Can they eat it? / Johnsongrass and sorghum
Can horses eat johnsongrass and sorghum?
No fresh, careful as hay. Cyanide after frost, drought or trampling; nerve damage with long grazing.
Young, frosted or drought-stressed plants make cyanide; months of grazing can cause a bladder and hind-end nerve condition. Properly cured hay is lower risk; grazing is the problem.
Rapid breathing, bright red gums, collapse (cyanide); dribbling urine and hind-leg weakness (long-term).
Call your vet now. Note what was eaten, how much and when; do not wait for signs.
Why it is dangerous
Johnsongrass and sorghum make compounds called cyanogenic glycosides. When the plant tissue is chewed or damaged, enzymes release hydrogen cyanide, which blocks oxygen use in the blood and tissues. Young regrowth, plants stressed by frost, drought or trampling, and wilted material hold the most. Long periods of grazing can also cause a bladder and hind-end nerve problem, so pasture is the bigger concern than cured hay.
How much is too much
For a 1,000 lb horse there is no amount of fresh, young, frosted or drought-stressed plant that is considered safe, so even a small grazing session on those is a reason to call your vet. Properly cured hay is lower risk and a small amount of it is usually not dangerous. Ponies, miniatures and metabolic horses are more sensitive, so treat any fresh grazing on them as urgent.
Horses
Full-size horses in work or at pasture should not graze johnsongrass or sorghum regrowth, especially after frost, drought or mowing. Check fence lines, ditches and field edges, since stands can spread there. Feed only well-cured hay from a source you trust. If a horse gets into a stand, note the time and amount, bring it in, and call your vet right away.
Ponies and easy keepers
Ponies, miniatures, seniors and insulin-resistant or laminitis-prone horses should be kept completely away from these plants, including in hay and bedding. Their smaller bodies and metabolic sensitivities make even modest exposure more serious. Watch for any sudden breathing change, red gums or weakness and call your vet immediately rather than waiting for signs to worsen.
Safe alternatives
Offer good-quality grass or orchard hay, cured and free of weeds, as the main forage. Mixed grass pasture that is well managed and clear of sorghum species is a safe base. For a treat, a few slices of apple or a small handful of carrot pieces work well, served in small amounts and kept to the usual daily treat limit.
Questions people ask
Is johnsongrass safe in hay?
Properly cured, dry hay is considered lower risk than fresh plants, but check hay for johnsongrass or sorghum stems and leaves before feeding. Avoid hay that was cut after frost or drought stress, and ask your vet if you are unsure about a batch.
My horse ate johnsongrass after a frost, what now?
Call your vet now and do not wait for signs. Tell them what was eaten, how much and when, and remove the horse from the pasture. Early treatment matters with cyanide exposure.
Can a horse eat johnsongrass at a show or in competition?
Check the specific rules of your competition and discipline, since requirements vary. In general, keep horses away from these plants at events and in transported hay, and let officials know if there is any suspected exposure.
Toxic for horses means: do not give it; if they ate it, call your vet or a poison line.
General information from veterinary guidance, not a diagnosis. If you are worried, call your vet or a pet poison line: ASPCA Animal Poison Control (888) 426-4435. Charges may apply.
Written by Hoofdeck editors · updated Nov 13, 2026 · from ASPCA Animal Poison Control, Merck Veterinary Manual and university extension guidance.