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A Poultry Vet’s Practical Overview on Mycotoxins in the Field

We’ve come a long way towards understanding the effects of mycotoxins and their modes of action over the past three decades, but there’s much more to learn as well. Experience from the field provides insight into the challenges of dealing with subclinical effects of mycotoxin contamination.

Fernando Lima, DVM

In Brief

• Mycotoxin contamination can produce subclinical signs that make diagnosing poultry problems challenging.
• Producers should consider continuous application of a mycotoxin deactivator as a preventative strategy, but with doses adjusted for the life cycle stage as well as lab analysis.

This article gives a practical overview of the effects of mycotoxins and mycotoxin risk management, based on 30 years of experience in the poultry field. Over the course of this experience, my thinking has evolved to better and more accurately understand where and how mycotoxins were really causing problems so the producer and I could decide how to manage it.

Both clinical and economical concerns are factors to be considered in the poultry business, particularly during periods of unstable profitability. And, as a vet, I discovered that it’s nearly impossible to make a clear diagnosis as to what is wrong with a bird in the presence of mycotoxin contamination, particularly since the toxicity tends to be more subclinical than clinical. As a vet, it is much easier to diagnose severe mycotoxicosis using post mortem analysis and lab support than subclinical occurrence. However, minor symptoms that continuously challenge birds are also bad for the bottom line and make impact evaluation much more difficult for any vet or poultry technician.

As a professional vet, it’s difficult or almost impossible to diagnose whatever it is under constant mycotoxin challenge. Better talk about making a general farm interpretation, cause in these days talking about diagnosis is quite difficult: most situations result from a combination of different possibilities which have most probably a “simple” cause and took bird’s health to a lot of different signs and agents involved.

Customer Case: 21-Day Old Chicks, Farm-Reared for Resale

Production: Typical production for domestic growing in southwestern Europe, frequently at high density (35/sqm)

Presentation and environment: Sporadic feed refusal, lack of uniformity and chicks prone to secondary infections, septicemia and peritonitis. Customer administered continuous application of antibiotics in an attempt to minimize infections, creating a problem when chicks are be sold to local markets and retailers.

Solution: Mycotoxin deactivator was applied (Mycofix). Losses were dramatically reduced and feed intake was improved.

Explanation: Minor contamination wasn’t killing the birds, but rearing under high stocking density created a high bacterial load. In conjunction with the immunosuppressive effects of mycotoxins, this allowed normal bacteria—mainly coliforms—to become more infectious and colonize various organs.

Mycotoxins’ Impact on Gut Health and Immunity

The structure and functionality of the intestine is crucial for the health of poultry. Maturation of the gut microbiota has a strong influence on the development of the intestinal epithelium and the modulation of the physiological functions required to maintain intestinal homeostasis (i.e., immunity, nutrient digestion, intestinal barrier integrity). In turn, these functions are essential for optimizing feed efficiency uptake and use of energy by the bird.

One of my main concerns is the fact that the immune system can be constantly weakened by mycotoxins. Mycotoxins are able to destroy the body’s first defense barriers and reduce immune response, both humoral and cellular. I’ve observed this situation by checking Gumboro and Newcastle serum titres: Whenever there was mycotoxin contamination, there was also a lack of uniformity. While lack of uniformity can happen on both broilers or breeders, many people only anticipate problems on broilers. However, lack of uniformity in brededers can affect embryo development and day-old chick uniformity, as well as maternal immunity.

    Trichothecenes (i.e. DON, T2 Toxin) leads to:

    • Dermotoxicity and lesions of the gastrointestinal tract epithelia and gizzard 
    • Decreased immunoglobuline synthesis and antibody response
    • With that, increased sensitivity to various pathogenic agents such as E. coli, Salmonella sp., etc.

    Ochratoxin A leads to:

    • Nephrotoxic and hepatotoxic issues
    • Reduction and inhibition of lymphocyte proliferation due to hypotrophy of the Fabricius Bursa
    • Reduction of IgA, IgG and IgM in the serum

    High levels of mycotoxins can also infrequently affect some organs directly, as hemorrhagic liver due to a combination of mycotoxins, nephrosis, gizzard ulcers, gastrointestinal tract hemorrhagic lesions or oral lesions,. The majority of problems were linked with a lack of self-defense to pathogen threats which should not generally be a problem. Birds, like other animals, have their own defenses. But when under continuous exposure to contamination, whether periodical or not, these mycotoxins fragilize the gut epithelia barrier and, by enter blood circulation, impact the immune system by way of the thymus, Bursa of Fabricius, bone marrow and primary avian lymphoid organs, as well as the spleen, mucosa associated lymph nodes and finally the liver which supplies all the nutrients to build antibodies and detoxify all existing “bad” metabolites.

    Additionally, in recent years, I’ve noticed increased incidence of bacteria-related problems such as Streptococcus, Enterococcus, Clostridia and others. I believe partly this happens due to increased sensitivity of birds, but also due to a lack of immune response. When the growth cycle is pushed, many different pathways are opened. Some feed substrate might not be digested, which can then feed the existing normal bacteria. When mycotoxins are also present, they disturb normal gut epithelia integrity and immune response and the whole system “collapses,” making the problem difficult to manage.

    Customer Case: A Broiler Integrator with Eight Houses and 400,000 Total Birds

    Presentation and environment: Frequent cases of wet litter in 308 Ross broilers raised up to 35 days old. No mortality but loss of performance, particularly at three weeks. Birds housed in intelligent houses with a controlled environment and an all in / all out system.

    Customer complained about feed quality, used acidifiers, probiotics, sporadically antibiotics when finding signs of necrotic enteritis. Several HPLC mycotoxin analyses found nothing. a few times, didn’t find anything (limit of detection!?).

    Solution: Client agreed that trying a direct application of Mycofix directly was the best next step. After application, cases of watery feces ceased. The problem was corrected without need to make additional dietary changes or add products.

    Explanation: Mild contamination below the limits of detection or undetectable with classic methods had occurred. Although mortality wasn’t impacted, mycotoxin contamination disturbed birds’ normal adsorption.


    Producers often struggle with whether to continuously apply mycotoxin deactivators as a preventative measure. Poultry margins are limited but we must consider that tiny losses are difficult to measure, even though they tend to be much costlier over a longer period. Vaccination and feed are the most expensive investments in the whole system and anything that interferes with their efficiency should be seen as very important.

    I truly believe mycotoxins are constantly present, though there are huge variations in contamination levels. They are not ubiquitous and so it makes sampling procedures very difficult. Frequent observations in the field are:

    • DON is associated with clostridia growth
    • FUM and DON are involved in several gut digestibility and inflammation issues, wet litter and diarrhea. Sub-clinical coccidiosis could easily disrupt as well.
    • Aflatoxins and trichothecenes affect liver function and protein metabolism and, worse than all other effects, lead to immunosuppression.

    I recommend all poultry managers consider continuous feed application with a mycotoxin deactivator that is certified and uses proven mode of action. This provides assurance that the main mycotoxins and their associated synergies are covered preventing subclinical effects ensuring that vets are able to diagnose the real causes of disease. It’s worth it to have a product against mycotoxins in starter's and grower’s phase, and eventually finishing phase, readjusting dosages according to any signs or lab analysis that indicates sporadic increase of contamination. The dosage should be optimized for economic reasons, but must still correspond with the contamination of the feed, and might vary from case to case. 


    Today’s analytical methods like those developed by Biomin and our partners are tools to help to manage mycotoxin risk, but not to decide whether we should prevent or not. It’s important to remember that the official guidelines on mycotoxin contamination levels, such as those from the European Union, are very different from the what we really see in the field, where effects are visible at much lower contamination levels, revealing more sensitivity than expected from the official guidelines. It’s in the hands of all professionals to recognize mycotoxins as a permanent threat, at all levels, and manage it to ensure their poultry business is sustainable and profitable.