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Do You Know What Your Horse is Eating?

by Wyoming Livestock Roundup

By Amy K. McLean, UW Equine Extension Specialist/Lecturer

Many horse owners tend to keep their horses on small acreages – 20 acres or less – and oftentimes the amount of land on which the horses are kept is not enough to support the horse without supplying additional forage.

Typically, 45 acres per horse are recommended, so an owner with three horses would need 135 acres to support them. Considering that most owners do not have such acreage, it’s not that uncommon to find horses on small acreages grazing down the land where they are kept.  

Overgrazing on small acreage can lead to many problems, such as desertification, increased weed populations and the chance your horse may consume poisonous weeds. If you’re a horse owner keeping horses on a small acreage, it’s important to avoid overgrazing your property by supplying additional hay and/or grain to your horse to prevent them from consuming deadly plants.

There are varieties of toxic plants that can be found in your horse’s environment. To learn more about identifying and controlling invasive weeds that may also be deadly to your horse, contact your local extension office. You can also find additional information on this USDA website about poisonous plants at

Some plants, such as Russian knapweed, houndstongue, yellow starthistle or sage, are extremely dangerous to your horse. Other varieties of weeds that are poisonous and can lead to selenium accumulation or toxicosis include gum weed, penstemon, prince’s plum and milkvetch, to list just a few. High levels of selenium in a horse’s diet can lead to hoof problems. The selenium will replace sulfur, which is needed by keratin, a primary protein in the hoof, and can lead to cracking, sloughing off of hooves and lameness.  

Other poisonous plants can cause liver damage and failure, problems with skin sensitivities and/or colic. Some plants have low levels of toxin and will have to be eaten over a long period of time before necrosis of the liver develops and leads to death, while some can be consumed just once and cause death. Such deadly plants include water hemlock and nightshade. If your horse suddenly dies, it’s never a bad idea to consider having a necropsy done so you can better pinpoint the cause of death and hopefully prevent it from occurring in the future.

How can one prevent such devastating outcomes with their horses? The most effective method is prevention, and being proactive versus reactive. Prevent your horse from consuming toxic plants by not overgrazing pastures, considering rotating pastures, supplying additional forage when needed, properly identifying toxic weeds, removing the weeds and cultivating plants that provide a source of good nutrition for your horse.

If you follow these three steps: 1) proper identification, 2) good weed control and 3) good pasture management, you should be able to decrease the chances of your four-legged friend ingesting a deadly plant.

For more information on toxic plants and pasture management, contact your local extension office. Also, consider attending a workshop on Healthy Horses and Pasture coming to a location near you that will discuss such management issues more in depth.

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