Cardiomyopathy in Sheep: Causes of Weakness, Collapse and Heart Failure
- See your vet immediately if a sheep is weak, collapses, breathes hard, or cannot keep up with the flock. Heart muscle disease can worsen fast.
- In sheep, cardiomyopathy is often linked to nutritional myodegeneration, also called white muscle disease, caused by low selenium and sometimes low vitamin E.
- Young, fast-growing lambs are at highest risk, but affected ewes and older sheep can also show weakness, poor exercise tolerance, or sudden death.
- Diagnosis usually combines a farm exam with bloodwork, muscle enzyme testing, selenium testing, and sometimes necropsy if a sheep dies suddenly.
- Early treatment may help some sheep, but severe heart involvement carries a guarded to poor prognosis even with prompt veterinary care.
What Is Cardiomyopathy in Sheep?
Cardiomyopathy means disease of the heart muscle. In sheep, it is not usually a stand-alone inherited heart condition like the term may suggest in dogs or cats. More often, it describes damage to the heart muscle from nutritional myodegeneration, commonly called white muscle disease, where low selenium and sometimes low vitamin E injure both skeletal muscle and cardiac muscle.
When the heart muscle is affected, the sheep may seem weak, tire quickly, breathe faster, collapse after exertion, or die suddenly. Some lambs show mostly muscle stiffness and trouble rising, while others have more severe heart involvement with signs of poor circulation or heart failure.
This is an emergency because the heart cannot repair severe damage quickly. A sheep that looks only mildly weak in the morning can decline later the same day. Fast veterinary assessment helps your vet decide whether treatment, monitoring, flock-level supplementation changes, or humane euthanasia is the most appropriate option.
Symptoms of Cardiomyopathy in Sheep
- Weakness or lagging behind the flock
- Collapse, especially after exercise or handling
- Rapid or labored breathing
- Stiff gait, arched back, or trouble rising
- Poor nursing, poor growth, or lethargy in lambs
- Sudden death
- Exercise intolerance or tiring quickly
- Pale mucous membranes or signs of shock
Mild cases may first look like a lamb that is stiff, slow, or less interested in nursing. More serious cases can include open-mouth breathing, collapse after being moved, or sudden death with little warning. See your vet immediately if a sheep cannot stand, is breathing hard, or worsens after exercise or transport. Because heart and skeletal muscle disease can happen together, even vague weakness deserves prompt attention.
What Causes Cardiomyopathy in Sheep?
The most important cause of cardiomyopathy-like disease in sheep is selenium deficiency, often with vitamin E deficiency contributing. Selenium and vitamin E help protect muscle cells from oxidative damage. When levels are too low, muscle fibers break down. In lambs, this can affect the legs, diaphragm, and heart. The result may be weakness, stiffness, breathing trouble, collapse, or acute heart failure.
Risk is highest in areas with selenium-deficient soils, in flocks without an appropriate sheep mineral program, and in rapidly growing lambs whose muscle demands are high. Lambs born to ewes with poor selenium status are especially vulnerable. Stored hay can also lose vitamin E over time, so diets that rely heavily on older stored feeds may increase risk.
Other conditions can mimic cardiomyopathy, including pneumonia, severe parasitism, clostridial disease, toxicities, and other causes of sudden death or weakness. That is why your vet should not assume every weak lamb has white muscle disease. The flock diet, mineral access, age of affected animals, and whether deaths are sudden all help guide the workup.
How Is Cardiomyopathy in Sheep Diagnosed?
Your vet will start with a physical exam and a careful flock history. Important clues include the sheep's age, growth rate, access to sheep-specific minerals, regional selenium status, recent feed changes, and whether multiple lambs are affected. On exam, your vet may find weakness, stiffness, rapid breathing, poor body condition, or signs consistent with heart strain.
Testing often includes bloodwork and muscle enzyme testing. Elevated AST, CK, and sometimes LDH support active muscle damage. Selenium status can be checked with whole blood or tissue testing, and low glutathione peroxidase activity may support deficiency. If a sheep dies, necropsy can be especially helpful because white streaking or pale areas in cardiac and skeletal muscle may confirm nutritional myodegeneration.
In some cases, your vet may also recommend fecal testing, respiratory evaluation, or additional lab work to rule out parasites, pneumonia, or other causes of collapse. Diagnosis is often based on the full picture rather than one test alone. That matters because treatment decisions and flock prevention plans depend on identifying the underlying cause accurately.
Treatment Options for Cardiomyopathy in Sheep
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or clinic exam
- Basic assessment of hydration, breathing, and ability to stand
- Veterinary-directed selenium/vitamin E treatment when appropriate
- Strict rest, low-stress handling, and nursing support
- Flock mineral and ration review
Recommended Standard Treatment
- Exam plus bloodwork
- Muscle enzyme testing such as AST and CK
- Selenium status testing when available
- Veterinary-directed injectable supplementation and supportive care
- Monitoring for worsening heart or respiratory signs
- Targeted flock-level prevention plan for ewes and lambs
Advanced / Critical Care
- Urgent stabilization for collapsed or severely distressed sheep
- Expanded lab testing and repeat monitoring
- Oxygen or intensive supportive care when available
- ECG or imaging referral in select cases
- Necropsy and tissue testing if a sheep dies suddenly
- Detailed whole-flock nutrition and supplementation review
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Cardiomyopathy in Sheep
Bring these questions to your vet appointment to get the most out of your visit.
- You can ask your vet whether this looks most consistent with white muscle disease, pneumonia, parasites, or another cause of weakness.
- You can ask your vet which tests would be most useful first, such as muscle enzymes, selenium testing, or necropsy if there was a sudden death.
- You can ask your vet whether the heart is likely involved and what signs would mean the prognosis is more guarded.
- You can ask your vet what level of activity restriction and handling changes are safest during recovery.
- You can ask your vet whether the rest of the flock, especially lambs and late-gestation ewes, needs evaluation or supplementation changes.
- You can ask your vet which sheep mineral product is appropriate for your region and ration.
- You can ask your vet how to avoid both selenium deficiency and selenium toxicity when correcting the diet.
- You can ask your vet what warning signs mean a sheep should be rechecked immediately or considered for humane euthanasia.
How to Prevent Cardiomyopathy in Sheep
Prevention focuses on balanced selenium and vitamin E nutrition. Sheep should have access to a sheep-specific mineral formulated for the region and ration. This matters because selenium needs vary by soil and forage conditions, and sheep should not be given mineral products intended for other species without veterinary guidance. In deficient areas, your vet may recommend strategic supplementation for ewes before lambing and for newborn or young lambs.
Feed quality also matters. Fresh green forage is a better vitamin E source than long-stored hay, so flocks relying on stored feeds may need closer nutritional review. Good records help too. If you notice weak lambs, poor growth, stiffness, or sudden deaths, document ages, diets, and pasture groups so your vet can spot a pattern quickly.
Do not supplement selenium on your own without a plan. Too little can contribute to white muscle disease, but too much selenium can be toxic. The safest approach is to work with your vet and, when needed, a flock nutritionist to match mineral intake to your area, forage testing, and production stage.