High oestrogenic clovers may be playing havoc in sheep production systems and some producers may not even know it.
With the potential to cause infertility, birthing problems and urethral blockages, high oestrogenic clovers are an issue many older farmers are familiar with but some younger farmers may not have ever heard of before.
To help create awareness of such clovers with the new generation of farmers, the Mackillop Farm Management group approached Agriculture Kangaroo Island to partner in applying for funding under Meat and Livestock Australia’s Producer Demonstration Site program and was successful.
The Good Clover, Bad Clover project, supported with co-funding from Sheep Connect SA and Natural Resources South East, started in April 2017 and will continue to run for three years.
Primary Industries and Regions SA livestock consultant Tiffany Bennett said the project aims to create producer awareness of potential issues and management strategies to deal with oestrogenic clover through coaching producers from 10 focus farms.
At the beginning, 160 producers were surveyed with the majority unaware of the presence of oestrogenic clover and not confident in identifying such clovers.
“Some 85 per cent of producers had never undertaken visual or laboratory analysis of their paddocks. Since, visual assessment and laboratory tests have been undertaken from 25 paddocks across 10 properties in south east SA and Kangaroo Island,” she said.
“Of the 25 paddocks, 20 paddocks had greater than 20pc oestrogenic clover present in the clover portion of the paddock.
“Of the 20 paddocks, 50 pc had the potential to cause fertility issues in ewes with visual assessments ranking them moderate to high.”
Ms Bennett said the high oestrogen levels was a trait of the early varieties of sub clover including Dinninup, Dwalganup, Yarloop and Geraldton, but the rest were considered safe.
“The four problematic varieties were sown up until the 1980s. New varieties have been developed but the old varieties persist due to large seed banks and hard seediness,” she said.
“They are identified using leaf markings, assessing the runner to determine if it is hairy or hairless and the calyx colour. A laboratory test is also available that measures the isoflavones on the plant which is the compound responsible for oestrogenicity of the clover.”
Isoflavones have an effect on sheep similar to that of natural oestrogen. “Clovers have higher levels of isoflavones when the plant material is green and actively growing. As the plant senesces and dies off, the level of isoflavones in the plant decreases,” she said.
“Silage and hay can have high levels. A silage sample taken in the project reported an isoflavones level of 6280 mg/kg and the threshold is 1000mg/kg at which fertility issues are likely to occur.”
Symptoms include lowered ewe fertility, increased difficult births, prolapse of the uterus, udder development in maiden ewes and wethers and urethral blockages in wethers.
Grazing impact costly
Primary Industries and Regions South Australia livestock consultant Tiffany Bennett said, from an industry perspective, it was difficult to know how widespread the issue of high oestrogenic clovers was.
“As a result of the project we have been contacted by many producers from other areas in SA such as the Barossa Valley, Adelaide Hills and Mid North with the presence of oestrogenic clovers confirmed,” she said.
“Knowing if the clovers are present on producers’ properties and how prevalent they are may highlight reasons for lost reproductive performance within their sheep flocks which will be affecting profitability.”
Paddocks with 20 per cent or greater oestrogenic clovers present are considered problematic, but Ms Bennett said they were difficult to eradicate and managing them through strategic grazing and agronomic strategies was most feasible.
“Grazing management includes grazing high risk paddocks with cattle or terminal lambs and not grazing high risk paddocks until they have senesced,” she said.
“Minerals will make little difference. Supplementary feed can help reduce the intake of the clover varieties, however this would not be the most cost effective strategy.”
Ms Bennett said if producers identify oestrogenic clovers in their system they should undertake a whole farm assessment to determine the risk the paddock with oestrogenic clovers pose.