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Noxious Weeds

Devils Tower — According to local legend, leafy spurge first arrived along Left Creek in northeast Wyoming shortly after the turn of the last century. Making its beginning as an ornamental plant in an area flowerbed, the weed began its march down the tributary of the Belle Fourche River, becoming a near monoculture in some areas.

Over the last 100 years efforts to control the noxious weed have included herbicides, biological control utilizing insects and the grazing of goats.

“We’ve pretty much thrown the kitchen sink at it in terms of weed control,” says ranch owner Ogden Driskill.

But, he says, it’s been in the last 20 or so years, since the ranch began utilizing insects for biological control and sheep and goat grazing, that they’ve truly seen results.

Driskill says they’ve more than doubled their carrying capacity on the ranch since implementing sheep and goat grazing.

“We’re getting to where 70 to 80 percent of the ranch doesn’t have much spurge on it,” says Driskill.

In the early ‘90s goats grazed on the ranch, followed by the presence of sheep and then a return to goats three years ago.

Driskill says goats eat fewer of the same plants as cattle, adding, “If you’re trying to get leafy spurge, goats are the preferred tool.”

“I don’t think you can kill spurge,” says Carolina Noya. “It’s here, but you can control it.”

Driskill agrees, noting that they’ll always need some type of control or management on the ranch. Since Noya arrived, he says the goat grazing has been managed the best it ever has.

Three years ago Noya responded to a job opportunity herding the goats that eat and help manage the leafy spurge along Left Creek and the Belle Fourche River. Responding to an adventuresome opportunity wasn’t new for Noya who left her native Holland over 20 years ago, pursuing a series of horse-related jobs and coming to Wyoming to work on the Allemand Ranch.

At the Driskills’ ranch near Devil’s Tower, Noya’s job was ensuring the goats safely travel from one patch of spurge to the next, bringing maximum benefit to the resources they’re working to improve. In a more general sense, Noya is making lemons into lemonade.

Cattle, the Driskills’ stock of choice, won’t eat spurge and tend not to graze where the plant is too thick. Sheep will eat the plant and over the years helped the Driskills bring the weed under control. Goats, according to Noya, are quick addicts when it comes to grazing on the latex-filled weed with roots that can reach over 20 feet below the earth’s surface.

Once the goats pass through an area, grazing on the spurge, cattle can more easily access the grass and other desirable plants beneath.

“There’s only about a 10 percent overlap between what cattle eat and what goats eat,” explains Greg Fink, Noya’s husband and the man in charge of delivering supplies, herder relief and the occasional rescue of a goat from the waters of the Belle Fourche River.

A quick believer in the program’s benefit, in 2010 Noya purchased goats and did so again in 2011. In 2010 Noya’s flock was comprised on nannies that kidded on the range. Death loss to mountain lions drove her toward yearlings for the 2011 grazing season. While death loss has been extremely low, herding the spry young critters is a little more work.
Driskill hosts Noya and her goats simply for the benefits the grazing brings to the ranch.

“It’s a good co-enterprise,” he says. “Hopefully she makes a good living, and it gives us weed control at an exceptionally low cost.”

In May of this year Noya’s goats, yearling Boers and Spanish goats, arrived from Texas weighing an average 40 pounds. Unloaded into pens, the first few weeks were dedicated to acclimating the goats to their new home and treating any illnesses following the long trip.

Never before grazing on spurge, Noya says, “For the first six hours the goats would just take a bit of spurge and move on. The next day they realized, ‘This is good.’ They cleaned the spurge out of the whole area, not because they were forced to, but because they like it.”

In the months that followed Noya’s goats turned yellow canopies into areas green with grass available for the cattle grazing to follow.

“If you didn’t know the spurge was there before, it doesn’t look like anything has been on it,” says Noya.

“They take management,” says Noya. “You can’t just turn them loose; you could if you’re willing to take the losses. Once you’re out of spurge, they will follow the spurge and end up at the neighbors.”

By herding the goats Noya and Driskill can work together, pinpointing which patches of leafy spurge to graze and for what duration.

As the first of October roles around Noya will trade life in a sheep wagon for a hot shower and a warm bed. Fattened on high protein feed other animals won’t eat, the goats will head to markets east of here, a little heavier than they were in May. Noya goes home with two benefits — having had the opportunity to care for the stock all summer and the belief she is leaving the Left Creek and Belle Fourche River drainages in better shape than she found them.

Driskill, who operates a weed spraying business in addition to his ranch, suggests that land managers consider multiple tools when managing weeds.

“Watershed type weed control problems are very rarely controlled by chemical,” he says.

Jennifer Womack is a freelance writer who can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it. or 307-351-0730.

“Larkspurs are poisonous plants that negatively impact the earning potential of beef producers in many western rangelands of North America,” says Ben Green, et. al. in their article, titled, “Mitigation of Larkspur Poisoning on Rangelands through the Selection of Cattle” that appeared in Rangelands magazine. “If ranchers are unfortunate enough to have large stands of toxic larkspur in their pastures, yearly herd mortality can be as high as 10 percent.”

Green, research pharmacologist at the USDA Agricultural Research Service  (ARS) Poisonous Plant Research Laboratory, has studied larkspur for 11 years and believes that larkspur toxicity can be mitigated through cattle selection.

Project genesis

Green notes that poisonous plants have been studied by USDA since 1894, and larkspur has been studied at the lab for many years, but he was particularly impacted while visiting a producer who had suffered cattle losses from the plant.

“We went to a producer’s field to try and understand what was going on,” explains Green. “He lost 30 animals and his bulls, and on seeing that, I understood how important this subject is for ranchers.”

He further adds that it was interesting to see that, while a number of animals died as a result of larkspur toxicity, another 30 to 40 cows in the pasture were unaffected.

“The other cows looked normal and healthy,” Green says. “We believed that the surviving animals must be resistant and have worked to identify those animals with a natural resistance to larkspur poisoning.”

Experimental setup

In setting up the project, Green says they first halter broke a set of steers. 

“We gentled all the steers and trained them to an exercise regimen,” he says. “Then, we administered a low dose of larkspur – strong enough to cause muscle weakness but not so strong to have other impacts.”

After administering the larkspur, Green notes that cattle were exercised around a track until they showed clinical signs of muscle weakness – a classic signal of larkspur poisoning.

“When they showed signs of weakness, we immediately let them recover,” Green says. “We measured the time from when they started walking until they showed weakness.”


It was easy to see which cattle were poisoned and which were more resistant, Green says.

“Very susceptible animals were so weak that they tired quickly,” he comments. “Resistant animals would walk and walk as if they weren’t poisoned at all.”

The study looked at five breeds of cattle – including Line One Herefords from USDA ARS Fort Keogh in Miles City, Mont., Angus, Holstein, Jersey and Brahman – to determine if breed affected susceptibility to larkspur poisoning. 

“Some breeds have more susceptibility to larkspur, especially the Line One Herefords,” he comments. “Those animals are a group that have been line bred for more than 50 years.”

Additionally, Brahmans were very susceptible, and the beef breeds in general were more susceptible than dairy cattle breeds.

“Every breed has resistance to larkspur poisoning,” Green comments. “The important thing is finding those resistant animals.”

Green also adds that the results of the study were very repeatable and resulted in very good data.

Next steps

After identifying that some animals within each breed do have resistance to larkspur, Green notes they have isolated DNA from both resistant and susceptible animals and sent it to GeneSeek, a genetics company, for genotyping.

“Right now we are working on the genetics with John Keele and other researchers at the USDA ARS U.S. Meat Animal Research Center,” Green comments. “We are hoping to find gene markers for both susceptibility and resistance, but if we find a genetic marker for one or the other, that would also be great.”

By identifying markers, he notes that producers would be able to identify susceptible or resistant cattle using genetic tests.

They will test their genetic markers by attempting to identify cattle in the lab that will be resistant and susceptible to larkspur, treating them with larkspur and testing them for muscle weakness, as was done in the initial study.

“Hopefully we have useable results for cattle producers within five to 10 years,” Green says.

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..


Larkspur Testing

USDA Agricultural Research Service Research Pharmacologist Ben Green notes that larkspurs vary in toxicity from location to location.

“At our lab, we do analyze larkspurs for producers who send samples in to determine their level of toxicity,” he says. “If producers have larkspur, we recommend they have it analyzed.”

Green notes that producers can obtain more information by calling the lab at 435-752-2941.

Lupine research

Lupine, another toxic plant, is also a subject of research at the USDA Agricultural Research Service Poisonous Plant Research Laboratory.

“Our lupine study is similar to the larkspur study,” says Research Pharmacologist Ben Green. “Pharmacologically, larkspur alkaloids block nerve transmission and lupine alkaloids activate nerve transmission, so we had to come up with a slightly different study.”

Lupine causes crooked calf disease and is also economically important for cattle producers.



Casper – At the Wyoming Weed and Pest Council Fall Conference and Business Meeting, held on Nov. 6-8 in Casper, UW Weed Extension Specialist Brian Mealor looked at weed species that haven’t been on the radar of the weed control community, but may pop up as invasive in the future.
    “A few of these weeds are currently spreading into new areas and are potentially problematic,” commented Mealor, naming Russian sage, white horehound and Ventenata Grass, among others.
Russian sage
    “We think this next one might be one of the next big weed species we have to deal with – Russian sage,” Mealor said. “It seems like everyone plants it in their landscaping because it actually grows.”
    “The horticultural catalogs have a suite of characteristics describing why we should plant it,” he explained. “It is drought tolerant, it establishes, it grows quickly, and it is resistant to deer and rabbit browsing.”
    “It sounds like a fantastic horticultural plant,” Mealor added, “but it also sounds like a fantastic weed.”
    While many are using the plant as an ornamental, he said it is starting to spread out of flowerbeds into yards and surrounding areas. Additionally, there are a number of options for ornamental species rather than Russian sage.
    Using a recognized Weed Risk Assessment method for determining whether or not plants should be introduced as ornamentals, Mealor did a basic analysis of Russian sage. The results of the analysis recommended that the species be rejected for adoption as a horticultural or ornamental species.
    “We can’t reject it now, because it has already been introduced, but what we can do is be aware of it and keep an eye out for it,” he mentioned.
    He also warned that research is needed for control mechanisms for the species.
    “We just don’t know what works for Russian sage,” Mealor said. “Maybe we need to do some work to get ahead of it.”
White horehound
    White horehound is another species of concern.         Like Russian sage, white horehound is a member of the mint family, and may pose control concerns.
    “There are a lot of occurrences of this plant in Wyoming,” Mealor showed. “It is more widely distributed in the southeast.”
    He also mentioned that the plant seems to be particularly prone to spreading after fire.
    As an example, Mealor said, “Three years ago, Wind Cave National Park reported 10 acres of the plant. They had a fire move through, and this year they reported 18,000 acres of the plant. There is potentially a relationship between fire and the species.”
    Though impacts are hard to define, he said that the rapid spread of the plant may be of concern.
    Mealor added that similar to many aromatic plants, white horehound is likely not palatable to livestock consumption, and the species may be one to keep and eye on.
Ventenata grass
    “This is one of the weeds that worries me the most,” commented Mealor of Ventenata grass. “We recorded it in the state in the 1980s in Sheridan County close to the border.”
    While Mealor was unable to locate the species this summer, he noted that it has appeared in Idaho and is problematic in that state.
    “Ventenata grass is a North African grass,” he explained. “It is an annual grass that has come to dominate the Great Basin.”
    When compared to cheatgrass, he mentioned that there are number of similarities between the species, but weed specialists in other part of the country have noted that they would prefer cheatgrass to this species.
    “Cheatgrass is at least good forage early in the spring,” he said. “Palatability of Ventenata grass is nothing.”
    Plant structure is also similar to cheatgrass, though the plants matures a little later, more in conjunction with the native perennial grasses, making it harder to control.
    “The awns are curved, whereas cheatgrass awns are straight,” Mealor said, also noting differences in the spikelet of the plant.
    “I worry we might just be driving by it,” Mealor added, noting that any doubt about plant identification should be checked out. “Like everything else, false positive are better than just driving by.”
    Mealor addressed several other species, including Dame’s Rocket, Moth Mullein and Rush skeleton weed in the Extension Column of the Nov. 3 edition of the Wyoming Livestock Roundup.
    Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Laramie – “While our mission is focused on the livestock industry, here was an opportunity where we were able to take our agricultural research that had been done, move it into the biomedical side and collaborate with plastic surgeons,” commented United States Department of Agriculture-Agricultural Research Service (USDA-ARS) Poisonous Plant Research Laboratory Supervisory Research Animal Scientist Kip Panter about the facility’s research with cleft palate repair.

Prior to their annual meeting, Wyoming Farm Bureau hosted a symposium for producers on Nov. 2, where faculty from the research facility in Logan, Utah presented some of their current research findings and projects.

Cleft palate

One manifestation of crooked calf syndrome is a cleft palate, explained Panter.

“Sometimes producers will get cleft palate and no other symptoms in these calves,” he said. “The only way they would recognize it is, when the calf nurses, milk will come out of its nose because the esophagus and the trachea are not separated.”

The clinical signs observed with crooked calf syndrome depend on the day of gestation that the pregnant animal is intoxicated.

“The susceptible period of pregnancy for this lupine induced crooked calf disease begins 40 days. This is when the embryo first starts to move,” continued Panter.

He noted that the animal develops a cleft palate because the toxin in the plant moves across the placenta and inhibits the embryo from moving.

“It’s essential that this embryo start to move to avoid a cleft palate because it allows the tongue to drop out of the roof of the mouth so the palate can close and come together, which ends the embryonic period and starts the fetal development,” stressed Panter.


“We published a paper in 1992 describing the cleft palate in the goat model and the mechanism,” said Panter.

Their research attracted the interest of Jeff Weinzweig, head of plastic and reconstructive surgery for Laheu Medical Clinic in Boston, Mass., who was researching cleft palate in children at the time.

“He read our article and called and said, ‘Is there any chance that you guys would collaborate with us to try and find a model that we can study cleft palate in children to try and find an improved treatment in children?’” said Panter.

The researchers had enough information by that time to produce a cleft palate in the goat models without other birth defects.

With prior research, Weinzweig determined that fetal intervention by a certain period in gestation would allow the fetus to heal completely.

“If we can do the surgery as a fetus before day 100 of gestation, the fetus has the ability to heal without scar tissue formation,” explained Panter. “He wanted to give that a try, so we said okay.”

The equivalent time period of gestation in fetal goats was selected for the study.

“We selected day 85 of gestation. We were right at the beginning of the third trimester,” he continued.

Conventional cleft palate surgery, like what is typically performed on six-month-old children, was done on the fetal goats.

“It worked,” proclaimed Panter. “The baby goats were born with an absolutely normal palate, and we did a whole bunch of research with that after they were born.”

Looking ahead

The research team has been working on the collaborative project for 10 years, and the project is still in progress.

“It’s not done yet because the surgery has not been approved by Food and Drug Administration to be done in people yet. It’s still at the animal phase,” said Panter.

Current treatments for children with cleft palate or cleft lip are extremely costly, both financially and time-wise, explained Panter.

“Right now, the cost of intervention in a child is between $700,000 and $1 million per child by the time the palate closure is done at three to six months of age, and they go through 12 to 15 major surgeries in their lifetime before they become adolescents and their facial structure quits growing,” he continued.

However, the experimental surgery the group has tested would dramatically reduce the number of surgeries and potential complication.

“Fetal intervention has the potential to repair that in utero and the children would totally avoid these surgeries and the complications that come after,” concluded Panter. “That’s the goal.”

Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Most ranchers realize annual forages can develop nitrate problems when drought occurs, but according to a Montana extension beef cattle specialist, nitrate toxicity can also occur in some common weeds. 

Rachel Endecott presented “Feeding Risks from Drought Impacted Feeds and Forages” during a recent Ag in Uncertain Times webinar. Endecott said nitrate toxicity from drought can occur in wheat, barley, millet, oats, corn, sorghum and sudangrass. It can also occur in weeds like redroot pigweed, common lambsquarters, kochia, wild sunflower, Russian thistle, witchgrass, Canadian thistle and black nightshade, which all have tendencies to accumulate nitrates, she said. 

Nitrate toxicity

“With weeds, nitrates tend to peak at the pre-bud to bud stages,” she explained. “The nitrate concentration will decrease as the weeds mature.”

In annual forages, Endecott said nitrates tend to accumulate the most in the stem or stalk, with the highest amount being in the lower third of the stalk. The leaves often have very little nitrates, and the grains have none. 

“Nitrate uptake is a normal part of plant metabolism,” Endecott continued. “Nitrate is converted to nitrites, which is then converted to ammonia for protein synthesis for the plant to grow.” 

Drought conditions favor nitrate accumulation. Since the conversion to ammonia occurs in the leaves, if the leaves are negatively impacted by drought, nitrate begins to accumulate in the stem, she explained. 

The nitrate conversion pathway is exactly the same in the rumen as it is in plants, Endecott continued. 

“What happens when there are high nitrate concentrations is it overwhelms the conversion pathway from nitrite to ammonia. The nitrite ion competes with oxygen for red blood cells, and the nitrite converts hemoglobin to met-hemoglobin. The met-hemoglobin is incapable of oxygen transport, so the animal develops a nitrate toxicity,” she explained.

If an animal is suffering from nitrate toxicity, symptoms can vary, but Endecott said producers should be on the look out for symptoms in chronic animals like reduced appetite, reduced milk production, rough hair and unthrifty appearance, weight loss or no weight gain, and abortion. 

Animals suffering from acute nitrate poisoning can have an accelerated pulse rate, labored breathing, muscle tremors, weakness or staggering gait and cyanosis. They may die without quick treatment. 

Testing forages

The best prevention for nitrate toxicity is testing forages. 

“There are no visual clues that a hay is high in nitrates,” she stated. “It may look really good, but it may also be high in nitrates.”

When harvesting hay, nitrates will accumulate more in the hay overnight because the plant can’t photosynthesize in the dark. 

“There will be a reduction in nitrates from morning to afternoon in grain hay as the plant photosynthesizes,” she said. “But, if it’s a hot sample, the drop in nitrates won’t be enough to get the hay into a safe range.”

If the forage test shows the sample is high, Endecott said producers have some options. 

“It can be diluted with other, low nitrate forages,” she said. “Producers can also avoid feeding it to more susceptible animals, like those that are pregnant, and find a feedlot full of steers.” 

“If the levels are too high to be adjusted to a safe level, a producer may have no option but to have a marshmallow roast and destroy the hay,” she added. 

Giving a bacteria bolus

If producers plan to utilize high nitrate feeds, they may want to consider dosing the cattle with a nitrate-utilizing bacteria bolus seven to 10 days before turnout. The bolus will help the rumen adapt to higher nitrates in feed. Endecott said the bolus is slow releasing and provides the nitrates with utilizing bacteria. 

“You will be in good shape if you keep them exposed to nitrate forage,” she explained to one producer. “However, if you take them off and put them back on, you will need to rebolus.”

For cattle grazing cornfield residue, Endecott urged ranchers to fence out corners and edges of a drought-stressed irrigated cornfield where the potential may exist for more nitrate problems. She also discouraged producers from leaving cattle on cornfields too long because of feed shortages, which forces the cattle to consume the stalks. 

“Generally, cattle prefer grazing the leaves and husks, which are low in nitrates, but they will eat the drought-stressed stalks if they are forced, too,” she said.

Gayle Smith is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to This email address is being protected from spambots. You need JavaScript enabled to view it..