Poisonous Plants for Livestock

Why do animals eat poisonous plants?

Extension publications point to a few common causes: pastures that are short on grass, new or hungry animals turned into an unfamiliar field, drought or frost that changes what is available, and toxic plants that get cut and baled into hay. Some plants are more risky at certain growth stages or after frost.

The risk is highest when animals have little else to eat, so good grazing management is the first line of defense.

Not every plant on a danger list is risky in every setting. Poisoning depends on the plant, the amount eaten, the animal species, and the time of year. Extension lists are written for a region, so use one for your area and ask a specialist how it applies to your animals rather than relying on a general internet list.

How do you find out what grows in your fields?

Walk every pasture, fence line, ditch, and hay field, especially in spring and after a dry spell. Photograph unfamiliar plants and ask your county extension office to identify them. Plants differ by region, so use a guide written for your state.

Keep a map of problem plants and update it each year. Check areas where animals gather, and areas where soil was disturbed, since weeds often start there.

Disturbed ground deserves attention. Areas that have been tilled, graded, or overgrazed, and spots where fill or hay was dumped, often sprout plants that were not there before. Check these places soon after the work and again later in the season, and keep animals off until you know what is growing.

• Walk fields, fence lines, ditches, and hay ground
• Photograph unknown plants for extension to identify
• Use regional guides for your state
• Map problem plants and check them each year

How do you lower the risk in pastures?

Keep grass thick and do not let animals graze fields down to bare ground. Rotate pastures, rest fields, and provide hay when grass is short. Fence off areas where toxic plants grow if you cannot remove them, and check fields before turning animals in.

Removal methods depend on the plant, and some are harmful to handle or become more dangerous when cut and wilted. Ask your extension office before you cut, spray, or pull anything, and follow every label.

Ornamental plants and garden waste can also be dangerous. Clippings thrown over a fence, shrubs along a pasture edge, and plants brought in by neighbors have caused problems for animals in many places. Ask your extension office which ornamentals in your area are a concern, and keep them well out of reach.

What about hay?

Toxic plants that are baled stay in the hay and animals may not be able to sort them out. Ask where your hay was grown, look at it before you buy it, and inspect bales as you open them. Hay that contains plants you cannot identify should be shown to your extension office or veterinarian.

Weeds in a hay field are a reason to adjust cutting and weed control for next year.

Know your animals' habits. New animals, young animals, and animals that have been without good feed are more likely to sample unfamiliar plants. Introduce them to a new field after they have eaten their fill of hay, and watch them closely for the first hours.

What are the warning signs of poisoning?

Signs vary by plant and species, so no list is complete. Possible warning signs include sudden unusual behavior, staggering, trembling, drooling, bloating, labored breathing, diarrhea, collapse, or animals found dead. Sometimes there is no warning before a loss.

Any of these signs, or knowing animals have eaten a suspect plant, is an emergency.

• Staggering, weakness, trembling, or collapse
• Drooling, bloating, or sudden diarrhea
• Trouble breathing or sudden changes in behavior
• Unexplained deaths in a group of animals

What should you do if you suspect poisoning?

Call your veterinarian immediately and describe what you see. Move animals away from the suspected plant or feed if you can do so safely, and keep a sample of the plant and the feed to show the veterinarian. Do not give home remedies or try treatments on your own.

Poultry and livestock disease reporting and biosecurity rules vary by state, so ask your veterinarian, your state veterinarian's office, or extension what applies if animals die.

Who can help you plan?

Your extension office can help with plant identification, regional lists, and pasture plans. Your veterinarian can advise on animal health and feed. Your NRCS service center may know of cost-share help for pasture improvements. Do not eat or taste unknown plants yourself, and keep children away from suspect plants and treated areas.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.