A perfect storm of events that appear to have caused the deaths of 15 head of cattle consuming Tifton 85 bermudagrass in the Texas county of Bastrop is brewing a tempest in other bermudagrass-growing areas.
University of Georgia Extension forage specialist Dennis Hancock has spent the past couple of days heading off erroneous reports that Tifton 85 bermudagrass is a genetically modified crop that is producing cyanide gas. One major TV network offered a retraction for labeling the grass as transgenic – four days after its initial report.
In reality, Tifton 85 is a hybrid bermudagrass developed in 1992 and now widely grown throughout the Southeast. Bermudagrass doesn’t produce prussic acid, but its closely related cousin, stargrass, like other forages, can do so under extreme circumstances. Tifton 85 is a hybrid of bermudagrass and stargrass.
“Tifton 85 was screened for cyanogenic compounds, the molecules that form prussic acid, before its release,” he says. “In the 20 years it has been in use, there have been no such instances that anyone has reported.
“I think this is a very, very isolated event. Prussic acid is a defense mechanism for the plant. Frankly, I think it’s a perfect storm of the extremes of the drought, timing of rain, the shape the cattle were in at the time of the incident, and a variety of other factors.”
These have been especially busy days for Ron Gill, Tom Hairgrove and Larry Redmon, Texas AgriLife Extension livestock specialist, animal health specialist and forage specialist, respectively.
“There’s a lot of information and misinformation that continues to circulate about this recent isolated case … ,” says Gill. “It should be known that there is not a widespread problem or concern related to this forage or its use for grazing livestock or the production of hay for livestock consumption.”
The animals died with clinical signs and preliminary diagnostic results consistent with prussic acid poisoning, says Hairgrove. They were in a pure field of Tifton 85.
Results of analyses of rumen contents and fresh forage from the field in question indicated potential prussic acid toxicity, he points out. But he, like Hancock, says no other reports of prussic acid toxicity on Tifton 85 have been made.
Millions of acres of Tifton 85 have been planted across the southeastern U.S., adds forage specialist Redmon. It’s easy to establish and has excellent drought tolerance and animal performance. Millions of cattle, horses, sheep and goats have grazed the hybrid without incident.
The cattle died in pasture severely drought-stressed the previous year. A moderate amount of fertilizer was applied in mid- to late April, and about 5” of precipitation fell within the previous 30 days. The pasture was at hay-harvest stage of growth, Redmon says.
“Thus, the pasture did not fit the typical young flush of growth following a drought-ending rain or young growth following a frost we typically associate with prussic-acid formation in other species of forage,” he says.
Monitoring for other signs of animal distress and sampling of plants for prussic-acid accumulation will continue, Hairgrove says.