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Livestock Production
Wednesday, March 22, 2017 2:45:59 PM
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Mycotoxins in poultry - Prevention is key!

 

Kevin Vanneste, Nuscience group

  

 

Mycotoxins pose a serious threat to the health and production levels in poultry farming. According to the FAO (Food and Agriculture Organization), approximately 25% of the crops worldwide are affected. Most common mycotoxins toxic to poultry are T2-toxin and Deoxynivalenol (DON) (Fusarium spp.), Aflatoxin B1 (Aspergillus spp.) and Ochratoxin A (Aspergillus and Penicillium spp.). Poultry is less susceptible to Fumonisins and Zearalenone (ZEA) (Fusarium spp.) although they can impair performance as well. ZEA is typically metabolized in the liver into β-ZEA which has a lower binding affinity for estrogenic receptors compared to α-ZEA.

 

Toxicity: Importance of Oxidative Stress

 

On cellular level, mycotoxins exert their toxicity by disturbing protein synthesis directly, or indirectly through interactions with RNA and DNA. In addition, most mycotoxins can induce lipid peroxidation leading to oxidative stress. The main target organs are the gastro-intestinal tract, liver, kidneys and immune system consisting of rapidly proliferating cells and having a high protein turnover rate. Because mycotoxins exert their toxicity on the basic building blocks in the body, i.e. protein, DNA and RNA, a wide range of essential metabolic processes are affected. Mycotoxins can for example suppress immunity by inhibiting antibody production and altering cytokine production by T-cells, making the birds more susceptible to all kinds of infections. Also, the gastro-intestinal tract may be severely impacted as oxidative stress and suboptimal protein synthesis will cause decreased villus regeneration and lower

 

intestinal barrier function. Finally, inhibition of protein synthesis indirectly contributes to increased oxidative stress by negatively impacting the production of antioxidant enzymes (e.g. superoxide dismutase and glutathione-S-transferase).

 

Symptoms

 

The symptoms of mycotoxins in poultry are diverse and vary according to the type of mycotoxin, the mechanism of toxicity and the primary target organs (Table 1).

 

Table 1:  Overview of most important mycotoxins affecting poultry and their corresponding symptoms.

 

 

Ingestion of mycotoxins at high levels may result in acute disease with high mortality and sharp decline in productivity. In most cases however, mycotoxins are present in lower concentrations and mainly cause chronic, nonspecific symptoms like immunosuppression and decreased productivity.

 

Diagnosis

 

Diagnosing mycotoxins can be difficult because of the wide variation of effects. However, when suboptimal performance is observed in absence of infection, nutritional deficiencies or other detrimental management and environmental factors, mycotoxins should always be suspected. Clinical signs and post-mortem lesions on target organs can reinforce suspicion of mycotoxins. Finally, feed samples should be collected and analyzed for definitive diagnosis. Good sampling consists of taking different feed samples from different locations in the feed, mixing them and taking the desired quantity for analysis. For rapid and accurate mycotoxin analysis, the Nuscience laboratory has implemented Quantitox (Figure 1). This analytical device uses an immunoreceptor assay and is capable of quantifying Fumonisin, DON, Ochratoxin A, Aflatoxin, Zearalenone and T2-toxin.

 

 

 
Figure 1:  Quantitox device

  

Prevention

 

Tackling mycotoxins asks for an integrated prevention strategy. Despite preventive measures on field and storage level, complete prevention of mycotoxins in the feed is impossible. Therefore, adding mycotoxin counteracting components in final feed is of high importance. Considering the great variety of mycotoxin structures, different strategies have to be combined in order to specifically target individual mycotoxins. 

  • Adsorption

 Adsorption or binding of mycotoxins by nutritionally inert adsorbing agents is a well-known strategy against mycotoxins. Suitable adsorbents have a high binding capacity, bind mycotoxins irreversible, have a low affinity for vital components in the feed (e.g. vitamins and minerals) and are stable over a broad range of temperatures and pH values. The binding mechanism is thought to be chemisorption which depends on the three-dimensional structure, the polarity and charge of both the mycotoxin and adsorbent. A standard toxin binder such as aluminosilicate for example can only bind polar and 'flat' mycotoxins (e.g. aflatoxins) due to its layered structure and polarity (Figure 2). Binding 'flat' but nonpolar mycotoxins (e.g. Zearalenone) can only be done by modification of the aluminosilicate to increase hydrophobicity.

 

 

Figure 2:  Adsorption of 'flat' aflatoxin by mycotoxin binder 

  • Biotransformation  
Biotransformation is the preferred strategy for detoxification of non-adsorbable mycotoxins. DON for example has a globular three-dimensional structure whereby it doesn't fit between the layers of previously mentioned mycotoxin binders. In this case, biotransforming agents such as microorganisms or enzymes thereof are used to degrade the mycotoxins or transform or cleave it to less or non-toxic compounds. The mycotoxins then lose their toxicity because of the altered chemical structure. 
 

  • Bioprotection  

The third not to be underestimated strategy consists of adding supporting components to the animal's diet. This strategy has no direct influence on mycotoxins but reduces their negative effects on animal health and performance.

 

Supporting additives can protect the animal's organs that are often targeted by mycotoxins. The liver for example, well-known for its detoxifying action in the body, can be supported in detoxifying the mycotoxins and will recover much faster after damage caused by mycotoxins. Additives will also help to counteract oxidative stress. As stated earlier in 'Toxicity: Importance of Oxidative Stress', mycotoxins cause oxidative stress by inducing the production of free radicals and inhibiting the synthesis of important antioxidant enzymes. The resulting imbalance between free radicals and antioxidant capacity can lead to serious tissue damage with impaired health and performance as result. Natural antioxidants based on plant polyphenols can help the animal to restore the right balance and reduce oxidative stress in poultry.
 

 

 

For more of the article, please click here.

 

Article made possible through the contribution of Kevin Vanneste and Nuscience group

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