Plants poisonous to livestock

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.

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