201
Mycotoxins are harmful substances produced by fungi in various foods and are
estimated to affect as much as 25% of the world’s crop each year. Most of these
mycotoxins belong to the three genera of fungi: Aspergillus, Penicillium, and
Fusarium. Although over 300 mycotoxins are known, those of most concern based
on their toxicity and occurrence are aflatoxin, vomitoxin, ochratoxin, zearalenone,
fumonisin, and T-2 toxin. They are produced in cereal grains as well as forages
before, during, and after harvest in various environmental conditions. The presence
of mycotoxins in feeds may decrease feed intake and affect animal performance. In
addition, the possible presence of toxic residues in edible animal products such as
milk, meat, and eggs may have some detrimental effects on human health. Fungal
contamination affects both the organoleptic characteristics and the alimentary value
of feeds and entails a risk of toxicosis. The biological effects of mycotoxin depend
on the ingested amounts, number of occurring toxins, duration of exposure to mycotoxin, and animal sensitivity. Mycotoxins display a diversity of chemical structures,
accounting for their different biological effects. Depending on their precise nature,
these toxins may be carcinogenic, teratogenic, mutagenic, immunosuppressive,
tremor genic, hemorrhagic, hepatotoxic, nephrotoxic, and neurotoxic. Mycotoxins
are metabolized in the liver and the kidneys and also by microorganisms in the
digestive tract. Therefore, often the chemical structure and associated toxicity of
mycotoxin residues excreted by animals or found in their tissues are different from
the parent molecule (Akande et al. 2006).
12.4 The Factors Affecting Mycotoxin Production
Mycotoxins to human and animal health have multiple factors affecting production
and/or presence of mycotoxins in foods or feeds. Hence, isolation and confirmation
of mycotoxigenic fungal species in foods or feeds don’t indicate the presence of
mycotoxins. Upon development of accurate and sensitive techniques for qualitative
and quantitative analysis of mycotoxins, researchers have found that various factors
operate interdependently to affect fungal colonization and/or production of the
mycotoxins. Factors that affect mycotoxin production and contamination can be
categorized as physical, chemical, and biological. Physical factors include environmental conditions conducive to fungal colonization and mycotoxin production such
as temperature, relative humidity, and insect infestation. Chemical factors include
the use of fungicides and/or fertilizers. Biological factors are based on the interaction between the colonizing toxigenic fungal species and substrate (Tola and
Kebede 2016).
Slightly higher CO 2 concentrations, interactions with the temperature, and the
availability of water can stimulate the growth of some mycotoxigenic species, especially under hydrous stress (Magan et al. 2011).
12 Fungal Mycotoxins
Mycotoxins are harmful substances produced by fungi in various foods and are
estimated to affect as much as 25% of the world’s crop each year. Most of these
mycotoxins belong to the three genera of fungi: Aspergillus, Penicillium, and
Fusarium. Although over 300 mycotoxins are known, those of most concern based
on their toxicity and occurrence are aflatoxin, vomitoxin, ochratoxin, zearalenone,
fumonisin, and T-2 toxin. They are produced in cereal grains as well as forages
before, during, and after harvest in various environmental conditions. The presence
of mycotoxins in feeds may decrease feed intake and affect animal performance. In
addition, the possible presence of toxic residues in edible animal products such as
milk, meat, and eggs may have some detrimental effects on human health. Fungal
contamination affects both the organoleptic characteristics and the alimentary value
of feeds and entails a risk of toxicosis. The biological effects of mycotoxin depend
on the ingested amounts, number of occurring toxins, duration of exposure to mycotoxin, and animal sensitivity. Mycotoxins display a diversity of chemical structures,
accounting for their different biological effects. Depending on their precise nature,
these toxins may be carcinogenic, teratogenic, mutagenic, immunosuppressive,
tremor genic, hemorrhagic, hepatotoxic, nephrotoxic, and neurotoxic. Mycotoxins
are metabolized in the liver and the kidneys and also by microorganisms in the
digestive tract. Therefore, often the chemical structure and associated toxicity of
mycotoxin residues excreted by animals or found in their tissues are different from
the parent molecule (Akande et al. 2006).
12.4 The Factors Affecting Mycotoxin Production
Mycotoxins to human and animal health have multiple factors affecting production
and/or presence of mycotoxins in foods or feeds. Hence, isolation and confirmation
of mycotoxigenic fungal species in foods or feeds don’t indicate the presence of
mycotoxins. Upon development of accurate and sensitive techniques for qualitative
and quantitative analysis of mycotoxins, researchers have found that various factors
operate interdependently to affect fungal colonization and/or production of the
mycotoxins. Factors that affect mycotoxin production and contamination can be
categorized as physical, chemical, and biological. Physical factors include environmental conditions conducive to fungal colonization and mycotoxin production such
as temperature, relative humidity, and insect infestation. Chemical factors include
the use of fungicides and/or fertilizers. Biological factors are based on the interaction between the colonizing toxigenic fungal species and substrate (Tola and
Kebede 2016).
Slightly higher CO 2 concentrations, interactions with the temperature, and the
availability of water can stimulate the growth of some mycotoxigenic species, especially under hydrous stress (Magan et al. 2011).
12 Fungal Mycotoxins