Sweet Clover (Dicoumarol) Poisoning in Ox: Bleeding Disorder in Cattle
- See your vet immediately if an ox has unexplained bleeding, pale gums, weakness, lameness from swelling, or collapse after eating sweet clover hay or silage.
- Poisoning happens when moldy or spoiled sweet clover converts coumarin compounds into dicoumarol, which blocks vitamin K recycling and prevents normal clotting.
- Signs may appear only after cattle have eaten contaminated forage for several weeks, so the problem can seem sudden even though exposure was ongoing.
- Diagnosis often includes feed history, physical exam, packed cell volume and bloodwork, and clotting tests such as prothrombin time.
- Treatment options may include stopping the suspect feed, vitamin K1, blood or plasma products in severe cases, and careful monitoring for internal bleeding.
What Is Sweet Clover (Dicoumarol) Poisoning in Ox?
Sweet clover poisoning is a bleeding disorder caused by dicoumarol, an anticoagulant that forms when sweet clover hay or silage becomes moldy or spoils during curing or storage. Dicoumarol acts like a vitamin K antagonist, so the liver cannot make normal clotting factors. In cattle, this can lead to slow blood clotting, bruising, internal bleeding, and sometimes sudden death after a stressful event such as calving, dehorning, castration, or surgery.
This condition is seen most often in cattle because they may eat contaminated forage over time before anyone notices a problem. Signs do not always appear right away. An ox may seem normal for weeks, then develop nosebleeds, bloody manure, swelling from internal hemorrhage, weakness, or collapse.
The good news is that outcomes can improve when the problem is recognized early, the suspect feed is removed, and your vet starts supportive care quickly. Mild cases may recover well, while severe bleeding emergencies need immediate veterinary treatment and closer monitoring.
Symptoms of Sweet Clover (Dicoumarol) Poisoning in Ox
- Bleeding from the nose, mouth, injection sites, or small wounds
- Pale gums or weakness from blood loss
- Bruising under the skin or large soft swellings caused by hemorrhage
- Lameness or stiffness if bleeding occurs into muscles or joints
- Bloody manure, dark tarry stool, or blood in urine
- Rapid breathing, fast heart rate, or exercise intolerance
- Poor appetite, depression, or sudden drop in production
- Collapse or sudden death in severe cases, especially after calving or procedures
When to worry: any unexplained bleeding in cattle is urgent, especially if there is a recent history of sweet clover hay, sweet clover silage, spoiled forage, or a wet harvest season. Mild cases may first show up as prolonged bleeding after dehorning, castration, injections, or calving. More severe cases can involve internal bleeding with few early outward signs. See your vet immediately if your ox is weak, pale, swollen, breathing hard, or bleeding anywhere.
What Causes Sweet Clover (Dicoumarol) Poisoning in Ox?
The problem is not fresh sweet clover itself. Poisoning develops when sweet clover forage is cured or stored under damp conditions and molds grow. During spoilage, plant coumarins are converted into dicoumarol, the toxic anticoagulant responsible for the classic bleeding disease in cattle.
Risk rises when sweet clover hay is baled too wet, stored in humid conditions, or made from lush stems that dry poorly. Silage can also be involved if fermentation or storage conditions are poor. White sweet clover and yellow sweet clover have both been associated with poisoning.
Cattle usually need to eat contaminated forage over several weeks before clotting problems become obvious. According to veterinary references, dicoumarol intake in the range of about 20-30 mg/kg of hay consumed over time is often needed to produce disease in cattle. Stressful events such as surgery, calving, or trauma may be what finally reveal the clotting defect.
How Is Sweet Clover (Dicoumarol) Poisoning in Ox Diagnosed?
Your vet will start with a feed and storage history, because that often provides the biggest clue. If an ox has been eating sweet clover hay or silage, especially forage that was damp, moldy, overheated, or poorly stored, dicoumarol poisoning moves higher on the list. A physical exam may show pale mucous membranes, bruising, swelling from internal hemorrhage, or active bleeding.
Testing usually focuses on blood loss and clotting ability. Your vet may run a packed cell volume or complete blood count to look for anemia, plus coagulation testing such as prothrombin time (PT) and sometimes activated partial thromboplastin time. In sweet clover poisoning, PT is often prolonged because vitamin K-dependent clotting factors are depleted.
Feed testing can help confirm dicoumarol exposure, but treatment should not wait if the history and clinical signs fit. Your vet may also rule out trauma, rodenticide exposure, severe liver disease, inherited clotting disorders, or other causes of hemorrhage. In herd situations, your vet may recommend checking other exposed cattle before procedures like dehorning or castration.
Treatment Options for Sweet Clover (Dicoumarol) Poisoning in Ox
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Urgent farm call or clinic exam
- Immediate removal of suspect sweet clover hay or silage
- Basic bloodwork or packed cell volume/total solids
- Limited clotting assessment if available
- Vitamin K1 treatment plan directed by your vet
- Strict rest and monitoring for worsening bleeding
Recommended Standard Treatment
- Full veterinary exam and feed history review
- CBC or PCV/TS plus chemistry as needed
- Coagulation testing such as PT and possibly aPTT
- Vitamin K1 therapy with recheck clotting tests
- Hospitalization or close on-farm monitoring
- Supportive care for anemia, weakness, and dehydration
- Herd-level guidance on feed removal and procedure delays
Advanced / Critical Care
- Emergency stabilization for active or internal bleeding
- Repeat CBC and coagulation monitoring
- Blood transfusion or plasma products when indicated
- Intensive hospitalization and fluid support
- Ultrasound or additional diagnostics to assess internal hemorrhage
- Vitamin K1 and ongoing reassessment of clotting recovery
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Sweet Clover (Dicoumarol) Poisoning in Ox
Bring these questions to your vet appointment to get the most out of your visit.
- Does this feed history fit sweet clover poisoning, or do you think another bleeding disorder is more likely?
- Which clotting tests do you recommend first, and how quickly can we get results?
- Does my ox need vitamin K1, and for how long should treatment continue?
- Are there signs of internal bleeding or anemia that mean hospitalization is the safer option?
- Should we test or monitor other cattle that ate the same hay or silage?
- Do we need to postpone dehorning, castration, transport, breeding work, or other procedures in exposed animals?
- Would feed testing for dicoumarol help guide herd management on this farm?
- What warning signs mean I should call back immediately or move this ox to emergency care?
How to Prevent Sweet Clover (Dicoumarol) Poisoning in Ox
Prevention starts with forage management. Sweet clover should be cut, cured, and stored in ways that reduce molding and spoilage. Avoid baling hay that is too wet, and watch closely for heating, musty odor, visible mold, or poor fermentation. If sweet clover forage quality is questionable, do not wait for bleeding signs before talking with your vet or feed advisor.
If you must use sweet clover hay of uncertain quality, some veterinary references note that alternating it with other roughage every 7-10 days may reduce risk, but this is not a substitute for good forage handling. Suspect lots should be removed from the ration when possible, especially for cattle near calving or those scheduled for dehorning, castration, or surgery.
Herd prevention also means planning ahead. Keep records on which groups received which forage, and alert your vet before any procedure if cattle may have eaten moldy sweet clover. In operations that grow or feed sweet clover regularly, choosing lower-risk forage sources and testing suspicious feed can help prevent a herd-wide bleeding problem.