As fall approaches, horse owners in Florida are being cautioned to diligently look over fields for creeping indigo, a non-native plant that can make horses gravely ill.
Experts say the plant is becoming more abundant in both central and northern areas of Florida. Horses that ingest too much of the weed (known to botanists as Indigofera spicata) become dull and uncoordinated, and can have ulcers on the tongue and whitening on the corneas of the eyes. Some horses experience convulsions and extreme colic.
First imported into the U.S. in 1933 to with the hope it could be used as both a livestock forage and ground cover, creeping indigo was abandoned for both uses after rabbits that grazed test plots died. Soon after, the neglected plants went to seed and invaded local areas, then spread southward.
For years, it was unclear what was causing the death of livestock in these areas, mainly during the late summer and fall. It was originally thought that horse deaths from creeping indigo were caused by toxic chemicals sprayed on trees in local fruit groves, hence the term, “grove poisoning.”
In the early 1990s, it was determined that creeping indigo was what was causing the neurologic conditions in horses. These symptoms included depression, recumbency, and loss of consciousness as the condition progressed.
This plant can also cause non-neurologic symptoms, as well, including weight loss, high heart and respiratory rate, poor appetite, high temperature, foaming at the mouth, dehydration, bad breath, light sensitivity and a prominent digital pulse without other signs of laminitis.
Horses that are rapidly removed from the pastures in which the plant grows may recover completely, but more often affected horses are left with an abnormal gait.
There is no effective treatment. The best way to prevent poisoning is to not allow horses in paddocks in which creeping indigo grows, or to remove the plants either physically or by killing them with herbicide.
It should be noted that dead plants retain toxicity, so they must be removed from fields. Additionally, animals that graze herbicide-treated fields should not have their manure composted, no should any grass clippings from the fields be composted.
Read more at the University of Florida.
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