2. Biological importance of AFB1 in poultry

Currently, more than 400 different mycotoxins are known, but only six are currently considered to be of worldwide importance, and aflatoxins are the most toxigenic and investigated mycotoxins worldwide because their natural occurrence can cause serious economic losses and health problems [2, 3]. In terms of toxicity and occurrence, aflatoxin B1 (AFB1) is the most important mycotoxin due to its hepatotoxic and hepatocarcinogenic effects, which can result in immunosuppression, anorexia with reduced growth rate, decreased egg production, reduced reproductivity, poor feed utilization, anemia, hemorrhage, and increased mortality [4, 5]. Furthermore, intoxication with AFB1 has been linked to other severe effects such as teratogen-

Due to the severe and harmful effects of AFB1, many methods to reduce its toxic effects have been proposed. The first and best attempt to prevent the effects of AFB1 is to minimize its production through good agricultural practices (GAP), including cultivating practices in fields as well as harvest, transport, and storage conditions [7, 8], all these steps are under GAP. However, since prevention is not always possible, decontaminating and/or detoxifying methods have been gaining attention as an alternative to reducing AFB1 contamination of feed and grains. Methods of detoxification can be physical, chemical, or biological treatments of contaminated feed or grains, and they can be as simple as the physical separation through screening, classification, and selection of damaged grains or as complex as gamma irradiation or chemical methods using ammonia, ozone, hydrogen peroxide, or some acids and alkalis [9– 14]. Nevertheless, many of these methods to detoxify aflatoxin-contaminated feed are not currently available because they cannot be applied on a large scale and in a cost-effective

manner or because many of them are impractical, ineffective, or potentially unsafe.

still under developing and it needs more in vitro and in vivo research [24].

Another approach to prevent aflatoxicosis in animals is the addition of adsorbents in the diet for binding aflatoxin in the gastrointestinal tract so that these compounds impede its adsorption in the intestine [15]. Adsorbents have been recurrently used because of their economic feasibility and suitability for nutritional perspective [16]. Many studies have demonstrated that aluminosilicates, mainly zeolites, hydrated sodium calcium aluminosilicate (HSCAS), and aluminosilicate-containing clays, can effectively reduce aflatoxins toxicity to animals; being these inorganic materials, the most thoroughly studied adsorbents [17–21]. Alternatively, both carbon-based organic polymers and synthetic polymers have been tested, and some of them are currently on the market [17, 22]. Even though the cost of these polymers could be the limiting factor for practical applications, their use can help to solve the problems related with the use of aluminosilicates and clay adsorbents, such as binding preferly just to aflatoxins, the possibility to adsorb important micronutrients, and the risk of natural clays to be contaminated with dioxins [7, 23]. Nowadays, there are some highly promising research on the effectiveness of synthetic and organic polymers in adsorbing aflatoxins, although this field is

On the other hand, biological methods to prevent aflatoxicosis have also been evaluated showing promising results [25–28]. Many microorganisms, including bacteria, yeasts, molds, actinomycetes, and algae, have been tested for their ability in the control of aflatoxin contamination, mainly through adsorption and degradation [29, 30]. Among the bacteria tested, probiotics have been identified as a good option to reduce the availability of aflatoxins in vitro. Additionally,

esis, carcinogenesis, and mutagenesis [6].

150 Mycotoxins - Impact and Management Strategies

Poultry species are probably the most sensitive food-producing animals to AFB1 toxic effects, and small amounts of it severely damage animal health and the profitability of the productive system, which results in substantial annual economic losses to producers [6, 34–39].

However, there are also differences in terms of susceptibility to AFB1 among poultry species, which could be due to differences in hepatic metabolism of AFB1 in these species. According to comparative toxicological studies, ducklings and turkey poults are the most sensitive species to AFB1, followed by goslings and young pheasants with intermediate sensitivity, and finally, the chicks showed to have relative resistance to AFB1 injury [40]. Toxicity and carcinogenicity of AFB1 occur after its bioactivation by the cytochrome P450 (CYP450) mixed function oxidase system, resulting in a highly reactive AFB1 8,9-epoxide (AFBO), which forms covalent adducts with cellular macromolecules such as DNA, RNA, protein constituents, and some enzymes [41–44]. Since metabolic activation of AFB1 to AFBO by CYP450 is especially efficient in poultry species [45], they are extreme sensitivity to the toxic effects of AFB1. Another possible reason which may also explain the differences in susceptibility of poultry species is the variation in phase II biotransformation enzymes, such as glutathione S-transferase (GST), that catalyze a conjugation reaction of AFBO with endogenous glutathione (GSH). Although avian species are highly efficient in producing AFBO, they are not able to conjugate it effectively with GSH, which indicates that they have low GST activity [46, 47].

The most noticeable effect of AFB1 on poultry is the impair of all important productive parameters, including body weight gain, feed intake, feed conversion efficiency, pigmentation, processing yield, egg production, male and female reproductive performance, and an increased mortality [35, 48, 49]. These alterations in the productive parameters are the result of the physiological effects of AFB1 consumption, of which liver damage is the most notorious, characterized by its enlargement, pale yellow coloration, petechial hemorrhages and hematomas on the surface, usually accompanied with proliferation of biliary ducts and depletion of lymphoid organs [50–52]. However, for poultry industry AFB1 contamination and consumption are important because of its ability to decrease resistance to common infectious diseases, including parasitic, bacterial, and viral infections, due to depression of the humoral and cellular immune responses [53–57].
