Blog Layout

Understanding and mitigating the risks of Pimelea.

With the perfect storm of events this winter, the pimelea growth has skyrocketed. Like the conditions seen in 2021 and 2022, late winter rainfall, followed by cold weather and limited tropical pasture growth has resulted in increased pimelea growth. 



Pimelea is a native plant to Australia and New Zealand, with 150 identified species, of 110 are endemic to Australia. Of the species found around Australia, a small number (4) are associated with poisoning in cattle. 

  • P. elongata
  • P. simplex subsp. continua
  • P. simplex subsp. simplex 
  • P. trichostachya

Figure 1. Pimelea plant species commonly found in QLD, NSW and SA. a) P. simplex subsp. simplex, (b) P. trichostachya and (c) P. elongata (source: Poisonous Plants of the Genus Pimelea: A Menace for the Australian Livestock Industry. Toxins 2023, 15, 374.)

All these plants are considered toxic to cattle and contain the toxic secondary metabolite simplexin. Cattle being the most susceptible to the toxic effects of simplexin, exhibiting distinct symptoms that often lead to long term affects and death in extreme cases. Current suggested management options of livestock include, providing feed supplementation, restricting access to infested pastures and the use of herbicides to reduce spread. Much of this advice is easier said than done, with producers needing to continue to utilise land, feed and input costs already being high and herbicides over large land parcels being too costly. 

Preferred Habitat & Environmental requirements 

As mentioned above, pimelea needs a perfect storm to flourish. All four poisonous species and sub species are annuals and require a specific set of conditions to grow. As a spring flowering plant, they grow well in winter following rainfall and dry summers suppress establishment. The plants abundance depends on the prevailing conditions and can be influenced by the intensity of inter and intra specific competition. Inter- and intra- specific competition refers to the competition for resources between individuals of different species (interspecific) and individuals of the same species (intraspecific). 

Timing of Outbreaks

The conditions that favour outbreaks of poisoning include low summer rain in the previous year 

  • Good autumn and early winter rain
  • Low spring/summer rain with a feed shortage 
  • Land with little perennial pasture either due to:
  • The nature of the land system
  • Insufficient summer rain to support perennial grasses, 
  • Past or present grazing practices.
  • Careful inspection is required following any rain fall of over 20mm in coolers times and 50mm in autumn and spring. 

Poison Action

The toxic component of Pimelea, simplexin, is considered a hydrocarbon fat, similar to fatty acids found widely within the body and other plant materials. Plants naturally synthesis and accumulate secondary metabolites (essential stress response) for a variety of different purposes, often attributed to survival. 



“The does that makes the poison” (Paracelsus 1493-1541), is a phase attributed to many toxic effects of compounds in the world. This phrase also applies to the toxic effects of Pimelea. It is regardless of the plant and/or the toxin’s abundance or distribution, it is the quantity of the intake and absorption that effects the animal. Simplexin toxin is highest in green and growing plants, however due to the smell of the green plant, stock generally avoid it. 

Signs of Pimelea Poisoning 

Pimelea poisoning shows in three types of symptoms

  • Fluid swellings often under the jaw, down the neck, brisket and can extend under the belly
  • Diarrhoea, dark foul smelling and sometimes contains blood 
  • Weight loss
  • Distended jugular veins with prominent pulse 
  • Pale mucus membranes 
  • Breathing difficulties 
  • Reluctance to move 
  • Decreased appetite 
  • Depression 
  • Becoming easily agitated and aggressive 


There are comments from many producers, that certain categories of stock are more susceptible than others. In general, all stock are susceptible to poisoning, dependent on intake irrespective of breed, sex and age. Cattle aged between 18-24 months were most affected as were cows, bulls and heifers. Steers and bullocks seem to be less susceptible, possibly due to producers growing these classes of stock on different country types for improved weight gains. Home bred stock usually avoid areas of high growth, especially when green. This could explain why stock are introduced into pimelea infested areas are more likely to show symptoms when compared to home bred animals. 


Supplementation with sulphur and urea have also ben reported as a tool for decreasing the impact of poisoning. This may be due to the increase protein intake, improving rumen function and increasing rumen passage rate, which may reduce time of absorption in the gut.

Treatment and Prevention 

There is currently no scientifically proven cure for pimelea poisoning. With no immune response triggered and no development of antibodies there is little evidence to suggest an antibiotic, antiviral or vaccine will be a viable treatment and prevention option. 


The QAAFI have been conducting many trials and in vitro research into different techniques for managing and preventing pimelea poisoning. 



A promising trail using different toxin absorbents has led to good results. The most effective binder was sodium bentonite at 12mg/ml, which bound 95% of the simplexin toxin. Both sodium and calcium bentonite remained bound to the toxin for the longest period. 

Reference: Gordon R, Hungerford N, Laycock B, Ouwerkerk D, Fletcher M. 2019. Adsorbents for the sequestration of the Pimelea toxin, simplexin. Poster 352 at the Northern Beef Research Update Conference, Brisbane, 2019 http://www.nabrc.com.au/wp-content/uploads/2019/09/NBRUC-Conference-Proceedings.pdf.

Other research suggests the possibility of using a biodegradable biopolymer as a rumen bolus to continually stimulate to production and proliferation of rumen bacteria that may detoxify the toxin. 


Although the recent wet weather has been welcomed by most, in some areas it has resulted in an unwelcome outbreak of the Toxic Pimelea Plant. 



Ask our friendly staff about our supplement range that can help mitigate the risks associated with Pimelea and reduce its toxicity.


References 

Fletcher, M.; Silcock, R.; Ossedryver, S.; Milson, J.; Chow, S. Understanding Pimelea Poisoning of Cattle. Department of Employment, Economic Development and Innovation, Brisbane, QLD, Australia. 2009. Available online: https://futurebeef.com.au/wp-content/uploads/2011/09/Understanding_pimelea_poisoning_of_cattle.pdf (accessed on 11 April 2023).


Gordon, R. J., Hungerford, N. L., Laycock, B., & Fletcher, M. T. (2020). A review on Pimelea poisoning of livestock. Toxicon, 186, 46-57.


Saleem, R., Bajwa, A. A., Campbell, S., Fletcher, M. T., Kalaipandian, S., & Adkins, S. W. (2023). Poisonous Plants of the Genus Pimelea: A Menace for the Australian Livestock Industry. Toxins, 15(6), 374.


Saleem, R. (2022). Germination triggers, persistence, and management of Pimelea trichostachya Lindl. in Queensland.

How Mineral Nutrition Impacts Health and Reproduction in Beef Herds

September 18, 2024
Trace minerals are vital to the reproductive performance of Beef herds. So even though they are a small inclusion into the diet of cattle herds, minerals pack a big punch, with deficiencies causing a reduction in production of up to 20-30%.
A herd of brown cows standing in a field looking at the camera

Protein for Pastures

April 18, 2024
Widespread summer rainfall has created a great pasture base for many producers going into winter. While this pasture base allows our producers to reduce the need to purchase hay or substitute feed, the quality of the pasture in winter will decline and will become a limiting factor to production. Understanding that diet quality effects passage rate in the rumen and therefore pasture intake is key to creating an effective supplement program, particularly during winter. Pasture quantity and quality are key drivers of production. As the winter months creep forward, nutrient density in pastures change, primarily associated with plant maturity. As grasses reach maturity, phase 4 or when seed head has lost all seeds, these plants are both low in protein and energy. During this time, it is important to assess grasses and provide stock with adequate protein and energy to prevent weight loss and maintain production. As plants mature and become more lignified, they become harder to digest. Due to this reduction in digestibility of plants, the movement in the rumen in slower and ‘gut fill’ increases. As a result, the animal is unable to consume the required pasture intake to meet daily requirements. Typically, tropical grasses, during winter have a Crude protein and metabolisable energy level of 6% and 5 MJ respectively. At this level, cattle cannot consume enough pasture to meet requirements, with particular emphasis on breeding stock with higher maintenance requirements due to pregnancy or lactation. Using supplements with high protein and mineral can allow cattle to digest dry pastures and provide supplementary protein for production.

Sulphur for Sorghum

February 21, 2024
Summer forage crops are a great source of feed and increases animal performance with excellent returns. As with other forage crops, the young green leaf and shoots of sorghum are the most digestible and initially have the highest feed value however sorghum has a toxic component in the plant when young, immature, and fast growing. Prussic acid poisoning has been recognised for many years in cattle grazing forage sorghum crops. There are many factors that influence the incidence of Prussic Acid poisoning, and the great news is, it’s preventable through management and nutritional supplements.
a herd of cows standing in a dry grass field

Phosphorus for Profit

May 5, 2023
Winter supplements in Northern Australia are focused towards supplying increased protein where grasses are lacking. This is by far one of the most important parts of supplements in winter and a key component of maintaining breeder weights or improving growing animal weight gains. One of the biggest myths is; “Cattle cannot absorb phosphorus during the dry season”, this simply is not true. The factor of the most limiting nutrient is the biggest determination of how well a nutrient is absorbed. Dry season supplements address protein and energy deficiencies, due to these nutrients being the most limiting in dry mature pastures. Once these issues have been addressed, other nutrients become limiting, and the need of these nutrients presents itself. Phosphorus in the dry season is the third most limiting nutrient so the need for phosphorus becomes apparent when protein and energy deficiencies are met through supplementation providing urea.

Mulga Supplementation

April 23, 2023
Mulga provides a valuable feed source for stock, particularly through dry periods or drought. Mulga land types extend over areas of New South Wales and Queensland rangelands covering an impressive 20% of Australia’s landmass. Mulga provides supplementary feed to low quality pasture due to the mulga leaf retaining its nutritive value where grasses energy and protein level decline as they mature and die off. It is always important to consider the nutritional requirements for your stock and how to best meet these requirements.  Important considerations when feeding mulga are the common deficiencies found in the plant and how supplements can counteract these problems and improve production. Stock can do very well on mulga; however, mulga has a low digestibility and much of the protein is bound by tannins.

Winter Protein Supplementation

April 4, 2023
Understanding that diet quality effects passage rate in the rumen and therefore pasture intake is key to creating an effective supplement program, particularly during winter. With the current season being drier than usual and many parts of Queensland and Northern New South Wales recording lower than average summer rain falls, it is time to start thinking about supplementation during Autumn and Winter. Pasture quantity and quality are key drivers of production. As the winter months creep forward, nutrient density in pastures change, primarily associated with plant maturity. As grasses reach maturity, phase 4 or when seed head has lost all seeds, these plants are both low in protein and energy. During this time, it is important to assess grasses and provide stock with adequate protein and energy to prevent weight loss and maintain production.  As plants mature and become more lignified, they become harder to digest. Due to this reduction in digestibility of plants, the movement in the rumen in slower and ‘gut fill’ increases. As a result, the animal is unable to consume the required pasture intake to meet daily requirements. Typically, tropical grasses, during winter have a Crude protein and metabolisable energy level of 6% and 5 MJ respectively. At this level, cattle can not consume enough pasture to meet requirements, with particular emphasis on breeding stock with higher maintenance requirements due to pregnancy or lactation.
two cows grazing in a field one brown and one black

Are You Weaning Ready?

March 29, 2023
Dry autumn forecast . The Bureau of Meteorology suggests that the coming months will be drier and hotter than usual across most of Australia from the recent long-term autumn 2023 forecast. Warmer than usual daytime temperatures and drier areas emerging in some parts of Southern Queensland and Northern New South Wales, weaning and early weaning supplement strategies may prove an advantage before winter descends.  Early weaning is often defined by weaning calves at a younger age than ‘normal’ practice. In Queensland, the ‘normal’ range of weaning is between 7-8 months, the range does extend either way dependent on environment. In extreme cases, early weaning (without milk replacer) can be performed safely and effectively down to 4-6 weeks of age, although calves that have reached 3-4 months are considerably easier to feed and manage. The main reason behind early weaning is the proactive management of breeding herds for improved productivity or due to feed scarcity. Pregnancy and lactation are a period in a cow’s reproductive cycle that causes extreme metabolic strain and can have drastic consequences on body condition, pregnancy rates, long term calf performance and possible deaths. The feed requirement for a cow with calf at foot are 50-65% higher than a dry cow, considerable damage to pastures can occur as a result of high forage demand. All calves are born with an underdeveloped rumen, and this continues to stay premature until calves come of an age where they start to forage. During the first few months, the rumen gradually develops, and rate of development depends on the nutrition, condition, and supply of milk from the cow and available feed in the paddock. Typically, calves can be functioning as normal ruminants between 3-6 months of age. Early weaned calves may not have a completely functioning rumen and most of their digestive tract functions largely like a monogastric animal (e.g., pigs), depending mainly on the abomasum and fourth stomach acting as the main digestive chambers. If a calf is old enough to be weaned from milk, a grain-based diet which can be readily digested should be provided as the main source of nutrition, as should hay/roughage to ensure the rumen continues to develop normally.
a cow and calf standing in a grassy field

Kidman Springs Phosphorus Supplementation Trial Demonstrates > 300% ROI

December 8, 2022
It is well documented that much of northern Australia is phosphorus (P) deficient and that P is required for almost every vital bodily function in cattle. However, supplement sales figures and industry feedback indicates that the majority of northern properties in P deficient areas are not supplementing their cattle with P over the wet season. Current thinking is that producers must not believe that they will get a good enough return feeding a P supplement to justify the expense and hassle of feeding supplement over the wet season. Past studies have shown that P supplementation increases growth, however, there have been few studies that have found a significant improvement in reproductive performance from P supplementation in northern Australia and quantified the benefit. This may be a reason why adoption has been so low.  A trial commenced in 2014 at the Victoria River Research Station, Kidman Springs, to quantify the benefits of P supplementation. This trial will provide producers in P deficient areas with definitive data on the effects of supplementing females with P so that they are able to make better informed supplementation decisions. Brahman heifers born in 2014 were randomly allocated to either a +P (where phosphorus was supplied in the supplement) or –P (where phosphorus was not included in the supplement) treatment and grazed in neighbouring paddocks that were tested as acutely P deficient. Treatments swap paddocks in May each year to minimise paddock effects. Treatments are managed exactly the same year round, with the exception that their loose lick supplements either contain P (+P) or do not (-P). Composition of lick fed to each treatment can be seen in Table 1. Note: Soil test Colwell P levels: Acutely deficient: ≤4mg P/kg | Deficient: 5mg P/kg | Marginal: 6-8mg P/kg

Mulga- Your Stock, Your Supplement - With Clynt Johnstone

December 8, 2022
Future Beef- Case study on the effectiveness of the right supplement on mulga country.

Pastures for Horses

December 8, 2022
DPI NSW- A good pasture will meet the nutritional needs of most horses including brood and lactating mares and growing foals, although working horses may require some supplementation.
More Posts
Share by: