Milk Fever in Dairy Cattle: Calcium Crisis at Calving

Milk fever (hypocalcaemia) is a metabolic disease affecting dairy cows at or shortly after calving, causing paralysis and death if untreated. It is one of the most common and welfare-significant periparturient diseases in dairy farming.

Key Facts

Milk fever results from a sudden drop in blood calcium as lactation begins — the mammary gland demands calcium faster than it can be mobilised
It most commonly affects older, high-producing cows in their third lactation or later
Clinical signs progress from restlessness and muscle tremors through recumbency (inability to rise) to coma and death
Cows down with milk fever are at immediate risk of bloat, aspiration pneumonia, and secondary injuries from inability to rise
Intravenous or oral calcium supplementation is highly effective when administered promptly — delay worsens prognosis
Sub-clinical hypocalcaemia (blood calcium low but without clinical signs) affects a much larger proportion of dairy cows
Prevention strategies include pre-calving anionic salt supplementation, magnesium supplementation, and managed dietary cation-anion difference (DCAD)

Welfare Considerations

Milk fever causes rapid progression from early weakness to complete recumbency and loss of consciousness. Cows unable to rise are at immediate welfare risk: they cannot access water, feed, or shade; they develop pressure sores from prolonged lying; and bloat from inability to eructate can cause respiratory distress. Without treatment, progression to coma and death occurs within hours to days. Even with prompt calcium treatment, some cows that have been recumbent for extended periods develop secondary complications — downer cow syndrome — from muscle and nerve damage that prevents recovery despite normal calcium levels. The key welfare intervention is prevention through DCAD management and proactive monitoring at calving.

What You Can Do

Implement DCAD nutrition programmes and pre-calving mineral management to reduce milk fever incidence
Monitor fresh cows closely in the first 24-48 hours after calving for early signs of weakness or reluctance to rise
Administer oral or intravenous calcium promptly when milk fever is suspected — do not delay waiting for confirmation
Ensure downer cows receive regular turning, deep bedding, and access to water and feed while unable to rise
Work with your vet to establish herd-level targets for clinical and subclinical hypocalcaemia rates
Support research into more effective and accessible prevention strategies for high-risk dairy herds