Cattle Deaths Caused by Poisonous Grass
When 15 cows dropped dead on a pasture in Central Texas in May, it marked the beginning of an agricultural mystery.
Jerry Abel raises cattle for rodeo events. After a roping exercise last May he set his cows to pasture on his ranch.
“The field adjacent to their pen, it wasn’t really good enough because of the drought for haying,” Abel said. “But there was quite a bit of grass on there. So we decided we could just turn the cattle out on it so they could graze some.”
Abel went on with his day’s work. A couple of hours later the cows started to bellow. He rushed back to investigate.
“There were some already dead, and the rest of them were on the ground, in convulsions and obviously dying,” Abel said. “And there was really nothing we could do. Out of the 18 that had been there, 15 of them died.”
They died after eating the fresh growth in the pasture. Prussic acid, a compound much like cyanide, had formed in the grass. At first, both USDA scientists and Texas Agrilife Extension researchers couldn’t believe what they had found.
“We were sure it had to be the grass,” Abel said, “though we did not know what, and just a short time after he had said it was the hay, they called back and said, no, it was prussic acid in the Tifton.”
Tifton 85 is a hybrid Bermuda grass that Abel grew to feed his cattle. It hit the market in the early 90s, and quickly became popular for its nutritional value and resistance to drought. It’s now planted throughout the south. But by all accounts this is the first time it’s turned deadly, says Larry Redmon, the state Forage Specialist for Texas Agrilife Services at Texas A&M.
“And there’s been literally millions of head of livestock raised on that grass on millions of acres,” Redmon said, “so it’s very unlikely that we would see that happen again.”
Redmon promoted Tifton use in the 1990s and has been one of the lead researchers looking into the incident in Elgin. Since it has attracted media attention, A&M has put out a press release calling the cattle deaths an “isolated incident.” Tired, hungry cows ate extremely new growth grass that had just been fertilized.
“I haven’t had hardly any phone calls or hardly any emails relative to the press release or the email that went out,” Redmon said. “I’ve had very few questions from county agents so I think if there’s any concern, I think the news media made a big concern out of it.”
In fact, the ranching communities of Central Texas are talking about it. Elgin rancher Brent Johnson says he doesn’t use Tifton 85, but he’d be cautious if he did.
“I guess I’d sure want to figure out what causes it,” Johnson said. “Apparently it killed these cattle in a matter of minutes.”
Jerry Abel also reports heightened concerns among his neighbors. And news of the deaths has reached as far north as Nebraska, where Joey Jones works as a grass feeding consultant, a profession that brings him in regular contact with ranchers.
“I just talked with one yesterday, Jones said. “He’s about to seed a pasture and he was thinking Tifton 85 and now he’s not thinking Tifton 85 because of this one story.”
Even researcher Larry Redmon, who told me that there’s little cause for concern, wrote in an email to agriculture extension agents that there is “the potential for cattle deaths when grazing Tifton 85.” That email included a list of precautions ranchers should take when grazing cattle, something the press release does not include. Redmon said the difference reflects the different audiences for each document.
“No, the initial email is completely in agreement with the news release,” Redmon said. “The initial email was directed to agency personal so that they would be able to answer question that might start coming into their offices.”
So what caused the grass to turn poisonous? Redmon says one theory is that last year’s historic drought was the culprit.
“Anything that causes stress can actually exacerbate that and cause the release of prussic acid in the plants,” Redmon said.
Back in Elgin, rancher Jerry Abel says, even if what happened in his field hasn’t happened again, people should pay special attention to their cattle when they’re grazing on Tifton.
“And we’ll probably be a little more careful than that,” Abel said, “just because we had the actual experience.”
Prussic acid has been found in other fields of Tifton 85 since the incident, though no more cattle deaths have been reported.