High Temps + Drought = Aflatoxins

By Pat Hoffmann, DVM – Director of Health and Biosecurity

Email phoffmann@genesus.com

Prolonged high temperatures and record drought conditions for much of this year’s US Corn Belt have made it possible for the corn crop to already be stressed and subject to aflatoxin.  As many know we are already starting to hear a lot around the swine industry about these potent mycotoxins.

Aflatoxin is a toxin produced by the fungi Aspergillus and Penicillium.  Four major toxins are produced (B1, B2, G1, G2). Toxin B1 is of greatest significance but all toxins are potent hepatotoxins. There are age-related differences because, like most other toxins, effects are dose-dependent on body size and composition. This results in young nursing or weaned pigs to be most susceptible. When the toxin is ingested by lactating sows and gilts the metabolites are passed on to the offspring via the milk.

Aflatoxins are not affected by heat, cold, or light.  They are also colorless, odorless and tasteless.  Detecting them in grain is often difficult because of the low concentrations and uneven distribution within grain bins.  The more grain is moved the more accurate the testing. Testing from field to the bin is problematic.

Clinical effects of the toxins include reduced feed intake, average daily gain, and feed efficiency.  The toxin is also immunosuppressive. Thus, a common sign of aflatoxicosis can often include an increase in prevalence of previously controlled secondary diseases.

Most disease is sub-acute or chronic due to daily ingestion of smaller amounts over time.  Signs of chronic aflatoxicosis damaging the liver include a reduction in overall size, fibrosis or scarring, and ascites.  This pathogenesis is called cirrhosis.

Ingestion of a large amount of aflatoxin causing acute disease can manifest as sudden death, excessive bleeding or hemorrhaging, and icterus.  In this case the liver may be swollen, fatty, and areas of necrosis (premature cell death).

Clinically diagnosing aflatoxicosis is often difficult due to the variation in clinical signs and gross lesions.  Secondary infections elevate the difficulty.  However, submitting feed samples and liver biopsies are the initial steps to a diagnosis.  The prognosis of swine already showing clinical signs is usually poor but is dependent on the severity of liver damage.

The distillation process in ethanol production can concentrate the toxins 3X in DDGS. Increased use of DDGS in swine diets could potentially lead to an increased incidence of aflatoxicosis.

In summary, aflatoxicosis is a disease associated with decreased feed intake, reduced average daily gain, and impaired liver function. These conditions are often seen in conjunction with an increase in secondary diseases. Aflatoxin is also considered carcinogenic in humans.

Contributions to this article were made by:
  • Dr. Steve Ensley, Veterinary Toxicologist, Iowa State University
  • Swine Disease Manual, 4th Ed. E.J. Neuman, A. Ramirez, and K.J. Schwartz, 2009

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This post was written by Genesus