SUDDEN DEATH IN LIVESTOCK
Rebecca Childers, Laboratory Technician Jennifer McCarthy,
Assistant Chemist
Robert Everson, Ph.D., Analytical Chemist
Laboratory Supervisor Stephen B.Hooser,DVM, Ph.D., Veterinary
Toxicologist, Head, Toxicology Section
The sudden death of large numbers of previously healthy
animals can often be attributed to poisoning. Within the
past few months, numerous cattle and swine deaths in Indiana
have been caused by a wide variety of toxic agents. This
winter, a large number of hogs died when they were fed
from a bucket in which an insecticide had been transported.
Insecticides which are used for field application are
so potent and concentrated that even the small amount
remaining in the bucket was enough to kill a large number
of animals.
Since January, three poisonings with 3 completely different
toxins have resulted in the sudden death of large numbers
of cattle. In the first, the owner noticed several dead
cows one morning. As he inspected the dead animals, 2
more cows dropped dead near him. Examination of the rumen
contents of these cows showed that they had accidentally
ingested clippings from Japanese yew bushes. Japanese
Yew is an evergreen shrub that is very commonly used for
ornamental landscaping. Even small quantities of this
plant are sufficient to kill an adult cow.
In the second case, again the owner arrived at the pasture
one morning and found many dead cows. At necropsy, no
Japanese Yew plants were found in the rumen. However,
analysis of the rumen contents revealed the presence of
an organophosphate
insecticide. In this case, the insecticide was also
found in the contents of the feed trough, where it had
inadvertently been incorporated.
In the third case, the owner arrived at his pasture early
one morning and discovered 3 dead cows. Over the next
24hrs, another 12 cows and calves died. At necropsy,
no Japanese Yew was found in the rumen. Analysis of the
rumen contents revealed no insecticides or other pesticides.
However, in this case, analysis of the hay showed that
it contained high
concentrations of nitrates as did the ocular fluid of
one of the dead cows. Removal of the hay prevented any
further deaths. Fortunately, in this case, the owner
realized that the deaths began within a day after putting
new hay bales in the pasture for the cattle. As soon as
the deaths began, he removed those bales and the deaths
soon ceased. Other hay, which was baled earlier in the
year, was unaffected. We suspect that a combination of
heavy fertilization, late summer drought, and the growth
of nitrate -accumulating plants all contributed to the
high nitrate concentrations found in these third cutting
hay bales.
From these cases, it is clear that there can be numerous
causes of sudden death in livestock. Often, a rapid diagnosis
is necessary to prevent further losses. Therefore, when
such cases occur, and in consultation with the owner,
referring veterinarian or (pathologist), and lexicologist,
a battery of tests will be started. These tests will begin
analysis for all of the most common causes of sudden death
in the affected species. This will greatly speed up the
time necessary to find the cause of the poisoning since
we will not have to wait for a negative result of one
test before proceeding onto the next. For cattle, this
testing would include assays for insecticides, alkaloids,
and nitrates. For sheep, copper would also be included.
Since horses are not as sensitive to nitrates, deaths
involving horses would not start with nitrate testing,
but would include monensin. While this approach will
add to the initial cost of testing, beginning all of the
tests immediately will allow the most rapid diagnosis
of the cause of the problem.
The battery of tests which will be run for each species
(and the tissues needed to run those tests) are:
