Mycotoxins in Poultry Feed
Uncovering which mycotoxins regularly contaminate poultry feed and the harm caused by mycotoxicosis in poultry.
Mycotoxins in poultry feed pose a constant threat to the poultry industry globally. Many of the feed ingredients found in typical poultry rations can be contaminated by harmful mycotoxins that are ingested by birds and have a number of serious consequences.
Some fungi produce mycotoxins on the field, while other fungi produce mycotoxins during the storage of grains.
The BIOMIN Mycotoxin Survey provides regular update on the occurrence of mycotoxins in the raw commodities and finished feeds based on thousands of samples collected from across the globe.
Effects of mycotoxins in poultry
Poultry farm animals have heterogeneous sensitivity to mycotoxins, as different species suffer from different toxic effects. Ducks, geese, and turkeys seem to be more sensitive to mycotoxicoses than chickens and quails. Young chickens are more sensitive to the effects of mycotoxins.
Aflatoxins in chickens
Aflatoxins are known to have a hepatotoxic effect in poultry and also a hepatocarcinogenic effect in exposed animals. The most common pathological lesions associated with aflatoxicosis in poultry are found in the liver, lymphoid organs, and testes, often occurring over a period of chronic exposure. In acute-subacute aflatoxicosis, the liver appears enlarged, pale yellow in color, friable, and usually the gall bladder is also enlarged and filled with bile.
The pancreas is usually small and depigmented and there could be hemorrhages on subcutaneous tissue and muscles. In chronic aflatoxicosis, the liver is small, firm, and rounded. Sometimes this organ is very small, rounded, and rubbery, and often complicated with ascites and hydropericardium. The other consistent lesions in aflatoxicosis can be found in the bursa of Fabricius, thymus, and spleen, all of which appear smaller than normal. In male parent stock breeder birds, the size of the testes could also be significantly reduced.
Various metabolic pathways of aflatoxins
The metabolic pathway of aflatoxins could be different. Aflatoxin B1 can enter the cell and be metabolized via monooxygenases in the endoplasmic reticulum to hydroxylated metabolites, which are further metabolized to glucuronide and sulfate conjugates. Or it can be oxidized to a reactive epoxide state, which undergoes spontaneous hydrolysis to AFB1-8,9-dihydrodiol and bind to proteins, resulting in cytotoxicity. The epoxide version can react with DNA or protein, or be detoxified by an inducible glutathione S-transferase to the glutathione (GSH)-conjugate. Both the DNA adduct and the protein adducts have proven useful as biomarkers in humans and laboratory animals.
The effects of mycotoxins in poultry are very complex and varies greatly according to their mechanism of toxicity affecting several organs and, in case of high contamination levels, may even lead to death of animals. When mycotoxins are present simultaneously in feed, they may have synergistic or additive effects.
Even at low levels of mycotoxins in feed, during sensitive period of production cycle or when exposed for long periods, can impair the immune system leading to the immune suppressive conditions. Aflatoxins, ochratoxin, trichothecenes, and fumonisins are known to induce immune suppressive effects in chickens, rendering them more susceptible to diseases (Singh et al., 1990, Ghosh et al., 1991). In addition, low level of mycotoxins can have an antimicrobial effect and can cause feed passage (Devegowda and Murthy, 2005).
AFB1 - Aflatoxin B1 ; FB1 – Fumonisin B1 ; DON – Deoxynivalenol; OTA – Ochratoxin A; ZEN – Zearalenone; FA – Fusaric acid; DAS – Diacetoxyscirpenol; CPA – Cyclopiazonic acid; MON – Moniliformin
Impact on gastrointestinal tract
Any mycotoxins present in feed are delivered straight to the gastrointestinal tract (GIT) of the birds, the organ most affected by mycotoxins. The gastrointestinal tract is the most important organ for converting feed into energy, and its ability to function properly is directly linked to poultry productivity. Gastrointestinal tract (GIT) is also the biggest immune organ in the body system.
Among the major mycotoxins, DON (deoxynivalenol), ZEN (zearalenone) and FUM (fumonisins) are often overlooked when considering their impact on poultry health and productivity since their clinical symptoms are not usually obvious or visible. However, there have been a number of scientific and commercial trials that prove these Fusarium mycotoxins are closely related to some important poultry diseases.
Impaired immunity at low mycotoxin contamination levels
Immunotoxic substances such as mycotoxins are unsuspected players in the failure of vaccines to provoke a proper immune response.
DON and its co-occurrence with FUM are known to modulate the immune function. One good example is the reduction in the number of antibody titres against vaccine programs in poultry. Several research results have shown that DON and FUM reduce antibody response to Newcastle Disease (ND) and Infectious Bronchitis Virus (IBV). In one experiment conducted in Austria, the feeding of a DON-contaminated diet decreased serum antibody titres against the IBV vaccine (Figure 4) compared to the control diet.
Mycofix® was able to counteract the effects of deoxnivalenol on IBV antibody titres in broilers.
Effects of mycotoxins in week one chicks
Week one chicks are at a crucial stage with seemingly minor issues having the potential to determine their health prospects in both the short and long term. Development of the intestinal tract and an active immune system is the central foundation of a healthy bird’s life, and it is exactly that which is at risk from early exposure to mycotoxins. Interference at this stage, even if low-level, can have disastrous results at a later stage. Low mycotoxin doses can combine with environmental stressors, even if they are out of the rearer’s control.
This combination can result in invisible losses, with subclinical effects that include:
- Disruption of gut health
- Greater susceptibility to disease
- More serious immune problems in later life
- Further losses to economic performance
- Signs of infection
Read more about the mycotoxin risk in 1-week-old chicks.
Diagnosis of mycotoxicosis in poultry
Clinical signs and pathological lesions on primary target organs can be used as an early warning system (EWS) for mycotoxin contamination in feed/raw materials.
Mycotoxin-induced illness, or mycotoxicosis, may be difficult to directly observe. There are several common clinical signs and pathological lesions of mycotoxicoses in poultry.
Signs of mycotoxin ingestion by birds include:
- A flock in a farm which consumed the same feed/raw materials are affected
- Antimicrobial treatment has little or even no effect on the disease
- Field outbreaks are seasonal and associated with specific feedstuffs
- Examination of the suspected feed reveals signs of fungal activity (Richard, 2012).
Even though the effects of mycotoxins are very complex and there is a great variation in possible symptoms, target organs, and pathological lesions from one mycotoxin to the other (Naehrer, 2012), presumptive diagnosis can be based on clinical signs, pathological lesions on target organs, especially when moldy ingredients or feed are evident.
Definitive diagnosis should be based on isolation, identification, and quantification of the specific mycotoxin/mycotoxins in feed ingredients or finished feed. Samples of feed and ingredients should be collected and promptly submitted for laboratory analysis. Multiple samples should be collected from different sites of mycotoxin formation zone (“hot spots”) (Whitaker et al., 2005, Krska and Schuhmacher, 2012).
Mycotoxin risk management in poultry
However, clay mineral binders are not an effective answer to all major mycotoxins. Especially not against trichothecenes mycotoxins since their structures are not suitable for adsorbing by binders. Biotransformation using microbes and enzymes is the most effective strategy. It provides reliable protection against mycotoxins, biodegrading them into non-toxic metabolites. The biotransformation is fast, specific and irreversible.
In addition to biotransformation, a bioprotection strategy is also important. Variety of feed additives is available that contains plant and algae extracts to provide a hepato-protective effect and to overcome the immune suppression caused by mycotoxins. A combination of different strategies can counteract the negative effects of mycotoxins in poultry more completely, especially in cases of multi-mycotoxin contamination with the poorly absorbed fusarium mycotoxins in poultry feed.