Will johnsongrass be bad for my horses?
I am relocating from Ohio to a farm in Cumberland County, Kentucky, with four horses. I just found out there is johnsongrass growing freely on the land I was going to pasture them on and bale hay on. From what I am finding, it can kill my horses. Is this true? Do I need to kill it off before I ever pasture them? And what if it gets baled with the hay?
Cumberland County Kentucky
Johnsongrass hay is capable of retaining high levels of nitrogen when it has been growing in droughty conditions before harvested for hay. If that is the case and affected hay is fed to cattle or horses, there is risk of nitrate poisoning, and this could lead to death of the animal. Suspected johnsongrass hay thought to contain high nitrogen levels can be tested to find what the N levels are and if it is safe to feed.
The other risk of toxicity is in fall when johnsongrass might receive a light frost, just enough to burn the leaves a bit without really killing the plant. Prussic acid (cyanide) is produced and is present for a short period of a few days. It then will dissipate and no longer be a threat.
Outside these two precautions, johnsongrass is a good nutritious forage and is preferred by grazing animals over other grasses when exposed to it.
Please feel free to ask any followup questions.
Greg Tompkins, Cumberland County Extension Agent for Agriculture (Retired)