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Toxic Plants Found in Horse Pastures

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By Ashlee Pigford and Kyla Szemplinski, MS. Spring has arrived in the Mid-south and with the warmer weather comes lush spring pastures grasses horses love to consume. However, those beautiful, lush green pastures could also contain plants that can be highly toxic to horses when consumed or even come into contact with.

In southern states there are numerous toxic plants that can be found in horse pastures. The toxicity of the plants depends on numerous factors such as: amount consumed, horse’s age, horse’s weight and what stage the plant is in. Generally, horses will avoid eating toxic weeds but if pasture grasses are scarce and the horse is hungry enough, horses might accidentally consume a toxic plant. Additionally, toxins can be found in hay, contaminated grain, ornamental plants and even grass clippings.

Hay fed to horses as round bales or square bales could accidentally be contaminated with toxins. A common toxic found in hay is mold, which can develop when hay is exposed to moisture. Moldy hay is easily identified by mold’s distinctive, musty odor and black or white spores appearing throughout the bale. A good management practice step to do before feeding hay flakes or bales to horses is to inspect each individual flake to prevent contamination. If your hay bales contain any mold, DO NOT feed part of those bales to horses. Discard instead as horses fed moldy hay are at high risk of colic. If you suspect your horse has accidentally eaten moldy hay, contact your veterinarian immediately.  

To prevent mold from forming on hay, owners should keep hay out of rain and other wet conditions as much as possible. Remove hay from the fields after it has harvested as soon as possible, place hay bales/round bales on pallets to keep off the ground, store hay under a solid foundation structure and cover hay with tarps. 

The Mid-south is home to a diverse range of toxic plants. The most common toxic plants include: Red maple (Acer rubrum,) Pyrolyzadine Alkaloids such as Crotalaria and Senecio, Oleander (Nerium oleander,) Yew (Taxus spp.,) Poison Hemlock (Conium maculatum,) Rhododendron, Azalea and Mountain Laurel, Johnsongrass (Sorghum halepense,) Cherry Trees (Prunus spp.,) Pokeweed (Phytolacca americana,) Nightshade plants, Jimsonweed (Datura stamonium,) Buttercup (Ranunculus spp.)

Most of these plants have distinct characteristics that help horse owners identify them such as flowerheads, berries, leaves or stems. With proper pasture management steps such as rotational grazing, mowing and seeding, toxic plants will generally not grow in horse pastures. For more information about these common toxic plants, owners should visit the UT links: https://utia.tennessee.edu/publications/wp-content/uploads/sites/269/2023/10/W784-A.pdf and https://utbeef.tennessee.edu/forages-poisonous-plants/ 

However, if owners notice toxic plants growing in their pastures, here are steps owners can do to prevent consumption: Pastures and fence lines should be mowed and checked for weeds, remove horses and apply horse pasture safe herbicides, red maple tree and cherry tree  access should be minimized. Check pastures after storms or high winds and remove leaves or down limbs. Avoid planting these trees on your property if possible. 

If owners believe their horse has consumed any toxic plants, contact your veterinarian immediately. Time is of the essence when dealing with toxicity as toxic plants can kill a horse within hours, if not less, and some toxicities are NOT treatable. 

As always, if you have any questions regarding toxic plants in your horse pastures, contact your county’s Extension office. For Shelby County residents, please contact the UT TSU Shelby County Extension office at 901-752-1207 during normal business hours Monday through Friday 8am-4:30pm.

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Red Maple Trees  are another common toxic tree found throughout the mid-south. Adobe Stock Photo.
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Johnsongrass. Horses that graze johnsongrass or other sorghum species over long periods often develop cystitis-ataxia syndrome. “Cystitis” is defined as inflammation of the urinary bladder, while “ataxia” is defined as incoordination of the muscles. The syndrome is caused by nerve damage to the spinal cord.
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Crotalaria. A toxic plant that can easily be identified by walking horse pastures. Adobe Stock Photos
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Poison Hemlock. A toxic plant that can easily be identified by walking horse pastures. Adobe Stock Photos

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