Lupinosis in Sheep
- Lupinosis is a toxic liver disease that happens when sheep eat lupin stubble, pods, or seed infected with the fungus Diaporthe toxica.
- Sheep may show reduced appetite, depression, jaundice, weight loss, weakness, stiff movement, or wandering behavior. Severe cases can become fatal within days.
- See your vet promptly if sheep look yellow around the eyes or gums, stop eating, separate from the flock, or seem weak and disoriented.
- Treatment is mainly supportive and starts with removing sheep from the source right away. There is no specific antidote, so early action matters.
- Typical US veterinary cost range is about $150-$500 per flock visit for exam and basic field assessment, with bloodwork, necropsy, and lab testing often bringing total case costs to roughly $300-$1,500+ depending on flock size and losses.
What Is Lupinosis in Sheep?
Lupinosis is a toxic liver disease seen in sheep after they eat lupin material infected by a fungus called Diaporthe toxica. Older references may call this fungus Phomopsis leptostromiformis. The toxin damages the liver, which can lead to jaundice, weakness, poor appetite, weight loss, and sometimes sudden deaths.
This condition is different from lupine alkaloid poisoning. In lupinosis, the main problem is a mycotoxin made by fungus growing on lupin stems, pods, stubble, or seed, especially after favorable wet conditions. Sheep are considered especially susceptible, and weaners are often affected because they tend to eat more stem material.
Lupinosis can show up as a rapid acute illness or as a more chronic liver dysfunction syndrome. In chronic cases, the signs may be subtle at first. A flock may look thrifty one week, then start showing poor condition, lagging behind, or low production. Because liver injury affects many body systems, some sheep also develop secondary photosensitization or pregnancy-related complications.
If you suspect lupinosis, involve your vet early. Fast removal from the source and supportive care can improve the outlook for mildly affected sheep, while delayed recognition can lead to heavy flock losses.
Symptoms of Lupinosis in Sheep
- Reduced appetite or complete feed refusal
- Depression, lethargy, or separating from the flock
- Jaundice or yellowing of the eyes, gums, or other mucous membranes
- Weight loss or poor body condition
- Weakness and not keeping up with the flock
- Stiff-legged gait and hunched posture
- Disorientation, wandering, head pressing, or getting caught in fences
- Deaths within days in severe outbreaks
- Abortions or reduced lambing performance
- Reduced wool production or tender wool
See your vet immediately if sheep have yellow eyes or gums, severe weakness, neurologic-looking behavior, or sudden deaths. Those signs can mean significant liver injury. Even milder signs like poor appetite, ill-thrift, or a few sheep hanging back from the flock deserve prompt attention when sheep are grazing lupin stubble or being fed lupin seed.
Lupinosis can look different from one flock to another. Some sheep become acutely sick and die quickly. Others show a slower pattern with weight loss, poor production, and vague behavior changes. Because several other diseases can mimic these signs, your vet may recommend testing rather than relying on appearance alone.
What Causes Lupinosis in Sheep?
Lupinosis is caused when sheep eat lupin plants or seed contaminated with fungal toxin. The fungus involved is Diaporthe toxica, which can colonize lupin stems, pods, stubble, and seed. It tends to grow well on dead lupin material under favorable conditions, especially after rain or damp weather.
In practical terms, the highest-risk situations often involve grazing lupin stubble after weather that supports fungal growth. Sheep may start eating more stem material once the more desirable seed is gone. That matters because many outbreaks are linked to stem consumption. Seed can also be a source if it is infected or visibly discolored.
Risk is not the same for every sheep. Weaners are commonly affected, likely because they eat less seed and more stem. Late-pregnant ewes may also be more vulnerable to complications because liver damage can increase the risk of pregnancy toxemia. Flocks on lupin paddocks should be watched closely in summer and autumn, and after rainfall events.
This is not a contagious disease passed from sheep to sheep. The core problem is toxin exposure from feed or pasture, so prevention focuses on paddock management, feed inspection, and early removal from suspect lupin material.
How Is Lupinosis in Sheep Diagnosed?
Your vet usually diagnoses lupinosis by combining the history, clinical signs, and testing. Important clues include sheep grazing lupin stubble or being fed lupin seed, especially after rain, plus signs such as jaundice, depression, poor appetite, and flockmates with similar illness. Because chronic cases can be subtle, even mild ill-thrift in a lupin-fed group can be meaningful.
A field exam may show yellow discoloration of the eyes or mucous membranes, poor body condition, weakness, or abnormal behavior. Your vet may recommend bloodwork to look for increased liver enzymes and other changes consistent with liver injury. In flock cases, testing a few representative sheep is often more useful than trying to test every animal.
If sheep have died or are severely affected, a necropsy can be very helpful. Postmortem findings may include a swollen yellow liver and generalized jaundice in the tissues. Laboratory evaluation of blood, liver, and sometimes brain tissue can help confirm the diagnosis and rule out other causes of jaundice, poor thrift, or neurologic signs.
Because several conditions can resemble lupinosis, your vet may also consider parasites, trace mineral problems, other plant toxicoses, Johne's disease, or infectious causes. That is why a structured flock workup is often the safest and most cost-conscious path.
Treatment Options for Lupinosis in Sheep
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Immediate removal from lupin stubble, suspect lupin paddocks, or contaminated lupin seed
- Quiet paddock or pen with easy access to shade and clean water
- High-quality grass hay or oaten-type forage as directed by your vet
- Avoiding high-protein lupin feeds and feed blocks while the liver is compromised
- Close observation of appetite, mobility, jaundice, and deaths within the group
Recommended Standard Treatment
- Veterinary flock exam and exposure review
- Bloodwork on selected sheep to assess liver damage
- Necropsy and laboratory submission on fresh deaths when available
- Supportive care plan tailored by your vet, including feed changes and nursing recommendations
- Monitoring for secondary photosensitization, pregnancy toxemia risk, and ongoing flock losses
Advanced / Critical Care
- Referral-level evaluation for valuable breeding animals or severe individual cases
- IV or intensive fluid support if your vet determines it is appropriate
- Serial bloodwork and close monitoring of liver function and hydration
- Tube feeding or advanced nursing support in selected cases under veterinary supervision
- Management of severe secondary complications such as photosensitization or pregnancy-related metabolic stress
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Lupinosis in Sheep
Bring these questions to your vet appointment to get the most out of your visit.
- Do these signs fit lupinosis, or are there other likely causes in this flock?
- Which sheep should we test first to get the most useful answers?
- Would bloodwork, necropsy, or feed testing help confirm liver damage or rule out other diseases?
- Should we remove the whole flock from this paddock right now, or only certain groups?
- What forage is safest while these sheep recover, and what feeds should we avoid for now?
- Are these sheep at risk for photosensitization, pregnancy toxemia, or other complications?
- What daily signs should tell us a sheep needs urgent recheck or euthanasia discussion?
- How can we inspect future lupin stubble or seed to lower the chance of another outbreak?
How to Prevent Lupinosis in Sheep
Prevention centers on managing exposure to infected lupin material. Sheep should be watched closely when grazing lupin stubble, especially in summer and autumn or after rainfall. Many outbreaks happen when sheep run short of seed and begin eating more stem, so paddock conditions matter as much as the sheep themselves.
A practical step is to remove sheep before lupin seed availability gets too low. Guidance from Western Australia links higher risk to paddocks with less than about 50 kg of seed per hectare, roughly 40 seeds per square meter. Weaner groups need especially close monitoring because they are more likely to consume stem material.
If sheep are being fed lupin seed, inspect it carefully. Discolored or moldy seed should raise concern. Seed infection is more likely after heavy rain during pod and seed maturation. If a notable portion of seed is discolored, your vet or an agricultural advisor can help you decide whether it is safe to feed.
Resistant narrow-leafed lupin varieties have reduced risk, but they are not immune. Good prevention still depends on paddock observation, feed inspection, and fast action after rain. If any sheep start lagging, losing appetite, or showing yellow mucous membranes, stop exposure and call your vet before losses spread through the flock.