When he was working as a veterinarian with sheep, goats and dairy cattle in India in the heat of summer, Dr Surinder Singh Chauhan was aware production was declining.
“People would say, ‘Oh, that’s just because it’s summer,’ and I said, ‘Why? Why is production going down?’ ”
In 2011, Dr Chauhan received a scholarship from the Australian Government’s Department of Foreign Affairs and Trade to come to the Dookie campus of the University of Melbourne, near Shepparton in rural Victoria, where climate-controlled facilities and 7000 sheep and other livestock awaited his research on the effects of heat stress in animals. A PhD, postdoctoral research in the US, and eight years later, Dr Chauhan has some of the answers – answers that could help the world produce enough food in the coming decades.
“Animals such as sheep and goats and dairy cattle are homeotherms,” he says. “Like us, they maintain their core temperature within a narrow zone. That zone is their comfort zone.”
At reasonable temperatures, homeotherms don’t have to expend much energy, but – because sweating isn’t an effective cooling system for them – once dairy cattle are exposed to temperatures above 25°C, or sheep above 28°C, there’s a problem.
“The energy which was going to be used for growth rates or milk, wool or meat production is now being directed elsewhere,” Dr Chauhan says. “An animal under heat stress will eat less and increase efforts to lose heat – it will increase blood flow towards the skin. In the effort to do that, some blood supply to the intestine is reduced, leading to insufficient oxygen in the gut, leading to leaky gut syndrome, and long-term damage. So, the animal’s not only eating less food, but it’s unable to properly utilise the food that it has eaten.”
In addition, the animals pant.
“It’s a very shallow respiration,” Dr Chauhan explains. “They are not getting enough oxygen, but they are losing too much CO2”, creating a damaging pH imbalance. As the animals eat less, their bodies can’t get enough antioxidants, and instead produce more free radicals. These problems lead to a lack of weight gain and a decrease in milk or wool production.
This problem can also cause the muscle tissue to become more alkaline, meaning that as a final product, the meat becomes tougher, discolours quicker and has a reduced shelf life.
Long-term, one of the solutions to this problem will be an increasing understanding of genetics, selecting breeds and genetic strains with better ability to handle heat. But in the shorter term, Dr Chauhan has hit upon one solution: feeding sheep a concentrated dose of vitamin E and selenium.
“Food intake goes down about 14–15% in heat-stressed sheep but, with the supplementation, we prevented that decline,” he says.
“The animals that were given the antioxidants did not show any open-mouth panting. And those animals’ free radical production did not increase.”
One challenge is detecting heat stress early enough to be able to make a difference.
“Once you see the behavioural signs, the production losses have already occurred,” Dr Chauhan says. He is looking at everything from thermal cameras (to be used when transporting animals, for example, in live export) or sensors that can measure gases.
“For example, if sensors can monitor expiration levels of carbon dioxide or hydrogen peroxide, it will give us an idea of pH balance and oxidative stress.”
Dr Chauhan says the climate-controlled facilities at Dookie allow researchers to compare animals’ responses in a normal climate with climates up to 42°C. In the summer of 2020/21, more extensive trials will hopefully take place on large sheep properties in natural conditions.
He says the research is vital for the future of agriculture in Australia as the frequency, length and intensity of heatwaves continue to rise.
Living on campus at Dookie, Dr Chauhan is aware how far he has come from growing up on a farm in a small village in northern India. His parents owned five dairy cows and two bulls, and he remembers that when he was in second grade there was an outbreak of foot and mouth disease.
“There was no veterinary hospital in my village and there were no roads, so animals couldn’t be transported,” he says. “That was the first time I thought I would like to be a vet.”
Years later, after training as a vet, he realised he could contribute even more to animal welfare and solve global problems by becoming an agricultural scientist.
“Looking for solutions is very exciting research. The demand for food is going up, and with temperatures going up, the production is affected. At the same time, we need to be more efficient at food production, because we can’t use any more resources than we already are.”
Sponsored by the Australian Council of Deans of Agriculture
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