ISSN 2398-2993      



Mike Reynolds

Nicola Bates

Synonym(s): Mycotoxin poisoning, Ryegrass staggers, Aflatoxicosis, Ergotism, Facial eczema, Slobbers, Fescue foot


  • Mycotoxicoses are diseases caused by secondary toxic metabolites produced by molds.
  • Cause: important mycotoxin-producing molds, include Penicillium spp, Claviceps spp, Phomopsis leptostromiformis, Rhizoctonia leguminicola.
  • Signs: vary depending on toxin and species. Mycotoxins affect almost all organ systems. Ergot and some Penicillium spp produce indole tremorgens which affect the nervous system.
  • Diagnosis: difficult. Mycotoxin isolation from feed, clinical signs and history, feeding trials.
  • Treatment: removal of toxin source; supportive therapy.
  • Prognosis: depends on toxin, dose and clinical course.



  • Mycotoxins are diverse, secondary toxic metabolites produced by molds, especially Aspergillus spp, Penicillium spp (aflatoxins, ochratoxins) and Fusarium spp (fumonisins).
  • Clinical signs are due to the action of these mycotoxins and not fungal growth or allergic reactions to foreign proteins within the affected animal.

Predisposing factors


  • Spoilage of feedstuff by fungi.
  • Depends on moisture content, viability, physical state of grain and insect activity.
  • Seasonal.
  • Climatic conditions.
  • TMR feeding may precipitate mycotoxins being widely disseminated to a greater number of animals.


  • Field fungi: grow under conditions prior to harvest, eg Fusarium spp, require relative humidity above 90%.
  • Storage fungi, eg Aspergillus spp, especially in leaky containers or after long periods of storage.
  • Note that this division of field and storage molds is not distinct, and some fungal species can affect feed under both field and storage conditions.


  • Ruminants are relatively resistant to mycotoxins but detoxification by rumen bacteria may be overwhelmed, and the risk of toxic effects is increased if multiple mycotoxins with synergistic effects are involved. 
  • Mycotoxins affect metabolic and anabolic processes in various organ systems.
  • Four general mechanisms affect carbohydrate metabolism, mitochondrial function, lipid metabolism or nucleic acid function and protein biosynthesis.
  • Mycotoxins may affect a variety of cellular processes.
  • May require activation by biotransformation.

Disruption of mitochondrial function

  • Aflatoxins, ochratoxins, rubratoxin.
  • Inhibit electron transport and uncouple oxidative phosphorylation.

Altered lipid metabolism

  • Reduced fatty acid and cholesterol biosynthesis.
  • Impaired lipid transport.
  • Disruption of sphingolipid metabolism (fumonisins).

Altered nucleic acid function and protein synthesis

  • Aflatoxin, trichothecenes.
  • Modification of DNA, inhibition of RNA polymerase, increased RNA breakdown.

Affect on carbohydrate metabolism

  • Aflatoxins, ochratoxin A, rubratoxin B, cyclochlorotine and citreoviridin.
  • Inhibit biosynthetic enzymes such as glycogen synthetase and increasing the activity of enzymes metabolizing glycogen precursors resulting in reduced hepatic glycogen and increased blood glucose concentrations.

Other mechanisms

  • Ergotism Ergotism and fescue foot Distal limb necrosis: the ergopeptine alkaloids inhibit D1-dopaminergic receptors and are partial agonists of alpha-1 adrenergic and serotonin receptors, resulting in vasoconstriction.
  • Slaframine: acts as a parasympathomimetic agent and stimulates exocrine and endocrine glands, particularly the salivary glands and pancreas.
  • Sporidesmin: undergoes cyclic reduction/auto-oxidation to produce superoxide radicals which cause tissue damage.


  • May be acute or chronic.


  • Not transmissible between animals.
  • Common source outbreaks.
  • Association with a particular feedstuff or spoilage of a particular feed source.
  • Field outbreaks seasonal and associated with particular climatic patterns.
  • May be difficult or impossible to identify cause.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Becker-Algeri T A, Castagnaro D, de Bortoli K, de Souza C, Drunkler D A & Badiale-Furlong E (2016) Mycotoxins in bovine milk and dairy products: A review. J Food Sci 81 (3), R544-52 PubMed.
  • Rodrigues I (2014) A review of the effects of mycotoxins in dairy ruminants. Animal Prod Sci 54 (9), 1155-1165 VetMedResource.
  • Johnstone L K, Mayhew I G & Fletcher L R (2012) Clinical expression of loitrem B (perennial ryegrass) intoxication in horses. Equine Vet J 44 (3), 304-309 PubMed.
  • Fink-Gremmels J (2008) Mycotoxins in cattle feeds and carry-over to dairy milk: a review. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 25 (2), 172-80 PubMed.
  • Hasso S A (2003) Non-fatal aflatoxicosis in Arabian horses in Iraq. Vet Rec 24 (152), 657-658 PubMed.
  • Lebars J & Lebars P (1996) Recent acute and subacute mycotoxicoses recognized in France. Vet Res 27 (4-5), 383-394 PubMed.
  • Diaz G J & Boermans H J (1994) Fumonisin toxicosis in domestic animals - a review. Vet Human Toxicol 36 (6), 548-555 PubMed.

Other sources of information

  • Kolosova A & Stroka J (2012) Evaluation of the Effect of Mycotoxin Binders in Animal Feed on the Analytical Performance of Standardised Methods for the Determination of Mycotocins in Feed. In: Food Additives & Contaminants: Part AResearchgate.
  • Plumlee K H (2004) Ed. Mycotoxins. In: Clinical Veterinary Toxicology. Mosby, USA. pp 231-281.
  • Willey T D & Morehouse L G (1978) Eds. Mycotoxicoses in Cattle. In: Mycotoxic Fungi, Mycotoxins and Mycotoxicosis. An Encyclopedic Handbook. Volume 2. Marcel Dekker Inc, USA. pp 9-171.

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