Texas cattle died while grazing – Prussic acid information

There’s been much concern about GMO bermudagrass killing cattle after reports from Austin, Texas this weekend claimed genetic modification of the grass caused a fatal release of cyanide gas. Don’t go crying “GMO kills” until you have done some research. (More detailed information on the difference between GMO and Hybrids here)

Bermuda grass has many hybrids throughout the country, including the noted Tifton 85 found in Texas, many formed from plant cross-breeding. My family grew Tifton-44 and Coastal bermuda hay crops to feed our cattle during the winter months. It’s a great grass that thrives in the Southern environment and provides great nutrition for cattle grazing pastures. Read more about tifton bermudas from the Georgia researchers who know most about their work. There’s also a load of great research and information found on the Georgia Forages website.

Virginia Cooperative Extension has shared some great information on prussic acid and nitrates found in cattle forages. The concentrations of these naturally occurring substances can be increased in young, rapidly growing plants, or mature plants that are stressed by drought and a number of other environmental conditions that can be found in Texas pastures. Learn more about it here.

Prussic acid can be found in a number of forages, including sorghum, sudan, brome, thistle, sweet clover, wheat, corn barley, and johnsongrass. This isn’t anything new to cattle grazing. It’s something that farmers should always be aware of with changes in forage growth and can be easily managed. If concerned about the levels of prussic acid or nitrates after a period of drought, frost, or rapid growth make hay rather than grazing. Allowing the plants a week or more to return to normal growth after the rain or to attain a height of more than 18″ before grazing helps too. Texas A&M (link) and Oklahoma State (link) also have great information resources on the subject.

For those looking for a more detailed description of the diagnosis, treatment and prevention of prussic acid poisoning, check out the Merck Veterinary Manual page.

Do you have any more concerns about managing the grasses cattle eat?

Leave a comment below and we’ll find an answer.


  1. We have had some prussic acid poisoning about 50years ago. It was in grain sorgums and johnsongrass in the summer when it is hot and dry and the plants were young. Johnsongrass is really poison after it has been mowed and starts to sucker out.

  2. Nature is not the warm fuzzy thing people think it is, which is not what people want to hear. Arsenic and strychnine are both poisons which occur naturally in various plants. Rattlesnake venom and poison oak are both “natural organic” products which are not that good for you.

    People think of hybrids as genetically modified. Hybrids will occur in nature, Genetically modifying a plant or animal is introducing genes into the DNA string which would not occur in nature.

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