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Warning to watch for oestrogenic subclover

16 July 2021


As spring approaches and sub-clover pastures reach maximum growth rates, producers are encouraged to look out for high oestrogen sub-clovers in pastures grazed by sheep to protect the health of their mob.

High oestrogen sub-clover: the problem

Sub-clovers with high levels of oestrogen can negatively affect sheep reproductive health. These pastures have been linked to increased rates of infertility, stillbirths and uterine prolapse in ewes, as well as increased lamb mortality.

High oestrogen sub-clovers are still commonly found in pastures throughout southern Australia. Around 20-25% of all pastures surveyed contained or were dominated by these old clover cultivars, including:

  • Yarloop
  • Dwalganup
  • Geraldton

The impact of these clovers on productivity is significant. Up to 8-10 million ewes in Australia are potentially affected by high oestrogen sub-clovers.

Raising awareness, lowering losses

To combat lamb losses due to these clovers, Meat & Livestock Australia (MLA) has conducted an extension-focused project in conjunction with the University of Western Australia (UWA). The focus of the project has been on raising awareness of the issue amongst sheep producers and consultants and providing training and information resources on the identification and management of high oestrogen sub-clovers in pastures.

As part of the campaign, a range of talks, industry forums, webinars and field days were hosted to engage over 1,000 producers and industry representatives to raise awareness of the risks of high oestrogen sub-clovers and to provide effective strategies to identify and manage these pastures.

Hundreds of free pasture sampling kits were also distributed as part of the campaign to enable producers to test pastures for the presence of high oestrogen sub-clovers. The kits also included a range of tools and resources to assist with pasture remediation if oestrogenic clover was detected.

Project impact

UWA’s Kevin Foster, who led the initiative, said that the project had been effective in raising awareness around the impact of oestrogenic clover on sheep reproductive health.

“Unfortunately, over the last few decades, there’s been a loss of industry and corporate knowledge around high oestrogen sub-clovers and how these can be managed,” Kevin said.

“High oestrogen sub-clover is still a huge factor in reproductive wastage in sheep in Australia – it’s just that we’ve lost the knowledge on how to identify these clovers and what impact oestrogenic clovers can have on the sheep.”

“So far, this project has been about advising producers, agronomists and consultants that oestrogenic clovers are still a significant factor in reproductive wastage in many sheep areas in Australia – and we’ve done that very well.”

“There’s been a major shift now in understanding among these groups and also with veterinarians on what the implications of oestrogenic clover are and the knowledge around how to identify it as a result of the project,” he said.

Time to check your pastures

MLA Program Manager – Sheep and Goat Productivity, Joe Gebbels, also affirmed the importance of managing high oestrogen sub-clovers to increase lambing and lamb survival rates.

“It’s been a great start to the season across much of southern Australia and with the high value of an additional lamb, don’t let oestrogenic clovers hold you back,” Joe said.

“Hard seeded oestrogenic clovers can persist over long periods and the good start to the season can see them increase quickly, reducing flock reproductive performance.”

“Understanding the prevalence of oestrogenic clovers on your farm and implementing a tailored approach to managing oestrogenic pastures is the key to ensuring your flock reproductive performance isn’t compromised.”