Wild parsnip is just one of many invasive weeds that we are seeing invade area roadsides,
uncultivated fields and pastures. Wild parsnip is poisonous to animals whether it is fresh or dried
and fed as hay. All growth stages of the plant are toxic to livestock, when eaten fresh or dried in hay. High concentrations of furanocoumarins have been found in the seeds as well.
Grazing livestock will generally avoid poisonous plants IF adequate forage of more desirable
species is available. Poisonings most often happen in spring, before grass growth is adequate to
meet animal needs, or during periods of drought when the pasture fails to regenerate quickly. But
poisonings can take place at other times, too…Certain areas in, or adjacent to, pastures can
contain a wide variety of non‐pasture plants. These areas include fencerows, barnyards and
pasture field margins. They can be quite attractive to livestock, even when there is good pasture
nearby. Some areas are more favorable to the growth of weedy or poisonous plants. Also, when
livestock are introduced to a new place, they are unfamiliar with the setting. These animals may
be hungry and willing to sample plants they would normally leave alone. Feeding hay, silage,
greenchop or other good feed prior to turning animals into an unfamiliar pasture will reduce the
animals’ tendency to consume them.
People sometimes toss clippings from poisonous ornamental plants around their property to
their livestock. The yew bush is very poisonous and is a common cause of livestock poisonings.
Livestock poisonings tend to be only occasional events…usually not widespread. Poisoning
should be suspected if: several animals in a herd or flock show -acute disorders of the central
nervous system or digestive track without a fever but with weakness and rapid weight loss.
Indications may include; sudden acceleration of heart beat, stomach and intestinal irritation,
general distress, or repeated attempts to void feces.
Signs of plant poisoning may differ in intensity depending on: kind of plant, stage of plant
growth, soil in which the plant is growing, amount eaten, amount and kind of feed eaten during
the time the poisonous plant was in the animal’s digestive tract, and the animal’s tolerance to the
poison. Overgrazing will result in weedier pastures, and could result in the establishment of
poisonous pasture weeds. Simply keeping livestock out of known problem areas can be a very
practical approach. It will also give you a chance to reduce or eliminate the problem plant
species and get better pasture established.
Learn to identify poisonous plants.Learn conditions under which these plants can be
poisonous. Develop a good grazing plan. Rotational or strip grazing allows desirable plants time
for regrowth. Improved grazing techniques will allow grasses and legumes time for regrowth
between grazings. This will also improve their ability to compete with undesirable plants.
Lack of water will make it more difficult for animals to metabolize and excrete any poisons
they may ingest while grazing. If intestinal irritation due to poisonous plant ingestion takes place,
dehydration can result. A good, fresh water supply can help minimize these problems.
Spot spraying or wiping with an effective applicator can be a practical way to control
poisonous plants. 2,4‐D, a common selective broadleaf herbicide, may actually make treated
plants more palatable to livestock before the plant dies and withers. Glyphosate is usually a good
choice for spot treatment.
A veterinarian will want to know what type of problem plant an animal may have eaten.
Weeds in this area that may be poisonous include; nightshade, black locust, brachen fern,
chokecherries, cocklebur, horsetail, jimsonweed,lambsquarter, milkweeds, oaks, pigweed, hoary
alyssum and wild parsnip.