Experts: Unique conditions have produced ‘perfect storm’ of mycotoxin concerns

March 01, 2017

The combination of a bumper fall crop and challenging winter weather conditions created a “perfect storm” for the production of mycotoxins this year, including some seldom seen in the U.S. and Canada. To discuss these issues NEOGEN recently hosted, “What’s Under the Tarp?,” a webinar where industry experts provided additional information and guidance.

Below are some of the main points the webinar covered, which included Dr. Gwendolyn Jones, head of product marketing for ANCO; Dr. Duarte Diaz, associate professor at the University of Arizona and Chuck Bird, NEOGEN’s international sales director.

Q1: What is the percent moisture that wheat, rye and soy should be dried to before storage?

A: Typically, we saw 14.5% for corn products, Dr. Duarte Diaz said. General practices for storage of grains indicate that they should be stored under 14-15% moisture to prevent fungal growth and deterioration. However, these values will depend on the type of mold and toxin being managed.

Less than 14% is a general guideline for most grains, he explained, but for high-risk commodities under heavy field infestation, such as wheat scabs appearing on wheat, it may be necessary to go under 13% moisture. For more information, visit the USDA’s Grain Inspection Packers and Stockyards Administration (GIPSA) guidelines here.

Q2: What mycotoxins are impacted by fusarium mold?

A: The list of fusarium-produced mycotoxins is quite extensive and currently exceeds 100 different toxins, Dr. Diaz said. Major groups are the Type A and B trichothecenes. Among those toxins we have some of the most important mycotoxins including T-2 toxin, HT-2 toxin, diacetoxyscirpenol (type A) and DON, as well as 15- acetylDON, 3-acetylDON and nivalenol (type B).

Other non-trichothecene mycotoxins are also produced by fusarium molds, with zearalenone and the fumonisins being the most important ones due to either their toxicity, their frequency in feeds/foods, or a combination of the two.

Q3: Does China or Australia provide specific mycotoxin guidelines?

A: China follows U.S. FDA regulations for aflatoxin, except that they only regulate B1 (not total), NEOGEN’s Chuck Bird said. For DON, China also follows FDA regulations, so 1 ppm is the limit for human food. They currently do not have any guideline levels for the other toxins, but would follow FDA’s recommendations.

Australia also follows U.S. FDA guidelines, but since most animals are “grazers,” in their country, the animal feed industry is much smaller compared to the U.S.

Q4: Are these guidelines for full feed or ingredients?

A: This differs between guidelines and countries, Dr. Gwendolyn Jones said. For example, the European Union provides guidelines on complete feedstuffs and ingredients (cereals and cereal by-products).

Q5: Regarding fertility and other performance parameters, how do aflatoxin levels impact animals?

A: Zearalenone has the most impact on fertility as it mimics estrogen, Mr. Bird said. Aflatoxin does not seem to have an impact on fertility at low levels, but at high levels (acute toxicity), it can have damaging effects overall. In addition, aflatoxin has the ability (even at low levels) to impair the immune system and make animals more susceptible to disease. In some ways it is a “silent killer” — the animal may present signs of a known disease, which could have been triggered originally by aflatoxin.

Q6: Are there studies on how mycotoxins impact humans?

A: Most of the literature related to human exposure is only on aflatoxin and fumonisin, Mr. Bird said. Cases of aflatoxicosis are frequently reported in rural Africa and typically are pronounced by above average cases of liver cancer. He said he believes aflatoxin is still considered to be the most potent natural carcinogen known.

Fumonisin was discovered in 1989 due to a significant drought in the U.S. and South Africa. The respective corn crops had high levels of aflatoxin but also contained fumonisin. The noticeable effects were found on horses that were experiencing seizures (crazy horse disease). When performing necropsies, it was discovered that their brains were partially liquefied. Both the USDA and the South African PROMEC institute worked together to identify high levels of fumonisin as the culprit.

The other very noticeable effect in both the rural parts of U.S. and South Africa can be very high rates of esophageal cancer — mainly isolated to the areas where “moonshine” production is common. In Africa, tribes would separate the moldy corn and ferment it to make alcohol and the esophageal cancer rates became quite high. Rural parts of Tennessee, Kentucky and the Carolinas also saw this same effect.

Significant mouse and rat studies were immediately conducted by both the FDA and PROMEC, but in the end, fumonisin was considered a “promotor” and not an “initiator” of cancer. Hence, the levels for human consumption are not nearly as aggressive as aflatoxin, Mr. Bird explained.

In terms of DON, the FDA has determined it does not cause cancer or have many other long term effects. However, extensive rat and mouse studies have shown potential GI issues, so the advisory level of 1 ppm for human food has been set.

Zearalenone, T-2 and ochratoxin all have also been evaluated in mouse and rat models and it’s been concluded they can cause human harm and possibly cancer. Due to the limited occurrence of these toxins, however, only the E.U. has published guideline levels. For more information, click here.

Q7: Which of the mycotoxins have the most impact on aquatic species growth?

A: Aflatoxin is the biggest threat to aquaculture, Mr. Bird said. Due to the liver toxicity in aquatic species, it can cause significant losses. Having said that, however, most aquaculture feed contains mainly “fishmeal” and not much corn, so the risk is somewhat mitigated. However, most large producers of aquatic feeds regularly test for aflatoxin.

Studies have shown that fish are not as sensitive to DON as swine or chickens, Dr. Jones said. In addition, catfish had no detrimental response to purified DON up to dietary levels of 10 ppm, but diets containing 15 and 17.5 ppm DON caused reduced growth. Other studies have shown trout fed 20 ppm DON will refuse feed. This factsheet provides a good overview on the impact of different mycotoxins on fish.

Q8: How big is the impact of El Niño/La Niña cycles in Canadian prairies?

A: Some regions of the world are impacted more directly by El Niño and La Niña than others, Dr. Diaz said. Generally speaking for Canada, El Niño typically is associated with milder than normal winter and springs with drought conditions being typical. The greatest impact tend to be centered on Manitoba and western Ontario, while southern Canada also tends to be drier during El Niño winters.

La Niña, on the other hand, is typically associated with cooler temperatures and heavier moisture, including heavy snowfall. Canadian air temperature tends to be below normal with west Quebec having the most significant effect. Precipitation can also be much higher in southern Canada, specifically southern British Columbia. Wheat harvests in the prairie region are typical in La Niña years. The impact of both El Niño and La Niña tend to be reduced as they move east, as eastern Canada is generally exempt from most of these effects, Dr. Diaz said.

NEOGEN offers the most comprehensive range of mycotoxin test kits as well as other food safety solutions. For more information, click here. To watch the original webinar, visit NEOGEN’s YouTube channel.

Category: Food Safety, Agriculture