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July
6, 2006
Toxic Plants
Pose Livestock Threat During Droughts
Toxic range plants
can become a serious threat to livestock during a drought, warns North
Dakota State University Extension Service rangeland management specialist
Kevin Sedivec.
A few of these toxic
plants are very deadly. They can kill an animal in less than a day.
Most toxic plants
found in pastures are unpalatable, which means livestock won’t eat
them under normal conditions, Sedivec says. However, during a drought,
the more palatable forages mature and dry up early, making the poisonous
plants more available for livestock to eat. The toxic plants often have
root systems that can reach water deep in the ground, so they stay green
longer, which makes them doubly attractive to livestock.
Also, producers inadvertently
may help toxic plants poison livestock. In drought conditions, producers
need forage, so they hay around sloughs. But wetlands are where plants
with the highest toxicity grow, according to Sedivec.
So far, toxic plants
pose the greatest danger in south-central and west-central North Dakota,
which are extremely dry this year.
The state has about
a dozen broadleaf plant species that are toxic to livestock. The worst
are:
- Water hemlock
– It’s found throughout the state and is one of the most
poisonous plants in the U.S. It’s found in wetland areas. The
root and bottom part of the plant are the most toxic. Livestock can
die within an hour of eating even a small amount of it.
- Arrowgrass –
It is found in southeastern North Dakota and grows best in soil covered
with water. It mainly affects cattle and sheep. The leaves, which contain
hydrocyanic acid, are the most toxic part.
- Locoweed –
It grows throughout the state. It is slightly more palatable than other
toxic plants, so livestock are more likely to eat it. The plant affects
horses more than cattle. It also poisons sheep and goats. It can cause
death, but it more commonly causes birth defects in livestock.
- Lupine –
It’s found in southwestern and western North Dakota in sagebrush
and aspen areas. It causes birth defects. Sheep are particularly susceptible
to it.
- Chokecherry –
It grows throughout the state in areas where moisture is plentiful.
Livestock will eat the leaves and twigs, but the animals must consume
a large quantity before they’re poisoned. This plant also contains
hydrocyanic acid.
Sedivec says an even
more common danger during droughts is nitrate poisoning from certain range
weeds that accumulate large concentrations of nitrate in dry conditions.
While nitrate is not toxic to animals, it can cause problems such as abortions
and death at high levels.
Three types of broadleaf
weeds – lambsquarters, kochia and goosefoot – are the primary
concern.
“They are extremely
common in pastureland throughout the state,” Sedivec says.
These weeds also are
somewhat palatable to livestock. Cattle deaths occur from nitrate poisoning
during every drought, he says.
He has this advice
for livestock producers during droughts:
- Minimize overgrazing
to limit the livestock’s contact with toxic plants.
- To minimize overgrazing,
wean young livestock early, use a rotational grazing system to lessen
the impact on any one pasture, find additional pasture or supplement
the livestock’s feed.
- If overgrazing
is the only option, check pastures for toxic plants and try to keep
livestock away from them.
- Try to avoid toxic
plants when haying wetland areas.
- Contact your veterinarian
if you have a sick or dead animal.
- Take advantage
of the FeedList, an NDSU database at www.ag.ndsu.nodak.edu/feedlist/
with information on people with feed to sell.
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Source: Kevin
Sedivec, (701) 231-7647, ksedivec@ndsuext.nodak.edu
Editor: Ellen Crawford, (701) 231-5391, ellen.crawford@ndsu.edu
Water Hemlock
Click here for a higher resolution image.
(3,659Kb TIF file)
Arrowgrass
Click here for a higher resolution image.
(765Kb TIF file)
Locoweed
Click here for a higher resolution image. (2,223Kb
TIF file)
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