Diseases - Sheep

Hypocalcaemia

Other Names

Milk Fever

Species

All.

Description

Hypocalcaemia is low blood calcium. Calcium is essential for many body functions especially muscle contraction, nerve conductivity and bone strength. Maintenance of normal blood concentrations is achieved by a combination of release from bone stores and absorption of dietary calcium from the gut.

Animals are at risk of hypocalcaemia when:

  • Bone stores are depleted - may occur with long term grain feeding or vitamin D deficiency (seen in low sunlight, vitamin A-rich grazing conditions of southern Australian winters).
  • There is sudden reduced intake and absorption from the gut - fasting associated with transport or yarding, sudden dietary changes, sudden climatic changes (hot or cold), and ingestion of plants containing oxalate.
  • Mobilisation from bones is too slow to meet an increase in demand - may occur in older, fatter animals.
  • Animals have high demand for calcium such as in early lactation and pregnant animals especially those with multiple foetuses.

The first three situations might occur in assembly points, the fourth at destination.

Clinical Signs and Diagnosis

Early signs include excitement and muscle tremors. Staggering gait, recumbency, paralysis, coma and death follow. There is no fever.

Diagnosis is based on clinical signs, presence of risk factors and response to treatment. Fragility of bones and sometimes healing rib fractures may be present in sheep with prolonged dietary deficiency. Blood samples will have low calcium concentrations.

Before kidding/lambing, pregnancy toxaemia is the main differential diagnosis. Some animals have both diseases. In pregnancy toxaemia, the onset is gradual over a few days and response to calcium is slight and temporary.

Laboratory confirmation requires 2 mL of serum submitted chilled for calcium and magnesium estimation. In dead animals, submit aqueous humor for calcium estimation taking care to minimise cellular contamination from the iris.

Treatment

Administer injectable calcium and magnesium solutions under the skin over the ribs. Massage well to speed absorption. Commercial solutions of calcium borogluconate are commonly used and should be warmed to body temperature before injection. A response is expected in a few minutes (burping, muscle tremors, voluntary movements) with full recovery usually within an hour. Treatment occasionally needs to be repeated. It is fatal if left untreated. Careful intravenous administration of calcium solutions may be considered for severe cases.

Prevention

Avoid selecting old, over-fat, pregnant ewes and does for live export. Avoid interruptions to food and water availability. Feed roughage as hay, chaff or pellets high in fibre (to increase dietary intake and gut absorption of calcium) in high risk animals or conditions.

Syndromes