Oestrogenic clovers remain a potential threat to lambing percentages on many farms, according to Rural Solutions SA livestock consultant Tiffany Bennett.
During the past year, the Good Clover, Bad Clover project found 40 per cent of the 25 paddocks assessed on 10 farms in the South East and Kangaroo Island had subterranean clover cultivars with high enough phytoestrogen concentrations to cause ewe fertility issues.
The four main problem cultivars – Yarloop, Dinninup, Dwalganup and Geraldton – have not been sown since the 1960s, but due to their hard seededness have persisted.
When the pasture stand is green the levels of isoflavones, diadzein and formononetin, are most potent and as the plant senesces (browns off) they break down.
Temporary infertility can occur in those ewes exposed at mating, or within six weeks of mating, but this can become permanent in ewes grazing oestrogenic pastures for two to three years.
A higher than normal incidence of difficult births can also occur in affected flocks.
Ms Bennett says the project has shone a light on a “forgotten problem”.
“It is more than 30 years since work was done so we now have a whole generation with a gap in identifying these clovers,” she said.
“Many high-risk paddocks are productive and finish lambs well so haven’t been renovated but as the next generation have taken over they have not had the experience with the issues that occur with oestrogenic clovers and many of the symptoms in sheep are being attributed to other issues.”
The project, managed by Mackillop Farm Management Group and Agriculture KI, found 10 of the 25 paddocks had the potential to cause fertility issues in ewes and 20 of the 25 had high concentrations greater than 20pc.
Ms Bennett says it is critical producers can identify the clover cultivars in their paddocks.
The best way to do this was through the leaf markings, the hairiness of the runner and the colour of the calyx, below the petals in the flower.
A laboratory analysis was also available to measure the phytoestrogen levels, with previous studies showing the threshold for fertility issues is less than 1000 milligrams a kilogram.
For an accurate result she said the sample should contain at least 40 leaves from across a paddock.
The next step of the Good Clover, Bad Clover project will be to implement a whole farm management plan with the 10 focus farms and follow the results through to scanning and lambing.
“We are not seeing the 30-40pc lambings reported years ago but there is a potential economic loss,” she said.
Dry sheep can also be affected by oestrogenic clovers with udder development and enlarged bulbourethral glands in wethers.
The project is funded by Meat & Livestock Australia, Sheep Connect SA and Natural Resources South East.
