Mycotoxins

August, 2015
Aaron Stam, Ag/4H Extension Agent, Seminole Tribe of Florida

Mycotoxins are chemicals produced by fungi that typically have a negative effect on animals and humans. The term 'mycotoxin' is usually reserved for the toxic chemicals produced by fungi that readily colonize crops. One mold species may produce many different mycotoxins, and the same mycotoxin may be produced by several species, thus making the identification of mycotoxin sources somewhat complicated. Specific environmental conditions are needed for the formation of the fungi that produce mycotoxins, but even when those conditions exist, the fungi may not be present. It is thought that frost in South Florida is a limiting factor to the fungi. Mycotoxins are invisible, and require lab testing to determine their presence, and type. They have been grouped into several categories including: Deoxynivalenol, Zeralenone, Fumonisins, Aflatoxins, and Ochratoxins.

Mycotoxins are nothing new to dairy producers. They can sometimes be found in corn silage and other grains or silage fed to dairy cattle.  Effects of mycotoxins in dairies have been reduced feed intake, reduced milk and butterfat output, suppression of the immune system, decreased rumen efficiency, and increased disease susceptibility. Mycotoxins are also anti-microbial and can change microbial populations in the gut and rumen. Other effects include inflammation and damage to digestive tracts, scours, reduced nutrient absorption, and impaired metabolism. Infertility, cystic ovaries, poor conception rates, embryo loss and abortions have also been blamed on mycotoxins.

In European beef cattle research, scientists have found many similarities to problems of US dairy cattle. In beef cattle it is known that mycotoxins can increase incidence of disease and reduce production efficiency. In the field animals experiencing a mycotoxicosis may exhibit a few, or many of the following symptoms: digestive disorders, reduced feed consumption, poor weight gain, rough hair coat or abnormal hair conditions, undernourished appearance, impaired reproduction, and an increased chance of acquiring an infectious disease. Some of the symptoms observed with mycotoxicosis may be secondary, resulting from an opportunistic disease, which is present because of immune suppression. Therefore, the progression and diversity of symptoms are confusing and diagnosis is difficult. (Hesseltine, 1986, Schiefer, 1990)

Dr. Cynthia Gaskill and Dr. Michelle Arnold, University of Kentucky Veterinary Diagnostic Laboratory have concluded ruminants consuming aflatoxins may display the following:

1. Decreased performance-

    a. reduced appetite, reduced feed efficiency, reduced weight gain
    b. Reduced milk production and potential for illegal milk residues

2. Signs of Liver Damage-

    a. Increased hepatic enzymes and bilirubin on serum chemistries
    b. Prolonged clotting times (hemorrhage/nosebleeds)
    c. Icterus (jaundice)
    d. Neurologic signs including depression, lethargy, ataxia
    (staggering), circling, recumbancy

3. Reduced immune competence-

    a. Vaccine failure or poor antibiotic response
    b. Decreased cell-mediated immunity, cytokine production,
    and nonspecific humoral factors such as complement, interferon,
    and some bactericidal serum components.

4. Abortion …may cross placenta and cause damage to fetal tissue.

5. Death

Several mycotoxins have estrogenic effects; the most common of these is Zeralenone (ZEN). ZEN can lead to hyperestrogenism (a medical condition characterized by an excessive amount of estrogenic activity in the body). In swine symptoms include swollen vulva, while the gilt is not in heat, which can lead to vaginal prolapse. Often internally enlarged, swollen and distorted uteruses are observed. When male swine have been exposed to ZEN, symptoms of “feminization” have occurred, such as enlarged nipples, testicular atrophy and swollen foreskin of the penis (Newberne, 1987).  Many producers believe ZEN has similar effects on cattle, including abortions, uterine problems, and numerous other secondary issues.
Dairy heifers that were fed ZEN had a greatly reduced conception rate:
Virgin dairy heifers fed 250mg of purified ZEN for three estrous cycles had an average conception rate of 62%, compared with 87% in control heifers  (Diekman and Green 1992). Hyperestrogenism may also decrease the longevity of the cow.

Many believe there are mycotoxins present in South Florida pastures, but little has been done in the ways of researching these mycotoxins on standing/growing forage. Several producers believe they are seeing symptoms of mycotoxicity in their beef cattle here in South Florida therefore, laboratory testing of grasses for mycotoxins has begun.

Because of the environmental variations and conditions required to produce the fungi that create mycotoxins, periodic testing of forages will be required to check for mycotoxins. I took my first forage samples on July 24th, 2015 and  submitted them to several laboratories for testing.  At this time, the results have not yet been received. I will continue monthly testing to see if mycotoxins can be identified in South Florida forages.

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