Ruth Correll


Fortunately, there has been plenty of rain this year in Wilson County. However, late summer and fall are times of the year to watch out for plant toxicity in livestock.

One place to look is in areas of where livestock may be penned or corralled. Toxic plants may be present in substantial quantities in these areas. Plants such as perilla mint, jimsonweed and pigweeds are often found in these type areas. Often desirable forages are limited in these areas unless provided.

Differentiating “good” vs. “bad” plants is a learned behavior, so toxicity is more likely in young animals and animals moved to a new location. A grazing management and supplemental feeding plan is essential to minimize problems.

Producers should be familiar with which plants can cause problems in their area, and try to avoid them. Drought stress can cause both pasture forages and weeds to accumulate toxic amounts of nitrates. Recently fertilized pastures are also at higher risk. Plants that have accumulated nitrates remain toxic after baling or ensiling. Test forages for nitrates to prevent poisoning

Prussic acid accumulates most often in sorghums, sudans and Johnsongrasses, but these plants can accumulate nitrates also. There is no test for prussic acid, but it dissipates when plants are baled or ensiled, so harvested forages are safe.

One of the most toxic plants found in croplands and pastures is sickle pod. Cattle will generally not graze the green plant unless other forages are scarce. However, they will readily eat the seedpods that are dry after a frost. The plant remains toxic when harvested in hay/balage/silage.

Pigweed or carelessweed is very common in areas where cattle congregate. Cattle will readily eat the young plants, but avoid the older plants unless forced to eat them. A common pigweed poisoning is when cattle are penned where pigweed is the predominant plant and no alternative hay or feed is provided.

Red root pigweed is more toxic than spiny root pigweed, but is less common. Pigweed can accumulate nitrates, so sudden death is the most common outcome. It also contains oxalates, so renal failure can also occur.

Black nightshade is common in croplands, and like pigweed, in often in high traffic areas. The green fruit is most toxic, so cattle should not have access to nightshade during this stage, and nightshade remains toxic in harvested forages.

Bullnettle and horsenettle are in the same plant family as nightshade. They are also toxic, although less so, and are usually avoided by livestock unless other forages are not available.

Perilla mint causes acute bovine pulmonary edema and emphysema (ABPE), usually in late summer. It grows in most of the central and eastern United States and is common in partial shade in sparsely wooded areas, and around barns and corrals.

As summer moves into fall, the potential for acorn toxicosis increases. Cattle have to eat large amounts usually to become sick, but those that are in poor body condition and hungry are more likely to do so.

Producers may be tempted to feed cattle prunings of ornamental plants, many of which are highly toxic. With careful planning, plant toxicities can be avoided. If you have questions on toxic plants and how to identify/avoid them, please contact your local veterinarian or Extension agent.

Ruth Correll is the UT Extension-TSU Cooperative Extension in Wilson County. Contact her at (615) 444-9584 or

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