Are there poisonous plants in your pasture?

Horses that have access to adequate forage generally avoid poisonous plants, but it's still important to be able to identify dangerous plants in your pastures. Young horses and "easy keepers" kept in dry lots are often willing to try anything green. Some plants become more palatable when sprayed with herbicide; horses may even seek-out these poisonous plants, even when alternative forages are available. To see pictures of some of the most common poisonous plants found in Virginia, click on the link below:

Common Virginia Poisonous Plants (PDF)

Excessive Salivation? Blame the Fungus, Not the Clover!

During the mid to late summer it’s common for us to get calls regarding excessive salivation in horses.

Provided that other causes have been ruled out (for example: mouth injuries and choke), excessive salivation in pastured horses, especially during the late summer, is most likely caused by the fungus Rhizoctonia leguminicola. This fungus grows on legumes of all kinds (not just red clover, as many horse-owners believe). White clover, aslike clover, alfalfa, ladino, and lespedeza can all induce slobbering if they harbor high enough quantities of the fungus. The fungus produces slaframine, and it's this mycotoxcin that actually causes the extreme salivation. In humid conditions, the fungus grows very quickly and is sometimes visible on plant leaves as gold, brown, or black spots or rings (which explains the name "black patch disease"), but may also require a microscope to identify. Excessive salivation is usually seen several days following initial consumption of fungus-ridden plants (although it can occur sooner), and it is not unusual for horses to generate 12-15 gallons of saliva per day. Because of this dramatic increase in saliva production, mild to severe dehydration can occur in horses, particularly during hot weather.

Slaframine content in stored forages, such as hay, decreases as time elapses. One study of baled red clover reported decreases in the amount of slaframine from 100 ppm (parts per million) to 7 ppm over a ten month period. Horses are the most common species affected, but cattle, sheep, goats and swine are also susceptible.

Generally, the treatment for slaframine overload is simply to remove the horse from the pasture, or discontinue feeding affected hay. Certain management practices can minimize the occurrence of this condition:

Sow no more than 40% legumes in pastures

Spot-check leaves of legume plants for telltale spots or rings during periods of high moisture

Utilize a drylot for horses if affected pastures remain wet for extended periods and feed supplemental hay

Mow pastures to maintain plant height at 3-4 inches

If these are not possible, then horses should be offered free-choice salt and water and monitored for signs of dehydration. If symptoms are severe, or persist, consult with your veterinarian.

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Information and updates geared specifically towards Virginia horse owners! We're working to build photo albums of local plants poisonous to horses, weed identification, pasture management tips, and more. Like our page and let us know what you'd like to see added!