Masked Mycotoxins: The Hidden Killers in Feed

Have you ever scratched your head wondering why pigs show mycotoxin-related symptoms when the mycotoxin analysis report shows undetectable or very low levels? Though we don't have the full answer yet, the latest information on masked mycotoxins might reveal some of the mystery.

Other well-known reasons contributing to this mystery include limitations associated with feed sampling, interactions among mycotoxins and interactions of mycotoxins with other nutritional and management deficiencies.

Weather conditions in North America, unfortunately, best suit the growth of molds and mycotoxin production in the field. This, coupled with faulty feed and feed ingredient storage, can increase the incidences of swine mycotoxicoses. Although not all mycotoxins have been tested for their toxicity against pigs, the most significant ones include aflatoxins, ochratoxins, T-2 toxin, deoxynivalenol (vomitoxin), fumonisins, zearalenone and ergot alkaloids.

Mycotoxicoses Diagnosis

We've all heard the comment "if you don't know why pigs are not doing well on your farm, blame it on mycotoxins." Though this sounds silly, there is a reason why people feel so. It is very difficult to relate a specific farm problem to mycotoxins until and unless a thorough investigation is made. These investigations usually involve on-farm symptoms, postmortem findings and mycotoxin analysis of feed.

Are these investigations accurate enough to result in a perfect diagnosis? The answer is probably no. Can we ever accurately diagnose on-farm mycotoxin issues? The answer is maybe, but there is still a long way to go in solving the mysteries around this unique subject.

Compared to poultry, symptoms of mycotoxicoses are more specific in pigs for some of the most common mycotoxins. These can include ZEA-induced reproductive disorders (hyperemic and enlarged vulva), fumonisins-induced pulmonary edema and DON-induced feed refusal. The effect of low mycotoxin levels on the pig's immunity can still go unnoticed, which makes it very hard for pork producers to diagnose the issue and take subsequent prevention measures. The mycotoxicoses symptoms, such as reduced feed intake, also can be due to poor management, nutrition and health.

Not a Perfect Analysis

A major source of error in mycotoxin analysis is inadequate feedstuffs sampling. Proper sampling protocols have been developed and published in an effort to minimize this source of error. However, even with such protocols, error is unavoidable because mycotoxin occurrences are not evenly distributed within a batch but rather are found in hotspots. To further complicate matters, there exist several different analytical techniques (for example, ELISA and HPLC). These can vary in accuracy and can be sensitive to interference from some dietary components such as those in distillers" dried grains with solubles.

Another source of error, which will be discussed in detail, is the potential presence of different chemical forms of mycotoxins or masked mycotoxins.

What are Masked Mycotoxins?

Scientific terminology for masked mycotoxins is conjugated mycotoxins, wherein the mycotoxin is usually bound to a more polar substance like glucose. The name masked mycotoxins was derived as these substances escape routine mycotoxin detection methods but can release their toxic precursors (such as DON and ZEA) after hydrolysis inside the gastrointestinal tract.

Here's a closer look at some of the masked mycotoxins.

  • Masked deoxynivalenol: Naturally contaminated wheat and corn samples from Slovakia have been found to contain glucose-conjugated DON, up to 29 percent of total DON. More recently, an increase in DON concentrations was reported of up to 88 percent when barley samples from North Dakota were treated with trifluoroacetic acid prior to analysis. Such acid treatment would hydrolyze all different conjugates of DON. In simple words, if the DON concentration is 1 part per million in grains, pigs may get exposed to up to 1.88 ppm DON at the gastrointestinal tract level.
    Most recently, even higher levels of bound DON were found in barley and beer, using a variety of analytical techniques. These findings indicate the importance of considering both DON and its conjugated forms while evaluating food and feed safety.
  • Masked zearalenone: In 2002, a study identified glucose-conjugated ZEA in samples of wheat. In 1990, researchers examined the stability of ZEA conjugate (ZEA-glycoside) during digestion in the pig's gastrointestinal tract. The metabolites detected in feces and urine samples were only zearalenone and alpha-zearalenol, demonstrating the fact that ZEA conjugates are decomposed during digestion in the gastrointestinal tract.
  • Masked fumonisins: The frequency of bound fumonisin routinely exceeded free fumonisin in samples of European corn and corn-based foods studied in 2008. Since fumonisins normally occur at high levels in corn, this finding should be taken seriously as the bound fumonisin can add to the total fumonisin concentrations absorbed into hogs" blood circulation. This finding also has public health importance as fumonisins are carcinogenic.
  • Masked type A trichothecene mycotoxins: In 1986, fatty acid esters of trichothecene Fusarium mycotoxins such as trichothecolone, scirpenetriol and T-2 tetraol were detected in banana fruits grown in India. Further research is needed on the potential occurrence of other masked mycotoxins in various feed ingredients.

Consequencesof Masked Mycotoxins

So what is the fallout from not knowing mycotoxins, especially masked mycotoxins, exist? Here are some to consider:

  • Underestimation of mycotoxin levels in feeds and feed ingredients and, thereby, questioning the validity of mycotoxin analysis as a tool to diagnose mycotoxicoses.
  • Underestimating the potential toxicity, ultimately leading to mycotoxin outbreaks in animals and subsequent economic losses.
  • Failure to implement mycotoxin prevention strategies.
  • Mycotoxin regulation authorities setting inaccurate limits on mycotoxin levels in feeds and feed ingredients.
  • Greater chances of mycotoxins getting into the food chain and causing a public health hazard.

It must be concluded that until we have a better understanding of the frequency, toxicity and nature of masked mycotoxins, mycotoxin analysis of pig feeds should be considered to often be an underestimation of correct values. It also should be noted that typically feeds are only analyzed for the presence of certain "indicator" mycotoxins. It is well established that mycotoxins rarely occur in isolation and that mycotoxins, when present in combination, can act synergistically to produce more-pronounced detrimental effects in the animal.

Pigs are highly sensitive to several mycotoxins as reflected in frequent field outbreaks and economic losses. Clear understanding of swine mycotoxicoses has been hindered by many factors. The latest research findings on masked mycotoxins have been able to throw some light on why at low or even undetectable levels of mycotoxins pigs exhibit reduced performance. Mycotoxin analytical techniques should be improved further so that masked mycotoxin concentrations are part of the total mycotoxin concentrations.

There is no doubt that mycotoxins cost the swine industry money, but exactly how much is a nagging question. A recent article in the Journal of Agricultural and Food Chemistry shed light on this area. It estimated an annual loss of $147 million to the U.S. swine industry if DDGS (fed at 20 percent) contaminated with one mycotoxin (fumonisin) is included in all the grow/finish-pig diets.

What could be the loss due to 500 known mycotoxins and thousands of unknown or masked mycotoxins? This could easily run into billions of dollars.