U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Poisonous Plant Research: Logan, UT
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                People

                    Staff Listing
                                    Careers


        


                    IACUC SummariesSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Pacific West Area Logan, Utah Poisonous Plant Research Docs





- Bulletin 415
- Stakeholder Meetings
- IJPPR
- ISOPP Main
- Poisonous Plants By Toxic Syndrome
- Arrowgrass
- Bracken Fern (Western Bracken)
- Bitter Rubberweed
- Broom and Threadleaf Snakeweed
- Chokecherry
- Copperweed
- Deathcamas
- False Hellebore
- Greasewood
- Halogeton
- Hemp Dogbane
- Horsebrush
- Larkspur
- Locoweed
- Lupine
- Milkvetch
- Milkweed
- Nitrate-accumulating plants
- Oak
- Other toxic plants
- Colorado Rubberweed or Pingue
- Poison Hemlock
- Ponderosa Pine
- Rayless Goldenrod
- Selenium-Accumulating Plants
- Sneezeweed
- Spring Parsley
- St. Johnswort
- Tansy Ragwort
- Threadleaf and Riddell's Groundsels
- Water hemlock
- Yew

Milkweed (Asclepias spp.)headline bar Milkweed (Asclepias spp.)Milkweed is a perennial that often bears blossoms and fruit at the same time. The plant may be 0.5-1.0 meters high. Greenish-white flowers are borne in umbrella-like clusters. Leaves may be narrow or broad. Leaves or other above-ground parts of the plant are poisonous. They contain several glucosidic substances called cardenolides that are toxic. Milkweed may cause losses at any time, but it is most dangerous during the active growing season.Several species of milkweed are poisonous to range animals. Labriform milkweed (Asclepias labriformis) is the most toxic. Other species in order of toxicity include western whorled milkweed (A.subverticillata), woollypod milkweed (A. eriocarpa), and Mexican whorled milkweed (A. fascicularis).Milkweed poisoning occurs frequently in sheep and cattle and occasionally in horses. Most livestock losses are a result of hungry animals being concentrated around milkweed-infested corrals, bed grounds, and driveways. Poisoning also may occur if animals are fed hay containing large amounts of milkweed.**Where and When It GrowsDistribution of the milkweeds.**Milkweed is often found in sandy soils of plains and foothills. It grows on ranges and abandoned farms, along roadsides, in pastures, in ditches, and in waste places. This plant gets its name from the milky juice that oozes out quickly when any plant part is broken. The plant starts growing in the early spring.**How It Affects Livestock**An average-sized sheep that eats 30-100 gms of green leaves of one of the more toxic species is likely to die of poisoning. It may die within a few hours or live 2 to 4 days. Although many milkweeds contain resinoids, most of the ones that cause fatal poisonings contain cardenolides (cardiac glycosides). These cardenolides are similar to digoxin causing electrolyte balances in heart muscle resulting in arrhythmias and cardiac failure.**Signs and Lesions of Poisoning**Depression, weakness, and staggered gaitDifficulty in breathing with expiratory grunting soundsDilation of pupilsRapid, weak pulse or other cardiac arrhythmiasLoss of muscular controlElevated temperatureViolent spasmsBloatingRespiratory paralysisCongestion of visceral organsRenal tubular degradation and necrosisGastroenteritis **How to Reduce Losses**Animals usually do not eat milkweed unless good forage is scarce or under conditions where plants freeze, etc. Livestock owners can reduce losses by keeping sheep out of milkweed along stock driveways when bands are trailed from one range to another. Supplemental feeding usually is beneficial during trailing. Hay contaminated with milkweed should not be fed to sheep or cattle. Milkweeds can be controlled with 2,4-D plus picloram (0.5 kg ae/Ac) or glyphosate at a spot spray. Follow all precautions for handling herbicides.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov