NUTRITION                                         PIH-129


               Mycotoxins and Swine Performance

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

William L. Flowers, North Carolina State University
Duane Miksch, University of Kentucky
Donald H. Scott, Purdue University
Trevor K. Smith, University of Guelph


     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


     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
                    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
                                           T-2 Toxin
                                         Resorcylic acid lactones
                      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

     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-

     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

     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

     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

     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

     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-

     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
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
EZ-Screen                      aflatoxin            color test
Environmental Diag.            ochratoxin           compared to
PO Box 908                     T-2 toxin            standards
Burlington, NC 27215           zearalenone
Afla Test-10                   aflatoxin            measures
Cambridge-Naremco                                   fluorescence
PO Box 1572
Springfield, MO 65801
Signal Accucup                 aflatoxin            color test
Int. Diagnostics
PO Box 799
Saint Joseph, MI 49085
SAM-A SAM-AZ                   aflatoxin            measures
Papillion Ag. Prod.            zearalenone          fluorescence
PO Box 1161
Easton, MD 21601

     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


     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.


     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

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.


     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.


CAST. 1989. Council for Agricultural Sciences and Technology Task
Force Report No. 116. Mycotoxins:Economic and Health Risks. Ames,
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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