I have been receiving a handful of calls to the office on which plants are considered toxic for different livestock. As fall foraging still allows for potential dangers, I wanted to discuss some of the common poisonous plants that you might find in your pastures. Most poisonous plants are non-palatable and the best way to discourage livestock from eating them is to provide adequate forages. Livestock may accidentally consume toxic weeds when eating other forages. Regularly walk pastures to identify any concerns to reduce the chances of poisoning in your herd.
Cyanogenetic Plants- These plants contain under certain conditions, prussic acid (hydrocyanic acid), which is a deadly poison that interferes with the oxygen-carrying ability of blood. Death in these cases is often rapid with little outward symptoms. Members of the prunus family, stone fruits, are in this category. The wild black cherry and choke cherry tree is a major cause of poison to livestock. Other common stone fruit trees include peaches and plums. When leaves are wilted on these trees, they go through a change that increases the amount of hydrocyanic acid and sugar levels. The sweetened leaves are more tempting to livestock. While the amount of hydrocyanic acid varies per leaves, in some cases it only takes a few handfuls of leaves to kill a horse or cow. These leaves lose their poison after they have become dry; the limp, green or partially yellowed leaves are the most dangerous. Keep in mind that small branches and leaves can travel distances during strong storms that can make their way into your pastures. This type of poisoning should be suspected when sudden death of animals follows windstorms or early sharp frosts.
Other members of the cyanogenetic plants include Sudan grass and sorghums, especially when damaged or frozen. Johnson grass is a common problem found in pastures. Watch for frost and the regrowth of sorghums after a harvest. If there is a frost and you want to graze one or more of these grasses, do not graze after a killing frost until plants are dry, which usually takes 5 to 7 days. After a non-killing frost, do not allow animals to graze for two weeks because the plants usually contain high concentrations of cyanide.
Alkaloid Plants- Deaths from alkaloid-containing plants usually result from severe digestive disturbances, pain, and nervous symptoms. Animals usually die in convulsions. The most dangerous plants in this category include water hemlock and poison hemlock. These hemlocks are considered highly poisonous to humans as well. Always be cautious when handling poison and water hemlock. Poisoning rarely occurs in livestock except in early spring when young plants are accidentally eaten, but the roots, stems, leaves, and flowers are always highly poisonous when ingested. Look for and learn to identify these plants in the summer when they are large and showy. The hemlocks are members of the carrot family and have showy, white, umbrella-like flower heads. Many members of the carrot family have a similar appearance and are not considered poisonous, but often irritate the skin when handling.
Common milkweed, horse nettle, jimsonweed, common pokeweed, cressleaf & common groundsel, pigweed, black nightshade, mountain laurels, and rhododendrons are all considered poisonous plants commonly found in Ohio. In common milkweed, livestock occasionally eat the topmost leaves, which are poisonous. Horse nettle has smooth, orange yellow berries that tend to be more poisonous than the foliage. All parts of Jimsonweed are considered highly poisonous. Common pokeweed can poison cattle, horses, sheep, and goats by eating the green leaves where pigs are more likely to be poisoned by the roots. Cattle are more susceptible to poisoning from common & cress leaf groundsel, however all grazing animals can be affected. All parts of both groundsels are considered poisonous. The leaves of pigweed are considered poisonous. Black nightshade is poisonous to livestock if they consume the foliage or the green berries. Once the berries ripen to a dark purple black color, they are not poisonous. Livestock might eat the poisonous leaves of mountain laurels or rhododendrons in the early spring before other forage is abundant.
Along with stone fruit trees, other trees can be a concern for livestock. Buckeye poisoning occurs from the nuts that fall from the buckeye trees. Animals develop signs of poisoning 16 hours after consuming toxic quantities. As little as 0.5% body weight of the animal can produce severe poisoning. Laxatives may be given to remove the ingested plant parts as fast as possible. Buckeye poisoning is important to watch for in the fall when buckeyes are abundant. The acorns and young shoots from oak trees can cause poisoning if consumed in large quantities. Horses tend to be more susceptible to tree species including Red Maple (when leaves have turned in the fall or are wilted), Box Elder (consuming the seeds), and Black Walnut.
Ornamental plants such as Yew, Larkspur, Oleander, Delphinium, Lily of the Valley, Lupine, Rhododendron, Morning Glory, English Ivy, Bracken Fern, and Holly are considered poisonous to livestock.
If you are concerned about certain plants or want clarification on identifying weeds, please call into the extension office to arrange a farm visit. Another option is taking photos of the plant including all visible parts. These photos can be brought into the office or emailed to me at [email protected]
Upcoming Events and Reminders:
• Now is a great time to be ordering your garlic to plant this fall if you haven’t already.
• The Ohio Valley Career & Technical Center is hosting an Agribusiness Co-Op Field Night where you can learn more about the OVCTC School Farm and see how students are growing their marketing and sustainable management, direct marketing local meat, and tour the farm. This event is Thursday October 5 from 5:30 – 8 pm. Deadline for registration is September 27th. Call (614) 247-9757 for any questions or to register.
• Ohio Master Gardener Conference- Join the 2023 MGV State Conference in Greene County October 12 – 14. The event will be held at the Holiday Inn in Fairborn, Ohio. This conference is a great networking and educational opportunity for all gardening enthusiasts. More information can be found online at- https://u.osu.edu/mgv2023greene/
