PHOTO: IMPEXTRACO
How to measure and counteract mycotoxicosis
Low levels of naturally co-occurring mycotoxins act synergistically on animal health and compromise performance. Prevention is the best solution but requires multiple strategies to be effective against a broad range of mycotoxins.
BY ARNO DUCHATEAU, IMPEXTRACO M
ycotoxins are toxic metabolites produced by moulds that can cause detrimental effects in animal production. Over 400 mycotoxins have been discovered today. They can be divided in
pre-harvest or post-harvest mycotoxins. Pre-harvest mycotoxins are produced by moulds that grow on the crops in the field, whereas post-harvest mycotoxins are produced during feed storage, transport or processing. Amongst all mycotoxins, there is a huge variety in molecular structure, size or polarity and effects on animal health. Moreover, mycotoxins are stable during chemical or heat treatments and hereby accumulate quickly in feed materials. The most documented toxins are aflatoxins (AFLA), trichothecenes, zearalenone, fumonisins and ochratoxins.
Feed analysis In EU maximal levels for AFLA B1 exist as well as guidance levels for the other mycotoxins. These levels are monitored by feed analysis in advanced labs. Besides the fact that mycotoxin analysis is difficult and unreliable, low levels of naturally co-occurring mycotoxins act synergistically in the animals. Thus, even below the EU guidance levels or below HPLC detection limits, mycotoxins cause harmful effects once ingested by animals.
Measure the effect on animal health Upon ingestion, bypassing the stomach and surviving the animal’s metabolism, the toxins will enter the intestinal
Increase in liver
colour due to my- cotoxins on a
scale from 0-4. Aflatoxins can
also induce a pale, yellow colour.
44 ▶ MYCOTOXINS | NOVEMBER 2021
lumen and cause their first effects on the gut barrier. Mycotoxins turn the gut into a leaky state by lowering the tight junction proteins. This state can be visualised (see image below) or measured by tight junction protein expression and gut morphometry or morphology parameters like villus length, width and crypt depth. This leaky gut allows more translocation of toxins or patho- gens into the animal’s system. The immune system will be triggered and a cascade of events can cause severe gut in- flammation. Moreover, mycotoxins are also known to sup- press the immune system, for instance reducing certain types of immune cells important in the first line of defence. In both cases, the immunomodulation is an ideal opportunity for pathogens to cause secondary diseases, like bacterial enteri- tis in monogastrics or mastitis in dairy cows. Measuring the immune response is possible with flow cytometry on blood samples, where every type of immune cell can be distin- guished based on certain specific surface markers, like recep- tors and major histocompatibility complex (MHC). Also the level of different cytokines can be measured in blood samples. After modulating the immune system, toxins will be transported by the blood to vital organs, such as lungs, liver and kidney. The liver is the organ which is naturally focused on detoxification as well as other important functions for storage and synthesis of protein and biochemicals. Mycotoxins can damage the highly specialised hepatocytes by inducing oxidative stress and a direct toxic effect. The free radicals will induce membrane instability and leakage of hepatocyte content. The induced liver damage can be observed by a change in liver colour or by measuring liver metabolites in blood samples of contaminated animals, like serum proteins (Albumin and globulin) and liver enzymes (Aspartate aminotransferase). Similar effects have been observed in the kidney. The kidney is the main organ of the renal system in animals and responsible for regulating the body fluid content, osmotic balance and excretion of waste products. The kidney cells are also affected by oxidative stress
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