NUTRITION PIH-129
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Mycotoxins and Swine Performance
Authors
Mark A. Diekman, Purdue University
M. Terry Coffey, Rose Hill, North Carolina
E. Dale Purkhiser, Michigan State University
David E. Reeves, University of Georgia
Les G. Young, University of Guelph
Reviewers
William L. Flowers, North Carolina State University
Duane Miksch, University of Kentucky
Donald H. Scott, Purdue University
Trevor K. Smith, University of Guelph
Fungi
Plants and animals may serve as excellent hosts for many
fungi. Spores from fungi (molds) are primarily spread by water
and air and come into contact with plants in the field or with
grain in storage facilities. Factors that influence the degree
of fungal infestation in grain are moisture, temperature and
availability of oxygen. Other factors such as insect population,
physical condition of grain or susceptibility of certain grain
hybrids will also influence whether fungal proliferation will
occur under a given set of environmental conditions.
In general, the livestock consumption of feedstuffs contain-
ing fungi is not toxic. Most fungal-infected grain is not toxic
because toxin-producing species of fungi must compete with non-
toxic species to grow; only a small portion of the fungal species
produces toxins; and suitable environmental conditions for fungal
growth may be different from the conditions suitable for toxin
production. Quality of the grain can be reduced by fungal
infestations, but most problems with livestock consuming fungal-
infested grain result from consumption of mycotoxins produced by
fungi.
Mycotoxins
Mycotoxins are toxins produced by fungi on or in grain or
feedstuffs when conditions are favorable for their development.
Fungi that produce mycotoxins of economic importance to pork pro-
ducers are Aspergillus, Penicillium, Claviceps and Fusarium.
These fungi produce the following mycotoxins: aflatoxins, ochra-
toxins, ergots, trichothecenes and resorcylic acid lactones
(Table 1).
Table 1. Feedstuffs that support growth of various fungi, the
genera and species of fungi commonly found, and the family of
mycotoxins and toxins that are known to impair performance of
swine.
_________________________________________________________________
Fungi Mycotoxins
Genera/ Family/
Feedstuffs Species Toxins
_________________________________________________________________
Corn, Wheat Aspergillus Aflatoxins
Rice, Barley flavus B1, B2
Oats, Rye parasiticus G1, G2
Milk nomius M1, M2
Blood Meal ochraceus Ochratoxin
Ochratoxin A
_________________________________________________________________
Stored Corn, Penicillium Ochratoxin
Wheat, Barley viridicatum Citrinin
_________________________________________________________________
Rye, Wheat Claviceps Ergot
Barley purpurea
_________________________________________________________________
Corn Fusarium Trichothecenes
Wheat, Barley graminearum Deoxynivalenol
Mixed Feed Diacetoxyscirpenol
Diacetylnivalenol
Nivalenol
T-2 Toxin
Resorcylic acid lactones
Zearalenone
moniliforme Fumonisin B1, B2
_________________________________________________________________
Aflatoxins. Aflatoxins are produced by Aspergillus flavus.
This fungus can germinate at lower moisture levels of 15% to 17%,
but infection and growth require higher moistures. Aflatoxin pro-
duction appears to be higher at grain moisture levels of 22% to
26% and temperatures of 82o to 90o F. Conditions for growth are
ideal when temperatures remain high both day and night, but
growth decreases dramatically at temperatures above 95o F.
Although Aspergillus flavus is abundant in the southeastern
United States, drought-stressed corn in Indiana and Illinois in
1978, 1983, 1988 and 1991 contained aflatoxin in scattered
fields.
The risk from aflatoxin-contaminated grain depends on the
age and health of the pig as well as the concentration of the
toxin in the feed. Symptoms occur with concentrations in the
parts per billion (ppb) range. Small amounts can depress perfor-
mance and general well-being. Aflatoxins suppress the immune
system and thus make pigs more susceptible to bacterial, viral or
parasitic diseases. These more subtle effects are insidious
because often they are unnoticed. Over time, profits are reduced
due to lost efficiency, slower growth and increased medical
costs. If levels are high enough, death may result. The direct
effects of aflatoxin on reproduction have not been determined.
Aflatoxin B1 has been the most extensively studied myco-
toxin. Young swine are extremely sensitive to aflatoxins but sus-
ceptibility decreases with age. At low concentrations (20 to 200
ppb), aflatoxin decreases feed intake, which in turn depresses
growth rate and immunity. The detrimental effects of aflatoxins
may be lessened by altering key nutrients in the diet. For exam-
ple, a reduction in average daily gain was observed when an 18%
crude protein diet was spiked with aflatoxin (182 ppb). If pigs
were fed a 20% crude protein diet with the aflatoxin (182 ppb),
no reduction in average daily gain was noted. Similar results
were obtained with the addition of .25% L-lysine HCL. Adding 5%
fat to diets prevented a depression in feed intake, but no
improvement in growth was observed.
High concentrations of aflatoxin (1,000 to 5,000 ppb) result
in acute effects, including death. Aflatoxin M1, a metabolite of
aflatoxin, has been found in milk of sows fed diets containing
aflatoxin. Piglets nursing sows consuming feed with 500 to 750
ppb of aflatoxin had increased mortality and slower growth.
Piglets were permanently stunted and performance was reduced to
market weight even though they were not exposed to aflatoxin
after weaning.
Ochratoxin. Ochratoxin A is the best characterized of
several structurally related mycotoxins produced by Aspergillus
ochraceus and Penicillium viridicatum. Ochratoxin A is found on a
variety of feedstuffs grown on the southeastern coast of the
United States. Ochratoxin at concentrations greater than 5 to 10
ppm in feed results in a number of pathological conditions. These
include impairment of kidney function, blood in the urine, enter-
itis, necrosis of lymph nodes and fatty liver changes. Ochratox-
ins have been found in wheat, barley, oats, corn, dry beans and
peanuts. The economic impact of ochratoxins has not been deter-
mined.
Ergot. Claviceps purpurea invades rye, wheat and barley
plants and produces alkaloid toxins termed ergot. Ergot reduces
weight gain, lowers reproductive efficiency and promotes agalac-
tia (lack of milk flow) in several livestock species. Signs of
ergotism include staggers, convulsions, temporary posterior
paralysis and loss of blood flow to limbs, ears and the tail.
This loss of blood flow sometimes leads to gangrene and eventual
loss of extremities.
Sows fed a diet containing .5% to 1.0% ergot develop agalac-
tia and farrow fewer and smaller live pigs as compared to sows
fed uncontaminated feed. Diets containing 1% ergot reduce the
growth of pigs. Higher concentrations cause feed wastage and slow
growth.
Ergot appears on the heads of rye, barley and wheat as hard,
black, elongated structures that replace kernels (sclerotia) at
harvest time. The black sclerotia can readily be seen at har-
vest. Grain with ergot should be stored separately and not fed to
young pigs and breeding animals. Growing-finishing swine should
not be fed diets with more than 10% to 20% of grain contaminated
with ergot.
Trichothecenes. Deoxynivalenol, frequently referred to as
DON, feed refusal factor or vomitoxin, is a mycotoxin produced by
Fusarium graminearum (Gibberella zeae) that occurs often on corn
(Gibberella ear rot), but also on wheat and barley (Head scab).
The fungus develops on corn after silking, during cool, damp
weather. Visual signs of Fusarium infection of corn include a
white to pink to reddish fungus starting at the tip of the ear
and developing towards the base. However, there is not neces-
sarily a direct relationship between the extent of visual signs
and the amount of toxin produced. Visual examination of corn ears
growing in the field for white to pink to reddish fungus may give
an indication of potential problems.
Vomitoxin is most prevalent in the upper midwestern United
States and the Canadian provinces of Ontario and Quebec. These
areas tend to have shorter growing seasons and have cool, damp
weather during the first month after silking. Since Fusarium
graminearum (Gibberella zeae) produces both deoxynivalenol and
zearalenone, contaminated feedstuffs may contain both of these
mycotoxins.
In pigs, vomitoxin at concentrations above 1 ppm may cause a
reduction of feed intake and consequently, rate of gain. As the
dietary concentrations increase above 5 ppm, depression of feed
intake may become severe and at 10 ppm, there will be a severe
feed refusal resulting in weight loss. The marginal reduction in
feed intake and weight gain caused by low levels of vomitoxin may
contribute to a substantial economic loss and may be more impor-
tant than vomiting.
Vomiting, as the common name of the toxin implies, is one of
the signs. Vomiting, however, does not usually occur unless the
dietary concentration of the toxin approaches 10 ppm or more. At
that level, the pig will initially consume a sufficient amount of
the diet to induce vomiting but, thereafter, the pig voluntarily
reduces intake so that vomiting ceases. Thus, one must be present
to observe the initial vomiting symptom. At concentrations
approaching 20 ppm, vomiting may be observed in pigs within
approximately 15 minutes of initial consumption. Feed consumption
resumes almost immediately after highly contaminated feed is
replaced with uncontaminated feed. No other visual signs or gross
pathology are apparent with vomitoxin.
Resorcylic acid lactones. Of all mycotoxins produced in
feedstuffs, zearalenone affects reproduction most seriously since
it mimics the reproductive steroids of the estrogen family.
Estrogenic compounds naturally produced by plants are commonly
referred to as phytoestrogens. Zearalenone is produced by
Fusarium graminearum (Gibberella zeae). It may occur with deoxy-
nivalenol in scabby wheat and in many cases with Gibberella ear
rot of corn. Zearalenone contamination is more likely to occur in
storage than in the field.
Of all domestic species and stages of maturity, the prepu-
beral gilt is the most sensitive to zearalenone. The genital sys-
tem of immature gilts exhibits gross and histologic changes after
ingestion of zearalenone. Gross changes include reddening of the
vulva, increased size and weight of the uterus and mammary
enlargement. In extreme cases, rectal and vaginal prolapses may
occur.
Although the gross and histologic changes that are induced
by zearalenone are well characterized in prepuberal gilts, it is
unclear what effect this hyperestrogenism has on puberty or sub-
sequent reproduction. Ingestion of diets containing 10 ppm
zearalenone has had variable effects on the onset of puberty in
gilts. However, results from several studies indicate that the
estrogenic properties of zearalenone are not permanent and that
gilts can successfully enter the breeding herd without a reduc-
tion in fertility after a two-week withdrawal from zearalenone
ingestion.
In cycling gilts or sows, zearalenone causes multiple repro-
ductive dysfunctions. Diets containing 25 to 100 ppm zearalenone
that were fed continuously from weaning to rebreeding produce
constant estrus, pseudopregnancy and ultimately infertility. When
cycling gilts are administered either 20 mg zearalenone or 2 mg
estradiol benzoate in the feed on days 6 to 10 or days 11 to 15
of the estrous cycle, the interval between estrus is extended.
Usually these gilts will return to estrus within 30 days after
zearalenone is removed from the diet and can be rebred and pro-
duce normal litters.
Numerous observations of Fusarium-contaminated feedstuffs
causing stillbirths, neonatal mortality, fetal mummification,
splay-leg of piglets, abortion, abnormal return to estrus and
other abnormalities have been reported. However, the specific
action of zearalenone in each of these situations is not well
characterized. In many cases, fungal-infected feedstuffs were not
assayed for zearalenone and conclusions are made from field
observations rather than from controlled experiments. Therefore,
it is possible that other mycotoxins in conjunction with
zearalenone are interacting to produce the effects.
When pregnant gilts are fed diets containing low concentra-
tions of zearalenone (3.6 to 4.3 ppm) from mating to day 80 of
gestation, embryonic development is not affected. Higher doses of
zearalenone (60 to 90 ppm) consumed by gilts from day 2 to 15
postmating completely arrest development of embryos. It appears
that the critical period for zearalenone to exert its detrimental
actions on embryonic development is days 7 to 10 after mating.
Not only is reproductive efficiency reduced when bred gilts con-
sume zearalenone during this early period of gestation because
embryos are lost, but it may be several months before these
females will return to estrus and can be bred successfully.
The lactating sow also is susceptible to zearalenone at high
concentrations. Sows fed 50 to 100 ppm zearalenone for 2 weeks
before weaning and for 63 days after weaning exhibit constant
estrus. Sows fed a diet containing 10 ppm zearalenone during the
last 14 days of lactation exhibit an extended interval from wean-
ing to estrus. However, fertility at the first post-weaning
estrus will not be adversely affected. Low concentrations of
zearalenone (2.1 to 4.8 ppm) fed throughout pregnancy and lacta-
tion will not affect postweaning rebreeding.
The effect of zearalenone toxicoses on sexual development of
boars has been evaluated in a few studies. Consumption of diets
containing 60 ppm zearalenone for 8 weeks does not alter libido
or semen quality characteristics of mature boars. Similarly,
mature boars consuming feed with 200 ppm zearalenone have normal
libido scores and normal sperm concentrations when compared with
boars consuming a normal ration. When prepuberal boars consume 40
ppm of zearalenone from 14 to 18 weeks of age, their libido
scores are lower than the untreated boars. This reduction in sex
drive is associated with a reduced concentration of blood testos-
terone, the male sex hormone responsible for sex drive. Feeding
diets containing lower concentrations of zearalenone (9 ppm) does
not influence sexual behavior of boars. Further experimentation
is needed to determine if prepuberal and postpuberal boars react
differently to diets containing zearalenone.
Fumonisin. Fumonisin is a more recently recognized family of
mycotoxins of concern to the swine industry. Fumonisin is pro-
duced by Fusarium moniliforme. Recently, acute pulmonary edema
(filling of the lungs with fluid) has been reported as a symptom
of fumonisin toxicity. All ages of pigs have been reported to be
affected. Mortality rates have been recorded in the range of 10%
to 40%. Only limited information is available on fumonisin. More
information will be generated as the incidence of problems with
this mycotoxin is identified.
Control of Fungal Growth
In order to have mycotoxins, there must be a feedstuff on
which a fungus can grow, a fungus capable of producing mycotox-
ins, and environmental conditions favorable for fungal growth and
mycotoxin production. To prevent the production of mycotoxins in
feedstuffs, each of these areas must be addressed. Since fungi
are commonly found in nature, keeping feed from being exposed to
fungi is impractical. Controlling factors that promote the
growth of fungi is a more practical approach.
Damaged feedstuffs are readily available food sources for
fungal growth. Anytime the kernel is cracked and the endosperm is
exposed, there is high probability of fungal growth. Drought-
stressed corn, kernels cracked during harvesting and screenings
are three examples. Even healthy corn in the field is at some
risk. Drought-stressed corn is less resistant to fungi and should
be considered to be of high risk. Proper operation of harvesters
will help to reduce the incidence of cracked kernels. Corn
screenings are excellent media for fungal growth and have been
incriminated in Fumonisin toxicity.
The two major environmental factors associated with fungal
growth are temperature and humidity. Anytime humidity exceeds
62%, temperature exceeds 80o F and grain moisture levels exceed
14% to 15%, there is a greater chance that fungi will grow. The
exception is zearalenone which is produced under cool tempera-
tures (less than 70o F) and moist conditions. Regardless of all
other factors, the critical point for controlling fungal growth
in storage is grain moisture levels. Grain that is dry when
placed in storage and kept dry (less than 14% moisture) will be
unlikely to support growth of fungi that produce mycotoxins.
Ground feed is an ideal source of food for fungal growth.
Therefore, it should be utilized rapidly. This is especially true
during periods of high humidity and heat. Feed storage bins
should be cleaned at frequent intervals to prevent bridging of
feedstuffs and creation of ``hotspots.''
Fungal inhibitors, such as propionic acid, may be effective
in preventing fungal growth on stored grains. However, producers
are cautioned that fungal inhibitors have no effect on mycotoxins
already present in the corn at the time of application. They
only prevent future growth of fungi. There are a number of com-
panies manufacturing products to curb fungal growth. Storage of
grain in oxygen-tight silos reduces growth of fungi on the grain
but has no affect on mycotoxins already present.
Detection of Fungi and Mycotoxins
There are four methods of detecting either the fungi that
produce mycotoxins or mycotoxins themselves: 1) visual inspec-
tion, 2) blacklight, 3) immunoassays, and 4) chromatography.
To detect Gibberella-damaged corn (Fusarium graminearum),
the ear or individual kernels can be visually evaluated. A red to
pink fungus, usually beginning at the tip of the ear, is a sign
of Gibberella-infected corn. Husks frequently are tightly adhered
to the ear in fungal-infested corn. Individual kernels infected
by Gibberella are usually shrunken, discolored and often display
a water-mark. If more than 2% to 3% of kernels display these
signs, the Gibberella fungus may be present and producing suffi-
cient levels of DON or zearalenone to adversely affect perfor-
mance.
A black light will cause a bright greenish-yellow floures-
cence to appear if Aspergillus flavus is present in the grain.
The black light is commonly used, especially at grain buying sta-
tions, because it is a very rapid procedure. The major drawback
is that it is only an indicator of the presence of Aspergillus
and not aflatoxin. The fungus may have been present, disappeared,
and left the mycotoxin to affect swine performance. This is com-
monly referred to as a "false negative reading". "False positive
readings" also are possible as foreign material also may cause
fluorescence. To perform the black light test, all kernels in the
sample should be cracked and viewed by an operator who is not
affected by color blindness. The black light test detects no
other mycotoxin producing fungi.
Table 2. Partial list of commercially available test kits for
mycotoxins.
_________________________________________________________________
Test Name/ Mycotoxin Test
Manufacturer Tests Type
_________________________________________________________________
Agri-Screen aflatoxin rapid radio-
Neogen Corp. vomitoxin immunoassay
620 Lesher Place T-2 toxin
Lansing, MI 48912 zearalenone
517/372-9200
EZ-Screen aflatoxin color test
Environmental Diag. ochratoxin compared to
PO Box 908 T-2 toxin standards
Burlington, NC 27215 zearalenone
1-800-334-1116
Afla Test-10 aflatoxin measures
Cambridge-Naremco fluorescence
PO Box 1572
Springfield, MO 65801
1-800-641-7515
Signal Accucup aflatoxin color test
Int. Diagnostics
PO Box 799
Saint Joseph, MI 49085
616/983-3122
SAM-A SAM-AZ aflatoxin measures
Papillion Ag. Prod. zearalenone fluorescence
PO Box 1161
Easton, MD 21601
1-800-888-5688
_________________________________________________________________
An immunoassay is sometimes referred to as a serologic assay
or ELISA (enzyme linked immunosorbent assay) test. Commercial
kits are available for detecting aflatoxin, DON and zearalenone.
They are easy to run and relatively inexpensive. They serve also
as relative indicators of the amount of mycotoxin within a test
sample. A partial list of commercial kits available from com-
panies is presented in Table 2.
Chromatographic tests, such as the minicolumn, the HPLC
(high performance liquid chromatograph) and TLC (thin-layer
chromatography) are used mainly in laboratory settings or in
situations where a more accurate indication of the mycotoxin con-
centration is needed. Chromatographic tests require sophisti-
cated techniques and equipment and are expensive to perform.
Test Sample Collection. Samples collected for testing
should be randomly taken from several locations within the batch.
It is not uncommon for there to be "hotspots" within a storage
compartment. While these "hotspots" have a relatively high con-
centration of mycotoxin, other areas may be very low. Using a
grain probe at several evenly distributed locations within a
storage compartment is an effective way to collect samples. Sam-
ples collected at periodic intervals from grain being augured
also is an effective sampling technique. A random sample from
multiple (10 to 30) locations of a large quantity is the most
useful. The sources of error in determining the aflatoxin content
of corn can be classified as sampling, subsampling or analysis
error. Sampling error accounts for 88% while subsampling and
analysis error account for only 12%. Obviously sampling is criti-
cal. Collect at least 10 one-pound samples from each lot of feed
or ingredients and thoroughly mix and grind the entire sample
before subsampling. To decrease the chance of fungal growth while
the samples are in transit to the laboratory, use paper instead
of plastic bags. Plastic bags retain moisture which promotes fun-
gal growth.
Utilization of Mycotoxin-Contaminated Feedstuffs
Decontamination
Producers often are confronted with finding a way to utilize
a contaminated feedstuff. Research has focused on the decontami-
nation of corn containing toxins via extraction, acid or base
treatment, physical separation or heat treatment. Roasting to
300o F has been shown to reduce the level of aflatoxin present by
50% to 60%, but some destruction of amino acids in the grain also
occurred. Ammoniation appears to be the most reliable method to
detoxify grain of aflatoxins. Procedures have been established
for on-farm processing of small batches of grain, but ammonia is
hazardous to handle, toxic and extremely corrosive. Treatment of
feedstuffs with anhydrous ammonia has not been approved by the
Food and Drug Administration (FDA). Although the technology
exists, there are no practical methods to economically decontam-
inate large volumes of mycotoxin-contaminated grain.
Blending
Feeding mycotoxin-contaminated products carries risk. Pro-
ducers must consider the consequences and work to minimize detri-
mental effects. Remember that young animals are most suscepti-
ble. If possible, segregate the contaminated grain and avoid
feeding it to nursery pigs, breeding animals or replacement
gilts. If all the grain is heavily contaminated, "clean" grain
should be purchased for the more susceptible animals in the herd.
Often, contaminated products are damaged and are of generally
lower quality. Knowing the concentration of mycotoxins in the
feed is important to allow proper utilization.
Increased awareness and monitoring have led to fewer market
outlets for grains containing mycotoxins. There are no official
FDA tolerances for any mycotoxins. This means a zero tolerance.
However, FDA has established an action level which permits grains
or feedstuffs to be marketed in interstate commerce with up to 20
ppb aflatoxin. At the present time, the tolerance for feed des-
tined for market hogs is 200 ppb and 100 ppb for the breeding
herd. Even though a tolerance level has been established, no
"safe" level has been established for any mycotoxin in any diet.
Blending contaminated and uncontaminated feeds can be diffi-
cult from both an economic and logistic point of view. FDA over-
sees blending of grains that are moved through market channels.
On-farm blending is only an option for those who desire to feed
mycotoxin-contaminated grain to their pigs. However, mixing con-
taminated grain with uncontaminated grain contaminates all of the
grain. Because of their susceptibility, 4- to 5-month-old
prepubertal gilts make excellent models to test suspect grain for
zearalenone. Swollen vulvas would indicate that zearalenone or
vomitoxin is present in the feed. Blending should only occur
shortly before the feed will be consumed. Using freshly mixed
feed will reduce the chance of growth of mycotoxin-producing
fungi and minimize contamination of the clean grains. For this
reason, separate storage is required for the contaminated and
uncontaminated products.
The producer must have sufficient uncontaminated grain in
order to blend quantities of highly contaminated products to
acceptable concentrations. For example, if 1,000 bushels of corn
are contaminated with 1,000 ppb aflatoxin B1, it would require
49,000 bushels of uncontaminated corn in order to dilute the
aflatoxin to 20 ppb. It may be difficult to purchase, store and
routinely blend sufficient quantities to dilute the concentration
to acceptable levels.
Ration Formulations
Interactions of aflatoxins with riboflavin, vitamin D, vita-
min A and thiamin have been reported. Fungi can destroy vitamins
in feeds. The destruction of vitamins in ingredients is of little
consequence since synthetic vitamins are added to diets. However,
after the vitamins are combined with other ingredients, reduced
potency can occur. Because of this always keep feed fresh. If
vitamins are supplied by a base mix or premix, the inventory
should be rotated to assure vitamin potency. Adequate vitamin
supplementation is particularly important when feeds contain
mycotoxins.
Binding Agents
Addition of non-nutritive binding agents such as sodium ben-
tonite and certain zeolites to contaminated feed have alleviated
growth depression in pigs. Research has shown that adding 10
lb/ton sodium bentonite almost completely prevented the growth
depression caused by feeding corn containing 750 ppb aflatoxin.
Similar benefits have been reported from the addition of anti-
caking agents (hydrated sodium calcium aluminosilicate) to diets
containing aflatoxin. However, addition of aluminosilicates did
not alter the effects of DON on performance of starter pigs.
Recent research has shown that these compounds are only partially
effective at binding toxins in the digestive tract and reducing
their absorption. The cost of these products varies, but many are
relatively inexpensive and appear to offer promise. They have not
been cleared for use by FDA as mycotoxin binding agents.
Table 3. Recommended maximum concentrations of toxin in swine
diets (modified from Michigan State University)
_________________________________________________________________
Dietary Concentration
_________________________________________________________________
Deoxynivalenol Zearalenone Aflatoxin
Pig ppm ppm ppb
_________________________________________________________________
Breeding Herd 1.0 2.0 100
Young 1.0 1.0 20
Growing 1.0 1.0 --*
Finishing 1.0 3.0 200
Young Males 1.0 3.0 --*
Old Males 1.0 3.0 --*
_________________________________________________________________
*Concentration not determined.
Summary
1. Fungi (molds) that are capable of producing mycotoxins
invade grains and feedstuffs during plant growth, matu-
rity, harvesting, storage, and processing.
2. Mycotoxin is a term used to specifically refer to tox-
ins produced by fungi on feedstuffs when environmental
conditions support their growth.
3. Aspergillus, Claviceps, Fusarium and Penicillium are
four genera of fungi of economic concern to the swine
industry. These fungi produce five families of mycotox-
ins, namely aflatoxins, ochratoxins, ergots, trichothe-
cenes and zearalenone.
4. Specific testing for the presence and quantities of
mycotoxins is essential to determine toxicity. The
presence of fungi only determines the potential for
toxins to be produced. Mycotoxins may be present after
fungi have lost their viability.
5. Recommended maximum allowable concentrations of toxins
in swine diets are listed in Table 3.
6. The potential for mycotoxins is reduced by timely grain
harvest, drying to 1% to 2-1/2% below maximum moisture
for storage (grain 14% to 15%), removal of all foreign
material, cracked kernels, routine aeration of stored
grains to prevent moisture accumulation, as well as
weevil and temperature control in the grain (less than
80o F). The use of fungal inhibitors, such as
propionic-acetic acid (1 to 2%) will help prevent fun-
gal growth in grain and finished feed.
7. A number of alternative methods can be used for detec-
tion of fungi. These include visual analysis, black
light, immunoassay and chromatography. Quantitative
tests for specific mycotoxins are essential to deter-
mine the value of infected grains.
8. There are no practical methods of economically decon-
taminating large volumes of mycotoxin-contaminated
grain. Dilution with clean corn may be helpful when
mycotoxin levels are near the lower threshold where
contamination begins to show slight animal effects. The
use of absorbing clays or binding agents such as sodium
bentonite or hydrated sodium calcium aluminosilicate
has been reported to be beneficial at levels of 5 to 20
lb/ton of feed when aflatoxins are near the lower
threshold of toxicity.
9. Performance testing and pig reaction to grains
suspected to be infected are useful methods of detect-
ing potential problems. Close observations of animal
behavior for feed refusal, reduced weight gain and
estrogenic stimulation are beneficial.
References
CAST. 1989. Council for Agricultural Sciences and Technology Task
Force Report No. 116. Mycotoxins:Economic and Health Risks. Ames,
IA.
Diekman, M.A. and G.G. Long. 1984. Mycotoxins and Reproduction in
Swine. Animal Nutrition and Health. July-August, p. 22-28.
Shull, L.R. and P.R. Cheeke. 1983. Effects of Synthetic and
Natural Toxicants on Livestock. J. Anim. Sci. 57:330-354.
Reference to products in this publication is not inteded to be an
endorsement to the exclusion of others which may be similar. Per-
sons using such products assume responsibility for their use in
accordance with current directions of the manufacturer.
NEW 6/92 (7M)
______________________________________________
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