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Cyanide may be cause of cattle deaths
Millions of acres have been planted with Tifton 85 Bermuda grass across the southeastern United States, including this field in Wilson County.
Wilson County NewsJuly 3, 2012 5,632 views 1 comment
Conditions are perfect for cattle death from forage sources, and one cattleman in Elgin recently lost 15 of 18 rodeo calves, just from turning them into a field to graze.
And unless producers are alert, this scenario could be repeated. Texas recorded the worst drought in state history last year. This was followed by abundant rainfall in the first quarter of 2012, and now the state has returned to drought-like conditions. This is the perfect setup for prussic acid, or cyanide, poisoning to develop in some forage, which has been attributed as the cause for the cattle loss in Elgin.
Talk has been rife as to the cause of death. Some are questioning the link of Tifton 85 -- a variety of Bermuda grass -- to GMOs (genetically modified organisms), while others report that the cause of the cattle’s deaths is unknown.
A local veterinarian and the county Extension office have confirmed the deaths of these animals were caused by prussic acid, after they consumed Tifton 85 forage.
According to a September 1998 North Dakota State University Prussic Acid Poisoning report, “Prussic acid, cyanide, or hydrocyanic acid are all terms relating to the same toxic substance. It is one of the most rapidly acting toxins which affects mammals.”
“Prussic acid is a potent, rapidly acting poison. Signs of prussic acid poisoning can occur within 15 to 20 minutes to a few hours after animals consume the toxic forage.”
Dennis Hale of the Wilson County office of the Texas AgriLife Extension Service confirmed the Elgin case involved Tifton 85. This is the first incident involving Tifton 85 that he is aware of. Other forages known to produce prussic acid include forage sorghums, Johnson grass, sudan grass, and grain sorghum.
In a June 26 “AgriLife Today” release, provided by Hale to the Wilson County News, the “Texas AgriLife Extension Service experts stated ‘the deaths of 15 cattle in Bastrop County ... were likely an isolated event and that no further problems are anticipated.’”
“Due to its ease of establishment, excellent drought tolerance, and excellent animal performance, literally millions of cattle, horses, sheep, and goats have grazed Tifton 85 Bermuda grass since its release without incident,” said Dr. Larry Redmon, AgriLife Extension state forage specialist.
“Many forage species, inducing Tifton 85, have the potential to produce prussic acid, a volatile and toxic compound,” said Dr. Tom Hairgrove, AgriLife Extension animal health specialist.
“However, those levels have not been known to produce problems with grazing livestock,” Hairgrove said. “While any livestock loss is unfortunate, currently this episode in Bastrop County appears to be an isolated incident.”
Hale explained the factors leading up to the incident.
Tifton 85 is a coastal grass with stargrass as one of its “parents.” Stargrass has a potential to have prussic acid, he said.
Hale explained conditions are perfect for prussic acid in the Elgin case.
After the 2011 drought, the Bastrop County rancher applied the pre-emergent, Prowl H20, for weed control. This was followed by a moderate amount of fertilizer, and then 5 inches of rainfall were received in the area, Hale said.
According to the Extension press release, Redmon said, the pasture was at a hay harvest stage of growth.
Hale said the rancher released the cattle onto the forage after a roping event. The animals basically “gorged themselves,” since they were hungry, thirsty, and stressed, Hale said.
“I have been around Tifton 85 for around 10 years and never heard of a problem,” Hale said. “It was the perfect storm ... ripe for the picking,” for prussic poisoning.
Hale emphasized that ranchers should always have water available, let animals graze in the morning hours, have hay available for consumption, and never turn hungry animals into a fresh pasture or field. Otherwise, “you are asking for a problem with bloating, prussic poisoning, or nitrate poisoning,” Hale said.
Farmers baling Tifton 85 or any sorghum grass should properly cure the hay and wait two weeks before feeding it to animals, Hale said. This will allow any acid to evaporate. See “Preventing losses” for more.
Wayne Deason, D.V.M., of Floresville confirmed on June 26 the cause of death as cyanide poisoning, and gave his insight. He said ranchers should be cautious when grazing their animals, since other fields in that county also have tested positive for prussic acid.
Deason has been receiving calls, but no cases have occurred in the local area, he said.
Deason said ranchers should be aware of the potential that Tifton 85 can cause prussic or cyanide poisoning. If they plan to plant the grass for hay or grazing purposes, soil testing may be needed prior to fertilizing.
According to the 1998 Prussic Acid Poisoning report, “Plants grown in soils high in nitrogen but low in phosphorus and potassium tend to have high cyanide concentrations.”
The same report mentions that “herbicides, such as 2,4-D, can increase prussic acid concentrations in forage for several weeks after application.”
Treatment is available in the event that cattle have consumed forage containing prussic acid, but there is a very short time to administer it, Deason said. See “Symptoms” for more.
Both Hale and Deason warn ranchers to be cautious when grazing animals in fresh fields, especially after drought-like conditions.
Conditions are favorable for more prussic acid poisoning, since the National Weather Service is predicting temperatures above normal and rainfall to be near normal through August.
Paul Yura of the National Weather Service Austin-San Antonio said June 22 that an El Niño weather pattern is forming. This pattern may bring more rainfall to the area in the fall.
If ranchers are concerned about their fields, plant samples may be sent to the Texas Veterinary Medical Diagnostic Laboratory (TMDL), P.O. Drawer 3040, College Station, TX 77841-3040, or call 409-845-3414.
For more information, call TMDL at 979-845-3414 (College Station), 830-672-2834 (Gonzales), or Hale at 830-393-7357.
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