Microsoft word - mold and mycotoxins in rabbit feed-12-12-07.doc
BOLETIM CIENTÍFICO No. 44 – www.micotoxinas.com.br
Mold and Mycotoxins in Rabbit Feed
Cristina Forbes, Ph.D.
Licensed Wildlife RehabilitatorSpecialty: rabbits
1. What are mycotoxins?
and toxins from mold
can be harmful and even deadly to rabbits. Molds usually grow
under specific conditions of temperature and humidity or in diseased/saturated soil. Moldy
feeds may cause a variety of health problems in rabbits and humans, especially respiratorydisease from breathing in mold spores. Moldy feeds are also less palatable and may cause a
reduction in feed intake, resulting in weight loss.
When molds are shocked by sudden fluctuations in temperature (freezes or hot spells), they
exude poisons called mycotoxins
Types of mold
that can be found in rabbit feed:
(yellow to yellow-green) -- found in corn, forages1, cottonseed, soybean2
and peanuts. Its toxin is carcinogenic, causes hemorrhaging of intestinal tract andkidneys, reduced feed intake and diarrhea, lung damage, diarrhea, liver cancer and
(brown to black) -- found especially in clover. Its toxin causes salivation,
(brown to black) -- most common in grasses including wheat, rye and barley.
Its toxin causes tremors and convulsions.
(green to green-blue) -- found in corn and small grains2. Its toxins cause
kidney damage, weight loss, reduced feed intake causing hemorrhaging of lung and
(white to pinkish-white) --- found in hays, forages, soybean and cereal
grains2. Its toxins cause feed refusal, acute gastrointestinal illness, immunesuppression, diarrhea, enteritis, weight loss, hemorrhages of the large intestine, shock
and reduced gastric and small intestine flow, necrosis of the GI tract, and death.
1 Alfalfa hay is considered a forage.
2 Rabbit pellets contain wheat middlings, soybean hulls and sometimes corn -- the
"pathway" ingredients for mycotoxin contamination.
are invisible, highly corrosive, deadly poisons which may persist in feed and hay
even when the molds that produced them are no longer present. Mycotoxins are nearly allcytotoxic, disrupting various cellular structures such as membranes, and interfering with vital
cellular processes such as protein, RNA and DNA synthesis. They destroy organ tissue byoxidizing protein, impact specific organs, and have immunosuppressive effects. Some of them
produce acute toxicity, evidenced by digestive disorders or dermatitis, but many more arecarcinogenic (capable of causing cancer), resulting in genetic mutations, or causing deformities
in developing embryos. Mycotoxins can have very pervasive, yet subclinical, effects on
animals' health that can easily go unnoticed. By the time the clinical symptoms of mycotoxinpoisoning are observed, significant damage has occurred.
Improper harvesting (putting up wet hay), packaging (in air-tight plastic bags) and storage orprolonged shipping may enhance the potential for mold growth. Dirty harvesting,
manufacturing/pelleting equipment and storage bins may contribute to mycotoxincontamination.
2. What are the symptoms of mycotoxin poisoning (mycotoxicosis)?
The symptoms are wide-ranging and similar to more well-known ailments. Mycotoxins may
problems (slowdown, delayed stomach emptying, stasis/colic,
hemorrhages of the large intestine, shock, reduced gastric and small intestine flow,necrosis of the GI tract, severe bloating, impaction, shutdown without blockage, refusal
to eat, weight loss, increased water consumption, vomiting, enteritis).
hemorrhages or bruising.
damage (liver lipidosis, hepatic lesions/fibrosis/swelling, degenerative changes
Central nervous system
problems (twitches, wobbling, convulsions, seizures,
paralysis, spasms, tremors, incoordination, depression, headache).
(increased susceptibility to multiple bacterial and viral infections).
problems (discharge, corneal ulcers, keratitis).
problems (pneumonia, lung lesions, pulmonary fibrosis, hemorrhages, respiratory
problems (hypertrophy of the adrenal cortex glands).
problems (impaired ovarian function, cystic ovarian degeneration
development, reproductive disorders, vaginal prolapse).
problems (damaged heart muscle, tachycardia).
problems (skin rash, ulcerations, lesions, burning sensation, sloughing of skin,
problems (depletion/irreversible damage/necrosis of the
myelopoietic cells in bone marrow and in splenic red pulp).
abnormalities (decrease in blood coagulation, hematocrit and white blood cell
count, leukopenia, calcium-phosphorus imbalance).
(increased vascular fragility, hemorrhage into body tissues or from
on mucous membranes.
Since few veterinarians are trained in toxicology, mycotoxicosis is usually misdiagnosed.
3. How can mycotoxin poisoning be diagnosed?
The poisoning may manifest as on-and-off, chronic or acute episodes, depending on theamount of toxic feed ingested and how consistently it was fed. The damage to internal organs
is cumulative over a period of time. A high incidence of gastrointestinal upsets (impactions,
etc.) and of disease associated with depressed immune function (Pasteurella, etc.) may beclues that a mycotoxin problem exists. Some clinical signs which may appear in a rabbit:
in the abdomen -- sudden onset, haunches flaring out, belly pressed
against or writhing on the floor, bunny might be lethargic and hide in a corner.
A radiograph (x-ray) series may reveal gut shutdown but no physical blockage
(barium barely drips through), sometimes severe bloating
. Often diagnosed as GI
stasis or stenosis without identifying the underlying cause.
Standard GI stasis treatments no longer work, GI motility drugs
(Cisaspride/Metachlopromide) lose their effectiveness either because the tissue along
the GI tract is necrotic/damaged or because of the overwhelming
deoxynivalenol(DON)-induced inhibition of gastric emptying
via serotonin receptor
(low body temperature).
high BUN and creatinine levels, calcium-phosphorus imbalance
(which may lead to chalky urine, organ calcification), abnormal levels of liver enzymes
associated with kidney/liver failure; low hematocrit/RBC due to internal bleeding.
in the mouth (strange chewing and tongue motion, difficulty swallowing, teeth
problems ruled out), stomach and esophagus.
Refusal to eat
, weight loss.
Presence of mucous
in the feces.
Rough hair coats.
or twitching in hind limbs.
Multiple bunnies fall ill simultaneously in the same household.
Food tests positive for mycotoxins.
An endoscopic examination may reveal ulceration along the GI tract
procedure is difficult to do on small animals.
may show: GI bruising (often subtle), hemorrhages, stomach/GI
ulcerations, mouth ulcers, kidney/liver damage (lesions, lipidosis, fibrosis, swelling,
While many mycotoxins can be measured in environmental samples, it is not yet possible to
measure mycotoxins in human or animal tissues.
4. What is the treatment for mycotoxin poisoning?
Break one-gram tablets of Carafate (sucralfate) into quarters. Administer 1/4
tablet orally every 8-12 hours mixed with water. Drop the 1/4 tablet into a feeding syringe,hold your finger over the tip, add some water, shake it well until it is dissolved, then invert the
syringe and bleed off the excess air before syringe feeding (from the side of the mouth, in the
gap behind the front teeth). Ideally, it should be given on an empty stomach (one-two hoursbefore meals). Sucralfate should be staggered 3-6 hours apart from other medications because
it tends to bind with other drugs (including cimetidine = Tagamet), reducing their absorptionand effectiveness. Although healing begins within one to two weeks, it should be administered
for at least 3-4 weeks (sometimes up to 8 weeks) to make sure healing is complete. Do notmiss a dose because it works cumulatively.
is a "cytoprotective" agent that binds to the ulcerated erosion sites to form a
protective barrier and promote healing. This prevents bacteria from crossing through thedamaged tissue along the lining in the GI tract and entering the bloodstream, which may cause
septicemia (blood poisoning). It is a very safe and effective drug.
(injectable Penicillin G) to guard against bacterial infection and
(in mild cases) or IV fluids (in severe cases) to flush out the toxins.
Treat for renal failure with supportive therapy.
If severe bloating occurs, the stomach might need to be pumped (carefully) to prevent it from rupturing.
Ask your vet whether other anti-ulcer drugs might be helpful. Prilosec
which suppresses the acid "proton pump" in the gastric mucosa, has proven very effective in
treating ulcers in horses (the closest physiological model to a rabbit; both are single-
stomached hindgut fermenters). Zantac
(Ranitidine HCl), which reduces the production of
stomach acid by inhibiting histamine, is much more effective than Tagamet
Note: Bunnies may have sensitive GI tracts for awhile. Fluids and sucralfate should be re-administered at any sign of discomfort during the following months.
5. What should I feed a rabbit who is suffering from mycotoxicosis?
Do not feed old hay and pellets. Buy new feed, a different brand if possible.
Fresh veggies might be the only food the bunny can tolerate for several weeks (the fiber in
hay might be too rough) due to its damaged GI tract. Provide a variety (kale, dandeliongreens, romaine lettuce, carrot tops, dill, fennel, mint, etc.) several times a day.
Keep hay and clean, fresh water available at al times. Oat hay and oat seed tops might be the first things the bunny will want to eat.
Feed wheat bran soaked in warm water (with wheat germ and Quaker oats added for taste)
then drained and cooled, once per day. This provides protein to help repair the damaged GItract.
The effects can be partial y counteracted by an antioxidant such as vitamin E. Vitamin A,
selenium and zinc, Thiamine and other B vitamins may prove beneficial. Milk thistle can behelpful in treating liver damage.
Vitamin K1 (menadione) can be administered to stop internal bleeding.
6. How can I tell if my bunny's food is contaminated?
Have al hay and pellets tested at an agricultural, university, or veterinary diagnostic
laboratory near you (do not
send samples back to the vendor).
Mix the feed wel before sampling. Mycotoxins are patchy, like "spots of mold on a loaf of
bread". Mixing the feed well increases the chances of detecting these poisons but the testsmight indicate lower levels than what the bunny actually ate (perhaps he ate from a "hot spot"
of concentrated toxins). Keep two extra samples aside for further testing.
Make sure you ask for numerical results in parts-per-billion (ppb), down to 50 ppb ifpossible. Many labs are geared for large, multiple-stomached ruminant livestock (like beef
cattle) so their detection levels may be set way too high (500-1,000 ppb). In this case, a feedthat tests "negative" may still be dangerous to single-stomached hindgut fermenters (like
rabbits and horses), who are much more sensitive to mycotoxins. See table below.
Test especially for DON (vomitoxin). It is a "marker" for other mycotoxins -- if it is present,
then other mycotoxins are probably present as well. Test for DON, T-2, Aflatoxin, Fumonisin,
Ochratoxin, Zearelanone (in that order of importance, depending on the money available fortesting).
When multiple mycotoxins are found together in a sample, their combined synergistic effect is usually more potent than any one alone.
Suggested Detection Levels for Mycotoxins
Make sure you choose a lab with detection levels as low
as or lower
than those suggested for
rabbits (above). The lower the detection levels, the better, since rabbits are one of the mostsensitive animals to these toxins. Be aware that some laboratories report test results in ppm.
7. How prevalent are mycotoxins in animal feed?
Mycotoxin contamination is not an uncommon occurrence in pet foods, especially in (but notlimited to) dog food. Corn, wheat middlings and soybeans are the usual "pathway" ingredients.
In the past few years, there have been several cases of dog food which contained
contaminated wheat middlings (the same ingredient found in many rabbit pellets). More thanone hundred dogs fell ill and many died. Mycotoxins were found in two well known brands of
dog food and the companies were forced to recall their products due to consumer pressure.
In a "sell it down the road" strategy, grain dealers often dump products which are deemed
"unfit for human consumption" on the pet food industry to avoid suffering economic losses.
There are few standards or government regulations in place, so pet food companies rarely feel
compelled to institute quality-control programs that detect mycotoxins in their products.
Of nearly 100 samples of rabbit feed (30 different products) from the caregivers of both sick
and healthy rabbits, from pet stores, from vet clinics, and shipped directly by companies tocustomers, then tested by several laboratories around the country, 30% have tested positive
for mycotoxins. Mycotoxins were found in alfalfa hay, timothy and alfalfa pellets, powderedfood intended for sick/baby rabbits, and seed-based feed used by breeders. Recent laboratory
test results suggest that the contamination is more prevalent among certain brands. 50% of
one specific product contained mycotoxins.
The feeds which tested positive came from households where bunnies were sick or had died.
Some samples which tested positive were not fed to rabbits. In two cases, the feed tested
positive before the bunnies showed any symptoms; one of these rabbits died a couple of
weeks later, both rabbits suffered severe kidney damage.
The mycotoxins found in rabbit feed so far were DON, T-2 and ZEAR. Keep in mind that there
are more than 400 mycotoxins and these products were only tested for a few. More sampling,testing and analyses of the effects of mycotoxins on domestic animals are needed. If you have
had or wish to have your feed tested, please let me know.
The Color of Good Hay
President, [email protected]
Dark Green -
This is the color of well-grown alfalfa.
Light-to-Medium Green -
The color of well-stored grass hay. The hay was carefully
harvested and has a good amount of the nutrients needed.
Bright Lime Green -
This usually denotes alfalfa hay that has been treated with propionic
acid (a preservative), which will not harm a horse.
The Appearance of Good Hay:
Stems are shorter and thinner. The stems are easy to bend and are not stiff or
Stems & Leaves -
Hays with a higher amount of leaves are more nutritious than hay which is
The bale should be light and easy to lift. If it is heavy, it may indicate that it is
moldy or that rocks or dirt have been baled into it.
The Color of Bad Hay:
Light/Medium Brown -
When the hay has a tint of brown, it contained too much moisture
when baled and stored. Brown hay has a musty odor and cakes together. The bale is stiff andthe strings have no elasticity.
Dark Brown or Black -
The hay was exposed to rain or heavy fog and dew. This hay is very
stiff and brittle, and has lost much of its nutrition.
Light Golden Yellow -
The hay has been bleached by too much sun, or is aged. Usually only
the outer layers become bleached. If the inside of the bale is yellow, most of the valuablenutrients have been lost.
The Appearance of Bad Hay:
The hay is stiff and brittle and the stems crack easily when bent. The bale may be
heavy and/or hard to split into individual flakes.
Dirt & Mold -
If the center of the bale appears matted together, and flakes are difficult to
separate, it usually indicates dirt and/or mold. Avoid bales that have a gray tint and ones that
May be infested by rodents, blister beetles or other animals and insects. Always
check every bale for this before feeding it to your horse. Discard any bales that you find animalparts in, no matter how small a part it is. Dead animal parts can carry serious diseases that
If the hay contains a large amount of weeds and/or un-identifiable plants, do not buy
it. Weeds may make hay less palatable, and may contain irritating contents such as burrs andthistles. The nutritional content of this type of hay is extremely hard to diagnose.
Other Important Points:
Inspecting Hay -
Before purchasing hay from anyone, be sure to inspect a few bales. Buy a
couple bales, cut them open and inspect them thoroughly. Check for mold, moisture, dirt,animal parts, insects, color, weeds, texture.and all of the above.
Find a reliable dealer in your area that will supply you with hay year-round
from the same fields. This will help decrease the likelihood of sickness or colic in horses that
are sensitive to feed-switching. It will also help ensure that the nutrition you are giving yourhorse remains consistent as to not upset his sensitive digestive tract. Problems may arise if
you regularly switch hay types, hay fields, and hay quality. Hiding
Bad Bales -
Some hay dealers will pull a trick on many customers by hiding the bad bales in
the middle of the load, where it is almost impossible to inspect them. They will sometimes put
the best-looking bales (the ones you are most likely to inspect) on the outside. To avoidgetting stuck with a load of hay like this, be sure to get the dealer's name, address and phone
number, and inform him that you expect a refund or replacement for any bale of less qualitythan the ones you have inspected.
First-cut hay -
When buying first-cut hay (hay that is the first cut of the year for that field),
be sure to check for excessive moisture and weeds. First-cut hay can be the most nutritious if
cut and cured properly, however, if it is not cut and cured properly it is likely to have excessive
moisture and mold due to spring showers.
Cheryl's goal is to educate horse owners on how to develop a trusting and respectfulpartnership with their horses. The training methods she uses and teaches are ones that
promote a horse's confidence and willingness to please.
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