Poisonous plants cost the livestock industry upward of $500 million annually due to animal losses and increased management costs. The economic impact of poisonous plants can be identified as both direct and indirect losses. Direct losses include imminent death of the animal, slow weight gains, weight loss, increase in calving intervals, abortions, birth defects and infertility. Indirect losses can be considered and identified as building and maintaining fences to reduce exposure to areas infested with poisonous plants, increases in feed and medical costs, overall decrease in forage availability and quality, decrease to land value and, of course, the cost of added stress to both the animal and producer.
It is your responsibility as an animal owner and operator to protect your livestock from toxic plants. If you are new to your area, it is extremely important to know what type of plants your herd may or may not be grazing on. Taking the time to do a thorough inventory of your grazing area could potentially save you hundreds to thousands of dollars later in the grazing season. If you are grazing public lands, it is important to work closely with other livestock owners and the land management agency to ensure pasture quantity and quality is maintained.
Common types of poisonous plants
Poison hemlock (Conium maculatum)
Poison hemlock. Getty Images.
Poison hemlock grows throughout the western U.S. It can be found growing along ditches, fencelines, roadsides and creek beds. Poison hemlock belongs to the carrot family and can be easily mistaken for wild parsley. Animals who have ingested poison hemlock may experience respiratory paralysis and convulsions within hours of consumption. Cattle only need to eat about 16 ounces of poison hemlock to show signs of toxicity. Pregnant cattle who consume poison hemlock can produce offspring with skeletal deformities including cleft palate and crooked calf disease. Cattle owners must also take caution when managing poison hemlock, as it is highly toxic to humans. Take care when handling poison hemlock and use gloves when handling this plant. Poisoning typically occurs after ingestion; however, dermal absorption may occur.
Water hemlock (Cicuta douglasii)
Water hemlock. Getty Images.
Although they share a similar name, water hemlock may incorrectly be identified as poison hemlock. The two plants share similar flowers; however, poison hemlock has fernlike leaves and a purple spotted stem, while water hemlock does not. Water hemlock can be found growing near wet soils primarily associated with ditches, stream banks, ponds and marshes. Animals may experience symptoms of poisoning as quickly as 90 minutes after ingestion. Symptoms include nervousness, excessive salivation, muscle twitching, increased breathing and pulse. This plant can also commonly be mistaken as parsnip. Livestock producers need to use caution when handling water hemlock, as it is also toxic to humans.
Lupine (lupinus species)
Lupine. Getty Images.
Lupine species can be found in the foothills and mountain ranges of the western U.S. Lupine toxicity is like signs of hemlock poisoning and includes labored breathing, nervousness, convulsions and birth defects. Lupine is teratogenic. Pregnant cattle ingesting lupine during early gestation (30-110 days gestation) can have offspring with crooked calf disease and other skeletal deformities.
Larkspur (delphinium species)
Larkspur. Getty Images.
Larkspur has been divided into three groups based on height at maturity: tall larkspurs, low larkspurs and plains larkspurs. High larkspurs can be found at higher elevations in deep moisture-rich soils. Tall larkspurs may begin growing as soon as the snow melts, but growth typically occurs in July. Low larkspurs can be found at lower elevations. They grow in early spring and grow the best when it is cold and wet. Plains larkspurs are found primarily in the plains of Colorado and Wyoming. Its growth begins in early spring before other plants. Since these plants bloom early, they may be the only forage available for cattle to graze on. Cattle typically leave tall larkspur alone; however, they should be removed from the area during the plants' flowering stage when palatability increases. Tall and low larkspur can be grazed once the plant loses its flowers and pods. Symptoms include nervousness, weakness, salivation, bloat, irregular pulse, sudden death and pulmonary congestion.
Milkweed (asclepias species)
Milkweed. Getty Images.
There are several species of milkweed that are toxic to livestock, with labriform milkweed being the most toxic. Milkweed plants that have narrow-shaped leaves are more toxic, while broad-leaf milkweed is relatively nontoxic. Narrow-leaf milkweed tends to be more palatable than broad-leaf. Milkweed is commonly found in sandy plains and foothills. It gets its name from the milky substance that oozes from the broken parts of the plant, usually the stem. This milky sap contains the highest concentration of cardiac glycosides. Symptoms of poisoning include labored breathing, weakness while standing, muscle twitching and rapid pulse. In extreme cases, animals may be found dead without exhibiting signs of toxicity. Milkweed toxicity can range from 0.05% to 2% of an animal’s bodyweight on a bodyweight basis. Animals are more likely to graze on milkweed after a frost or when other forage is not available.
Conclusion
Animals that are affected by poisonous plants may manifest different symptoms. Animal species, weight, age, health and reproductive status can affect how animals respond to poisonous plants. If you notice any sudden changes to animal deposition or neurological changes (drooling, staggering, labored breathing), these can potentially be caused by plant poisoning. Contacting a veterinarian as soon as symptoms are observed can potentially save the animal. When moving an animal that may be experiencing a toxic response, avoid stressing the animal by moving them slowly and quietly. Often veterinary intervention may be too late.
To protect your animals from poisoning, it is important to identify any poisonous plant growing in your grazing area. Once identified, learning more about their life cycle and time of which they are most toxic to your animal is beneficial. Furthermore, knowing this information can help you plan your grazing strategy for the year. If you manage areas infested by poisonous plants, avoid grazing livestock until it’s safe for animals to consume those plants. Always provide adequate amounts of feed and fresh water. Keeping your livestock full will reduce the chance of grazing on unwanted toxic plants. If you are running young cattle, or cattle that have little to no experience grazing areas with poisonous plants, be wary of letting them graze near toxic plants, as they may not be familiar with the area and accidentally consume unwanted plants. Provide adequate amounts of mineral and salt supplements. You can place supplements in areas away from poisonous plants to persuade animals to graze away from them.
If you believe a plant may be poisonous, take a sample to bring to your local veterinarian or local extension office for proper identification. Always wear gloves when handling potentially toxic plants, especially hemlock species. For any corrective action to take place, it is important to properly identify any potentially poisonous plant.
