Horsemanship – Preventing Poisonous Plants in Horse Pastures

poisonous plants in horse pasturesEvery year, horses mysteriously become ill from no apparent cause.  Laminitis, anemia, kidney disease or kidney failure, poisoning and other symptoms can suddenly appear.  Poisonous plants can also be responsible for mare reproductive loss syndrome.  Many of these illnesses can be traced back to the horse having ingested a poisonous plant or plant product.

There are a wide range of flora that can cause problems.  Fall is a particularly risky time for illnesses caused by poisonous plants.  The growth of many plants starts slowing down in preparation for going dormant over winter.  With not as much to choose from – especially with drought conditions making grass hard to find – horses may be tempted to munch on what remains.  Sometimes, animals that have poor diets and suffer from mineral deficiencies may be enticed to eat poisonous plants.

Many different parts of a plant can be poisonous, and some poisonous plants have multiple parts that can cause problems. The most common parts of the plant that are poisonous are: leaves, roots, seeds/nuts, flowers/blooms and stems.  Fruits off of some trees can also be toxic or cause problems, especially if horses have free access to them and eat a large amount of the ripe fruit.

Luckily, many toxic plants naturally don’t appeal to horses and they will avoid them when possible.  But some plants, such as locoweed, are extremely addictive and horses will continue to eat these plants every chance they get.  Hungry or thirsty horses are more likely to eat poisonous plants, especially those left out on overgrazed land. The danger of poisonous plants is increased after wildfires as they seem to be the first to regrow and do so more quickly.

The types of poisonous plants can vary depending on location, climate and grazing conditions.  In many cases, an entire type of plant will be poisonous.  In others, it may be a certain species.   In still others, such as nightshade, they become more toxic as they wither and die and can become easily blown into a pasture where they can mix with hay left on the ground to feed.  Even with a pristine pasture, horses can be poisoned accidentally, as in eating wilted leaves of the red maple tree or from being bedded on shavings made from black walnut trees.

Knowing when a poisonous plant has been ingested can be difficult to determine as often the damage is done over a cumulative period and symptoms may not occur until after the horse is no longer exposed to the plant. These toxins are often metabolized before the symptoms become obvious, making it hard or impossible to test for them.  If you suspect your horse has eaten a plant that is poisonous, the first course of action is to call your veterinarian. He will be able to tell you what to do for your horse until they get there. If you know what your horse has eaten, let your veterinarian know.  If you can find it, but don’t know what it is, have a sample available to show your veterinarian when he arrives.

The best way to keep your horse toxin-free is to check your pastures, especially along BOTH sides of the fence.  If you take your horse to an unfamiliar area – to a show or camping – don’t let your horse graze unless you know that all the plants within his reach are safe.  Also, always know where your hay comes from.  Only buy your forage from a reputable dealer of hay for horses (many poisonous plants do not effect cattle since they have a different digestive system).  Poisonous plants often like to hide on the edge of fields and hay grower may inadvertently bale poisonous plants in with their hay.

For a list of the Top 10 poisonous plants for horses, go to:

Kelly O’Neill is owner of a boarding stable for retired show horses.  She has over 20 years of horse care expertise, with extensive experience in the care of the senior horse. Kelly has been a groom for two professional rider/trainers and has assisted in feeding, blanketing, turnout, medications and vet/farrier visits at several barns before opening one of her own in 1998. She now writes on her knowledge and love of horses for both fun and as the premiere writer for Classic Equine Equipment.