I know johnsongrass is poisonous to livestock (goats, in my case) after it's been frosted but before it totally dries. Is fresh johnsongrass harmful after cutting it green but before it dries completely?
The danger is when the plant is in the wilt stage. After cutting there is a danger for a short time but once it cures out similar to hay production it would be safe. Right after cutting there are a lot of changes that happen to forages and it is during this process that the toxin can develop. It is not assured that it will be present but it is a risk until it cures out.