In Southwest City, Missouri rancher John Hamilton turned his back on his herd while moving them to another pasture this week. When he turned back 10 of his cattle were convulsing on the ground. Four of the cows died.
Veterinarian Ken Leach with Southwest City Vet Clinic says the cattle died from "Johnson Grass Bloat".
He says severe drought conditions will cause grass to emit prussic acid that can cause death within a few minutes after ingestion.
If grass with a nitrate problem is bailed, Dr. Leach says it can stay in the hay for years.
"A lot of times it is after they have bailed the hay, then they let it grow back up, then you get drought, that's what a lot of our plants problems has been on its been bailed early in the year and the plant is growing up and it's stressed," says Dr. Leach.
The deadly grass is not restricted to our area. Some cattlemen have lost their entire herds in Texas to toxic Bermuda grass.
You can have grass tested at local USDA Extension offices.