Mycotoxins are highly toxic secondary metabolic products of moulds. They are generally produced by Fusarium, Aspergillus and Penicillium species and found on common feedstuffs such as grains. They may cause different toxic effects in animals, called mycotoxicoses, varying from immune suppression, estrogenic or neurotoxic effects to death in severe cases.
The sensitivity to the various mycotoxins differs between animal species. The sensitivity also depends on other factors such as those that are toxin-related (type of mycotoxin consumed, level and duration of intake), animal-related (sex, age, breed, general health, immune status, nutritional standing) and environment-related (farm management, hygiene, temperature). Therefore, it is very difficult to detect and diagnose problems related to mycotoxins in the animal.
The discussion about the potential risk of mycotoxins in companion animals has increased following numerous recalls of different pet food products in recent years. Mycotoxins certainly represent a potential health threat to companion animals.
Dry pet food is of particular concern because of its high cereal content. Professor Böhm et al. (2008) investigated 76 dry dog food samples from Austria for their mycotoxin contamination. The results of this survey showed that 97% of all tested samples were contaminated with deoxynivalenol with concentrations up to 1386 ppb. Zearalenone was found in 47% (concentrations up to 664 ppb) and fumonisins in 42% (concentrations up to 568 ppb) of the dry dog food samples.
What are the possible mycotoxin effects that can be observed in pets?
Aflatoxins are the most commonly known mycotoxins as they are potential carcinogens and can be toxic to the liver. Loss of appetite, jaundice, lack of energy, vomiting or death has been described in dogs and cats exposed to aflatoxins (Hussein et. al. 2001). In addition, it was observed, that death generally occurs in 3 days with LD50 levels ranging from 0.5 to 1.0 mg/kg in dogs and 0.3 to 0.6 mg/kg in cats depending on the age of the animal (Hussein et. al., 2001).
It was reported that hundreds of dogs were killed after aflatoxin ingestion in the period from November 2008 to January 2009. Samples of the dog foods consumed showed contamination levels of aflatoxins up to 150 ppb (Feedinfo 2009 and All About Feed 2009). Additionally, Compas et al. (2009) investigated 180 dog food samples in Brazil for the presence of fungi which could produce mycotoxins. A. flavus and A. parasiticus were the prevalent species found and were considered a potential risk for production of aflatoxin B1 in feedstuffs where environmental storage conditions were not adequate.
The sensitivity of different pet species to aflatoxins expressed as oral LD50 levels is varied; with rabbits at 0.3 mg/kg of body weight (BW), cats at 0.55 mg/kg of BW, dogs at 1.0 mg/kg of BW and guinea pigs at 1.4-2.0 mg/kg of BW. These pet species are more sensitive than for example mice (9.0 mg/kg of BW) or hamsters (10.2 mg/kg of BW) (Hussein and Brasel, 2001). In guinea pigs affected by aflatoxins, pale liver syndrome increased with the dose of aflatoxins (CAST Report 2003). In addition, aflatoxins have been associated with equine deaths after consuming corn contaminated with a total aflatoxin concentration of 130 ppb. (Vesonder et al., 1991).
Other commonly found mycotoxins are ochratoxins (OTA). Similar to other animal species, the kidney is the primary target organ of OTA in pets with dogs being particularly susceptible. In one study, a daily dose of 0.2 mg OTA/kg BW for 2 weeks or a single dose of 7.8 mg OTA/kg body weight was lethal to young male beagle dogs. Clinical signs of OTA in dogs varied from anorexia, weight loss and vomiting to increased body temperature, dehydration, and prostration (Boermans and Leung 2007). Pühringer et al. (2007) investigated the ochratoxin A content of 101 feline kidneys and 55 cat food samples. The kidney samples (38 were contaminated with ochratoxins A) contained 0.31 – 5.18 µg of ochratoxin A/kg whereas the content in the cat food was very low with 0.31 – 2.41 µg ochratoxin A/kg (14 samples were positive). The results of this study suggested an increased dietary ochratoxin exposure in the cats but did not correlate with the pathological findings in the different kidney samples.
Fusarium mycotoxins (trichothecenes, zearalenone and fumonisins) are of main concern to companion animals because many feed ingredients are known to contain these toxins. For example, zearalenone and fumonisin B1 were found in 84 and 100% of pet food samples, with the highest levels being 299.5 and 1410 µg/ kg of feed respectively (Leung et al., 2006).
In general, trichothecenes cause negative effects on the immune system and lead to digestive disorders (such as vomiting, diarrhoea or feed refusal) or haemorrhages (EFSA 2004). In one study, food consumption was significantly reduced at levels of 4.5 µg/kg deoxynivalenol in dog food and 7.5 µg/kg deoxynivalenol in cat food (Hughes et al. 1999) and vomiting was noted. As in other animals, trichothecenes induce feed refusal, loss of appetite, reduced performance, weight loss and an unthrifty appearance in dogs (CAST Report 2003).
Zearalenone, an oestrogenic Fusarium mycotoxin, has been reported to cause problems in the reproduction system of all animal species (EFSA 2004). A 7-day dietary exposure of 200 µg zearalenone/kg of BW/day in female dogs showed cell damage in ovaries, oedema and hyperplasia and there was a general pathological change in the canine reproductive system (Boermans and Leung, 2007).
Fumonisins are other important Fusarium mycotoxins found mainly in corn. The most abundant group is fumonisin B1, representing up to 70% of food-borne fumonisins. Fumonisins inhibit sphingolipid synthesis and metabolism and damage various organs in animals (Voss et al. 2007). In horses, fumonisins can cause Equine Leukoencephalomalacia (ELEM), also called “hole-in-the-head-disease” due to liquefaction of neural tissue in the brain. ELEM is also characterized by feed refusal, lameness, blindness and depression. Death may occur 4 to 12 hours after the first symptoms are observed (Marasas et al., 1988).
Effective mycotoxin management
Mycotoxins are possible contaminants of pet food thereby possessing a potential health threat to companion animals. Pre- and post-harvest controls like “Good Agricultural Practice” or proper storage can reduce but not prevent the risk of mycotoxin contamination. Therefore, in order to protect companion animals from the hazardous effects of mycotoxins, feed additives are indispensable.
These feed additives protect animal health by deactivation of the mycotoxins in contaminated feed. They deactivate the toxins directly in the gastrointestinal tract of animals, based either on adsorption of those mycotoxins with suitably located polar functional groups, or biological degradation – bio-inactivation.
Unike® and Toxynil® product lines from NUTRIAD represent specially developed feed additives that protect pet animals from mycotoxicoses by adsorption, bio-inactivation, organ, immune and antioxidant system support and represent an optimal solution for mycotoxin management for companion animals.
Radka Borutova DVM, PhD,
Business Development Manager, Nutriad International, Belgium
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