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Science backs climate-change lambing shift

By Sue Webster, SQNNSW Innovation Hub
27 July 2026

Central western Queensland sheep producers Peter and Kimble Thomas are trialling later joining to avoid heat stress impacts on reproduction – a move validated by recent research.

The Ilfracombe producers saw a 20% increase in lambing rates among 1,000 merino ewes that were lambed in September last year (2025), compared to the previous year’s drop.

This year, they are expanding the trial to 4,500 ewes joined over a five to six week period. Already, preg-testing has seen rates lift from an average 120% to up to 145%. Twinning rates have lifted from 20-30% to 41-50%.

The Thomases are changing their lambing to avoid heat loads of a longer, hotter spring, a move validated from research at Adelaide University, and by University of Southern Queensland earth scientist Dr Mahdiyeh (Maddy) Razeghi, whose work with Desert Channels Queensland interrogated local climate data.

Peter said last season’s September lambs had good survival rates. “They just seemed a lot healthier,” he said. “We aimed for a gestation over the cooler months. Research suggests lamb birth weights are compromised due to excess heat stress over pregnancy. We are trialling moving our flock’s reproduction cycle away from the summer months.

“We’re certainly getting a lot more pregnancies. The compromise to the change is that we are lambing into our poorer pasture conditions.”

Lambing outside optimal pasture conditions has required supplementary feeding. Peter and Kimble are using a grain-based blend of sorghum, barley and faba beans.

“Yes, it increased the feed bill, but that’s why we’re trialling it,” he said. “We believe we can keep on top of things by having a tighter lambing interval, a second scanning and earlier weaning.”

He added that earlier weaning should also boost ewe condition scores, which could also benefit future fecundity.

Producing lamb in this summer-dominant rainfall zone, in country where temperatures are regularly high, requires adaptability, he said. “Dr Razeghi’s weather observations would suggest that the summer period is getting longer, which creates challenges to grazing animal performance,” he said.

The UniSQ researcher analysed 50 years of Bureau of Meteorology (BoM) weather data for eight key towns in western Queensland: Boulia, Longreach, Barcaldine, Tambo, Birdsville, Blackall, Winton and Windorah.

Maddy looked at temperature, the number of hot days and cool nights, the timing of rainfall and the impact on evaporation.

Her update of the climatic conditions revealed more daytime heat, fewer cool nights and a definite shifting in the seasons - specifically in relation to rainfall timing.

“In some of the towns we can see that the summer is getting longer and spring is getting hotter,” she said.

Her findings validate the observations among locals. “It aligns with the local knowledge, which will help producers adapt. They have to change their practices to adapt with the heat in the spring, and the reduced rainfall.”

Replacing guesswork with science is satisfying, she said. “What makes me personally happy is that the science here is backing the deep local knowledge that landholders have.

“What we're doing is backing their story, backing their guesses, backing their explanation about their land, with hard science. That's the beauty of this work.”

The results of her work was presented in a range of recent workshops across central western Queensland, attended by more than 50 producers. Maddy said the effect of a changing climate on surface and groundwater supplies was uppermost in the discussions.

“That’s something they said is absolutely important to them,” she said. “Wet season variation was discussed, based on what the data shows for each town. Again, the findings aligned with their observations.”

Her work was funded by Desert Channels Queensland, the Rural Economies Centre of Excellence, the Remote Area Planning & Development Board, UniSQ and Southern Queensland and Northern NSW Innovation Hub.

Hub director Bruce McConnell said there was already spin-off research underway. “Scientists here at the UniSQ are looking at accumulated heat load on livestock. With the shoulder periods of autumn and spring increasing, and not having cooler nights to recover, livestock start accumulating heat stress over time,” he said.

More broadly, he explained the drought hub’s role in extending and adopting university research: “To help producers get access to this science, to actually make the changes on the ground to handle the next drought.

“It's an investment in drought mitigation and drought resilience, rather than waiting for a crisis to happen.”

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SQNNSW Innovation Hub Media & Communications Manager Lisa Yorkston: via email or 0427 076 446. 

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The SQNNSW Innovation Hub receives funding from the Australian Government’s Future Drought Fund.

Posted: 27 July 2026