Today I read something quite unexpected:

Preliminary tests revealed the Tifton 85 grass, which has been here for years, had suddenly started producing cyanide gas, poisoning the cattle.


What is more worrisome: Other farmers have tested their Tifton 85 grass, and several in Bastrop County have found their fields are also toxic with cyanide. However, no other cattle have died.

GM grass linked to Texas cattle deaths

It seems to me that one should logically assume, in a first instance, that someone put the cyanide on the grass, instead of assuming it was produced by it.

Is this particular claim based on a study? Are GM organisms prone to mutate after a few years (15 in this case) in this manner? Is Tifton 85 known to produce cyanide at all?

Or is it biased reporting playing on fear of GM crops?

  • What specifically is meant by "cyanide gas" - according to the CDC, cyanide exists in various forms: "Cyanide can be a colorless gas, such as hydrogen cyanide (HCN) or cyanogen chloride (CNCl), or a crystal form such as sodium cyanide (NaCN) or potassium cyanide (KCN)."
    – Stuart F
    Sep 20, 2022 at 10:28

2 Answers 2


The first important point that is completely misrepresented in most articles I've seen about this is that Tifton 85 is not a genetically modified grass, but was created conventionally by crossing Tifton 292 and Tifton 68. See this article about the history and creaton of Tifton 85 bermudagrass for more information.

Using this event to highlight the dangers of GMOs is ignorant at best, this grass is a conventional hybrid, not a GMO.

It is known that certain plants and also grasses can produce cyanide in amounts that are dangerous to livestock (see "Potential for Hydrocyanic Acid Poisoning of Livestock by Indiangrass or Effects of Cyanogenic Plants on Fitness in Two Host Strains of the Fall Armyworm (Spodoptera frugiperda)).


A quick look around seems to show that although uncommon, it is not unique to have range animals poisoned by cyanide. It does not seem to be a "GM" issue(?). Many plants produce cyanide as a defence mechanism against browsers (mainly snail sized).

If the plant is under stress (like when a drought occurs) the levels and concentration of this toxin increases and can be lethal to larger animals.

We should also remember that a cow eats a LOT of grass, so even a little in each adds up quickly. There is also the possibility that the source of the cyanide (which itself is still only tentative) may not be the GM grass but other field plants like Johnsongrass.

I would also suspect that 15 years is enough for any organism, especially agricultural plants, to mutate irrespective of its parentage (GM or otherwise)


Plants Poisonous to Livestock
Cattle deaths blamed on natural poisoning

  • Don, I think you mean grazing not [browsing](en.wikipedia.org/wiki/Browsing_(predation)), but I am not sure enough to make the change myself.
    – Oddthinking
    Jun 24, 2012 at 5:09
  • Some extra information that I had to look up: The question talks about "cyanide gas", where Don's references talk mainly about Prussic Acid. Prussic Acid is a common name for Hydrogen Cyanide, which boils to make a gas at 26°C.
    – Oddthinking
    Jun 24, 2012 at 5:15

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