By DELANIA TRIGG, City Editor
Gainesville Daily Register
Cooke County —
Local cattle are being poisoned by something they eat every day — grass.
Veterinarian Justin Hartman of Refinery Road Veterinary Clinic, said he’s seen several herds of local cattle poisoned by certain types of sorghum species plants, mostly Johnsongrass and sudan.
“What’s happening is that when these plants are under stress they produce cyanide or prussic acid,” Hartman said.
He noted that cyanide poisoning of cattle and horses is not common.
“Before this week, in the past eight or nine years, I think I can only remember one case,” he said.
The cause of the cyanide build up is fairly simple.
Sudangrass, sorghum and some other plant species produce substances called cyogenic glycosides during their growth cycles. Under certain conditions, these glycosides break down and release prussic acid or cyanide.
The trigger, Hartman said, is stress.
“The most common form of stress would be drought but really we aren’t in a drought this year,” he said.
He theorizes that hot, dry conditions in early spring, followed by a period of a week or two of heavy rains have something to do with the high cyanide concentrations in some plants, but admits no one is really sure why some years are worse than others.
“This is something that we can’t predict. We can’t tell what year is going to be a bad year. But this year, for some reason, the plants are producing quite a bit of prussic acid,” he said.
So far, Hartman said he and his colleagues have investigated and treated livestock in at least seven locations.
“Last week we had five (reported) incidents of prussic acid poisoning, and we had two separate incidents Wednesday,” he said.
Hartman said the cases do have some common denominators: Ranchers grazed their cattle in lots that had been closed to grazing for some time.
“In the case that I saw yesterday, a rancher had a small enclosure full of hay and wanted to graze that off so he let his cows in,” he said.
One of the rancher’s bulls was sickened and one of his cows died — apparently of cyanide poisoning, Hartman said.
“A lot of times these cattle lots are closed and grass grows up in the lots and ranchers move some of their cows into an these empty lots,” he said.
The results can be deadly cyanide poisoning.
Identifying effected areas of grazing land isn’t easy, Harman admitted.
“There’s no way that you can look at the grass and tell if it’s effectuated. Some grasses can be wilted and not have prussic acid. There’s no way to know. Prussic acid is produced when the plants are under stress, but not every time the plant is under stress do they produce prussic acid,” he said.
Testing for prussic acid is available through agencies such as Texas A&M University’s AgriLife Extension system.
But testing grasses does have some drawbacks.
“You have to test these plants early because cyanide begins to leave the sample as soon as the plant starts to die,” he said.
Choosing which plants to test can also be tricky.
“What if only one plant out of 100 plants has actually produced prussic acid? A negative test doesn’t tell you that you’re absolutely safe. But a positive test can indicate you have a problem,” he said.
While cyanide poisoning is uncommon, Hartman said it is important for cattle producers and ranchers to be aware of the signs of prussic acid poisoning.
Cyanide works by disrupting the body’s ability to use oxygen leading to some distinctive symptoms.
“Of course the body system which uses the most oxygen is the nervous system,” he said. “Early signs of cyanide poisoning include symptoms of depression. Cattle will stand still and stare or maybe look off to one side for a long time. As the conditions worsens the cattle will start to pant as their body tries to take in more oxygen. Eventually, effected livestock will stumble, collapse and stop breathing.”
The prognosis depends on the amount of the poison ingested and how quickly the rancher or veterinarian recognizes what’s going on.
Cattle or horses can be treated for cyanide poisoning, Hartman noted.
“We do have an antidote that we give for prussic acid poisoning,” he said, adding, “The treatment isn’t something we give unless the cattle are down or really severely effected because the treatment can cause another form of poisoning. It’s not something that we give (without thought).”
Not all livestock die after ingesting cyanide.
“Most animals that survive for two hours recover. If they’re standing, they have a very good chance of recovery. If they are down, the prognosis is more guarded to poor depending on how severely affected they are,” he said.
Horses are another story.
“Horses usually don’t have the acute collapse and the problems we see in cattle. But prussic acid poisoning can cause a chronic neurological disease which is just as bad. Horses often don’t recover from it,” he said.
Horses that are poisoned by cyanide often lose control of the muscles in their hind legs, leaving them prone to bowel and bladder problems, he said.
Hartman has some advice for ranchers looking to protect their herds from ingesting prussic acid.
“Use caution whenever cows are moved to areas that contain grasses that they haven’t been in before.
He also said farmers and ranchers can decrease the chances of their containing high concentrations of cyanide by allowing it to cure in the sun for a few days.
Dr. Tam Garland, a Texas A&M toxicologist, said recent weather condition likely to blame for prussic acid in some plants.
“I think the thing about it is certain plants are more apt to accumulate prussic acid (in their tissues) and certain weather conditions are more apt to cause (this accumulation),” she said. “Spotty showers, and hot weather are stressors to the plant. This condition is more common during years with certain weather patterns.”