • Higher milk production through increased productivity: Cows that are more comfortable in hotter temperatures are likely to have higher feed intake, improved milk production and better fertility. By breeding heat-tolerant cows, you can help ensure your herds continue to produce high milk yields, even in hotter conditions.

  • Improved animal welfare: Heat stress can significantly impact the health and well-being of dairy cows. By breeding cows with the slick gene, you can help alleviate the effects of heat stress on your animals, reducing the risk of heat exhaustion, dehydration, and other related health issues.

  • Better cow health: Heat stress can cause health problems for cows, such as reduced fertility and milk quality. You can reduce the risk of these problems by breeding for heat tolerance.

  • Better Adaptability: With climate change leading to more unpredictable weather patterns, breeding heat-tolerant cows can help you prepare for extreme weather events, such as heat waves, droughts, and bushfires. Heat-tolerant cows are better adapted to survive in hotter and drier conditions, making them a valuable asset if in regions with a higher risk of heat stress.

  • Lower costs and resource usage: Cows that are better at coping with heat stress require less energy and resources to keep them cool, which means lower costs for you. Greater efficiency equals lower operating costs, too.

The next step in having a heat-tolerant dairy herd

Breeding cows with genetic traits to improve their coping with the heat is an exciting development for the dairy industry. 

Heat-tolerant cows are better at maintaining their milk production during the summer months, which means they're more productive and profitable for farmers. And with temperatures tipped to rise in New Zealand by 2040, this scientific breakthrough courtesy of Kiwi scientists is now needed more than ever on farms.

So, if you're a farmer in an increasingly hot environment and need resilient and sustained operations, investing in heat-tolerant cows is something to start planning for now. By utilising innovative breeding programs and technology, you’ll not only make a big difference in your bottom line while improving the welfare of your herd, but you’ll help create a brighter and more sustainable future for the dairy industry.

- The Dedicated Team of, 2023-03-02