While fall panicum grass is generally not toxic to horses, there are certain growing conditions that will make it become toxic. Researchers do not know why the grass becomes toxic under certain conditions but it becomes hepatotoxic and can cause liver disease in horses and photosensitization. Fall panicum that has become toxic will contain steroidal saponins.
It can be difficult to prevent fall panicum grass poisoning since most of the time it is not toxic to horses. To be on the safe side, though, you should just eliminate all fall panicum grass from your horse’s pasture and hay field. If you purchase hay from another source, verify that there are no potentially toxic plants in the hay including fall panicum grass.
Fall panicum grass is known by several different names including fall panic grass, spreading witch grass, spreading panic grass, sprouting crabgrass, spreading panicum, and kneegrass. It is a fibrous rooted annual summer grass that has a zigzag growth pattern. The peak growing season for fall panicum grass is between June and July; it then reproduces from seeds in late summer or fall.
If you suspect that your horse has ingested a plant that is making them ill, remove them from their pasture immediately and keep all hay away from them until your veterinarian is called out to do an assessment and make a diagnosis. Your horse may at first seem mildly colicky and be suffering from depression. But these warning signs should not go unchecked. You will notice symptoms such as:
Most fall panicum grasses are not toxic to horses and they will eat it regularly in their pasture and in their hay. But there are certain conditions that will cause the grass to become toxic, containing steroidal saponins which when ingested in large quantities by horses can lead to liver damage and secondary photosensitization.
Researchers are not sure why fall panicum grass becomes hepatotoxic only under certain growing conditions. The toxins remain potent even when dried so your horse can easily be poisoned by toxic fall panicum grass that has been cut and dried for their hay.
Your veterinarian will need samples of your horse’s hay and any grasses that they have been eating in their pasture for an analysis. While you are waiting for your veterinarian to arrive, you can collect the samples and have them ready.
When your veterinarian arrives, they will conduct a full physical examination of your horse. They will pay close attention to your horse’s mouth looking for any plant fibers that might still be present for an analysis.
After the physical examination, your veterinarian will want to do a complete blood count, or CBC, as well as a urinalysis and fecal examination. These tests will help to eliminate other possible causes for your horse’s illness. Your veterinarian will also want to run tests on your horse’s liver, checking for any decrease in productivity.
There is no specific treatment for fall panicum grass poisoning in horses. Your veterinarian will recommend that supportive care be started immediately. This will include intravenous fluids that will help keep your horse hydrated as well as flush as much of the toxins from their system as possible.
If your horse is suffering from photosensitization, a topical ointment will be prescribed to alleviate the sunburn. Your horse will need to be kept out of direct sunlight until the toxins have been completely flushed from their body. This will keep them from sun burning even more.
Should your horse be suffering from severe liver disease or failure, your veterinarian may recommend euthanasia.
Horses that are only mildly ill from fall panicum grass have made full recoveries with supportive care and removing all of the toxic grass from their diet.
Horses that are moderately ill from the toxins in fall panicum grass have a guarded prognosis. Their care in much more intensive and they will require longer recovery times. Euthanasia has been required on several cases where liver disease has already begun.
Horses that are severely ill from the plant will have a poor prognosis. The liver has already begun to deteriorate and euthanasia is generally recommended.
To prevent your horse from becoming ill from fall panicum grass poisoning, eradicate any of the plants from your horse’s pasture and be diligent about what hay they are being fed. Practice good pasture management and do a weekly walk-through searching for plants that can harm your horse.
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