People that raise livestock have an increasing awareness that poisonous plants can affect their animals. Part of this is due to the ever increasing population of horse owners and the growth in management intensive grazing systems. But do not forget that you do not only have to watch your pasture ground closely, but your hayfield or purchased hay as well.
Poisonous plant questions are also more frequent in dry years as droughts create situations in which animals often graze plants they would otherwise not eat and producers may harvest fields or plants that are not usually harvested to have adequate feed stock for the winter. Additionally, weeds not usually considered toxic might become poisonous under certain condition. For example, weeds may become more palatable to livestock following an herbicide application in a pasture or fencerow. This may result in animals eating plants they would normally avoid consuming. All areas of the country have different species of concern and your local extension agent or university may be of assistance.
What are the Plants That Cause Animal Poisoning?
The book “Poisonous Plans of the Midwest” (Evers and Link 1972) includes 70 species. Also, Indiana lists 53 plants as potentially poisonous to animals on their “Indiana Plants Poisonous to Livestock and Pets” web site… http://vet.vet.purdue.edu/toxic/cover1.htm
Laatly, I highly recommend the Purdue University Guide to Toxic Plants in Forages… https://www.extension.purdue.edu/extmedia/ws/ws_37_toxicplants08.pdf
Many universities offer outstanding websites and documents, usually complete with photos and the information you require.
Below is partial list of plants common in the Midwest that are capable of affecting animal health and the toxin they contain.
The list below is in the following format:
woods and open areas; all part poisonous
pastures, esp. wet areas; causes sharp drop in milk production; toxin lost on drying forage
common in fencerows and woods
cultivated fields, pastures; esp. sandy soils; seedlings and seeds toxic
Apocynin & other glycosides
all plant parts have milky sap; fields and roadsides
horses are particularly sensitive
wet or dry areas of pastures and roadsides; all parts toxic
seldom eaten because of spines
Alkaloids and others
all plant parts toxic
Nitrate and Oxalate
common field weed; high in feed value
Solanine and other glycoalkaloids
all parts poisonous under certain condition; ripe berries almost nontoxic
acorns and young leaves and shoots are of concern
oxalate and Nitrate
common field weed; many species; prostrate and tumble pigweed common in pastures
roadsides, edges of fields and waste areas where soil is moist; all parts highly toxic
These excerpts were taken from an article by Jerry Doll, University of Wisconsin, Poisonous Weeds of Pastures & Forages. Remember your local extension service can help you with identification, control, and challenges you may face. Be safe, know what is growing in your pasture and hay fields. Be safe and drop by for more on weeds throughout different regions of the United States.