Heart Murmurs in Sheep: What a Cardiac Murmur Can Mean

A heart murmur is an extra or unusual sound heard between normal heartbeats when your vet listens with a stethoscope. The sound happens because blood is moving in a turbulent way rather than a smooth one. A murmur is a finding, not a diagnosis by itself.

In sheep, that turbulence may come from a structural problem inside the heart, such as a congenital defect, or from a body-wide problem that changes blood flow, such as anemia, fever, or infection. Merck notes that animals with heart disease may have no obvious signs at first, and that murmur loudness does not always match how serious the disease is.

Some sheep with murmurs stay stable for long periods, especially if the murmur is mild or linked to a temporary issue. Others develop poor thrift, breathing changes, fluid buildup, or sudden decline if the underlying problem affects heart function. That is why the next step is not guessing what the murmur means, but working with your vet to identify the cause and decide what level of care fits the sheep, the flock, and your goals.

Heart murmurs in sheep generally fall into two broad groups: structural murmurs and functional murmurs. Structural murmurs happen when blood moves abnormally through a malformed or damaged heart. Merck lists ventricular septal defect as a recognized congenital cardiovascular defect in sheep, and this defect can create a loud systolic murmur even when the opening is relatively small.

Acquired structural disease is also possible. Infection affecting a heart valve, often called endocarditis, can create turbulent flow and a new murmur. In large animals, endocarditis is an important rule-out when a murmur appears along with fever, weight loss, or signs of chronic illness. Valve leakage or other less common cardiac abnormalities can also be involved.

Functional murmurs are caused by changes outside the heart that alter blood flow. Veterinary references commonly list anemia, fever, infection, low blood protein, pregnancy, obesity, or poor body condition as possible causes of these murmurs. In sheep, heavy parasite burdens, blood loss, chronic disease, or severe inflammation may contribute to this kind of murmur.

Because the same sound can come from very different problems, your vet will focus on the whole picture: age, body condition, temperature, parasite risk, growth history, and whether the sheep has signs of heart failure or systemic illness.

Diagnosis starts with a full history and physical exam. Your vet will listen to where the murmur is loudest, whether it happens during systole or diastole, and whether there are other clues such as fever, pale membranes, jugular changes, edema, or abnormal lung sounds. Merck emphasizes that diagnosis of heart disease in animals relies on signalment, history, physical findings, and targeted testing rather than the murmur alone.

The next step is often bloodwork. A complete blood count can help look for anemia or inflammation, while chemistry testing may show dehydration, protein changes, or organ effects from chronic disease. If infection is suspected, your vet may recommend additional testing based on the sheep's age, flock history, and regional disease risks.

If the murmur seems likely to be cardiac, echocardiography is the most useful advanced test. Merck notes that Doppler echocardiography helps identify valvular regurgitation, increased flow velocity, and abnormal blood movement within the heart. This is the best way to confirm defects such as ventricular septal defect or to assess valve disease. Chest radiographs and ECG may be added in selected cases, but ECG is not a screening test for murmurs.

In field settings, diagnosis may be staged. Some sheep need only an exam and basic lab work, while others benefit from referral imaging if the animal is valuable, breeding stock, or showing progressive signs. Your vet can help match the workup to the likely cause and your management goals.

Not every heart murmur can be prevented. Congenital defects can occur before birth, and some structural heart problems are not predictable in an individual lamb. Still, good flock health lowers the risk of functional murmurs and may reduce the chance that a serious problem goes unnoticed.

Work with your vet on parasite control, nutrition, and routine flock monitoring. Preventing severe anemia from parasites or blood loss is one of the most practical ways to reduce murmur risk in sheep. Prompt treatment of wounds, lameness, chronic infections, and postpartum illness may also help lower the risk of bloodstream infection that could affect the heart valves.

Breeding decisions matter too. Lambs with confirmed congenital heart defects or poor unexplained thrift are usually not ideal breeding candidates. A pre-breeding or pre-purchase exam can help identify murmurs early, even though more testing may be needed to know what they mean.

The most useful prevention step is early evaluation. If your vet hears a murmur, ask what follow-up is appropriate now, what can be monitored, and what signs would change the plan. That approach supports both animal welfare and practical flock management.