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Sulphur for Sorghum

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. 

What is Prussic Acid?

Prussic Acid is hydrogen cyanide. Sorghum, silk sorghum and some woody plant species can accumulate cyanide within the plant. In the plant, cyanide naturally exists as part of plant compounds in a non-toxic form called cyanogenic glycosides. When plant cells are damaged, through chewing, trampling, freezing, heat stress or any other stress factors, the cyanogenic glycosides combine with a specific enzyme to product hydrogen cyanide. Prussic Acid is a potent fast acting poison which enters the blood stream and inhibits oxygen utilisation by the cells. In plan words, this causes the animal to suffocate from within the body. 


Factors influencing prussic acid levels 

  1. Stress – a plant that is under stress, particularly moisture stress, will have higher prussic acid causing compounds than plants that are not stressed, this is heightened again, if the plant in below 50cm tall. 
  2. Stage of growth – the level of prussic acid decreases as the plant matures, plants 0.8-1m have a significant lower risk of prussic acid, provided the plant is not stressed. 
  3. Sorghum type – different types of sorghum species have different prussic acid levels. Sudan grasses are considered to have low levels, whereas sweet sorghums and grain sorghums have high levels of compounds that contribute to the production of prussic acid. 
  4. Soil nutrients – high nitrogen level within the plant can increase the prussic acid content, as can low soil phosphorus levels.

Symptoms of Prussic Acid poisoning

There are key symptoms of prussic acid poisoning, however it is always advised to get a diagnosis from a registered veterinarian. 


Key symptoms include; 

  • Muscle trembling 
  • Staggers
  • Deep and rapid breathing 
  • Frothing from the mouth 
  • Gasping respiration


Collapse, coma and death may occur in extreme cases. Cattle have the ability to detoxify prussic acid with the correct nutritional supplements. 

Preventing Prussic Acid poisoning

Prevention is King! Management and nutrition of the plant and animal are key to preventing prussic acid poisoning. Recommended grazing management strategies for forage sorghum are; 


  1. SULPHUR – Supplementary Sulphur is a must when grazing forage sorghum. More detail about sulphur supplements are in the next section 
  2. Plant height – plants should be above 80cm tall for grazing. 
  3. Stock condition – stock should not be starving or hungry prior to grazing forage sorghum crops. Making sure cattle are full of supplement dry feed before introducing to forage sorghum crops helps lower the incidence of prussic acid poisoning at first introduction. 
  4. Salt – all forage sorghum varieties are low in salt, animals that have a supplement containing salt will perform better. 

Sulphur Supplementation 

Feeding a product high in sulphur, like Nutramix’s Forage promix, is a simple and effective way to supply sulphur to cattle that are grazing forage sorghum crops. When stock are grazing forage sorghum, particularly as the sole source of feed, they will become sulphur deficient due to the increased use of sulphur within the body and forage sorghums being typically low in sulphur. The significant effects of prussic acid may not be the obvious signs of sulphur deficiency, however loss in weight gains and poor animal performance are key indicators. Sulphur deficiency is exponential when prussic acid level is high. Sulphur is a key component in the prussic acid detoxification process within the animal. So long as the animal has an adequate sulphur intake, they can detoxify prussic acid.

Forage Promix

Nutramix’s Forage Promix, is the ideal supplement to aid in increase sulphur intake on forage crops this summer. Detoxify and increase production through the specifically design and formulate low consumption drylick. Suitable for all classes of livestock include sheep. With an unbeatable nutritional analysis, the Forage Promix is the only supplement any grazier should consider this forage feeding season.

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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
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.
a herd of cows standing in a dry grass field

Phosphorus for Profit

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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

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two cows grazing in a field one brown and one black

Are You Weaning Ready?

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a cow and calf standing in a grassy field

Kidman Springs Phosphorus Supplementation Trial Demonstrates > 300% ROI

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