Late summer and early autumn are typically relatively dry across most of the United States. A combination of heat, lack of rain and overgrazing leaves many pastures sparse. In this situation, livestock can be tempted by the leftovers: weeds. Weeds, flowering plants and even some trees can pose dangers in the form of toxic plants.
Sometimes tall and spiny, other times appearing relatively innocuous, many toxic weeds exist throughout the U.S., and it’s easy to get overwhelmed trying to learn about them all (not to mention toxic flowers and trees). Below are brief descriptions of some common toxic plants, but this is not an exhaustive list. Here we’ll focus on plants toxic to four-legged livestock. Hobby Farms has published a list of plants toxic to poultry and there are many overlaps. For the most complete guide to toxic plants in your location, contact your local university livestock extension service.
This beautiful wildflower (pictured above) is the only source of nutrients for monarch butterfly larvae yet is toxic to all livestock and pets. In fact, monarchs have evolved so milkweed toxins don’t harm their larvae, but rather make the butterflies themselves toxic to predators. The good news? This plant is extremely unpalatable to our livestock. So please do plant this pollinator-friendly plant in your gardens but out of reach of your grazing animals.
These beautiful flowering bushes (azaleas are shown above) are common in landscaped yards, but all three related plants are extremely toxic, and curious browsers such as goats are frequent victims. Signs of toxicity in livestock include salivation, vomiting and abdominal pain, and ingestion can be lethal. The best advice if you have small ruminants is to keep them away from landscaped areas.
Plants in the Pasture
Every part of this plant is toxic, especially to pigs, cattle, sheep and goats. Pigweed contains nitrates, toxic compounds that accumulate over time until they cause organ damage.
A weed with small yellow flowers, this plant contains toxins that affect the liver. Accumulation over time leads to liver failure, which in livestock is clinically manifested as weight loss, jaundice, diarrhea and skin photosensitization.
These beautiful flowers are toxic to all animals, livestock and humans included. Foxglove contains a chemical that acts on the heart, affecting its rhythm. Acute exposure can lead to cardiac arrhythmias and death. Keep livestock away from gardens and take proper precautions with small children.
This plant contains a chemical called tremetol, and its name can help you remember a common sign of toxicity: When it’s ingested by cattle, they will typically show muscle tremors. Horses will more often develop heart failure.
Interestingly, the trees that produce delicious fruit also produce deadly leaves containing cyanide. When the leaves fall and wilt (not only a threat in the autumn but also whenever a branch comes down in a storm) and livestock ingest them, and the cyanide prevents the body’s cells from using oxygen. Affected animals succumb to respiratory distress.
Black walnut toxicity is seen in horses when shavings from this type of tree are used for bedding. Black walnut exposure causes acute laminitis (inflammation of the sensitive tissue in the hooves).
Although it seems like a dangerous world out there in the pasture, you can do several things to help your livestock avoid toxic plants. For one, become familiar with the most common toxic plants in your geographical area. Then, in early spring and late fall, walk your pastures and paddocks to see what’s growing. If you identify toxic plants, consult your local extension agent on the best way for control.
If pasture is sparse, bulk intake with roughage such as hay, or control grazing areas with electric tape to keep your animals from resorting to forbidden food. If you have neighbors, educate them on not throwing yard clippings over the fence for extra “feed.” Keep in mind that decorative foliage and small ruminants don’t mix. If you’re in a more developed area, don’t let your goats browse near the house where decorative landscaping might exist.