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Of the more than 3,000 plant species found in Pennsylvania more than 40 can cause serious health problems for grazing livestock and in many instances death. University and government researchers estimate that at least 5% if not more of the reported livestock deaths in the country each year are attributed to ingestion of poisonous plants or plant parts.

Poison hemlock and water hemlock are two highly toxic members of the carrot family often found in wet pastures and along streams and ditches here in the Northeast. Other poisonous plants frequently found in grazing situations are Indian tobacco, white snakeroot, buttercup species, milkweeds, bracken fern, jimsonweed, corn cockle, and Solanaceae species – such as horse nettles and ground cherries. The toxins in these plants can kill all types of livestock with just a few bites. Normally animals will not graze toxic plants unless forced to do so. When poisonings do occur it is often associated with overgrazed pastures or from hay contaminated with these weeds. Horses are often accidently poisoned because of where they were tethered.

What I’d like producer’s to pay particular attention too especially now that cattle values are at an all-time high, is that when cows ingest sub-lethal amounts of poison hemlock during early gestation, at around 40 and 70 days of pregnancy – which would be last August for those cows calving now; the toxins from poison hemlock may not kill the cow, but it can cause the developing fetus to be born with cleft palate, crooked legs, and a malformed spine. This birth defect is known as curly calf syndrome and it is more common out West where lupines grow wild. Lupine’s also having the same type of toxin as poison hemlock. The USDA-ARS has done extensive research on lupine poisoning.

Horses and sheep are more susceptible to some plant poisons than cattle. Anyone who has or intends to reclaim an old abandoned homestead, or create a new pasture, needs to be aware of the cultural landscape plantings that are toxic to horses in particular. The leaves of red maples and the leaves and fruits of cherries, horse chestnuts, beeches, and oaks are quite toxic to horses and livestock. Rhododendrons, yews, and boxwoods are also highly toxic. Other landscape shrubs that are toxic include privets, hollies, barberries, ornamental cherries, and all lilies. Edible plants like rhubarb are quite toxic to pigs. Lastly, many landscape plants can quickly become invasive and spread to idle fields. It is therefore quite possible that some of the broadleaf weeds in grass hay fields destined to become dry hay could be poisonous.

One of the best ways to prevent accidental poisonings is to know the vegetation composition in your pastures and hay fields. Don’t plant or discard any landscape clippings where livestock graze and don’t plant fruit bearing trees, especially cherries or apples, along fence lines or property lines where animals can reach over the fence. Fruit tree seeds contain toxic cyanogenic glycosides – while an apple a day may keep the doctor away, a cup of its seeds can kill instantly.

If your animals do get out, pay particular attention to what landscape plants they might have eaten and in what quantity. Talk to the person you purchase hay from and ask about specific weeds to make sure they are also aware of the dangers of these poison plants. If you are unsure about the identification of a particular plant hire a crop management or landscape consultant to survey your property for noxious, invasive, and poisonous plants of concern. Your local cooperative extension professional can also assist you. Cornell University’s “Weeds of the Northeast” and the University of Pennsylvania’s on line flora guide (www.paflora.org) and their publication “The Plants of Pennsylvania” are examples of publications that can assist landowners with identifying poison plants. Penn Veterinary Medicine’s computer aided learning module on poisonous plants (www.research.vet.upenn.edu/poisonousplants) is another resourceful web source.
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Melissa Bravo of Meadow Lake Farm Consulting Services is a certified crop advisor and land management consultant with a master degree from Penn State in Weed Science. She also conducts poisonous and invasive vegetation assessments. From 2005-2012, she worked as the acting botanist/weed specialist for the PA Department of Agriculture’s noxious and poisonous plant unit and managed the state’s giant hogweed eradication program. Melissa lives and farms in Tioga County. She can be reached at 814-574-4067.

Pictures: poison hemlock; crooked legs and cleft palette associated with poison hemlock poisoning on day 40 or day 70 of pregnancy.