Vomitoxin
Encyclopedia
Vomitoxin, also known as deoxynivalenol (DON), is a type B trichothecene
, an epoxy
-sesquiterpene
oid. This mycotoxin
occurs predominantly in grains such as wheat
, barley
, oat
s, rye
, and maize
, and less often in rice
, sorghum
, and triticale
. The occurrence of deoxynivalenol is associated primarily with Fusarium
graminearum (Gibberella zeae) and F. culmorum
, both of which are important plant pathogens which cause Fusarium head blight in wheat and Gibberella ear rot in maize. A direct relationship between the incidence of Fusarium head blight and contamination of wheat with deoxynivalenol has been established . The incidence of Fusarium head blight is strongly associated with moisture at the time of flowering (anthesis), and the timing of rainfall, rather than the amount, is the most critical factor. However, increased amount of moisture towards harvest time has been associated with lower amount of vomitoxin in wheat grain due to leaching of toxins Furthermore, deoxynivalenol contents are significantly affected by the susceptibility of cultivars towards Fusarium species, previous crop, tillage practices, and fungicide use
F. graminearum grows optimally at a temperature of 25 °C and at a water activity above 0.88. F. culmorum grows optimally at 21 °C and at a water activity above 0.87. The geographical distribution of the two species appears to be related to temperature, F. graminearum being the commoner species and occurring in warmer climates. Deoxynivalenol has been implicated in incidents of mycotoxicoses in both humans and farm animals.
When compared to other trichothecene
mycotoxins which can form in grains and forages, vomitoxin is relatively mild. Reduced feed intake, and the accompanying decrease in performance, are the only symptoms of vomitoxin toxicity livestock
producers will likely encounter. This response to vomitoxin appears to occur through the central nervous system
. Vomitoxin belongs to a class of mycotoxins (tricothecenes) which are strong protein
inhibitors
. Inhibition of protein synthesis following exposure to vomitoxin causes the brain to increase its uptake of the amino acid
tryptophan
and, in turn, its synthesis of serotonin
. Increased levels of serotonin are believed to be responsible for the anorexic effects of DON and other tricothecenes. Irritation of the gastrointestinal tract may also play a role in reducing feed intake... This fact may also partially explain the high incidence of paraesophageal stomach ulcers observed in sows off feed during feed refusal.
Trichothecene
Trichothecenes are a very large family of chemically related mycotoxins produced by various species of Fusarium, Myrothecium, Trichoderma, Trichothecium, Cephalosporium, Verticimonosporium, and Stachybotrys...
, an epoxy
Epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
-sesquiterpene
Sesquiterpene
Sesquiterpenes are a class of terpenes that consist of three isoprene units and have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be acyclic or contain rings, including many unique combinations...
oid. This mycotoxin
Mycotoxin
A mycotoxin is a toxic secondary metabolite produced by organisms of the fungus kingdom, commonly known as molds. The term ‘mycotoxin’ is usually reserved for the toxic chemical products produced by fungi that readily colonize crops...
occurs predominantly in grains such as wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
, barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
, oat
Oat
The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed...
s, rye
Rye
Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...
, and maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, and less often in rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
, sorghum
Sorghum
Sorghum is a genus of numerous species of grasses, one of which is raised for grain and many of which are used as fodder plants either cultivated or as part of pasture. The plants are cultivated in warmer climates worldwide. Species are native to tropical and subtropical regions of all continents...
, and triticale
Triticale
Triticale is a hybrid of wheat and rye first bred in laboratories during the late 19th century. The grain was originally bred in Scotland and Sweden. Commercially available triticale is almost always a second generation hybrid, i.e., a cross between two kinds of primary triticales...
. The occurrence of deoxynivalenol is associated primarily with Fusarium
Fusarium
Fusarium is a large genus of filamentous fungi widely distributed in soil and in association with plants. Most species are harmless saprobes, and are relatively abundant members of the soil microbial community. Some species produce mycotoxins in cereal crops that can affect human and animal health...
graminearum (Gibberella zeae) and F. culmorum
Fusarium culmorum
Fusarium culmorum is a plant pathogen and the causal agent of seedling blight, foot rot, ear blight, stalk rot, common root rot and other diseases of cereals, grasses, and a wide variety of monocots and dicots. In coastal dunegrass , F. culmorum is a non-pathogenic symbiont conferring both salt...
, both of which are important plant pathogens which cause Fusarium head blight in wheat and Gibberella ear rot in maize. A direct relationship between the incidence of Fusarium head blight and contamination of wheat with deoxynivalenol has been established . The incidence of Fusarium head blight is strongly associated with moisture at the time of flowering (anthesis), and the timing of rainfall, rather than the amount, is the most critical factor. However, increased amount of moisture towards harvest time has been associated with lower amount of vomitoxin in wheat grain due to leaching of toxins Furthermore, deoxynivalenol contents are significantly affected by the susceptibility of cultivars towards Fusarium species, previous crop, tillage practices, and fungicide use
F. graminearum grows optimally at a temperature of 25 °C and at a water activity above 0.88. F. culmorum grows optimally at 21 °C and at a water activity above 0.87. The geographical distribution of the two species appears to be related to temperature, F. graminearum being the commoner species and occurring in warmer climates. Deoxynivalenol has been implicated in incidents of mycotoxicoses in both humans and farm animals.
When compared to other trichothecene
Trichothecene
Trichothecenes are a very large family of chemically related mycotoxins produced by various species of Fusarium, Myrothecium, Trichoderma, Trichothecium, Cephalosporium, Verticimonosporium, and Stachybotrys...
mycotoxins which can form in grains and forages, vomitoxin is relatively mild. Reduced feed intake, and the accompanying decrease in performance, are the only symptoms of vomitoxin toxicity livestock
Livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...
producers will likely encounter. This response to vomitoxin appears to occur through the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
. Vomitoxin belongs to a class of mycotoxins (tricothecenes) which are strong protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
inhibitors
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
. Inhibition of protein synthesis following exposure to vomitoxin causes the brain to increase its uptake of the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
and, in turn, its synthesis of serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
. Increased levels of serotonin are believed to be responsible for the anorexic effects of DON and other tricothecenes. Irritation of the gastrointestinal tract may also play a role in reducing feed intake... This fact may also partially explain the high incidence of paraesophageal stomach ulcers observed in sows off feed during feed refusal.
- Human foods: Vomitoxin is not a known carcinogenCarcinogenA carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
as with aflatoxinAflatoxinAflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, the most notable ones being Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known...
. Large amounts of grain with vomitoxin would have to be consumed to pose a health risk to humans. The U.S. Food and Drug Administration has established a level of 1 ppm (parts per million) restriction of vomitoxin. - Companion animals: Dogs and cats are restricted to 5 ppm and of grains and grain byproducts and that the grains not exceed 40% percent of the diet.
- Livestock and farm animals: In animals and livestockLivestockLivestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...
, vomitoxin causes a refusal to feed and lack of weight gain when fed above advised levels. Restrictions are set at 10 ppm for poultryPoultryPoultry are domesticated birds kept by humans for the purpose of producing eggs, meat, and/or feathers. These most typically are members of the superorder Galloanserae , especially the order Galliformes and the family Anatidae , commonly known as "waterfowl"...
and ruminating beefBeefBeef is the culinary name for meat from bovines, especially domestic cattle. Beef can be harvested from cows, bulls, heifers or steers. It is one of the principal meats used in the cuisine of the Middle East , Australia, Argentina, Brazil, Europe and the United States, and is also important in...
and feedlot cattle older than 4 months. Ingredients may not exceed 50% of the animal's diet. Dairy cow limits are set at 2 ppm.
External links
- A comprehensive review on vomitoxin
- Microbiology of Animal Feeds
- Detailed information on different mycotoxins
- DON vendor's page from FermentekFermentekFermentek Ltd. is a biotechnological company, located in Atarot industrial zone, Jerusalem, Israel, specializing in the research, development and manufacture of biologically active, natural products isolated from microorganisms as well as from other natural sources such as plants and algae.The main...
- How Vomitoxin production is impacted by wheat resistance and growth stages