Keeping mycotoxins out of DDGS

by Arvin Donley
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In 2009, the U.S. ethanol industry exported a record 5.64 million tonnes (nearly $1 billion worth) of dried distillers grains and solubles (DDGS) — an increase of 24% over the previous best total in 2008.

Once just a tiny portion of profit for the U.S. ethanol industry, DDGS — the animal feed byproduct of ethanol production from grain — now accounts for 10% to 20% of the industry’s revenue.

As the use of DDGS in feed rations around the world continues to expand, especially in countries such as Mexico, Canada, China, Turkey and Thailand, concerns about mycotoxin contamination, particularly in corn-based DDGS, have increased. This is primarily due to the fact that concentrations of mycotoxins can be doubled or even tripled during the ethanol/DDGS production process, as only about one-third of the original grain remains as distillers grains.

"The thing the fuel ethanol plant does during the ethanol production process is remove the starch from the corn," said Charles Staff, executive director and chief executive officer of the Louisville, Kentucky, U.S.-based Distillers Grains Technology Council.

"Starch makes up two-thirds of the corn. Therefore, if there are mycotoxins present, they are concentrated up to three times in the remaining portion of the corn."

Dan Keefe, the U.S. Grains Council manager of international operations for DDGS, noted that mycotoxins do not generally occur in great numbers in U.S. corn. It takes the right environmental conditions to allow the growth of specific fungi that produce mycotoxins, which are more likely to be present in corn that has been exposed to extremely wet or dry weather conditions.

"Most years, mycotoxins in corn are very limited, but this is something we watch for and ethanol plants watch for in the corn they process," Keefe said.

Ethanol plants employ a variety of mycotoxin testing methods for incoming corn, including the use of test strips that provide quick and accurate results.

"Ethanol plants are aware through spot checking or communications between themselves that there is an increased potential for certain types of mycotoxins," Staff said. "Usually there are one or more specific mycotoxins creating problems due to climatic conditions. When they become aware of that, they begin testing individual loads of corn. Some plants buy directly from the farmer and some buy from elevators, which themselves check for mycotoxins. The whole goal is to do enough testing to try to prevent and reduce the amount of corn coming in with mycotoxin problems."

FDA STANDARDS

The presence of mycotoxins in feed grains or ingredients may cause illness and death in livestock. They also pose a potential hazard to human health because pathogenically they can be carcinogenic and immunosuppressive.

The most common symptoms in swine that are fed contaminated feed include depressed growth, infertility, decreased litter size, low piglet birth weights, immunosuppression, liver damage, oral lesions and tremors. Chronic intoxication can result when low-level, long-term exposure to a single and/or multiple mycotoxins occurs.

Because of the potential hazard, the U.S. Food and Drug Administration (FDA) has established regulatory levels of mycotoxins for the use of feed ingredients as animal feed. Action levels for aflatoxin in animal feed were established for different animals and at different production stages in August 2000 (see charts, pages 64 and 65).

The FDA action level represents the minimum limit at which the FDA can take legal action to remove feed ingredients from the market.

While there are several mycotoxins that can contaminate corn, aflatoxin is of greatest concern because it is a carcinogen and can be transferred to cow’s milk. The FDA sets an action level for aflatoxin in feed of less than 20 parts per billion (ppb) and for milk at less than 0.5 ppb. In the U.S., aflatoxin is a common problem in the South, but it has shown up sporadically in other areas, including the Midwest.

Fumonisin is another mycotoxin of concern for which the FDA has issued guidance values ranging from a low of five parts per million (ppm) for ingredients used for horse feeds, up to 100 ppm for ingredients going into feed for poultry raised for slaughter. Horses are particularly sensitive to fumonisin. Generally, feed ingredients should be below 20 ppm fumonisin when used for swine and below 10 ppm fumonisin when used in dairy diets.

Other mycotoxins like deoxynivalenol, zearalenone, T-2 toxin and ochratoxin can also contaminate corn and be concentrated in the distillers grains. The FDA advises that in the case of deoxynivalenol, feed ingredients for beef cattle and chickens should contain less than 10 ppm, while ingredients for swine and dairy cattle should contain less than five ppm.

Some methods of mycotoxin decontamination do exist. Research has indicated that several chemicals and processes can destroy some of the mycotoxins during the fermentation process or in the distillers grains after production. Research has also identified feed additives, such as beta-glucans, which can reduce the toxicity of mycotoxins by reducing mycotoxin absorption in the animal. Reduced intestinal absorption results in less exposure to the animal and less transfer to milk in ruminants.

STUDY YIELDS PROMISING RESULTS

A recent study provided some reassuring information regarding the mycotoxin threat to both U.S. and global buyers of DDGS.

In 2009, the National Corn-to-Ethanol Research Center (NCERC) released a white paper on mycotoxin levels in U.S. DDGS. Data collected from two independent data sets — a research study by Iowa State University and Novecta, and two publications by South Dakota Cooperative Extension and Biomin. The research included 235 DDGS samples collected from 20 ethanol plants in seven states and 23 export shipping containers over several years (2006-2008). The study found that:

• No samples contained aflatoxin or deoxynivalenol levels higher than the Food and Drug Administration guidelines for use in animal feeds.

• No more than 10% of the samples contained fumonisin levels higher than the lowest FDA guidelines for use in animal feed.

• None of the samples contained a T-2 toxin higher than the detection limit, and most samples contained zearalenone levels lower than the detection limit.

• The containers used for exports shipping of DDGS did not seem to contribute to mycotoxin production.

In a NCERC data set of 20 samples, any samples containing detectable mycotoxins were well below the tolerable guidelines for use in animal feeds.

The study noted that in the Asian Pacific market, there is a concern about the time, environment and shipping procedures of DDGS from the U.S. to foreign markets.

"The concern is that these factors support or enhance mold growth of the DDGS product," the study said. "This study investigated the mycotoxin content in DDGS before and after shipment from a port in the United States to a port in Taiwan."

The result was that the shipping containers used to export DDGS were not found to contribute to mycotoxin production or concentration.

Keefe said the study should answer some of the questions that international buyers have had regarding the safety of U.S. DDGS. "The fact that mycotoxins are detectable in some DDGS samples has no relationship with their toxicity in any animal species because the detectable level is much below a level that would pose a concern," Keefe said. "The important takeaway from the report is that U.S. DDGS is a safe and consistent product and that shipping U.S. DDGS via containers does not increase the chances of mycotoxin production within the product."

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