Milk fever — clinically known as hypocalcaemia — is one of the most common metabolic disorders of dairy cows, occurring at or near calving when calcium demand for colostrum and milk production exceeds supply. It causes severe welfare impacts and is largely preventable with good management.
Clinical milk fever causes progressive neuromuscular dysfunction: cows become weak, unsteady, collapse, and without treatment develop lateral recumbency, coma, and death. The progression from mild weakness to collapse can occur within hours. Even subclinical hypocalcaemia (low blood calcium without collapse) impairs muscle function, increases risk of other metabolic diseases, and reduces immune function.
The experience of collapse, inability to rise, and loss of control represents significant distress. Cows that remain down for extended periods develop secondary muscle damage (downer cow syndrome), causing additional pain and often permanent injury.
Clinical milk fever affects 3-8% of dairy cows in high-producing herds, rising to 25-40% in some populations of older cows. Subclinical hypocalcaemia may affect 40-60% of multiparous cows at peak risk. Given global dairy cow populations of ~265 million, the scale of welfare impact is enormous.
Intravenous calcium borogluconate is highly effective when administered promptly — most cows recover within 30 minutes of treatment. The welfare priority is recognizing affected cows early and treating promptly. Delayed treatment leads to irreversible complications including downer cow syndrome, abomasal displacement, and death.
Prevention is welfare-superior to treatment. Effective prevention strategies include:
Cows that fail to rise after calcium treatment ("downer cows") represent a significant welfare challenge. Recovery requires intensive nursing, frequent repositioning to prevent nerve and muscle damage, provision of food and water, and careful assessment. Prolonged recumbency without improvement requires timely euthanasia decisions to prevent unnecessary suffering.
Milk fever incidence is a validated welfare indicator in dairy herd assessments. Target rates below 2% clinical milk fever and below 25% subclinical hypocalcaemia are achievable with good nutrition management. Herds consistently exceeding these thresholds should review their transition cow nutrition programs.