- Every year, poisonous plants cause
death, temporary and chronic pain and
illness, abortions, decreased productivity,
and birth defects to hundreds of thousands
of grazing and browsing livestock.
Horses, sheep, cattle, llamas, alpacas,
goats, and pigs are affected. The annual
economic loss amounts to
hundreds
of millions of dollars. For complicated
reasons of plant and animal evolution,
well-nourished herbivores will generally
avoid eating most toxic plants. The
toxins in some plants make them unpalatable
to animals-they either smell or taste
bad. Animals learn from other animals,
particularly their mothers, to avoid
some of the other poisonous plants.
Still other poisonous plants produce
a disagreeable physiological sensation
soon enough after digestion that animals
learn not to eat them at all or they
stop before consuming toxic quantities.
But these mechanisms of safe eating
are not fool-proof. As noted, above,
poisoning does occur and when it does,
it can be devastating to both animal
and owner. There are a variety of reasons
why livestock eat poisonous plants.
There are some to which livestock has
been found to be attracted. Some unpalatable
plants appear to lose their disagreeable
odors or tastes when dried (as in hay);
a significant cause of poisonings is
consumption of toxic plant parts mixed
in hay, silage, grain, or processed
feed. Some typically safe plants become
toxic when fertilized or treated with
certain herbicides. They may simultaneously
become more palatable. Weather stresses
and other natural conditions may convert
the non-toxic to toxic. Probably most
importantly, if put into a situation
where only poisonous plants are available
or where they make up a large percentage
of available forage, livestock will
eat them.
- Pasture management is critical.
- Learn about plants in pastures
and the animals that will graze
there. Seek help from Extension
agents and others, if necessary.
Some options:
- Eliminate or fence securely around toxic plants, especially if animals may find them palatable or if they are highly toxic or abundant. NOTE: If you grub out highly poisonous plants such as the various Water hemlock species (Cicutu spp.), take appropriate precautions to protect yourself and others, especially children.
- If animals will have access
to less palatable toxic plants,
Ensure that they always have
adequate safe forage available.
Check plant levels and types
periodically. Do not overgraze.
- Watch carefully in early spring
or late fall when toxic plants
may be more prevalent that others.
- Know which plants are drought
resistant. They may be the only
food available under some circumstances.
- Watch out for toxic plants
that are evergreen from fall
to spring.
- Ensure that animals have adequate water, as well as salt and mineral supplementation, if needed.
- Avoid giving access to plants
during their toxic season(s).
- Check on your pastured animals
regularly and know the signs
of poisoning to allow prompt
action in case poisoning occurs.
- Be careful with herbicides
(including those that may be
applied by others, e.g., local
government entities).
- Learn about
their direct effect on animals,
whether animals have been found
to be attracted by application of the
product and, if palatablicy is likely
to increase, know about the inherent
toxicity of those plants.
- Be prepared to identify and
respond appropriately to toxic
plants when animals will be taken
into unfamiliar areas. New poisonous
plants may be eaten simply because
the animal has no experience
with them.
- Avoid driving animals through
areas with high concentrations
of toxic plants, particularly
if they are hungry.
- When tying, picketing, or staking
animals, identify, and avoid
areas where they are likely to
consume toxic plants. If at all
possible find a place that is
grassy, rather than leafy. Most,
although not all, wild grasses
are safe forage. (Be able to
identify and avoid Triglochin
maritima (known in most areas
as Seaside arrowgrass) and Zigadenus
spp. (commonly known as Death
Camases, but there are several
other commons names).
- Do not assume that others know
about poisonous plants. Feeding
animals "treats" seems
to be an almost irresistible
urge of humans. Educate both
adults and children who may come
in contact with animals so that
they know not to feed them leaves,
fruits, etc. (This exercise will
also alert children to the whole
issue of poisonous plants. Many
plants are at least as dangerous
for children to eat as livestock.)
Consider providing visitors with "official
treats" that animals like
and can safely eat.
- If animals are rented or lent
to others, orient the temporary
caretakers to toxic plants along
with other instructions on care
and handling. Provide plant identification
resources to be taken along with
the animals.
- When selling animals, ensure
that buyers are aware of toxic
plants. Consider providing pertinent
materials to the new owners.
- Do not feed yard or garden
vegeration (clippings or trimmings)
to livestock.
- Try to arrange to walk uncut
hay fields before buying and
check hay when feeding. Buy grain
and processed feeds from reputable
sources.
- Consider removing toxic trees
and scrubs in corrals, pastures,
and yard that could be accessible
to livestock. Of course, the
urgency of this measure depends
on the toxicity of the plants.
- Anticipate accidental circumstances
such as leaves blown by wind
or the fact that animals sometimes
get out.
- The safest course during Christmas
and other holiday is to avoid
feeding trees or other greenery
to livestock. Although Pinus
pondersoa (Ponderosa pine, among
other common names) is the most
commonly referenced harmful member
of the Pinus genus, other species
and other conifers also may be
toxic especially if consumed
in large quantities over a short
period. Many common types of
holiday decorative greenery can
be deadly.
- Check branches and tree limbs
brought down in pastures by storms
to ensure that they are not from
toxic trees.
- Establish a connection with
a veterinarian before an emergency
arises. Locate a practitioner
familiar with your species of
animal(s) and involve him or
her in routine care.
- Ask for information about any
plants in the area that may already
have caused problems. If other
animals have been poisoned by
local plants, there is a good
chance that local veterinarians
at least will be aware of that.
They also may have some good
advice to give you about prevention
or response or both.
- If you will be taking animals
into a situation where veterinarian
assistance will be difficult
to obtain, ask you veterinarian
to discuss some prudent actions
to take in the event of poisoning.
- Always notify a veterinarian
when plant poisoning is suspected.
Be prepared to provide him/her
with as much information as possible
about the situation.
- Discuss appropriate supportive/symptomatic
care you may be able to provide
to sick animals and be prepared
to provide it until assistance
arrives.
- Try to identify any suspect
plants.
- Get a samples.
- Inspect the area where the
animal was grazing. Try to determine
the amount and duration of consumption.
- Observe and make careful note
of any physiological or behavioral
signs the affected animal may
exhibit.
- Keep an open mind and investigate
other possible toxic agents to
which a sickened animal may have
been exposed, as well as the
possibility that another type
of illness may be involved.
Whether or not animals will be sickened by ingesting particular toxic plants is also a complex matter. Not all species of livestock are equally affected by or susceptible to various plant toxins. For example, it is thought at this time that only equines contract "chewing disease", a devastating illness involving irreversible brain damage caused by consumption of toxic amounts of Centaurea scllstitialis or Centaurea repens (commonly known as Yellow starthistle & Russian knapweed, respectively). The relative health of the individual (or, if a ruminant, of the microflora in its rumen) can figure into how well it can handle some toxic substances in the plants it consumes. The digestive systern of some animal species can adapt to be able to detoxify higher levels of toxins with exposure. A substantial quantity of some plants must be ingested to trigger illness or death. A couple of leaves of other plants can kill. Despite all of these variables
(and more), experts agree that
plant poisoning can be minimized.
The best means is a combination
of effective use of good information
about toxic plants and the provision
of adequate amounts of safe alternative
food. In the unhappy event that
poisoning occurs, being informed
may facilitate effective response. On a personal note, when I began
my book, I understood the grave
potential of plant poisoning,
but had not had any direct experience
with it. Then in the midst of
writing it our neighbors had
to put down five horses due to
Russian knapweed poisoning mentioned
earlier in this article. Just
after the book was published,
one of our pack llamas plucked
a large mouthful of a young Water
hemlock plant as we prepared
to cross a stream. Although almost
certainly not a lethal dose for
a 300 pound animal, I'm convinced
that I prevented him from being
sickened by recognizing and forcibly
removing the plant matter from
his mouth. Shirlev
Weathers, co-owner of Walsh & Weathers Research
and Policy Studies and Rosebud
Llamas Utah. excerpred this article
from her new book, Field Guide
to Plants Poisonous to Livestock
- Western U.S. This book is designed
to help livestock owners recognize
over 100 toxic western plants
and provide adequate basic knowledge
to consider effective animal
or pasture management responses
when those plants are present.
Possible physiological & behavioral
signs of poisoning are also provided
as well as treatments. The Following list was submitted
by Martin English DVM: This is not a complete list
of all poisonous plants. *Field Guide
to Plants Poisonous to LivestockâWestern U.S.;
Shirley A. Weathers; ISBN: 0-9660397-3-4, Rosebud
Press; |
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