plants poisonous to horses in wyoming

By Emily Eschbacher is toxic to horses when they eat a wning horses can be one of green two-grooved milkvetch plant. Othe great joys of rural living in Selenium poisoning can lead to Wyoming. Horses can ease chores confusion, weakness, clumsiness, involving livestock and provide rec- loss of appetite, hoof problems, reation for landowners, but, for the hair loss, and blindness in horses. horse lover, they can become part This plant can also poison cattle 5 and sheep. of a family and hold a very special place in hearts. Houndstongue While Wyoming provides a (Cynoglossum officinale) is beautiful backdrop for raising and commonly found in fields and riding horses, be aware certain roadsides. During its first year, plants can threaten horses’ health. houndstongue is simply a group of Plant poisonings are relatively rare large leaves that grow in a circular in horses; however, they are pos- rosette pattern. The leaves are sible when certain conditions exist. rough and resemble a hound’s Horses usually only eat poison- tongue. The second year, the plant ous plants when other good for- grows stalks up to 4 feet tall and ages are unavailable. Stressed or blooms with reddish-purple flow- overgrazed pastures often lead to ers. Each flower produces four conditions where these unfriendly spikey, green-yellow nutlets that plants pop up. stick easily to clothing or an Here are five plants horse own- animal’s coat. Houndstongue is ers should watch for along with poisonous to horses because it the effects they can have on their contains concentrations of harmful animals. alkaloids, which can seriously af- Two-grooved milkvetch fect the liver. Dried houndstongue (Astragalus bisulcatus) is com- is tastier to horses than fresh mon in dry soils. Two-grooved houndstongue and poses a risk milkvetch has leafy stems and baled in hay. A horse can con- purple, pink, blue, or white flowers sume as little as 7-10 grams of that grow in cone-like clumps. The houndstongue a day for two weeks flowers leave behind seed pods and develop liver disease (that is with two visible grooves running the equivalent of about two dried along each pod. The plant soaks plants per day). Continual grazing up selenium from the soil, which on houndstongue can be deadly for horses.

fall 2008 7 Dave Powell, USDA Forest Service, Bugwood.org Death camas Silky locoweed Russian knapweed

Death camas (Zigadenus plains of Wyoming. The stems and its leaves and stems are covered venenosus ) can be found in a variety of leaves are covered in silvery hairs, with stiff hairs. Russian knapweed locations, often alongside wild onions. and clumps of white or purple flowers contains a toxic lactone that causes It has a central stalk with a cluster of grow on leafless stalks. Locoweed chewing disease in horses. Affected white or cream-colored flowers, flat contains a dangerous alkaloid that horses may stop grazing, hold food grass-like leaves at its base, and an can cause nerve damage, severe in their mouths, or develop frothy underground bulb. All parts of the plant weight loss, and reproductive prob- saliva. Russian knapweed poison- contain toxic alkaloids highly poisonous lems after a few weeks of grazing ing occurs when toxins accumulate to both livestock and humans, so be on the plant. Horses can also begin in a horse’s system over time, so careful not to mistake it for wild onion. to prefer locoweed after grazing on horses must continuously graze on An onion will smell like an onion, and it initially. Watch for nervousness, about 60 percent of their body weight death camas does not. Symptoms of depression, irregular gait, problems before signs of poisoning will occur. horse poisoning by death camas include with eating or drinking, dull coat, and Because it takes so much of the plant increased or irregular pulse, weakness, staring. Locoweed is rarely fatal, but to poison a horse, only pastures over- stumbling, excess frothy saliva, and dif- most animals will never fully recover run with Russian knapweed are of ficulty breathing. The effects of the tox- from poisoning. serious concern to the horse owner. ins can take place quickly, so poisoned Russian knapweed (Centaurea These are only a few examples. A animals are often found dead before repens) is found in many soil types. helpful resource for identifying poi- owners notice the warning signs. It stands up to 3 feet tall with cream- sonous plants is A Guide to Plant Silky locoweed (Oxytropis seri- colored buds and purple flowers that Poisoning of Animals in North America cea) is one of several “crazy weed” resemble thistle blooms. Its buds by Anthony P. Knight and Richard G. varieties found in the foothills and have scales around the base, and Walter. It provides pictures and more in-

8 BARNYARDS & BACKYARDS Russian knapweed Two-grooved milkvetch Houndstongue

depth information about the plants and their effects on livestock. Plant Identification for Landowners Landowners can also prevent and For additional information on poisonous plants, visit the U.S. Department control poisonous plants through bet- of Agriculture (USDA) Agricultural Research Service’s (ARS) Poisonous ter pasture management practices. Plant Research Laboratory Web site: www.ars.usda.gov/Main/site_main. There are articles on pasture manage- htm?modecode=54-28-20-00 ment and horse health that ran in pre- For help identifying poisonous plants on your property, contact your local vious issues of Barnyards&Backyards weed and pest control district (www.wyoweed.org/addresses.html) or your lo- available online at barnyardsandback- cal University of Wyoming Cooperative Extension Service (CES) office http://ces.( yards.com under the Archives link on uwyo.edu/Counties.asp) the left side of the Web page. From For pasture management information and assistance, contact your local Summer 2005, there is “The Basics Natural Resources Conservation Service (NRCS) field office (www.wy.nrcs.usda. of Stocking Rate Calculations,” from gov), or call (307) 233-6750) or a CES office. Spring 2005, “Race for the Green,” and from Summer 2008, “Healthy Sources: Pastures Mean Healthy Horses.” A Guide to Plant Poisoning of Animals in North America by Anthony Knight These articles will provide additional and Richard Walter. information on managing your small The USDA ARS’s Poisonous Plant Research Laboratory, UMC 6300, Logan, UT 84322 acreage with horses in mind. www.ars.usda.gov/Main/site_main.htm?modecode=54-28-20-00

Emily Eschbacher was a summer intern in Casper for the Small Acreage Outreach Project, of which Barnyards&Backyards magazine is a part.

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