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Toxic Plants in Drought Stressed Pastures

Many pastures in southern Wisconsin are severely stressed from the current drought.  When pasture forages are in short supply,  livestock may eat plants they typically avoid, and cases of livestock poisoning may occur.   

Plant poisoning is a function of both concentration of the toxin in the plant and the amount of plant material an animal eats.  Some plants are highly toxic, resulting in fatality from just a few bites, but even low toxicity plants may result in fatality if intake is sufficiently high and/or other feeds are not available.  Common toxic plants of concern that we may find in southern Wisconsin pastures include:

  • Horsenettle (Solanum carolinense )
  • Black Nightshade (Solanum nigrum)
  • Jimsonweed (Datura stramonium)
  • Pigweed (Amaranthus spp.)
  • Lambsquarter (Chenopodium album)
  • Buttercup (Ranunculus spp.)
  • Black Locust (Robinia spp.), Oak (red) (Quercus spp.),  Cherry (Prunus spp.) 
  • Bracken Fern (Pteridium aquilinum)
  • Milkweeds (Asclepias spp.)
  • Poison Hemlock (Conium maculatum)
  • Horse Tail (Equisetaceae spp.)

Other less common plants may also be harmful to livestock. Your County UW Extension office can assist with plant identification, and these online resources are also helpful:

Try to identify unknown plants in your pasture to determine if they are potentially toxic species, and manage livestock and pastures to avoid poisoning as well as minimize overgrazing of pastures during dry conditions. Confine animals to a single pasture or feeding area with water and shade, and provide feed resources until after the drought breaks. Consider early weaning of calves to reduce cow nutrient demands and maintain calf growth. If needed, reduce farm animal numbers if other feed resources are not available or too costly.