Combating pimelea toxicity

Project update summary: Combating pimelea toxicity

  • To date, the most promising rumen fluid sample to overcome Pimelea toxicity, came from Dorper sheep. More rumen fluid samples are still to be tested.
  • 21 bacterial species have been isolated from the rumen fluid samples. The most promising of these are being tested for their ability to degrade the toxin in Pimelea, which is simplexin. Over time, the most promising bacterial species may be developed into a rumen inoculum (drench).
  • Rumen microbial diversity was similar between livestock affected and not affected by Pimelea toxicity. Feed supplements and licks had the greatest effect on rumen microbe diversity. • Laboratory trials showed sodium bentonite (Trufeed®) at a concentration of 12mg/ml was the most effective rumen adsorbent, binding 95 per cent of the simplexin toxin. 
  • Biodegradable biopolymer materials have been tested to develop a rumen bolus that could trickle feed small amounts of simplexin into the rumen. This would help sustain a small population of bacteria that could degrade the simplexin toxin, even when cattle are not grazing on Pimelea plants. To date, the most promising bolus is a polyhydroxyalkanaoate (PHA)/Pimelea/sugar mixture. The next step is to test the biodegradability of the bolus (without the Pimelea toxin included) in live, fistulated cattle. Animal ethics approval has been obtained. Rumen boluses may also have a role in slow-release drug delivery.
Diane Ouwerkerk from the Department of Agriculture and Fisheries (DAF) with the artificial rumen at Ecosciences laboratory in Brisbane where field-collected rumen fluid samples are tested for ability to breakdown Pimelea plant material and degrade the simplexin toxin.


Producer pledges of cash and in-kind support in 2017 and 2018 with matching funds from Meat and Livestock Australia’s MLA Donor Company highlighted the the importance of addressing the severe impact of Pimelea to the cattle industry across inland Australia. This initial project enabled collection of 110 rumen fluid samples from affected and non-affected cattle and other ruminants (goats, sheep and kangaroos). These timely rumen samples are the basis of the ongoing research into a rumen drench. In 2019, MLA invested $1.5million of producer levy funds into toxic plant research, with combating Pimelea toxicity as a first priority. No further call-in of producer pledges was required with this significant injection of research funding from MLA for a three-year period. Researchers Associate Professor Mary Fletcher (QAAFI) and Diane Ouwerkerk (DAF) send progress reports to MLA throughout the project. The following is a research project update showing the 2019 results from the MLA project milestone report and proposed on-going research.


Associate Professor Mary Fletcher,
Principal Research Fellow,
Centre for Animal Science,
Queensland Alliance for Agriculture and Food Innovation,
The University of Queensland.
T: +61 7 344 32479
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