Understanding and Combatting Mycotoxins in Poultry Feed08 October 2015
Understanding the occurrence and prevalence of mycotoxins and their effects on poultry is becoming more and more imperative as research over the last couple of decades has shown that mycotoxins are commonly prevalent in majority of feed ingredients.
Latest enzymatic deactivation technologies are also helping to eliminate the mycotoxins that cannot be bound by using binder products.
A worldwide mycotoxin survey in 2013 showed that 81 per cent of around 3,000 grain and feed samples analysed had at least one mycotoxin.
This was higher than the 10-year average (from 2004 to 2013) of 76 per cent in a total of 25,944 samples, according to a study released this year by a research team including scientists from Biomin, the University of Missouri-Columbia, the Christian Doppler Laboratory for Mycotoxin Metabolism, University of Natural Resources and Life Sciences Vienna (BOKU), the Department of Animal Sciences at Purdue University West Lafayette and Texas A&M University.
The researchers said that the increase in the number of positive samples in 2013 could have been because of improvements in detection methods and their sensitivity.
Mycotoxins can affect the animals either individually or additively in the presence of more than one mycotoxin, and may affect various organs such as gastrointestinal tract, liver, and immune system, essentially resulting in reduced productivity of the birds and mortality in extreme cases.
While the use of mycotoxin binding agents has been a commonly used counteracting strategy, considering the great diversity in the chemical structures of mycotoxins, the researchers said that it was obvious that there is no single method that can be used to deactivate mycotoxins in feed.
Therefore, different strategies have to be combined in order to specifically target individual mycotoxins without impacting the quality of feed.
Enzymatic or microbial detoxification, referred to as “biotransformation” or “biodetoxification,” uses microorganisms or purified enzymes from the microorganisms to catabolize the entire mycotoxin or transform or cleave it to less or non-toxic compounds.
However, the awareness on the prevalence of mycotoxins, available modern techniques to analyse them, the effects of mycotoxicoses, and the recent developments in the ways to safely eliminate the mycotoxins from the feed are very minimal among the producers.
The review paper, Prevalence and effects of mycotoxins on poultry health and performance, and recent development in mycotoxin counteracting strategies, presented at the symposium “New Strategies to Counteract the Effects of Mycotoxins on Poultry Health and Performance,” held at the annual meeting of the Poultry Science Association last year looked at the progress being made to tackle mycotoxins in poultry feed.
The term “mycotoxin” is derived from “mykes” meaning fungi and “toxicon” meaning poison and are produced by moulds. There are over 200 species of moulds that produce mycotoxins.
Analysis of grain and feed samples worldwide has indicated that it is possible to have grains with extremely high concentrations of mycotoxins, although the overall mycotoxin contamination is low. These data also revealed that mycotoxin contaminated grains typically contain more than just a single mycotoxin.
Mycotoxins produce a variety of diseases, “mycotoxicoses”, directly or in combination with other primary stressors such as pathogens.
These diseases are exhibited by symptoms and lesions, which can be used to clinically diagnose the presence of mycotoxins although these symptoms are not just straightforward.
Acute cases caused by eating high levels of mycotoxins may result in death and a marked decline in the productivity of poultry.
However, the research says that in most cases, mycotoxicoses is chronic and caused by low-level ingestion of fungal metabolites, resulting in measurable decline in performance and the occurrence of nonspecific changes, including subcutaneous haemorrhage in broilers and immunosuppression.
The research says that analysis of feed for mycotoxins is imperative in order to diagnose mycotoxicoses in chronic cases, apart from the evaluation of history, clinical and post-mortem evaluation of flocks and microscopic examination of tissues.
The recognition that mycotoxins affect health and productivity of poultry has led to intensive research on counteracting methods over the last few decades, including detection and elimination or detoxification of mycotoxins.
The most well-known approach to detoxify mycotoxins is through the use of binders. This involves the use of nutritionally inert adsorbents with the capacity to bind and immobilise mycotoxins in the gastrointestinal tract of animals, reducing their bioavailability.
Although this approach successfully eliminates the risk of certain mycotoxins, it does not work comprehensively on all of the mycotoxins relevant to the poultry industry, the research says.
Altering the molecular structure of the mycotoxin through biotransformation has been proved to detoxify the non-adsorbable mycotoxins.
Suppression of mycotoxicoses requires an integrated approach from detection to detoxification
Aflatoxins (AF), zearalenone (ZEN), ochratoxin A (OTA), fumonisins (FUM), trichothecenes such as deoxynivalenol (DON), and T-2 toxin are some of the mycotoxins that can significantly impact the health and productivity of poultry. In general, contaminated feeds usually contain more than one mycotoxin.
Valid determination of mycotoxins and their metabolites is a crucial step in any intervention, mitigation, or remediation strategy to cope with the deleterious effects of mycotoxins to livestock
In general, methods for determining mycotoxins can be divided into chromatographic methods, immunochemical methods and “other” methods, which include direct spectroscopic methods.
The conditions under which fungi and mycotoxins are produced in agricultural commodities depend a lot on environmental factors such as the availability of water and temperature.
The study says that a slightly raised CO2 concentration can also stimulate growth.
Extreme weather situations, heavy rain and drought lead to plant stress making them more susceptible to fungal infections.
As part of a proper mycotoxin risk management, surveying the mycotoxin occurrence is very important to allow feed and animal producers to assess the risk of using certain feed ingredients or feeds from different regions and an annual worldwide survey programme was launched in 2004 to discover the extent of mycotoxin contamination in feeds and feed ingredients on a global basis.
During the decade between 2004 and 2013, 76 per cent of the samples contained detectable amounts of at least one mycotoxin, but the research team said that over the years, there were differences with regard to the prevalence of mycotoxins worldwide.
As part of the annual mycotoxin survey, the 2013 results revealed DON and FUM presence in more than half of finished feed and feed ingredient samples analysed.
The research shows that recent literature has implicated physiological and immunological effects of mycotoxins at lower and more common levels of contamination.
As many of the mycotoxins and their metabolites inhibit protein synthesis, tissues with high levels of protein synthesis and turnover, such as those within the gastrointestinal tract (GIT) can be particularly susceptible to their toxic effects. In particular, the GIT is repeatedly exposed to mycotoxins at concentrations likely higher than other organ systems.
The intestine can also serve as a site of metabolic activation or deactivation for particular mycotoxins.
The effect of the mycotoxins can be to hinder the immune response from the animal making it less able to respond to pathogens and making it more susceptible to infection.
Poultry species are considered to be less sensitive to mycotoxins, particularly toxins from Fusarium, compared to other species, such as the pig. Many experiments in poultry have reported toxic effects of mycotoxins but at doses not expected in the field.
However, recent research has shown that at levels lower than those that would cause overt clinical mycotoxicoses, mycotoxins modulate immune functions and may decrease resistance to infectious disease.
Recent epidemiological data indicate high correlation between outbreaks of Newcastle disease and AF contamination of broiler rations.
Ducks and broilers fed with concentrations of DON ranging from 3 to 12 mg/kg diet also had decreased antibody titres to common vaccines (Newcastle disease, infectious bronchitis) and a reduction in the mass of the bursa of Fabricius.
For both DON and AF, the effects seen in the bursa of Fabricius, and the subsequent impact on antibody, might be a direct consequence of the inhibition of protein biosynthesis.
There is also growing evidence that, depending on the level and length of exposure to the toxins, a biphasic response can be expected.
The research says that there is a need to pay closer attention to the effect of doses lower than those that would cause overt clinical symptoms.
Unlike pathogen exposure, there are no visible clinical signs of mycotoxin intoxication as most of the time these fungal metabolites are normally found at low levels.
However, mycotoxins are able to affect activated and proliferating cells, damage epithelial tissue, increase intestinal permeability, and, therefore, may result in a weakened immune system.
As a consequence, when a pathogen enters the organism, an appropriate and efficient immune response cannot be mounted, and eventually results in stronger clinical signs.
Mycotoxins vary in their chemical structures, which results in vast differences regarding their chemical, physical, and biochemical properties. While the biochemical properties define the toxicity of mycotoxins, chemical and physical properties determine the methods that can be used to detoxify them.
Considering the great variety of mycotoxin structures, the researchers say that hat there is no single method, which can be used to deactivate mycotoxins in feed.
Therefore, different strategies have to be combined in order to specifically target individual mycotoxins without impacting the quality of feed.
The best known method for mycotoxin deactivation is “binding” with the use of binding agents, which are referred to as mycotoxin binders, adsorbents, or enterosorbents.
They can be of organic (microbial) or inorganic (mainly clay minerals) nature.
Another method is “bio-protection,” which uses different substances (algae, plant ingredients, etc.) that protect vulnerable organs such as the liver and strengthen the immune system of animals.
Enzymatic or microbial detoxification, sometimes referred to as “biotransformation” or “biodetoxification” use microorganisms or purified enzymes thereof to catabolize the entire mycotoxin or transform or cleave it to less or non-toxic compounds.
The inclusion of binding agents or “enterosorbents” in the diet has been given considerable attention as a strategy to reduce foodborne exposures to mycotoxins.
The use of clay-based materials for toxin binding is not new. For centuries, humans and animals have been reported to eat clay minerals, a process known as geophagy. The consumption of edible clays for various purposes by people and animals in developing countries (and the United States) is common and in most cases is considered to be beneficial to health
The inclusion of non-nutritive clay minerals in the diet of animals has been widely adopted for reducing toxin bioavailability and exposure from contaminated feeds.
Due to low feed inclusion requirements and easy management of AF enterosorbents, the widespread acceptance of these products by the farm animal industry has led to the introduction of a variety of diverse materials and/or complex mixtures for AF binding.
These have been labelled as mycotoxin enterosorbents, binders, sequestrants, interceptor molecules, trapping agents, adsorbents, toxin sorbents, and so on.
These materials (and/or mixtures) are reported to contain smectite clays, zeolites, kaolinite, mica, silica, charcoal, and various biological constituents including chlorophyllins, yeast products, lactic acid bacteria, plant extracts, and algae.
In extensive studies in animals and humans, calcium dioctahedral smectite clay (NovaSil, NS) and similar montmorillonite clays have been reported to significantly decrease AF exposures and toxic effects following ingestion of doses up to 20 g/kg of diet. Research with NS and other materials suggest that potential AF enterosorbents should be rigorously evaluated in vitro and in vivo.
These should meet the following criteria, the study says:
• Favourable thermodynamic characteristics of sorption
• Tolerable levels of priority metals, dioxins/furans, and other hazardous substances
• Safety and efficacy in multiple animal species
• Safety and efficacy in long-term rodent studies
• Negligible interactions with vitamins, iron, and zinc
However, the adsorption efficacy of binding agents or enterosorbents is limited to only a few mycotoxins, such as AF, ergot alkaloids, and some other fungal toxins, while binders have been shown to be ineffective for trichothecenes.
Therefore, alternative approaches for efficient detoxification of mycotoxins are required.
The approach to use microorganisms and their enzymes to detoxify specific mycotoxins not only works for non-adsorbable mycotoxins, but for all other toxins for which respective microbes can be isolated from the nature.
This approach has been known for a long time, even longer than the binder concept.
One of the microorganisms which has been further developed into practical application is Trichosporon mycotoxinivorans, a yeast strain capable of detoxifying OTA and ZEN. Application of this yeast in poultry diets has been proven to detoxify OTA.
Many pellet binding products and flowing agents (clay minerals) or feed materials (yeast and their derivatives) with the claim of mycotoxin binding and or detoxification have been used in animal feeds worldwide.
However, regulations for mycotoxin binders and deactivators have not been implemented in many parts of the world for various reasons. This, the research team says, negates the guarantee on the safety and efficacy of the product to the user.
It is, therefore, important to have guidelines in place, which prove safety and efficacy of additives under different in vitro and in vivo conditions.
To overcome this unsatisfactory legal situation, recently the European Commission established a new group of technological feed additives for the reduction of mycotoxins in feed.
In 2010, the European Food Safety Authority (EFSA) published guidelines with stringent requirements, e.g. the binding capacity must be demonstrated; mycotoxin degradation products must be safe for target animals and consumers; minimum three in vivo studies with significant efficacy at the lowest recommended dose; relevant biomarkers of each individual mycotoxin have to be used to demonstrate the efficacy of the product, for the evaluation of mycotoxin deactivating products.
Hence, understanding how mycotoxins occur and the concentration of contamination in feed is essential to ensure effective counter measures.
Specific analysis to determine the type and amount of mycotoxin contamination is needed, so that either the latest enzymatic technologies can be used to eliminate the mycotoxins that cannot be bound by using binder products.
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