HAY MAKER
Well-known member
Prussic Acid Poisoning Likely
On Drouthy Sorghum Regrowth
By Colleen Schreiber
FREDERICKSBURG – Any rain across the drouth-stricken state is always a welcome relief, but unfortunately those who were blessed to get the recent rains now must be particularly cognizant of prussic acid poisoning in drouth-stressed sorghums like Johnsongrass.
"With this little bit of rain that some of us had, prussic acid problems are going to be tremendous," warns Dr. John Reagor, head of the Texas Veterinary Medical Diagnostic Laboratory at College Station.
The biggest problem with prussic acid in sorghum occurs when it's first coming up or in regrowth. It's drouth-stressed regrowth that Reagor expects will cause problems over the next three weeks or so.
Gillespie County, he says, has the highest submission rate to the diagnostic lab of any county in the state when it comes to prussic acid poisoning.
The toxin found in stressed Johnsongrass is prussic acid. Prussic acid, Reagor explains, contains a sugar and hydrogen cyanide.
"Hydrogen cyanide is extremely toxic, and as long as the sugar molecule and the hydrogen cyanide are hooked together, it doesn't cause problems.
"You don't lose horses to prussic acid because that sugar/cyanide is not broken down in the low pH of a horse's stomach, but in the high pH rumen of a sheep or goat or a cow the cyanide is released and absorbed, and it causes death within five to 10 minutes.
"If you turn a cow into a sorghum pasture that is high in high prussic acid, she could take a bite and drop dead before she got 10 steps away."
During a drouth, Johnsongrass in a coastal bermuda field, Reagor notes, can be a real nightmare.
"I recommend shredding those areas where the Johnsongrass is growing. Let it dry for about three days and then turn the cows in."
Johnsongrass, Reagor says, also causes nitrate poisoning.
"Nitrate is converted to a nitrite in the rumen, and the nitrite causes fairly acute death, usually within two to four hours."
Nitrate and prussic acid levels, he notes, decrease as the plant matures.
"If you're cutting sorghum hay, if it's likely to be high in prussic acid, let it lie in the field for a couple of days until it bleaches out and there is no green left. That way you can be sure the glucose/cyanide complex has volatilized."
Pigweed, sometimes known as carelessweed, also causes nitrate poisoning. In fact, Reagor says, pigweed is the most notorious nitrate accumulator in the state.
"If you're pulling samples from a drouth-stressed sorghum field to send to the lab for analysis, make absolutely sure you also include the pigweed, because it may have five times the level of nitrate as the sorghum."
Recently, in his typical practical, down-to-earth and straight-speaking manner, Reagor shared his extensive knowledge of toxic plants with a group of hill country landowners attending an educational event hosted by Fort Dodge Animal Health and the Extension service.
"In a drouth year, toxic plants are always a problem," Reagor told listeners. "And in a drouth year like this year, they have been a real nightmare."
As far as goats are concerned, Reagor told listeners, twinleaf senna is by far the most toxic plant in the state.
"There is no telling how many goats died from eating twinleaf senna this year," he said. "I know where this plant is on our place and I started watching it, and as soon as it had four leaves I knew we would start seeing twinleaf poisoning show up in the lab. Sure enough, the very next week we had samples coming in from goats."
Twinleaf is also toxic to cattle and horses, but sheep, he said, are resistant to twin leaf. In fact, in some country, he believes sheep have helped control twinleaf.
Twinleaf, a warm seasonal perennial with a taproot about the size of one's thumb, grows on hillsides with very shallow caliche soils. Knowing where toxic plants grow, Reagor commented, makes it much easier to manage for them.
"Because I know the kind of soils twinleaf grows on, I can identify it driving down the highway going 75 miles per hour."
This plant has a pretty orange flower, but the identifying characteristic, Reagor said, is its twin leaves which are mirror images of each other.
"Very, very few plants have leaves like that. In fact, in this part of the world I don't think any do," he commented.
When there is enough moisture, twinleaf makes a seedpod. Some areas, he noted, had sufficient spring rains and twinleaf bloomed, made seed pod and matured. Most of those plants, he said, probably have dropped their leaves. However, in some areas where spring rain was particularly short, those plants are just sitting there halfway dormant.
"I have seen twinleaf bloom as late as October, so if we don't get any rain until September, in October it could jump up and get fresh growth and goats will eat it all over again," he warned.
The toxin in twinleaf that causes the problem has not been identified. That toxin, whatever it is, destroys muscle, Reagor said. In cattle it primarily affects the skeletal muscle.
"A cow that has eaten too much twinleaf will get down. She'll be a bright, alert downer. You think she's going to get up tomorrow, so you carry her hay, feed and water, and she's eating and drinking, and you come back the next day and she's still eating, and then the next day she dies. What happens is that muscle damage progresses from skeletal muscle to cardiac muscle, and when the heart muscle goes, you know what happens."
Few cows that get down with twinleaf ever get up, he said.
"If I had one that was down, I'd probably still carry her feed and water because that's not going to cost you much, but the chances of her getting up are not very good," he reiterated.
With goats the symptoms are much more extreme.
"Some goats get down with twinleaf, but most often the toxin goes directly to the heart. Most times animals have acute death, and particularly so with goat kids."
Phosphorus-deficient cows, Reagor noted, relish twinleaf.
"If you're just feeding salt and we have a year like we had this year with twinleaf, then chances are you probably had a bunch of dead cows."
A good phosphorus mineral supplementation program, Reagor said, is one of the best ways to lessen twinleaf poisoning in cattle, but calves are a different story.
"We can't stop calves from eating twinleaf with a good feed or good nutrition program; neither can we stop goats and goat kids."
Cocklebur is one of those plants hated by sheep and goat producers because it contaminates wool and mohair, but it is also poisonous to all classes of livestock, Reagor said. Historically, cocklebur poisoning caused the most problems in pigs, but sheep, goats and cattle have also died after consuming this plant.
From a toxicology standpoint the problem is with the seedling. At this stage of growth, he noted cocklebur is difficult to identify unless it's dug up.
"If you carefully dig it up it and it has the bur attached to it, then you definitely know what you're dealing with."
The cocklebur seedling contains a toxin that destroys the liver. Rarely are there clinical signs.
"If an animal eats enough cocklebur seedlings today —and it doesn't take much — that animal will probably be dead tomorrow," Reagor told listeners.
As soon as the plant matures, the toxic agent is no longer a problem. The toxin, however, is also found in the seed.
"Typically we don't have animals eating the seed, but we have seen problems where there is a heavy infestation of it in a cotton field and that seed goes through the ginning process and gets mixed in with the cottonseed."
Reagor turned next to oleander, an introduced evergreen ornamental shrub. Oleander, he said, is extremely toxic. In fact, he identified it as the most toxic plant in the state.
"It only takes five leaves to kill a horse and less than one leaf to kill a goat," Reagor told listeners. "Someone once sent in one stem of an oleander bush with one leaf left on it along with three dead calves, so oleander is something to treat with a lot of respect," he reiterated.
There are also documented cases where young children died after eating a hotdog roasted on an oleander stick.
"Not only will it kill any mammal that eats it, it will also kill insects," Reagor noted.
Wilted clippings or dead oleander leaves are typically what cause the problem.
"Oleander leaves growing on a tree, they tell me, are bitter," he said. "Very seldom do animals eat those green leaves, but as soon as it begins to wilt, they really eat it.
"Oleander will freeze back to the ground. Those dead leaves that fall on the ground and blow down the street are just as toxic as when they're live and growing," Reagor stressed.
The toxin found in the oleander is also water-soluble, he noted, so if leaves fall in a dog's water dish and the dog drinks the water, the dog will die.
The toxin in the oleander leaf is a cardiac glycoside. It causes a fast heart rate, then a really slow heart rate, and then sudden death. Essentially, whatever eats it suffers from an acute heart attack.
An animal that comes to the diagnostic lab can be definitely identified as having died from oleander poisoning if Reagor is lucky to find enough of a leaf to look at the cuticle covering under the microscope. The cuticle of the oleander leaf, he said, has distinct holes with hair in them.
"That's important, because it takes so little to kill an animal that we're not going to find it easily. We have to look real hard."
Reagor concluded his remarks on oleander by telling listeners that the best prevention for oleander poisoning is to simply not have it on the property.
"My wife and I are plant nuts, but the only plant that won't ever grow on my property is oleander. If it was already growing on a place we bought, it would be gone quickly.
"I gave a program many years ago out on one of these fancy ranches and this woman was very proud of these two oleander bushes in her yard. After they heard my talk, the husband wanted to get rid of them because he was very proud of a Longhorn cow he had.
"About two years later I had the rumen contents of that cow submitted to me. I don't know what happened to the oleander bush, nor do I know what happened to the wife, but I do know that it caused the death of that cow."
White snakeroot, with its characteristically white root, grows on shady canyon sides. The plant is found extensively in the northeastern states, in the Smokey Mountains for example, but is known to occur in places like Kerr County in the deep canyon country.
This plant, Reagor said, is extremely toxic to goats. The biggest problem occurs with animals not familiar with the plant.
"I remember a case where a guy who had a place in Leakey came to Fredericksburg and bought a bunch of goats. He drenched them and turned them out, and they were dead the next day.
"When the plant is real lush and young you may lose up to 90 percent of your goats if they're not familiar with the plant."
The toxin, tremetone, causes liver damage in sheep and goats. The toxin affects all animals including cattle and horses, though the clinical signs in these animals are typically cardiac-related.
Tremetone is passed from a lactating female to her young, and while the lactating female is protected, the offspring is not.
"Humans who drink the infected milk get what is referred to as milk sickness," Reagor said. "This is what killed Abe Lincoln's mother."
As for management, Reagor told listeners that if they intend to introduce new animals to country that has white snakeroot, they should do so after the plant has matured.
"It's not very palatable at that point and they won't eat it very readily, but they'll eat enough of it that they'll get sick from it but not die, and then they learn not to go back to it," he explained.
Smallhead sneezeweed, which grows around the edge of water primarily in the western half of Texas, was another toxic plant mentioned by Reagor. While it is unpalatable and animals really have to be forced to eat it, Reagor said he mentioned it because it is probably the most toxic native plant.
"I have seen fallow deer eat it and die, and llamas too, much more readily than sheep and goats."
This erect branching herb has an odorous smell, but the best identifying characteristic, he said, is the leaves which extend down the stem to form a winged stem.
"Smallhead sneezeweed causes severe gastroenteritis, maybe to the point of diarrhea, but most victims die before we get them," he said.
Sesbania, more commonly known as rattlebox, most often occurs in East Texas, though Reagor said it is also found along the Pedernales River.
"I didn't know it occurred there until a case came to the diagnostic lab, a pen full of dead goats.
"It's extremely toxic," Reagor told listeners. "It only takes two ounces to kill a cow. Animals that consume the seed are usually going to be dead within 24 hours."
Animals that are raised with sesbania typically leave it alone as it has an odorous smell and is most likely unpalatable. However, during the winter, when the plant is dead and dry, it no longer smells, and it's a plant that holds its seeds.
"So if you have animals that haven't been exposed to this plant, certainly don't introduce it to them during the winter," he told listeners.
Sesbania seedlings are also toxic, they don't smell bad, and their palatability apparently improves when the plant gets about six inches tall.
The best failsafe advice, Reagor offered, is "don't move new animals to a pasture that has dry seedpods or in the spring when the seedlings are coming up."
Sesbania poisoning, he said, is difficult to diagnose.
"The lesions caused by this plant are minimal. Sometimes we can identify it in the rumen contents if we get the cotyledon leaf, but it is a real chore to get done.
"So without wearing out some shoe leather and taking time to look in the pastures, many times it's difficult to prove that we've had sesbania problems."
Lantana, a fairly common plant that often grows wild, was the first of several that Reagor discussed that cause photosensitization, which is nothing more than very severe sunburn. The malady in sheep and goats is commonly referred to as swellhead.
"The ears get thick; you see swelling around the nostril and eyelids, anus and vulva, anywhere there is non-pigmented skin that sunlight gets to."
Like white snakeroot, Reagor noted, lantana has serrated edge leaves opposite branching leaves, but unlike white snakeroot its stem is square.
The seeds, he noted, are what cause the problems.
"We also don't have a lantana at my house," Reagor commented. "My wife would love to have an old antique lantana, and we could have one with one caveat — she's got to keep the seeds picked off it. The berries turn black, the birds like them, and they in turn scatter the seeds, and I don't want this plant to become naturalized in my pastures."
The number one plant that causes photosensitization in sheep and goats, he told listeners, is kleingrass. Horses also have problems with kleingrass.
"Kleingrass in my opinion is a wonderful grass because I have cows and it doesn't bother cattle, but if I had sheep and goats, I would not have a pure stand of kleingrass.
"I know that people have gotten by having it mixed in, but a pure field is a no-no for sheep and goats," he told listeners.
The younger, more nutritious plants, Reagor added, are the most toxic. As for dry hay, if the plants were high quality when they were cut then the toxicity is just as great.
Like lantana, kleingrass causes liver damage and photosensitization.
Likewise, puncturevine or goathead, an annual weed so named for its flattened fruit which resembles a goathead, also causes liver damage and secondary photosensitization. All parts of the plant are toxic at all growth stages, but a wilted plant is the most toxic, he noted.
Carpetweed, or caltrop, has a little bigger leaflet, little bigger stem and about the same size bloom without the stickers, Reagor said. It causes a totally different kind of damage. The toxic agent, which is unknown, causes nerve damage, primarily peripheral nerve damage. This plant is toxic to cattle, sheep, goats and rabbits.
He showed a picture of Angora billies that had been sitting around for days like dogs.
"If they just get a little bit of the plant they may just be uncoordinated the rest of their life," Reagor noted. "If they eat enough, the nerve damage may be great enough to sit down or they could get enough that they're down on all four legs and eventually go into convulsions and die."
Caltrop problems, he told listeners, are most commonly associated with disturbed bare ground.
"We don't do much rootplowing here in the rocks, but a little farther west we see this plant come in after rootplowing, and those areas tend to have the most problems. Still, we all need to be aware of it."
Silverleaf nightshade is one of those toxic plants that grows everywhere. The problem with this plant comes not from eating the leaves but rather from eating the berries.
"I've seen problems in sheep, goats, cattle, even penned deer, and there's usually some kind of extenuating circumstance that makes them eat it," Reagor commented. "The extenuating circumstance this year has simply been drouth and nothing else out there to eat."
This plant can cause either, and/or both central nervous system or GI problems.
Reagor warned against spraying any toxic plant with a herbicide and leaving animals exposed to the treated plant, but he particularly warned against it with silverleaf nightshade.
"This plant is not very palatable, but when it's sprayed with 2-4-D, when it's dying it makes a lot of sugar, and if an animal learns that all of a sudden this plant tastes good, then we have a lot of consumption and a lot of problems. So get the animals out and keep them out until these plants are dry," he stressed.
Finally, Reagor talked about problems with peavine, a showy annual legume that in the Edwards Plateau is localized to the red sandy soils. The plant also has a characteristic seedpod, usually three or four poking up together.
Peavine is toxic to sheep, goats and cattle.
"If an animal has peavine poisoning, it's best to go ahead and euthanize her, because you can mess with her for two or three weeks but she's never going to get better."
Peavine is also one of those toxic plants, Reagor said, that causes more damage to animals that are not accustomed to it. The toxins in peavine, he explained, are detoxified and metabolized by rumen bacteria after the bacteria get used to it.
"So if you have an animal that eats a little bit all along, the bacteria learn to handle it, but don't move an animal in that's not used to it if it's green and lush."
On Drouthy Sorghum Regrowth
By Colleen Schreiber
FREDERICKSBURG – Any rain across the drouth-stricken state is always a welcome relief, but unfortunately those who were blessed to get the recent rains now must be particularly cognizant of prussic acid poisoning in drouth-stressed sorghums like Johnsongrass.
"With this little bit of rain that some of us had, prussic acid problems are going to be tremendous," warns Dr. John Reagor, head of the Texas Veterinary Medical Diagnostic Laboratory at College Station.
The biggest problem with prussic acid in sorghum occurs when it's first coming up or in regrowth. It's drouth-stressed regrowth that Reagor expects will cause problems over the next three weeks or so.
Gillespie County, he says, has the highest submission rate to the diagnostic lab of any county in the state when it comes to prussic acid poisoning.
The toxin found in stressed Johnsongrass is prussic acid. Prussic acid, Reagor explains, contains a sugar and hydrogen cyanide.
"Hydrogen cyanide is extremely toxic, and as long as the sugar molecule and the hydrogen cyanide are hooked together, it doesn't cause problems.
"You don't lose horses to prussic acid because that sugar/cyanide is not broken down in the low pH of a horse's stomach, but in the high pH rumen of a sheep or goat or a cow the cyanide is released and absorbed, and it causes death within five to 10 minutes.
"If you turn a cow into a sorghum pasture that is high in high prussic acid, she could take a bite and drop dead before she got 10 steps away."
During a drouth, Johnsongrass in a coastal bermuda field, Reagor notes, can be a real nightmare.
"I recommend shredding those areas where the Johnsongrass is growing. Let it dry for about three days and then turn the cows in."
Johnsongrass, Reagor says, also causes nitrate poisoning.
"Nitrate is converted to a nitrite in the rumen, and the nitrite causes fairly acute death, usually within two to four hours."
Nitrate and prussic acid levels, he notes, decrease as the plant matures.
"If you're cutting sorghum hay, if it's likely to be high in prussic acid, let it lie in the field for a couple of days until it bleaches out and there is no green left. That way you can be sure the glucose/cyanide complex has volatilized."
Pigweed, sometimes known as carelessweed, also causes nitrate poisoning. In fact, Reagor says, pigweed is the most notorious nitrate accumulator in the state.
"If you're pulling samples from a drouth-stressed sorghum field to send to the lab for analysis, make absolutely sure you also include the pigweed, because it may have five times the level of nitrate as the sorghum."
Recently, in his typical practical, down-to-earth and straight-speaking manner, Reagor shared his extensive knowledge of toxic plants with a group of hill country landowners attending an educational event hosted by Fort Dodge Animal Health and the Extension service.
"In a drouth year, toxic plants are always a problem," Reagor told listeners. "And in a drouth year like this year, they have been a real nightmare."
As far as goats are concerned, Reagor told listeners, twinleaf senna is by far the most toxic plant in the state.
"There is no telling how many goats died from eating twinleaf senna this year," he said. "I know where this plant is on our place and I started watching it, and as soon as it had four leaves I knew we would start seeing twinleaf poisoning show up in the lab. Sure enough, the very next week we had samples coming in from goats."
Twinleaf is also toxic to cattle and horses, but sheep, he said, are resistant to twin leaf. In fact, in some country, he believes sheep have helped control twinleaf.
Twinleaf, a warm seasonal perennial with a taproot about the size of one's thumb, grows on hillsides with very shallow caliche soils. Knowing where toxic plants grow, Reagor commented, makes it much easier to manage for them.
"Because I know the kind of soils twinleaf grows on, I can identify it driving down the highway going 75 miles per hour."
This plant has a pretty orange flower, but the identifying characteristic, Reagor said, is its twin leaves which are mirror images of each other.
"Very, very few plants have leaves like that. In fact, in this part of the world I don't think any do," he commented.
When there is enough moisture, twinleaf makes a seedpod. Some areas, he noted, had sufficient spring rains and twinleaf bloomed, made seed pod and matured. Most of those plants, he said, probably have dropped their leaves. However, in some areas where spring rain was particularly short, those plants are just sitting there halfway dormant.
"I have seen twinleaf bloom as late as October, so if we don't get any rain until September, in October it could jump up and get fresh growth and goats will eat it all over again," he warned.
The toxin in twinleaf that causes the problem has not been identified. That toxin, whatever it is, destroys muscle, Reagor said. In cattle it primarily affects the skeletal muscle.
"A cow that has eaten too much twinleaf will get down. She'll be a bright, alert downer. You think she's going to get up tomorrow, so you carry her hay, feed and water, and she's eating and drinking, and you come back the next day and she's still eating, and then the next day she dies. What happens is that muscle damage progresses from skeletal muscle to cardiac muscle, and when the heart muscle goes, you know what happens."
Few cows that get down with twinleaf ever get up, he said.
"If I had one that was down, I'd probably still carry her feed and water because that's not going to cost you much, but the chances of her getting up are not very good," he reiterated.
With goats the symptoms are much more extreme.
"Some goats get down with twinleaf, but most often the toxin goes directly to the heart. Most times animals have acute death, and particularly so with goat kids."
Phosphorus-deficient cows, Reagor noted, relish twinleaf.
"If you're just feeding salt and we have a year like we had this year with twinleaf, then chances are you probably had a bunch of dead cows."
A good phosphorus mineral supplementation program, Reagor said, is one of the best ways to lessen twinleaf poisoning in cattle, but calves are a different story.
"We can't stop calves from eating twinleaf with a good feed or good nutrition program; neither can we stop goats and goat kids."
Cocklebur is one of those plants hated by sheep and goat producers because it contaminates wool and mohair, but it is also poisonous to all classes of livestock, Reagor said. Historically, cocklebur poisoning caused the most problems in pigs, but sheep, goats and cattle have also died after consuming this plant.
From a toxicology standpoint the problem is with the seedling. At this stage of growth, he noted cocklebur is difficult to identify unless it's dug up.
"If you carefully dig it up it and it has the bur attached to it, then you definitely know what you're dealing with."
The cocklebur seedling contains a toxin that destroys the liver. Rarely are there clinical signs.
"If an animal eats enough cocklebur seedlings today —and it doesn't take much — that animal will probably be dead tomorrow," Reagor told listeners.
As soon as the plant matures, the toxic agent is no longer a problem. The toxin, however, is also found in the seed.
"Typically we don't have animals eating the seed, but we have seen problems where there is a heavy infestation of it in a cotton field and that seed goes through the ginning process and gets mixed in with the cottonseed."
Reagor turned next to oleander, an introduced evergreen ornamental shrub. Oleander, he said, is extremely toxic. In fact, he identified it as the most toxic plant in the state.
"It only takes five leaves to kill a horse and less than one leaf to kill a goat," Reagor told listeners. "Someone once sent in one stem of an oleander bush with one leaf left on it along with three dead calves, so oleander is something to treat with a lot of respect," he reiterated.
There are also documented cases where young children died after eating a hotdog roasted on an oleander stick.
"Not only will it kill any mammal that eats it, it will also kill insects," Reagor noted.
Wilted clippings or dead oleander leaves are typically what cause the problem.
"Oleander leaves growing on a tree, they tell me, are bitter," he said. "Very seldom do animals eat those green leaves, but as soon as it begins to wilt, they really eat it.
"Oleander will freeze back to the ground. Those dead leaves that fall on the ground and blow down the street are just as toxic as when they're live and growing," Reagor stressed.
The toxin found in the oleander is also water-soluble, he noted, so if leaves fall in a dog's water dish and the dog drinks the water, the dog will die.
The toxin in the oleander leaf is a cardiac glycoside. It causes a fast heart rate, then a really slow heart rate, and then sudden death. Essentially, whatever eats it suffers from an acute heart attack.
An animal that comes to the diagnostic lab can be definitely identified as having died from oleander poisoning if Reagor is lucky to find enough of a leaf to look at the cuticle covering under the microscope. The cuticle of the oleander leaf, he said, has distinct holes with hair in them.
"That's important, because it takes so little to kill an animal that we're not going to find it easily. We have to look real hard."
Reagor concluded his remarks on oleander by telling listeners that the best prevention for oleander poisoning is to simply not have it on the property.
"My wife and I are plant nuts, but the only plant that won't ever grow on my property is oleander. If it was already growing on a place we bought, it would be gone quickly.
"I gave a program many years ago out on one of these fancy ranches and this woman was very proud of these two oleander bushes in her yard. After they heard my talk, the husband wanted to get rid of them because he was very proud of a Longhorn cow he had.
"About two years later I had the rumen contents of that cow submitted to me. I don't know what happened to the oleander bush, nor do I know what happened to the wife, but I do know that it caused the death of that cow."
White snakeroot, with its characteristically white root, grows on shady canyon sides. The plant is found extensively in the northeastern states, in the Smokey Mountains for example, but is known to occur in places like Kerr County in the deep canyon country.
This plant, Reagor said, is extremely toxic to goats. The biggest problem occurs with animals not familiar with the plant.
"I remember a case where a guy who had a place in Leakey came to Fredericksburg and bought a bunch of goats. He drenched them and turned them out, and they were dead the next day.
"When the plant is real lush and young you may lose up to 90 percent of your goats if they're not familiar with the plant."
The toxin, tremetone, causes liver damage in sheep and goats. The toxin affects all animals including cattle and horses, though the clinical signs in these animals are typically cardiac-related.
Tremetone is passed from a lactating female to her young, and while the lactating female is protected, the offspring is not.
"Humans who drink the infected milk get what is referred to as milk sickness," Reagor said. "This is what killed Abe Lincoln's mother."
As for management, Reagor told listeners that if they intend to introduce new animals to country that has white snakeroot, they should do so after the plant has matured.
"It's not very palatable at that point and they won't eat it very readily, but they'll eat enough of it that they'll get sick from it but not die, and then they learn not to go back to it," he explained.
Smallhead sneezeweed, which grows around the edge of water primarily in the western half of Texas, was another toxic plant mentioned by Reagor. While it is unpalatable and animals really have to be forced to eat it, Reagor said he mentioned it because it is probably the most toxic native plant.
"I have seen fallow deer eat it and die, and llamas too, much more readily than sheep and goats."
This erect branching herb has an odorous smell, but the best identifying characteristic, he said, is the leaves which extend down the stem to form a winged stem.
"Smallhead sneezeweed causes severe gastroenteritis, maybe to the point of diarrhea, but most victims die before we get them," he said.
Sesbania, more commonly known as rattlebox, most often occurs in East Texas, though Reagor said it is also found along the Pedernales River.
"I didn't know it occurred there until a case came to the diagnostic lab, a pen full of dead goats.
"It's extremely toxic," Reagor told listeners. "It only takes two ounces to kill a cow. Animals that consume the seed are usually going to be dead within 24 hours."
Animals that are raised with sesbania typically leave it alone as it has an odorous smell and is most likely unpalatable. However, during the winter, when the plant is dead and dry, it no longer smells, and it's a plant that holds its seeds.
"So if you have animals that haven't been exposed to this plant, certainly don't introduce it to them during the winter," he told listeners.
Sesbania seedlings are also toxic, they don't smell bad, and their palatability apparently improves when the plant gets about six inches tall.
The best failsafe advice, Reagor offered, is "don't move new animals to a pasture that has dry seedpods or in the spring when the seedlings are coming up."
Sesbania poisoning, he said, is difficult to diagnose.
"The lesions caused by this plant are minimal. Sometimes we can identify it in the rumen contents if we get the cotyledon leaf, but it is a real chore to get done.
"So without wearing out some shoe leather and taking time to look in the pastures, many times it's difficult to prove that we've had sesbania problems."
Lantana, a fairly common plant that often grows wild, was the first of several that Reagor discussed that cause photosensitization, which is nothing more than very severe sunburn. The malady in sheep and goats is commonly referred to as swellhead.
"The ears get thick; you see swelling around the nostril and eyelids, anus and vulva, anywhere there is non-pigmented skin that sunlight gets to."
Like white snakeroot, Reagor noted, lantana has serrated edge leaves opposite branching leaves, but unlike white snakeroot its stem is square.
The seeds, he noted, are what cause the problems.
"We also don't have a lantana at my house," Reagor commented. "My wife would love to have an old antique lantana, and we could have one with one caveat — she's got to keep the seeds picked off it. The berries turn black, the birds like them, and they in turn scatter the seeds, and I don't want this plant to become naturalized in my pastures."
The number one plant that causes photosensitization in sheep and goats, he told listeners, is kleingrass. Horses also have problems with kleingrass.
"Kleingrass in my opinion is a wonderful grass because I have cows and it doesn't bother cattle, but if I had sheep and goats, I would not have a pure stand of kleingrass.
"I know that people have gotten by having it mixed in, but a pure field is a no-no for sheep and goats," he told listeners.
The younger, more nutritious plants, Reagor added, are the most toxic. As for dry hay, if the plants were high quality when they were cut then the toxicity is just as great.
Like lantana, kleingrass causes liver damage and photosensitization.
Likewise, puncturevine or goathead, an annual weed so named for its flattened fruit which resembles a goathead, also causes liver damage and secondary photosensitization. All parts of the plant are toxic at all growth stages, but a wilted plant is the most toxic, he noted.
Carpetweed, or caltrop, has a little bigger leaflet, little bigger stem and about the same size bloom without the stickers, Reagor said. It causes a totally different kind of damage. The toxic agent, which is unknown, causes nerve damage, primarily peripheral nerve damage. This plant is toxic to cattle, sheep, goats and rabbits.
He showed a picture of Angora billies that had been sitting around for days like dogs.
"If they just get a little bit of the plant they may just be uncoordinated the rest of their life," Reagor noted. "If they eat enough, the nerve damage may be great enough to sit down or they could get enough that they're down on all four legs and eventually go into convulsions and die."
Caltrop problems, he told listeners, are most commonly associated with disturbed bare ground.
"We don't do much rootplowing here in the rocks, but a little farther west we see this plant come in after rootplowing, and those areas tend to have the most problems. Still, we all need to be aware of it."
Silverleaf nightshade is one of those toxic plants that grows everywhere. The problem with this plant comes not from eating the leaves but rather from eating the berries.
"I've seen problems in sheep, goats, cattle, even penned deer, and there's usually some kind of extenuating circumstance that makes them eat it," Reagor commented. "The extenuating circumstance this year has simply been drouth and nothing else out there to eat."
This plant can cause either, and/or both central nervous system or GI problems.
Reagor warned against spraying any toxic plant with a herbicide and leaving animals exposed to the treated plant, but he particularly warned against it with silverleaf nightshade.
"This plant is not very palatable, but when it's sprayed with 2-4-D, when it's dying it makes a lot of sugar, and if an animal learns that all of a sudden this plant tastes good, then we have a lot of consumption and a lot of problems. So get the animals out and keep them out until these plants are dry," he stressed.
Finally, Reagor talked about problems with peavine, a showy annual legume that in the Edwards Plateau is localized to the red sandy soils. The plant also has a characteristic seedpod, usually three or four poking up together.
Peavine is toxic to sheep, goats and cattle.
"If an animal has peavine poisoning, it's best to go ahead and euthanize her, because you can mess with her for two or three weeks but she's never going to get better."
Peavine is also one of those toxic plants, Reagor said, that causes more damage to animals that are not accustomed to it. The toxins in peavine, he explained, are detoxified and metabolized by rumen bacteria after the bacteria get used to it.
"So if you have an animal that eats a little bit all along, the bacteria learn to handle it, but don't move an animal in that's not used to it if it's green and lush."
