Mycotoxin biomarkers - is the hype justified?

When it comes to monitoring mycotoxin risk, analysis of feed and individual feed ingredients is the widely accepted approach. Although feed analysis is well-established, challenges still exist but those can be minimized through various tactics including implementation of a robust sampling technique, for example. An alternative approach which has garnered attention in recent years is the use of mycotoxin biomarkers – assessing mycotoxins via analysis of blood or other biological matrices (urine, bile, feces, tissue, etc.) collected directly from animals. While innovation has led to advances in analytical techniques which have enabled development of mycotoxin biomarker testing for use in scientific settings, there are still many gaps in our understanding of how to best use such testing including how to interpret biomarker results. These shortcomings especially limit in-field application of mycotoxin biomarker testing. This article will provide insights into the use of mycotoxin biomarkers and highlight some of the key challenges with this approach.

When it comes to mycotoxins, there are typically two types of biomarkers described:

1. Biomarkers of exposure: measure of the mycotoxin itself and / or its metabolite(s)

• E.g., Aflatoxin M1 presence in milk --- well-established so this is one biomarker that has commercially available testing options

2. Biomarkers of effect (sometimes described as mechanism-based biomarkers): measure of a biological response caused by a mycotoxin such as an alteration in a protein or an enzyme

• E.g., sphinganine-to-sphingosine ratio (Sa:So) caused by fumonisins --- this is the best-know mechanism-based mycotoxin biomarker in livestock species

Biomarkers of effect need to be specific so looking at something such as markers of oxidative stress will not work since there are many potential causes of oxidative stress. It’s impossible to tell what caused the shift in such markers – it could be a mycotoxin such as deoxynivalenol (DON), various other mycotoxins, or a wide range of other potential stressors. This is also true for other common measures such as acute phase proteins and cytokines. This lack of specificity is one reason that identification of biomarkers of effect is tricky.

Additionally, through the literature, you will find different reported responses to mycotoxins or variable toxic effects due to species, dose, duration, breed, etc. Even within the same herd or flock, high variation in responses are observed. This could be due to a variety of reasons including:

• • Kinetics: differences in metabolism, excretion, etc.

• Differences in metabolism across species have been identified for some mycotoxins but many mycotoxins have not been extensively studied to truly understand differences --- what could be a potential biomarker in one species might not be a good measure in another

• Example: In swine, DON is naturally detoxified to DON-glucuronide which is more water soluble and enhances excretion via the urine whereas in poultry, DON is metabolized into DON-sulfate

• Sampling time: influence of time span since last feed intake relative to sampling

• Weight / age: differences in body compartment composition

• Feed intake: lower feed intake implies lower toxin intake (or greater feed intake could lead to greater toxin intake)

• Unknown factors: other factors such a sex could be influential (evidence of this exists in mice but not widely investigated in livestock species)

All of these factors contribute to a lack of repeatability which is an additional hindrance to establishing valid mycotoxin-related biomarkers.

An additional challenge is that there is currently a lack of biomarker reference values – this is two-fold. First of all, in contrast to mycotoxin analysis in feed, no reference materials or proficiency tests exist for the evaluation of mycotoxin biomarker methods which is a limitation on the laboratory or analytical side of things. Secondly, studies across different species and various mycotoxins have not shown correlations between the levels of exposure-based biomarkers and clinical signs or the severity of mycotoxicosis. No established thresholds exist for interpreting what level(s) of biomarkers mean. Without a scientific basis to justify thresholds or suggested cut-points, you can’t meaningfully interpret biomarker results or know how to use such data.

Perhaps one day we will be able to assess mycotoxin risk via measurement of mycotoxin-related biomarkers. Until we learn more through scientific studies to determine valid and reliable biomarkers as well as establish interpretation thresholds, the hype is not justified and your best bet is to analyze feed. If you would like to submit feed samples and quantify your risk to mycotoxins, please contact your dsm-firmenich representative to learn more about our complimentary mycotoxin analytical services.