Mycotoxins and Animal Production

8/14/2019 Mycotoxins and Animal Production

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Mycotoxins and Animal Production

Manoj Sharma and R. S. Bal

Krishi Vigyan Kendra, Kapurthala 144 620 Punjab, India

[email protected]

Mycotoxins are poisons produced by a type of fungus known as molds. These

molds develop on various feedstuffs including roughages and concentrates, and

produce mycotoxins in the field before harvest, or post-harvest, during storage,

processing, or feeding. Mold growth and the production of mycotoxins are often related

to the extremes in weather conditions which can cause plant stress or hydration of

feedstuffs. Similarly, poor storage conditions affect feedstuff quality adversely and the

feeding conditions. The most favourable conditions for mold infestation are a

temperature range from 23F to 140F with approximately 70% humidity with sufficient

oxygen, physical damage to the commodity, a wide range of pH because molds do not

grow well at extreme low or high pH levels and presence of fungal spores. However, the

requirements for mold growth vary with the type of mold, for example, Aspergillus

species grow at lower moisture levels but aflatoxin production takes place at with higher

temperatures, whereas Fusarium species generally require higher moisture levels andare able to grow at much lower temperatures. It is pertinent to note that conditions most

suitable for mold growth do not necessarily indicate the optimum conditions for

mycotoxin formation. For example, the Fusarium molds associated with alimentary toxic

aleukia grow prolifically at temperatures of 77F to 86F without producing much

mycotoxin. However, at near freezing temperatures large quantities of mycotoxins are

produced without much mold growth.

TheAspergillus, Fusarium, and Penicillium molds produce mycotoxins which are

detrimental to cattle health. The mycotoxins of greatest concern are aflatoxin, which is

produced by Aspergillus spp., deoxynivalenol (DON), zearalenone, T-2 Toxin, and

fumonisin, which are produced by Fusarium spp. and ochratoxin produced by

Penicillium spp. Several other mycotoxins, produced by these and other molds, are
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known to be prevalent at times, including derivatives of those listed previously. A lack of

observation and lack of simple analytical techniques has probably made it difficult to

understand the prevalence of these and other mycotoxins and their impact on animal

production.

Fusarium commonly affects maize, wheat, barley, and also is found in oats, rye,

and triticale. It causes field diseases such as head blight (scab) in small grains, and ear

and stalk rots in maize, which are characterized by yield loss, quality loss, and

mycotoxin contamination.Aspergillus flavus and aflatoxin in maize are favored by the

heat and drought stress is enhanced by insect damage before and after harvest.

Mode of Action and Symptoms:

Mycotoxins increase disease incidence and reduce production efficiency in

cattle. They exert their effect by making alteration in nutrient content, absorption, and

metabolism, changes in the endocrine and neuro-endocrine function and suppression of

the immune system .The resulting symptoms are often nonspecific, making a diagnosis

difficult. The difficulty of diagnosis is increased due to limited research, occurrence of

multiple mycotoxins, nonuniform distribution, interactions with other factors, and

problems of sampling and analysis.

The observations which can be can be helpful in diagnosis are that mycotoxins

should be considered as a possible primary factor resulting in production losses and

increased incidence of disease whereas documented symptoms in ruminants or other

species and specific damage caused to target tissues can be used as a guide to

possible causes. Similarly, postmortem examinations may indicate no more than gut

irritation, edema, or generalized tissue inflammation. Rule out other possible causes,

such as infectious agents or other toxins. Analyze feeds for common mycotoxins.

Observe for responses to simple treatments, such as dilution or removal of the

contaminated feed.

The dairy units suffer from a mycotoxicosis typically have a loss in milk

production. Fresh cows perform poorly and generally have an increased incidence of


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disease. Usually there is intermittent diarrhea, sometimes with bloody or dark manure.

Cows may not respond well to typical veterinary therapy. Symptoms may be nonspecific

and wide ranging like reduced feed intake. feed refusal, unthriftiness, rough hair coat,

undernourished appearance, subnormal production, increased abortions or embryonic

mortalities, silent heats or irregular estrus cycles, expression of estrus in pregnant cows,

decreased conception rates. There may also be a higher incidence of disease,

particularly in fresh cows, such as displaced abomasum, ketosis, retained placenta,

metritis, mastitis, and fatty livers.

Aflatoxin

Aflatoxin, produced primarily by Aspergillus flavus, is a mycotoxin of major

concern, because it is carcinogenic and is commonly found in ground nuts and

maize. Milk levels of aflatoxin will be about 1.7% the concentration found in the total

ration dry matter. Aflatoxin residues can be found in tissues, and thus, cattle should not

be fed aflatoxin-contaminated diets for 21 days prior to slaughter.

Aflatoxins often cause nervous symptoms in affected animals. The reproductive

effects of aflatoxins include abortion, the birth of weak, deformed calves and reduced

fertility caused by reduced vitamin A levels. Although no level of aflatoxin is consideredsafe, the degree of toxicity is related to level of toxin, duration of feeding, and the

amount of other stresses affecting the animal. Levels above 300 ppb to 700 ppb are

considered toxic to cattle . Impure sources of aflatoxin produced by culture are more

detrimental than equal amounts of pure aflatoxin.

Deoxynivalenol (DON) or Vomitoxin

DON is a Fusarium-produced mycotoxin and is one of the more commonly

detected mycotoxins. Incidence may be as high as 50% to 80% of feeds. DON is the

primary mycotoxin associated with swine health problems including feed refusals,

diarrhea, vomiting, reproductive failure, and deaths. In cattle, DON has been associated

with reduced feed intake and milk production. It is speculated that other specific


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mycotoxins may be present with DON in naturally- contaminated feeds which enhance

the toxicity. DON serves as a marker which indicates exposure of feed to a situation

conducive to mold growth and mycotoxin formation. A positive DON analysis suggests

the possible presence of other mycotoxins or factors more toxic than DON itself. A

dietary level of 300 ppb to 500 ppb DON may cause problems when fed to cattle.

T-2 Toxin

T-2 toxin, a Fusarium-produced mycotoxin occurs in a fairly low proportion of

feed samples .It results in reduced feed consumption, loss in yield, gastroenteritis,

intestinal hemorrhages, and death. T-2 is known to suppress immunity and interfere

with protein synthesis. It is toxic to the intestine, lymphoid tissues, liver, kidney, spleen,

and bone marrow. A calf given T-2 via a stomach tube developed severe depression,

hind quarter ataxia, listlessness, and anorexia. T-2 is a severe gastrointestinal tract

irritant, which can cause hemorrhage and necrosis of the intestinal tract. Diarrhea is

usually present but may not be hemorrhagic. With high levels of T-2, there can be

congestion and irritation to the stomach, intestines, liver, lungs, and heart. T-2 may not

occur alone and thus, naturally-contaminated feeds may contain other similar toxins.

Zearalenone (F-2)

Zearalenone is a Fusarium-produced mycotoxin which elicits an estrogenic

response in monogastrics. As with other mycotoxins, its occurrence is dependent on

seasonal weather conditions, with zearalenone being more prevalent in wet and cool

seasons. Large doses cause abortions in cattle. Other cattle responses may include

vaginitis, vaginal secretions, poor reproductive performance, and mammary gland

enlargement of virgin heifers. Zearalenone may result in poor feed intake, a loss of milk

production, poor conception, and increased reproductive tract infections.

Other Mycotoxins


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Many other mycotoxins may affect ruminants but are thought to occur less

frequently or be less potent. Diacetoxy-scirpenol, HT-2, and neosolaniol may occur

along with T-2 toxin and cause similar symptoms. Fumonisin is less potent than other

mycotoxins, but in large amounts can affect cattle. Ochratoxin has been reported to

affect cattle, but it is rapidly degraded in the rumen. Thus, it is thought to be of little

consequence except for pre-ruminants.

Testing of Mycotoxins

Analytical techniques for mycotoxins are improving. Several commercial

laboratories are available and provide screens for a large array of mycotoxins. Cost of

analyzes has been a constraint but can be insignificant compared with the economic

consequences of production and health losses related to mycotoxin contamination.

Collection of representative feed samples is a problem primarily because molds

can produce vary large amounts of mycotoxins in small areas making the mycotoxin

level highly variable within the lot of feed. Samplings of horizontal silos show

mycotoxins to be highly variable throughout the silage, however, the silo face appears

to have higher levels. Because mycotoxins can form in the collected sample, therefore,

it should be preserved and delivered to the laboratory quickly for analysis. Samples canbe dried, frozen, or treated with a mold inhibitor before shipping.

Prevention and Treatment

Prevention of mycotoxin formation is essential since there are very few ways to

completely overcome problems once mycotoxins are present. Ammoniation of grains

can destroy some mycotoxins, but there is no practical method to detoxify affected

forages. Following accepted silage-making practices aimed at preventing deterioration

primarily through elimination of oxygen is a very important mycotoxin-preventative

management practice. Some additives may be beneficial in reducing myco-toxins

because they are effective in reducing mold growth. Ammonia, propionic acid, and

microbial or enzymatic silage additives are partially effective at inhibiting mold growth.


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Silo size should be matched to herd size to ensure daily removal of silage at a rate

faster than deterioration. Feed bunks should be cleaned regularly. Care should be taken

to ensure that high moisture grains are stored at proper moisture content and in a well-

maintained structure. Grains or other dry feed, such as hay, should be stored at a

moisture content (

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Mycotoxins and Animal Production