Aflatoxin is a secondary metabolite produced by toxigenic strains of A. flavus and A. parasiticus. Chemically, aflatoxins belong to the bifuranocoumarin group, with aflatoxins B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2) being the most toxic. Liver is the main organ affected by these toxins.
Poultry is considered as the most susceptible animal species to aflatoxins. A meta-analysis (Andretta et al 2011) carried out on broiler performance in response to mycotoxins showed that aflatoxin (average concentration 0.95mg/kg of feed) and ochratoxin had the biggest effects on broiler performance. Aflatoxins on average significantly reduced feed intake by 10% and growth rate by 12%. Aflatoxins also significantly increased liver weight by 22% and the weight of kidneys, lungs, gizzard and the heart. Aflatoxins presented the most important effects of all mycotoxins on organ weight in broilers.
Occurrence of aflatoxins in feed ingredients
Global mycotoxin surveys for 2015 feed and feed ingredient samples revealed that 20% of complete diets were contaminated with Aflatoxin of which 5% at a level of Aflatoxins above risk threshold. The feed ingredient most frequently contaminated with aflatoxin above risk threshold level was corn.
Aflatoxin production occurs primarily in regions with tropical or subtropical climates. Hence, from a European perspective, imported feed such as peanut cake, palm kernel, copra and corn gluten meal (depending of origin) is considered to be the most common source of exposure.
A recent review (Pinotti et al 2016) on the global occurrence of mycotoxins states that aflatoxins are most often detected in Southern Europe, Africa, South Asia and Southeast Asia (average values of positive samples higher than 30%).
Regulatory guidelines for aflatoxin limits in poultry diets
In Brazil, the presence of aflatoxins in corn is regulated by the Ministry of Agriculture through Decree 183 of March 21, 1996 and Resolution 274 of October 15, 2002 of the National Sanitary Surveillance Agency, which established a maximum limit of 20 μg/kg for the sum of aflatoxins B1, B2, G1 and G2.
In the EU the presence of undesirable substances (chemical contaminants) in feed is controlled by EC Directive 2002/32 (as amended). The Directive sets maximum permitted levels (MPLs) for substances that are present in, or on, animal feed that pose a potential danger to animal or human health or to the environment, or could adversely affect livestock production. Currently, aflatoxin B1 is the only mycotoxin with MPLs. MPLs of aflatoxin B1 have been set as low as reasonably achievable in order to protect animal and public health. The aflatoxin B1 limit for poultry diets in the EU is 20 μg/kg.
In the US the Food and Drug Administration (FDA) has established guidelines for the maximum toxin level that can be safely fed to the animal. See table below.
FDA’s action levels for aflatoxin in poultry feed
FDA aflatoxin guidelines