MYCOTOXINS - THEIR IMPACT ON POULTRY HEALTH AND PERFORMANCE

MYCOTOXINS

Aflatoxin is responsible for poor weight gain and feed efficiency, reduced egg production and egg weight, increased liver fat, change in organ weights, reduction in serum protein levels, carcass bruising, poor pigmentation and liver damage, vaccination failures, poor antibody titers and disease outbreaks. Farmers facing economic losses due to reduced feed consumption, growth rate, bone firmness, egg production and excessive mortality at high dietary concentrations of Ochratoxin. Fumonisins causes diarrhea, decreased feed intake and body weight gain, thymic atrophy, multifocal hepatic necrosis, biliary hyperplasia and rickets. Trichothecens causes oral lesions at low concentration but at higher concetration in feed responsible for feed refusal, decreased body weight gain, reduce egg sheel quality and hen day egg, decreased the size of bursa of fabricius, proteinemia and immunosuppression. Zearalenone is a lipophilic and nonsteroidal oestrogenic mycotoxin. Hydroxysteroid dehydrogenases convert zearalenone into α-zearalenol and β-zearalenol. α-zearalenol display a remarkably higher oestrogenic potency. The mechanism by which mycotoxins exert its action as shown in the below figure. 

NEW EMERGENT MYCOTOXINS

♦       CYCLOPIAZONIC ACID

Cyclopiazonic acid (CPA) is responsible for central nervous system disorders like ataxia, paresis, paralysis and opisthotonus. The CPA impacts calcium absorption which causes gizzard erosion and can effect on egg shell and bone density. A decrease in the weight of bursa of fabricius leads to weakened immune response after vaccination, followed by an increase in the weight of liver, kidneys and forestomach. High level of CPA ingestion can cause decreased weight gain, poor feed conversion and high mortality.

♦       MYCOPHENOLIC ACID

Despite having acute toxicity, mycophenolic acid may be an important indirect mycotoxin. It is highly immunosuppressive, thereby paving the way for bacterial and fungal infections.

♦       MASKED MYCOTOXINS

Mycotoxins also occur in conjugated form, either soluble or attached to macromolecule. The conjugated form of mycotoxins can emerge either after the metabolization of living plants, fungi and mammals, or after food processing. To protect from xenobiotic compounds (e.g. pesticides, mycotoxins), plants get converted to more polar metabolites, which were further stored in vacuoles or conjugated to biopolymers, such as cell wall components. Mycotoxins can conjugate with sugars, amino acids and proteins. Some mycotoxin conjugates like 3-acetyl deoxynivalenol and 15-acetyl deoxynivalenol, can be found in Fusarium contaminated cereals. Depending on the type of linkage to proteins, starch, pectins, hemicellulose, cellulose and lignin, it is conceivable that at least some of the bound mycotoxins could become bioavailable in the digestive tract of animals.

INTERACTIONS AMONG MYCOTOXINS

Most of the mycotoxin studies showed a synergistic or additive interaction on animal performance. It was observed that a combination of mycotoxins, at concentrations that individually should not cause negative effects, may negatively affect bird’s health and performance (Table-1).

Table-1: Interactions among various mycotoxins and their combinations

*Note: DAS – Diacetoxyscirpenol; DON – Deoxynivalenol; T-2 toxin – Type A trichothecene mycotoxin.

TOLERANCE LEVEL

As mycotoxins are harmful, European Food Safety Authority (EFSA) has recommended the maximum tolerance level for different mycotoxins for poultry feed and raw materials. The tolerance limits were shown in Table 2 and the limits varies for each mycotoxin. Global occurrence data reported during the past 10 years on the incidences and maximum levels of mycotoxins in raw cereal grains suggest that the grains were possibly contaminated with atleast single mycotoxin (Table-2).

Table-2: Various mycotoxin tolerance levels and incidences

DETECTION

Enzyme-linked immunosorbent assay (ELISA) is commonly used for the analysis and detection of mycotoxins in feed and feed ingredients. Increasing incidence of multi-mycotoxin contamination and their synergistic effect on performance, force the feed producer think forward to detect multi-mycotoxins within short time limit. High performance liquid chromatography (HPLC) has open the path to detect multiple mycotoxins simultaneously in a sample. The latest technique using liquid chromatography coupled to mass spectrometry, increased this potential phenomenally, to detect hundreds of mycotoxins simultaneously in a sample. This new development led to the detection of masked and emerging mycotoxins, which are neither routinely screened nor regulated by legislations.

CONCLUSION

To prevent the mycotoxin contamination, excellent management at every level of feed raw materials production, processing and storage is essential. Practically, it is very difficult to check all the batches of raw materials to detect mycotoxins having detrimental effect on bird, for every level of feed producer. Newly emergent mycotoxins, masked mycotoxins, synergism of mycotoxin where they are individually within the permissible limit, made the situation for compulsory inclusion of toxin binder in feed. Considering the criteria of non-digestible, specific to mycotoxin binding, without impacting feed nutrients and with narrow range of dosing, toxin binder should be selected. Recent technology of hybrid nanosilicate and synthetic tectosilicate for mycotoxin management, having in vitro and in vivo proven efficacy against all the major mycotoxins, will give complete protection to poultry birds in all the seasons. 

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