Ochratoxin: a risk for human and animal health

• environmental conditions, such as temperature and water activity
• The type and integrity of the seeds.

While A. ochraceus grows better on oilseeds (peanuts and soybeans) than on cereal crops, P. verrucosum may develop better on wheat and corn.

The presence of OTA in animal feed varies from country to country. The highest amounts have been reported in northern Europe and North America (World Health Organisation, 2002).

Effects of OTA on Animal Health and Production

[register]Food contaminated with OTA has its greatest economic impact on monogastric animals.  Ruminants are more resistant than monogastrics to the toxicity of this mycotoxin.

• In general, exposure to contaminated food reduces animal growth rates and affects animal production.

Pigs are generally considered to be the most susceptible species to nephrotoxicity caused by Ochratoxin A. Nephropathy, without renal impairment, was observed in sows fed diets containing 1 mg OTA/kg feed for two years. On the other hand, sows fed diets containing 0.2 mg OTA/kg feed showed no nephropathy signs during the same period(EFSA, 2006).

In another study carried out with pigs, ingestion of feed containing 25 μg of OTA/kg decreased feed efficiency, daily weight gain and final body weight (Malagutti et al., 2005).

The poultry industry is also affected by Ochratoxin A contamination. Turkeys, chickens and ducklings are susceptible to this toxin. Typical signs of avian ochratoxicosis are:

• Reduction in weight gain
• Poor feed conversion
• Decreased egg production
• Poor eggshell quality
• Nephrotoxicity

Numerous studies revealed that even exposure to low levels of OTA (0.5 mg/kg feed) altered yields. Including reductions in feed intake, growth rate and poor feed conversion efficiency (Wang et al., 2009).

A reduction in egg production and egg weight was recorded in laying hens when the animals received an OTA-contaminated diet at levels of 2 and 3 mg/kg (Verma et al., 2003).

The following signs have been observed:

• Weight loss
• Diarrhea
• Excess urine excretion
• Kidney injuries

in chickens fed a diet contaminated with 2mg of OTA/kg (Hoehler and Marquardt, 1996).

Presence of OTA in animal products 

The presence of OTA in food products of animal origin can occur as a result of both direct fungal contamination of animal products or from indirect contamination through contaminated food. The latter is usually the main cause of mycotoxin contamination problems.

Little information is available on the rate of transfer of this toxin to the milk of dairy cows. In dairy sheep, the remainder was less than 1% (Boudra et al., 2005). It is believed that the concentration of OTA in human milk or other non-ruminant mammals may be higher than that of ruminants (Müller and Müller, 1998).

• Residues of OTA have also been detected in the muscle of chickens and in eggs (Piskorska-Pliszczyńka and Juszkiewicz, 1990).

The presence of Ochratoxin A in human food products both from plant and animal origin has been recognized as a potential danger to human health globally.

The strongest associations were observed with plant-based foods and to a lesser extent, with animal-based foods.

Mitigating the effects of Ochratoxin A in the animal industry

Several different strategies have been employed to reduce the risk of Ochratoxin A entering the animal feed industry or its transfer into the food chain.

For this purpose, acids (such as propionate) are usually included in feed to prevent mold growth and mycotoxin production.

• However, mycotoxins can contaminate ingredients before they reach food factories, due to complications related to the control of climate and environmental conditions.

Rigorous risk management protocols in food factories to prevent contaminated grains from being incorporated in animal feed, mycotoxin elimination from raw materials through chemical and physical methods, or the administration of OTA contaminated diets to less susceptible animal species, all represent alternative strategies considered by the feed industry.

The formal establishment of risk management protocols to identify mycotoxin contaminated ingredients is considered mandatory for food safety assurance.

However, mycotoxin analysis with the use of ELISA are not very sensitive. On the other hand, near-infrared (NIR) spectroscopy is likely to improve control strategies used within the food milling industry.

As a precautionary measure, it is important to ensure a quality control of each batch to confirm the absence of caked products and/or corroded, broken or damaged grains by insects.

Many physical methods, including the application of high temperature or heat drying, have been carried out to detoxify Ochratoxin A. However, once it it released into food, this type of mycotoxin is very difficult to destroy.

In case Ochratoxin A poses a risk for a certain feed, several treatment methods have been tested to eliminate or reduce its harmful effects in animals. These include the use of specific adsorbing agents that block mycotoxins found in digestive contents or microorganisms which are capable of biotransforming mycotoxins into non-toxic metabolites. As well as the use of antioxidant compounds.

The use of adsorbents that bind to mycotoxin efficiently in the gastrointestinal tract, presents a promising and inexpensive approach to reduce the negative effects of  OTA within the animal industry.

• Hydrated calcium-sodium aluminosilicate, activated charcoal, bentonite and cholestyramine, and esterified glucomannan have been used in animal feed to decrease the adverse effects of OTA.

• Other substances, such as antioxidants, have also been evaluated to decrease the toxicity of OTA in several species.

• Abdel-Wahhap et al. (2005) and Özçelik et al. (2004) found that melatonin exhibits a preventive effect against oxidative stress induced by Ochratoxin A and structural damage to the kidney through its role in free radical scavenging and/or the prevention of lipid peroxidation.

• Grosse et al. (1997) also demonstrated that the incorporation of alpha-tocopherol into the diet decreased DNA damage caused in the kidney by 58% with a single administration of OTA in mouse and rat kidneys.

• In other studies, the addition of a plant extract (artichoke extract) or sesame seed to laying hen diets showed protection against the suppressive effect of Ochratoxin A on egg production and the toxic effect on various internal organs (Stoev et al., 2010).

Conclusion

Food contamination by Ochratoxin A has sparked widespread public concern around the world. The main reasons arise from the fact that this mycotoxin is considered a nephrotoxic and carcinogenic agent, being the cause of several kidney diseases.

OTA is found mainly in cereals and oilseeds and to a lesser extent, in animal products. However, several strategies are being carried out in the animal feed industry to prevent or reduce food contamination by this toxin.

The most applicable method so far is the establishment of risk management protocols to identify and prevent the incorporation of contaminated ingredients within animal feed.

Current mitigation strategies include the use of binding agents designed to block the absorption of OTA from the gastrointestinal tract, or microorganisms and enzymes capable of biotransforming mycotoxins into non-toxic metabolites.

Source: Denli y Perez, 2010

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