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Mycotoxins are naturally occurring secondary metabolites secreted by moulds, mostly belonging to the genera Aspergillus, Fusarium and Penicillium. These mycotoxins that contaminate crops, pastures, and animal feeds have a significant negative impact on animal health and productivity. To date more than 700 mycotoxins have been identified, however, only a few mycotoxins are of agricultural importance: aflatoxins (AFLA), fumonisins (FUM), zearalenone (ZEN), trichothecenes namely deoxynivalenol (DON) and T-2 toxin, ochratoxin A (OTA) and ergot alkaloids.
Moulds and mycotoxins are commonly produced on crops when in the field (field fungi) but can also be formed at harvest or ensiling, or during storage and processing (storage fungi). Climate and weather conditions such as rainfall, relative humidity, and temperature are key determinants of the extent and profile of mycotoxin contamination. However, factors such as crop cultivar, fungal strain, soil pH, agricultural practices, insect damage and post-harvest handling of crops also play a role. As a result, the profile and extent of mycotoxin contamination are variable and can differ from season to season, between crops and across regions. Research has identified that the Fusarium-derived mycotoxins, namely DON, FUM and ZEN are the most prevalent mycotoxins in South Africa. Polycontamination of crops and livestock feeds with multiple mycotoxins is a real challenge and occurs as several mycotoxigenic fungi can simultaneously contaminate a single crop or feed ingredient and most fungi can produce more than one type of mycotoxin. Unlike monogastric animals, ruminants are fed complex diets rich in multiple grains, hays/straws, by-products, and silages increasing their potential exposure to mycotoxins. This polycontamination creates mycotoxin cocktails that can have additive or synergistic negative effects on the animal.
Consumption of feed contaminated with mycotoxins can cause various animal health-related problems. The primary means by which mycotoxins exert their effects include:
The signs can vary depending on the specific mycotoxin, the amount of mycotoxin ingested, the period of exposure and the interaction of various mycotoxins. Clinical symptoms can be observed at high levels of mycotoxin contamination but are not often observed in practical situations. Instead, the symptoms of mycotoxicosis are typically wide-ranging and non-specific making diagnosis difficult. Symptoms may include reduced feed intake, reduced production, digestive upsets (e.g., diarrhoea), impaired reproductive performance, increased susceptibility and incidence of disease, and poor response to veterinary therapy.
Chronic or sub-acute mycotoxicosis arises from the continuous consumption of low levels of multiple mycotoxins over time with no presentation of clinical signs. This sub-acute mycotoxicosis leads to problems such as a reduction in feed efficiency, increased disease incidence, poor reproductive performance, sub-optimal productive performance and increased veterinary costs. Sub-acute mycotoxicosis is now widely considered to be the most important impact of mycotoxins leading to the greatest economic loss.
Sub-acute mycotoxicosis occurs because of the alteration of ruminal fermentation and the damage done to the gut. Mycotoxins such as DON and AFLA impair rumen motility and fermentation leading to a reduction in diet digestion, volatile fatty acid (VFA) production, and microbial protein synthesis, thereby reducing the nutrients available to the animal. Further down the digestive tract, in the gut/intestine, nutrient absorption is reduced by the synergistic action of DON and FUM on gut health and integrity. Deoxynivalenol damages the intestinal cells, causing irritation of the tissues, shorter villi length and death of intestinal cells, resulting in a reduced surface area for nutrient absorption and alteration of the action of nutrient transporters. Fumonisins worsen the situation by preventing the repair of intestinal cells.
As the intestinal barrier also plays a crucial role in immunity, the damage caused to this tissue by DON and FUM will alter intestinal barrier function and allow for the passage of pathogens into the bloodstream increasing the susceptibility of animals to disease.
Mycotoxins are one of the most immunosuppressive factors coming from feed, with aflatoxins trichothecenes and fumonsins all modulating both innate and adaptive immunity.
(Adapted from: Surai & Dvorska, 2005)
Mycotoxins are invisible, tasteless, chemically stable, and resistant to heat, making them difficult to eliminate in feed. While there are some practices that can reduce mycotoxin contamination, the presence of mycotoxins in livestock feed is unavoidable. Reducing the exposure of animals to these toxins is critical and requires a robust mycotoxin risk management strategy focused on detection, prevention, and mitigation. Regular analysis of high-risk feedstuffs such as silages, hominy chop and cereals or cereal-derived products can help identify potential threats. Silages contribute significantly to mycotoxin contamination in ruminant diets and good silage management is essential to avoid further growth of moulds and mycotoxins during storage or at feed-out.
Besides prevention, the most common strategy to reduce the animal’s exposure to mycotoxins is to decrease mycotoxin bioavailability by incorporating a mycotoxin-adsorbing additive into the feed, which targets a reduction in mycotoxin uptake and distribution to the blood and target organs. The challenge here is that mycotoxins vary in size, shape, and other physiochemical properties, making some mycotoxins easier to bind than others. The key to combatting mycotoxins is to use a broad-spectrum solution capable of effectively targeting a range of mycotoxins.
Prevention is the best way to fight mycotoxins. At Vitam International, we believe in taking a proactive approach to managing mycotoxin risk and in partnership with Olmix Animal Care, we have developed a comprehensive mycotoxin risk control program focused on evaluating mycotoxin risk and offering expert advice and technical support both at farm and feed mill level. At the core of our mycotoxin risk management programme lies our unique, patented MMi.S technology from Olmix Animal Care the only mycotoxin binder in its class capable of binding most mycotoxins, with high efficacy against deoxynivalenol (DON) and fumonisins (FUM), proven at gut level.
Surai, P. & Dvorska, J. (2005). Chapter 5: Effects of mycotoxins on antioxidant status and immunity. In: The Mycotoxin Blue Book. Pub. Nottingham University Press. Ed. Diaz, D. pp 93 – 137.
