The Curious Case of the Poisoned Cows

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Wired Magazine - Science Blog 6/29/12

The Curious Case of the Poisoned Cows

On a bright morning in early June, a Texas rancher named Jerry Abel turned his small herd of cattle out to graze. The 18 cows moved hungrily into that field of fresh grass. Within a few hours, only three were still alive.

Abel’s 80 acre ranch sits just a little east of Austin and the story was strange enough that on Sunday a local CBS affiliate picked it up. “There was nothing you could do,” Abel told KEYE about his desperate efforts to save the animals. “Obviously, they were dying.”

The television reporter apparently saw the evil hand of science at work in the episode, at least that was definitely the message in the story: “Genetically modified grass linked to cattle deaths.“ Alternatively, she just didn’t do her homework because the grass in question – Tifton 85 - is not a GM product. It’s a decades old hybrid grass developed by Georgia agricultural scientists as a high-protein, easily digestible forage.

The CBS story was immediately circulated – and by circulated, I mean embraced – by anti-GM activists and bloggers. I wrote a summary of this for the Knight Science Journalism Tracker earlier this week which detailed both the activist enthusiasm for the story (one suggested that GM grass was practically producing chemical warfare agents) and the rapid corrective response from science writers who knew what “hybrid” actually meant. The you-got-this-wrong message was so strong that CBS News corrected the story within a day.

Heat and drought stress are very, very bad for plants.

[Melissa G]

1. Wow! That's amazing.

I think we had some cases of this during another previous drought. I forget this when I pick up a blade of grass and think of chewing on it in the summer...

The part of the article that really articulates the core of the piece is below:

As we all know, Texas is in the midst of a sustained and destructive drought. And as it turns out, there’s quite a bit of research showing that forage grasses can become surprisingly poisonous when they are stressed by heat and drought. To that end, I refer you to this article from the University of Wyoming titled, “Managing Forages to Minimize Prussic Acid Poisoning.” Or “Livestock and Prussic Acid Poisoning” from Ohio State University. Or “Preventing Prussic Acid Poisoning of Livestock” from Oregon State University. And as it also turns out, the Tifton 85 grass in Mr. Abel’s field is a hybrid of Bermuda grass and star grass. And star grass is one of those cyanogenic plant species we’ve just been discussing.

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2. Yep

Prussic Acid poison will kill them about 45 minutes after you turn your cattle loss on most all the maise, milo, sudan, haygrazer hybrid, but some are worse than others.

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3. Drought Raises Concerns For Nitrate Poisoning

Drought-stricken forages that accumulate nitrates can kill grazing livestock, quickly. The problem is showing up already in some Midwestern states and could be a concern in Ohio too.

"We're getting reports of cattle dying," says Rob Kallenbach, a University of Missouri forage specialist. "As hot weather without rain continues, we expect to hear of more death losses. It happens at the start of every drought."

Large grasses, such as corn, sorghum and sudangrass hybrids, are most often the cause of problems, Kallenbach says. Many plants, even ryegrass and fescue, can accumulate nitrates when soil moisture becomes short.
http://farmprogress.com/ohio-farmer/story.aspx/nl0_27nl/drought-raises-concerns-nitrate-poisoning-0-61185

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4. Amid Cattle Deaths in Central Texas, an Agricultural Mystery

The sudden death of 15 cows on a Central Texas pasture in May was more than a tragedy for the rancher. It marked the beginning of a search for answers that has pointed directly to the grass on which the cows were grazing. Read the full story at StateImpact Texas.

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