Mycotoxins in general
Mycotoxins are highly toxic secondary metabolic products of molds on almost all agricultural commodities worldwide. They occur under natural conditions in feed as well as in food. Several studies proved that economic losses occur at all levels of food and fed production, including crop and animal production, processing and distribution 1 2 3. According to the FAO (Food and agriculture organization) 25% of the world’s crop harvests are contaminated with mycotoxins 4. There are currently more than 400 mycotoxins known. There are six major classes of mycotoxins that frequently occur: aflatoxins, trichothecenes, fumonisins, zearalenone, ochratoxin and ergot alkaloids 5 . They are formed by different kinds of fungi and each fungi species can produce more than one mycotoxin. The major classes of these mycotoxin-producing fungi are listed in the table below 6 .
Classification of mycotoxin-producing fungi 6
Mycotoxins differ in their structure, which explains the great variation of symptoms (see table: "Selected mycotoxins and their basic symptoms"). The main toxic effects are carcinogenicity, genotoxicity, nephrotoxicity, hepatotoxicity, oestrogenicity, reproductive disorders, immunosuppression or dermal effects 2. There are several factors which influence symptoms 5:
- Type of mycotoxins consumed, intake level and duration of exposure
- Animal species, sex, breed, age, general health, immune status
- Farm management: hygiene, temperature, production density
- Possible synergism between mycotoxins simultaneously present in feeds
Moreover, mycotoxins can occur even though negative analytical findings. Firstly, mycotoxins often occur in so-called “hot-spots” and therefore they might stay undetected if sampling procedures were not carried out in a correct way 7 8 9 . Secondly, masked mycotoxins could appear in the feed. Masked mycotoxins are chemically modified mycotoxins by specific biochemical reactions in which mycotoxins can be bound to certain feed ingredients including e.g. glycosides, glucuronides, fatty acid esters and proteins. Consequently, these masked mycotoxins are not detectable with conventional analytical methods, i.e. in regular testing samples will show up as having no contamination whilst containing mycotoxins in a bound form. 10 11 12 However, in the course of the digestive process, masked mycotoxins are released again and affect the animal. 13 14
Each plant can be affected by more than one fungus and each of them can produce more than one mycotoxin. Consequently, there is a great probability that many mycotoxins are present in one feed, thus increasing the odds of interaction between mycotoxins and the occurrence of synergistic effects, which are of great concern in livestock health and productivity. Synergistic effects can already occur at low levels when the combined effects of two mycotoxins are much greater than the individual effects of each toxin alone. In contrast additive effects that occur when the combined effects of two mycotoxins are equal to the sum of the effects of each toxin given alone. 15 16 17 18
Selected mycotoxins and their basic symptoms 19
Examples of contaminated corn
Mycotoxins are often invisible, tasteless, chemically stable and resistant to temperature and storage. They resist the normal feed manufacturing processes.
Mycotoxin producing fungi can be divided into two groups 20 :
- Field fungi (Fusarium sp.) produce mycotoxins in the field (“pre-harvest”)
- Storage fungi (Aspergillus and Penicillium sp.) occur after harvest (“post-harvest”)
However in special cases like under unusually hot or dry conditions Aspergillus and Penicillium species can also affect crops during the growing season. On the other hand field fungi can continue growing and produce mycotoxins during transport and storage. 21
1 Robens, J., & Cardwell, K. (2003). The costs of mycotoxin management to the USA: Management of aflatoxins in the united states. Journal of Toxicology - Toxin Reviews, 22(2-3), 139-152.
2 Bryden, W. L. (2012). Food and feed, mycotoxins and the perpetual pentagram in a changing animal production environment. Animal Production Science, 52(7), 383-397.
3 Wu, F. (2007). Measuring the economic impacts of fusarium toxins in animal feeds. Animal Feed Science and Technology, 137(3-4), 363-374.
4 http://www.fao.org/food/food-safety-quality/a-z-index/mycotoxins/en/ (20nd August 2012)
5 CAST Report (2003). Mycotoxins: risks in plant, animal, and human systems (Richard, J. L and Payne, G. A. eds.) Council for Agricultural Science and Technology Task Force report No. 139, Ames, Iowa, USA.
6 Weidenbörner, M. (2001) Encyclopedia of Food Mycotoxins, Springer-Verlag, Berlin.
7 Miraglia, M., De Santis, B., Minardi, V., Debegnach, F., & Brera, C. (2005). The role of sampling in mycotoxin contamination: An holistic view. Food Additives and Contaminants, 22(SUPPL. 1), 31-36.
8 Shephard, G. S., Berthiller, F., Burdaspal, P. A., Crews, C., Jonker, M. A., Krska, R., Whitaker, T. B. (2012). Developments in mycotoxin analysis: An update for 2010-2011. World Mycotoxin Journal, 5(1), 3-30.
9 Andersson, M. G., Reiter, E. V., Lindqvist, P. -., Razzazi-Fazeli, E., & Häggblom, P. (2011). Comparison of manual and automatic sampling for monitoring ochratoxin A in barley grain. Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment, 28(8), 1066-1075.
10 Berthiller, F., Schuhmacher, R., Adam, G., & Krska, R. (2009). Formation, determination and significance of masked and other conjugated mycotoxins. Analytical and Bioanalytical Chemistry, 395(5), 1243-1252.
11 Berthiller, F., Dall'Asta, C., Schuhmacher, R., Lemmens, M., Adam, G., & Krska, A. R. (2005). Masked mycotoxins: Determination of a deoxynivalenol glucoside in artificially and naturally contaminated wheat by liquid chromatography-tandem mass spectrometry. Journal of Agricultural and Food Chemistry, 53(9), 3421-3425.
12 Lancova, K., Hajslova, J., Poustka, J., Krplova, A., Zachariasova, M., Dostalek, P., & Sachambula, L. (2008). Transfer of fusarium mycotoxins and 'masked' deoxynivalenol (deoxynivalenol-3-glucoside) from field barley through malt to beer. Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment, 25(6), 732-744.
13 Gareis, M., Bauer, J., Thiem, J., Plank, G., Grabley, S., & Gedek, B. (1990). Cleavage of zearalenone-glycoside, a "masked" mycotoxin, during digestion in swine. Zentralblatt Fur Veterinarmedizin.Reihe B.Journal of Veterinary Medicine.Series B, 37(3), 236-240.
14 Berthiller, F., Krska, R., Domig, K. J., Kneifel, W., Juge, N., Schuhmacher, R., & Adam, G. (2011). Hydrolytic fate of deoxynivalenol-3-glucoside during digestion. Toxicology Letters, 206(3), 264-267.
15 Grenier, B., & Oswald, I. P. (2011). Mycotoxin co-contamination of food and feed: Meta-analysis of publications describing toxicological interactions. World Mycotoxin Journal, 4(3), 285-313.
16 Speijers, G. J. A., & Speijers, M. H. M. (2004). Combined toxic effects of mycotoxins. Toxicology Letters, 153(1), 91-98.
17 Kubena, L. F., Edrington, T. S., Harvey, R. B., Buckley, S. A., Phillips, T. D., Rottinghaus, G. E. and Casper, H. H. (1997). Individual and combined effects of fumonisin B1 present in Fusarium moniliforme culture material and T-2 toxin or deoxynivalenol in broiler chicks. Poult. Sci. 1239-1247.
18 Huff, W. E. and Doerr, J. A. (1981). Synergism between aflatoxin and ochratoxin A in broiler chickens. Poult. Sci. 550-555.
19 Richard, J. L. (2007). Some major mycotoxins and their mycotoxicoses-an overview. International Journal of Food Microbiology, 119(1-2), 3-10.
20 Weidenbörner, M. (2007) Mycotoxins in Feedstuffs, Springer-Verlag, New York.
21 Dawlal, P., Barros, E., & Marais, G. J. (2012). Evaluation of maize cultivars for their susceptibility towards mycotoxigenic fungi under storage conditions. Journal of Stored Products Research, 48, 114-119.