Although dairy cattle are generally better suited to colder climates, it is highly likely that over time, Australian dairy cows have become more heat tolerant and have acclimated to the warmer weather. 

Dairy cattle belong to the species Bos taurus, one of the two species of cattle in Australia. Bos taurus cattle are most suited to colder climates versus Bos indicus (think Brahman with lots of loose skin to help lose heat and keep cool) that are better suited to the heat and humidity of Northern Australia and Asia.

It is highly likely that over time, due to natural selection, Australian dairy cows have become more heat tolerant than their ancestors. Cows that cope better with the heat will be more likely to reproduce and populate future generations.

Despite this, heat stress in dairy cattle is a very important issue and requires specific management. It is known to impact milk production, current and future fertility and even influence the health of the unborn calf. Research continues in this area.

Dairy Australia has an educational program for farmers known as 'Cool Cows' to provide farmers with up-to-date scientific information on heat stress to minimise its impact on their dairy herd. Farmers are provided with advice on how best to keep their cows cool during the warm months using approaches such as sprinklers and water misters; specifically designed shading; and management and husbandry changes. The program also allows farmers to be automatically alerted to high risk times of the year through an email/SMS service.

Resources

Ahmed, B.M.S. et al., 2017. Cows exposed to heat stress during fetal life exhibit improved thermal tolerance 1. Journal of Animal Science, 95(8), pp.3497–3503

Garner et al., 2017. Responses of dairy cows to short-term heat stress in controlled-climate chambers. Animal Production Science, 57(7), p.1233