*Aflatoxin Occurrence, Detection, and Novel Strategies to Reduce Toxicity in Poultry Species DOI: http://dx.doi.org/10.5772/intechopen.107438*

growth-selected lines of Japanese quails of USDA experimental facilities in 1980s. This observation had thereafter led to the genetic selection of Japanese quails for resistance to acute aflatoxicosis by breeding survivors from a population of quails, which were given a single oral dose of aflatoxin that resulted in high mortality [271]. After five generations of selection, an 11-fold increase in resistance was attained in one of the aflatoxin-resistant lines. The next group of workers observed genetic variation in certain physiological parameters of selected commercial broiler populations and suggested the feasibility of genetic selection of chickens for infusing resistance to aflatoxicosis [272]. Many other researchers had observed genetic variation in a nonselected population of chickens [273].

The other successful directional selective breeding for AFB1 resistance was also reported [274]. Under their breeding trials, two populations of broiler chickens [Athens-Canadian (AC) versus another broiler commercial stock] were subjected to genetic selection for resistance to aflatoxicosis by exposing the respective chickens from each of the stocks (two) with a single oral dose of aflatoxin, which was capable of resulting in 40–70% mortality, otherwise. A simultaneous, non-selected control group was also maintained, which was not exposed to any AFB1. As for the selection method, the birds surviving the aflatoxin challenge were propagated as breeders, for subsequent generations. According to the outcome of their study, rapid progress was visible within the AC population for resistance to aflatoxin, whereas only moderate progress for AFB1 resistance was attained in the commercial broiler stock. After five generations of selection in the AC population, LD50 values of 9.42 and 17.05 milligrams aflatoxin per kg body weight (BW) were determined for both the non-selected and selected lines. Similarly, after four such generations of such selection in above commercial broiler population, LD50 values of 6.05 and 8.02 mg aflatoxin/kg BW were determined for the non-selected and selected lines, respectively. These experiments demonstrated that genetic progress for AFB1 tolerance could be achievable in chickens, but the quantum of such progress for resistance to AFB1 could be influenced by the population's background, meaning response to such genetic selection for such AFB1 resistance or tolerance was always a subject of genetic constitution of the hosts.

On a practical front, there have been couple of studies that attempted direct breeding of ducks for tolerance or resistance to AFB1's presence in diets, on selectivebreeding platforms, way back in 1980s, after which very little progress has been registered in duck-producing countries. The obvious interpretation could be that ensuring a diet with minimal cutoff levels for AFB1, which was achievable using toxin binders, mold inhibitors, etc., was probably preferred to (better than) raising stocks with resistance to AFB1.

#### *5.6.1 Epigenetic studies on aflatoxicosis*

Epigenetics is the study of heritable phenotypic alterations caused due to change in chromosomal topology rather than change in DNA sequence [275, 276]. The underlying epigenetic processes such as chromatin remodeling, non-coding RNAs (micro RNAs), DNA methylation, acetylation, deacetylation, histone modification, etc., are affected by prolonged exposure to aflatoxin, causing alteration in protein synthesis and thereby the gene expressions. Aflatoxin-B1 mainly induces DNA methylation, which plays a critical role in the development of all most all cancer types owing to its silencing effect on tumor suppressor genes [277]. In this process, the fifth carbon of the cytosine in dinucleotide 5'-CG-3′ is selectively methylated to form 5-mC [278, 279]. Aberrant methylation of promoters in eukaryotic cell may lead to silencing

#### *Aflatoxin Occurrence, Detection, and Novel Strategies to Reduce Toxicity in Poultry Species DOI: http://dx.doi.org/10.5772/intechopen.107438*

of regulatory genes especially tumor suppressor genes and thereafter, affect their signal pathways and lead to development of disease and cancers. Alteration in cellular epigenome compromises genomic stability and alters gene expression, which thereby affect the central dogma of molecular biology and ultimately phenotypic characters.

Few human studies have been reported in literature detailing the epigenetic changes which accompany aflatoxin-exposure, across various vital organs such as white blood cells, egg yolk, plasma, etc. It has been reported that maternal exposure to aflatoxin during early embryonic development leads to formation of aflatoxin albumin (AF-alb) adducts and genome-wide differential DNA methylation patterns of white blood cells for 71 CpG sites, including in genes related to growth and immune function [280]. It has been reported to cause various types of cancers such as colon cancer [281], sarcomas [282], lung cancer [283], ovarian cancer [284], leukemia [285], urological cancer [286], breast cancer [287], Hodgkin lymphoma [288], including cardiovascular diseases [289] and schizophrenia [290].

Though epigenetic approaches raise hopes for a long-term strategy to overcome aflatoxicosis problems in ducks, the literature is just hollow, except some rudimentary reports. The ICAR-DPR's own annual report [95] indicated that most significant aflatoxicosis-induced production losses peaked and precipitated only in alternate generations/years, despite emergence of naturally arisen dietary aflatoxins (10–50 ppb ranges throughout the year) since last decade, which suggest that epigenetic sensitization of the ducklings/ducks every generation at early or perinatal stages, which are usually the phases of methylation-induction processes in an epigenetic regime. The RC, CARI (now a regional Station of Directorate on Poultry, Research, Bhubaneswar, India) has just concluded a large-funded program on epigenetics research in ducks, which has shown positive feedbacks through better egg-production recorded from AF-sensitized ducks versus the controls, thus signifying feasibility of such approaches in coming decades.

#### **6. Conclusions**

Almost all classes of poultry are physiologically vulnerable and susceptible to aflatoxins, especially the AFB1, which produces acute, chronic, mutagenic, and teratogenic toxicity along with causing millions of dollars per year damage to the poultry industry, worldwide. The high frequency and levels of AFB1 recently found in food supplies, particularly, poultry feed of various countries indicate wide exposure of poultry birds to this toxin, which still remain uncontrolled. The most appropriate analytical method differs according to the nature of detected mycotoxin, e.g., for AFs, ZEN, OTA, HPLC fluorescence, and LC-MS/MS are commonly used, while for trichothecenes, GC-MS is mainly preferred. Due to the increasing abundance of AFB1 in poultry feed, several approaches are being evolved to counter or eliminate poisoning/toxicity so as to improve safety and palatability of food products. Between pre- and post-harvest strategies, there are many options available to reduce the toxicity to a great extent. Large-scale implementation of these techniques could make a large impact worldwide to reduce the aflatoxin related toxicities such as growth impairment, histopathology of organs, and immunosuppression in poultry birds. Development of suitable method for detection of aflatoxin in field level and environment-friendly detoxification keeping in view the food safety will be beneficial strategies for achievement of poultry products, which will be safe and secured for human consumption. Quality control of feed ingredients; prevention of fungal growth with reduction in concomitant aflatoxin production; use of efficient detection method and suitable environment-friendly detoxification

methods, are essential to the feed manufacturers to reduce the exposure to aflatoxin and to make the poultry production a profitable enterprise. Among various classes of AFB1-susceptible poultry species, recent research on epigenetics in ducks has shown some positive feedbacks regarding feasibility of such approaches in upcoming decades, while needs to develop poultry species genetically resistant to Aflatoxins through direct selection may not find a great favor from primary breeders anymore, in twenty-first century despite promising results documented during late-twentieth century.
