Don’t PoisonYour Cattle

@Above: The delphinium may be an innocuous flowering perennial in the family garden, but on therange as larkspur, it is one deadly customer.

174 ■ ANGUSJournal ■ August 2007

Grazing your cattle onuntried pasture might

be an opportunity to cutproduction costs, butbefore releasing youranimals on unfamiliar

ground, it is a good ideato look at what they will be ingesting.

by Ed Haag

In the garden the delphinium is an innocuous flowering perennial, but on

the range as larkspur, it is one deadlycustomer. Consider the following: A beefproducer leases a pasture in southern Idahoand, ignorant of the consequences ofgrazing larkspur, he releases more than 200animals onto the site.

“In four days he lost 54 head, includingseveral bulls,” says James Pfister, U.S.Department of Agriculture (USDA)research rangeland management specialistand an authority on toxic plants that killlivestock.

Pfister adds that the beef producer was noneophyte to the cattle business, but he wasnew to the area and had no knowledge ofthe dangers of cattle consuming larkspur.His ignorance of the plant and its effects onlivestock only exacerbated the problem,Pfister recalls.

“One of the characteristics of larkspurpoisoning is that it is a neuromuscular toxinthat causes paralysis in the cattle,” he says.“They go down, and they can’t breathe. Ifyou get them excited and move themaround, you are going to make it worse.”

Upon losing 20-some animals, the ownerhurried to remove them from the area,Pfister continues. “They took them out ofthere on the run, and they killed almost 30head more.”

Unfortunately, such a misadventure is notuncommon in the western states, Pfistersays. Larkspur poisoning sporadically killsfrom 5% to 15% of the cattle on NorthAmerican mountain rangelands.

Karen Launchbaugh, associate professorof grazing management and animalbehavior at the University of Idaho, believesthat larkspur’s toxicity in relation tolivestock cannot be overemphasized.

“For cattle, tall larkspur [is the] mostdangerous plant in all of North America,”she says. “It kills more range animals thananything else.”

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Canadian livestock research shows thoseanimals that consume as little as 0.7% oftheir body weight in larkspur during a one-hour period will die from the effects ofmethyllycaconitine, a diterpenoid alkaloidthat is a powerful neuromuscular blockingagent.

Launchbaugh adds that larkspur’sdeceptively inviting appearance does little todiscourage cattle from indulging in thisdeadly feast. “It is very green and leafy andhas a lot of good forage value,” she says. “Butit has this alkaloid that is really toxic at fairlylow levels.”

Her work with another alkaloid-containing plant indicates that cattle areparticularly susceptible in drought yearswhen they are more likely to have low bodycondition scores (BCS).

“Our studies show that animals in lowbody condition tend to eat those poisonousplants sooner and eat more of them thanthose in higher condition,” saysLaunchbaugh, adding that this presents adouble hazard because cattle in low bodycondition have immune systems that are lessequipped to respond to the toxins than cattlein higher body condition.

Know your nemesisBoth Pfister and Launchbaugh agree that

while there are numerous native plants thatcontain lower levels of the same alkaloidcompound — lupine and vetch are only twoof the more common — tall larkspur andlow larkspur are by far the leading cattlekillers in the western United States. These aretwo plants every beef producer in the Westshould be intimately aware of, Pfister says,noting that while they are very closelyrelated, each one requires its ownmanagement strategy and should be viewedas separate from the other.

Tall larkspur is found growing in theRocky Mountains, in moist draws or coulees,at snow accumulation sites and on hillsidesat higher elevations. It needs some shade anda well-drained, fertile soil. The commonhabitat of the plant is aspen forests. Larkspurmay be found in recently cleared land thathas been left unbroken. At its maximumheight, the hardy perennial can reach adramatic 6 feet (ft.), sporting long stalks ofdeep blue flowers andthe characteristic spursof the delphiniumflower group.

“Typically it is going togrow at 7,000 to 12,000feet,” Pfister says, noting thatthese elevations encompassa significant portion of theWest’s traditional summercattle range.

Range researchers such as Pfister andLaunchbaugh have focused much of theirattention on determining at what stages thetwo types of larkspur are of highest risk tocattle. Pfister breaks the annual growth cycleof the tall larkspur into three stages:

@ the vegetative stage, when it isproducing leaf mass;

@ the flowering stage, when it blooms; and

@ the pod stage, when it produces the pea-like seedpods.

While toxicity is high in the vegetativestage, the danger to cattle is diminished bythe fact that they seem more interested ingrazing on plants other than the younglarkspur.

“Even though it is toxic early on, there isusually a four- to six-week period, if otherforages are available, [during which] arancher has an opportunity to graze on talllarkspur ranges and not run into too manyproblems,” Pfister says. As the plant maturesthe alkaloids concentrate in the flowers and

the pods. Once the plant

enters the bloomingstage, that grazing

opportunity ends.“Typically, if the cattle aregoing to eat the plant it isgoing to be in the flowerand pod stages,” Pfister says.“We call it the toxic windowbecause it is a four- to six-

week period when the plant is relatively toxicand the cattle will eat a lot of it.”

At a 9,500-ft. elevation, tall larkspursbegin flowering about July 15-25, and finishflowering about three weeks later.

Pfister notes that the duration of the toxicwindow is not always the same every year.Cooler, wet weather extends that period;while hot, dry weather shortens it. The high-risk period ends when the pods mature andshatter. In mature plants, only the seeds areconsidered poisonous.

“Once the pod shatters, larkspur can begrazed with impunity,” Pfister says.

Low larkspur, unlike its taller cousin, takesconsiderably less time to develop and reachmaturity. It emerges in the early spring andhas a tendency to bolt with the advent ofwarm weather. Canadian range scientistspoint out that the reason they consider lowlarkspur a danger to cattle in the spring isbecause it reaches a grazable height beforemost grasses do. The low larkspur that isfound in pastures can kill livestock if thepasture is grazed too early.

Pfister notes that while the threat fromlow larkspur is real, it is short-lived.

“The growth cycle of low larkspur —from the time it emerges until the time thepods shatter — is about six weeks,” Pfistersays, adding that by July low larkspur in mostlocations is no longer a threat to cattle.

He notes that low larkspur, with a

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Safeguarding

@USDA research technician Gus Warr assesses a larkspur stand.

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maximum height of 18 inches (in.),produces a lot less biomass than tall larkspur.“Physically there is just a lot less there for acow to get poisoned on,” Pfister says.

When assessing the risk of low larkspurpoisoning, he recommends marking out ayard square in an area where the largestconcentration of larkspur plants is located.“If you see five plants within that square, thatis considered high density. But if you walkfive or six paces before locating a singleplant, that would be considered low density,”Pfister says. “Typically a cow has to eat 1,000to 2,000 low larkspur plants to be killed. Ifthe plant density is low, then the risk is low.”

Larkspur strategiesIn the research paper “Mitigating Financial

and Non-financial Livestock Losses Due toLarkspur,” available at www.behave.net/ecosystem/Money/Larkspur120905.pdf, Pfisterand his colleagues at Utah State University(USU) evaluated several strategies to control

the effects of larkspur on a cattle operation.These ranged from not changing the grazingmanagement strategy to hiring a rider toprevent cattle from grazing on larkspur-infested areas.

In the study, the authors point out thatthe response to the presence of larkspur willdepend directly on the effect the plant ishaving on a particular operation. They addthat in scenarios where losses are infrequentand all alternatives involve a substantialoutlay in time or money, the practicalapproach might be to not change practices.

For Pfister, one of the most practicalapproaches dealing with larkspur is to heedthe growth cycle of the larkspur and grazecattle in known larkspur areas before andafter the toxic window. He notes this mightinvolve a task as simple as changing thegrazing schedule to reduce the likelihood ofcattle coming in contact with larkspur whenthe risk is greatest.

When developing a grazing schedule

around the toxic window, remember that talland low larkspur flower at different times ofthe year and as a result have totally differentperiods of high risk. The toxic window forlow larkspur is around the last two weeks ofMay through the first two weeks of June.With tall larkspur, it is usually from the lasttwo weeks in July through August.

One of the more interesting strategies toprevent cattle from eating larkspur is the useof aversive conditioning. Developed by MikeRalphs, USDA rangeland scientist, it involvesfeeding a cow up to 20 bites of fresh larkspurthen dosing it with lithium chloride (LiCl;200 mg/kg body weight; 3.1 oz. for a 1,000-lb. cow) through a stomach tube. It has beenfound that the cow associates the taste of thelarkspur with the illness induced by LiCl.This has proved to be an effective deterrentprovided that the animal is not reintroducedto larkspur consumption by animals thathave not received the aversion treatment.

To Pfister, how larkspur is distributed willoften dictate the measures used to control it.“Sometimes it is found in dense clumps,which usually make it easier to manage,” hesays. “If it isn’t widely distributed, herbicidemight prove cost-effective.”

Even in government forest allotments,where spraying native plants with herbicideis sometimes discouraged, the option ofusing riders to separate the cattle from thelarkspur can be a practical option when theplants are concentrated into well-definedareas, Pfister says.

Responding to larkspur poisoning As Launchbaugh points out, the toxic

alkaloids in larkspur affect cattle byinhibiting nerve impulses at the junction ofthe nerves and muscles, causing muscleparalysis.

Some of the symptoms of larkspurpoisoning are constipation, bloating, muscleweakness, staggering and inability to stand.Later stages include respiratory failure anddeath. An affected animal should be keptquiet, with its head elevated, and it shouldnot be moved because stress will exacerbatethe situation. A veterinarian should be calledimmediately.

Ranchers grazing their cattle in isolatedareas that are known to have larkspur shouldconsult with their herd veterinarian andestablish a treatment contingency plan.

Pfister notes that animals that arepoisoned and recover have no residual toxinsafter a couple of days and are safe to send toharvest.

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176 ■ ANGUSJournal ■ August 2007

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@Tall larkspur kills morecattle than any otherNorth American plant.

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