Excess temperatures cause low flocking concerns in sheep

climate change sheep fertility
Photo: elemery 123rf

High temperatures during critical periods of the reproductive cycle of sheep result in 2.1 million fewer lambs produced in Australia each year, costing sheep farmers an estimated $97 million annually.

The work, conducted by a transdisciplinary team of researchers from the University of Adelaide and South Australian Research Development Institute (SARDI), found that days above 32°C during the week of mating caused the significant loss of potential lambs.

Published in Nature Food, the study found annual losses of potential lambs would increase to 2.5 million if median global warming increased by 1°C, and 3.3 million if it increased by 3°C.

“This modelling is important as it demonstrates that heat events threaten the sustainability of sheep production, both within Australia and globally,” study leader A/ Prof William van Wettere said.

Not only does heat stress decrease the number of lambs born, but it can also reduce lamb birthweight by between 0.6-1.4kg.

“If the effects of birthweight are accounted for, economic losses could increase to $168 million under our current climate, and $203 million and $278 million for the 1°C and 3°C temperature scenarios, respectively,” A/Prof van Wettere said.

The research—informed by climate data and modelling—showed many sheep are not able to thermoregulate during periods of heat, leading to effects on the animal’s fertility.

But the researchers have identified readily available strategies to improve thermoregulation and improve sheep fertility during summer, for example, a tool that has been developed that producers can use to understand and quantify the impact of heat stress on fertility of their flock.

The researchers are now investigating whether selectively breeding animals who thermoregulate more effectively can improve the climate resilience of sheep flocks, and how sheep thermoregulation and behaviour affect fertility during periods of heat.

“We are interested to know whether sheep who seek shade or those who are more active during periods of heat are impacted differently,” A/Prof van Wettere said.

“Ultimately, we seek to provide sheep farmers with strategies which they can easily implement to safeguard their enterprise from the impacts of current and future climate.”

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