Plants poisonous to livestock

Mike<metzgerm@msu.edu> Metzger, Michigan State University Extension - May 17, 2012

Poisonous plants can be found in pastures and stored forages. Be sure to check your pastures for poisonous plants before turning your livestock out to graze.

Livestock can be poisoned or injured by certain plants while grazing or being fed stored feed. Many common weeds in Michigan can poison livestock. Some poisons act very fast. In these cases, by the time the symptoms are evident, the chances of saving the animal are very slight. It is important to learn to recognize these weeds beforehand and prevent poisoning from occurring. Most of these weeds can be controlled chemically or mechanically. In some cases, it may be more practical to simply fence off infested areas so that the animals do not have access to particularly hazardous weeds. In the chart below are several pasture plants that are toxic to livestock. An internet search can help to visually identify these plants.

**Table 1. A partial list of plants common in Michigan that are capable of affecting animal health and the causal agent (toxin) they contain.**
Species	Toxin	Comments
bracken fern	thiaminase	woods and open areas; all part poisonous
buttercups	protoanemonin	pastures, esp. wet areas; causes sharp drop in milk production; toxin lost on drying forage
chokecherry	prussic acid	common in fencerows and woods
cocklebur	hydroquinone	cultivated fields, pastures; esp. sandy soils; seedlings and seeds toxic
hemp dogbane	apocynin & other glycosides	all plant parts have milky sap; fields and roadsides
hoary alyssum	unknown	horses are particularly sensitive
horsetail	thiaminase	wet or dry areas of pastures and roadsides; all parts toxic
horse nettle	alkaloids	seldom eaten because of spines
jimsonweed	alkaloids and others	all plant parts toxic
lambsquarters	nitrate and oxalate	common field weed; high in feed value
nightshades	solanine and other glycoalkaloids	all parts poisonous under certain condition; ripe berries almost nontoxic
oaks	gallotannins	acorns and young leaves and shoots are of concern
pigweeds	oxalate and nitrate	common field weed; many species; prostrate and tumble pigweed common in pastures
poison hemlock	many alkaloids	roadsides, edges of fields and waste areas where soil is moist; all parts highly toxic

It should be noted that most of these weeds are unpalatable and animals will usually not graze them if given the choice. One of the most important steps in preventing animal suffering or loss is good pasture management. Keeping the desirable forage species producing throughout the grazing season reduces the possibility of animals grazing poisonous weeds.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).