>What are the health results for cattle fed old grain that may have
>Do these weaken immune system as well as provoke a toxic reaction?
yep, if they really contain mycotoxins..
At a given dose, aflatoxin reduces weight gain in growing
animals, but disease resistance in the same animal may be reduced
already by about half that dose.
Aflatoxin causes a broad variety of symptoms, which is very
depending on the animal species. However, in all animals, aflatoxin
can cause liver damage, decreased reproductive performance, reduced
milk or egg production, embryonic death, teratogenicity (birth
defects), tumors, and suppressed immune system function, even when
low levels are consumed. Symptoms are very soon seen in pigs and
much earlier than in cattle.
Aflatoxin-contaminated feed not only reduces animal performance
and overall health, but it also creates risks of residues in
milk. Aflatoxin is secreted into milk in the form of aflatoxin M1
with residues approximately equal to 1 to 2 percent (1.7 percent
average) of the dietary level. This ratio is not influenced
greatly by milk production level since higher producing cows
consume more feed and have a slightly higher transmission rate.
Due to risks of milk residues, dietary aflatoxin should be kept
below 25 ppb.
This level is conservative due to:
(1) nonuniform distribution of aflatoxin in grain and feed,
(2) uncertainties in sampling and analysis, and
(3) the potential for having more than one source of aflatoxin in
Replacement animals may tolerate 50 to 100 ppb aflatoxin.
DON has been associated with reduced milk production in dairy
cattle, vomiting by swine consuming contaminated feed or their
refusal to eat feed containing the toxin, and inhibiting
reproductive performance and immune function in several animal
species. Dairy cattle and poultry are relatively insensitive to
the dietary concentration s of DON likely to be found in feeds.
In dairy cattle DON is associated with reduced feed intake, lower
milk production, elevated milk somatic cell counts, and reduced
reproductive efficiency. Milk production loss appears to occur
when diets contain more than 300 ppb DON.
Although controlled research has shown no cause and effect
relationship between DON levels and reduced milk production,
field observations have shown that reductions in milk output of
25 pounds per cow were seen when DON was 500 ppb or more.
This suggests that DON may serve as a marker for feed that was
exposed to a situation conducive to mold growth and mycotoxin
The possible presence of other mycotoxins, or factors more toxic
than DON, seems likely.
Dietary levels of 300 to 500 ppb DON in dairy feeds indicate
mycotoxin problems and warrant attention.
and the next:
Zearalenone mimics the effect of the female hormone estrogen and,
at low doses, increases the size or early maturity of mammary
glands and reproductive organs. At higher doses zearalenone
interferes with conception, ovulation, implantation, fetal
development, and the viability of newborn animals.
Zearalenone causes estrogenic responses in dairy cattle, and
large doses of this toxin are associated with abortions.
Other responses of dairy animals to zearalenone may include
reduced feed intake, decreased milk production, vaginitis,
vaginal secretions, poor reproductive performance, and mammary
gland enlargement in virgin heifers. Establishment of a tolerable
level of zearalenone for dairy cattle is difficult, and is at
best only a guess based on a meager amount of data and field
As with DON, zearalenone may serve as a marker for toxic feed.
It is suggested that zearalenone not exceed 250 ppb in the total
T-2 toxin and its chemical relatives cause irritation,
hemorrhage, and necrosis throughout the digestive tract, depress
the regenerative process in the bone marrow and spleen, impair
immune system function, and cause changes in reproductive organs.
Affected animals show signs of weight loss, poor feed
utilization, lack of appetite, vomiting, bloody diarrhea,
abortion, and (in severe cases) death. T-2 and DAS in cattle feed
further results in unthriftiness, decreased feed consumption,
slow growth, lowered milk production, and sterility. An outbreak
of the hemorrhagic bowel syndrome and death of some animals can
occur in herds of cattle and swine.
Fumonisin is a mycotoxin which has only recently been discovered.
Thus it has not been extensively studied. Nonetheless, it is
known that in most animals fumonisin impairs immune function,
causes liver and kidney damage, decreases weight gains, and
increases mortality rates.
In dairy cattle T-2 toxin has been associated with feed refusal,
production losses, gastroenteritis, intestinal hemorrhages, and
T-2 has also been associated with reduced immune response in
calves. Data with dairy cattle are not sufficient to establish a
tolerable level of T-2 in the diet. Therefore, a practical
recommendation may be to avoid T-2 in excess of 100 ppb in the
total diet for growing or lactating dairy animals.
Aflatoxin and other mycotoxins can have considerable effects on
beef cattle although the problems are usually less critical than
for swine and poultry. Consumption of feeds highly contaminated
with aflatoxin may reduce growth rate and increase the amount of
feed required per pound of gain. Calves are generally more
sensitive to feed contamination than adult cattle. In affected
calves, some cases have revealed severe rectal straining and a
prolapsed rectum. Lactating cows show a significant reduction in
milk yield. Research has shown that high levels of aflatoxin can
also cause liver damage in adult cattle. Feeding a high level of
aflatoxin may also depress immune function, resulting in disease
outbreaks. The effects of aflatoxin fed to cattle depend on the
level of aflatoxin in the ration, the length of the feeding
period, and the age of the animal.
If aflatoxin-contaminated feeds must be fed to beef cattle,
follow these guidelines (on a dry matter basis):
* Creep feeds and diets for gestating and lactating beef cows
should contain less than 20 ppb of aflatoxin.
* Unstressed, growing-finishing cattle in excess of 400 pounds
may be fed diets containing up to 100 ppb of aflatoxin.
* Diets for stressed feeder cattle should contain no more than 20
ppb of aflatoxin.
Stressful conditions include weaning, shipping, extreme heat or
cold, diseases, and parasites. * Animals destined for slaughter
should receive aflatoxin-free diets for at least 3 weeks before
Table. Allowable Aflatoxin in Grain for Beef Cattle
Percentage of Grain Aflatoxin Level in Total Diet
in Diet 20 ppb 50 ppb 100 ppb
20% 100 ppb 250 ppb 500 ppb
40% 50 ppb 125 ppb 250 ppb
60% 33 ppb 83 ppb 167 ppb
80% 25 ppb 63 ppb 125 ppb
This table assumes that aflatoxin is contained only in grains.
This assumption is not always correct.
Landwirtschaftl. Untersuchungs- u. Forschungsanstalt (LUFA)
(Governm. Inst. for Agricult. & Environm. Res.)
67346 Speyer, Obere Langgasse 40 (GERMANY)
Dept. of Seed Sci., Microscop. Analysis & Plant Pathol.
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