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Supplementation to reduce the impact of mycotoxins and insufficient magnesium

Did you know there are no significant impacts of potassium or crude protein on magnesium absorption in grassfed cattle?

Project start date: 21 March 2017
Project end date: 31 August 2020
Publication date: 18 September 2020
Livestock species: Grassfed cattle
Relevant regions: Victoria, South Australia, Northern Territory, Tasmania
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Download Appendix (0.7 MB)


In southern Australian grassfed beef systems, dark cutting is a major cause of carcase non-compliance with Meat Standards Australia guidelines and is caused by low muscle glycogen levels at slaughter. Low muscle glycogen levels are negatively affected by a lack of magnesium absorption or ingestion of mycotoxins in pastures. 

This project studied the impacts of varying levels of potassium (K) and crude protein on muscle glycogen, as well as the effect of magnesium and mycotoxin binder supplementation on the prevalence of dark cutting. 

While there were no significant impacts of K or crude protein on magnesium absorption, magnesium supplementation was recommended in circumstances where pasture magnesium levels are low, rumen flow rates are high, or total dry matter intake levels are insufficient.


The main aims of this project were to determine the impact of:

  • varying levels of crude protein and K on glycogen
  • magnesium supplementation on dark cutting incidence
  • mycotoxin binder supplementation on dark cutting incidence.

Key findings

  • This project has provided additional knowledge towards the understanding of nutritional factors and their effect on the incidence of dark cutting in grazing beef enterprises in southern Australia.
  • Varying levels of K and crude protein did not appear to impact muscle glycogen stores in the grassfed cattle.
  • Magnesium supplementation was only effective in increasing muscle glycogen when magnesium absorption was limiting.

Benefits to industry

The results of this project highlights the importance of maximising pasture intake or replacing pasture with hay to provide the best chance of ensuring adequate magnesium intake through the growing season, not just to prevent dark cutting, but for a range of other benefits that magnesium provides.

MLA action

The outcomes of this project are being used to prepare ‘Tips n Tools’ (see Appendix) for distribution to producers and promotion through print and electronic media. MLA’s Edge and Profitable Grazing Systems programs will be reviewed to include some of the key findings of this research.

More information

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Primary researcher: University of New England