Milk fever (hypocalcemia) around calving causes acute recumbency and progressive paralysis in dairy cows, representing one of the most common and preventable welfare emergencies in dairy farming.
Milk fever is both acutely distressing and progressively damaging if not treated promptly. The recumbent cow experiences disorientation, inability to rise, progressive pressure sores on hips and hocks, and the discomfort of ruminal stasis and bloat. Without treatment, coma and death follow. Even with treatment, delayed intervention leaves cows with secondary muscle damage ("downer cow syndrome") that requires days to weeks of recovery and may be irreversible. Subclinical hypocalcemia — affecting many more cows — is a welfare problem through its effects on immune function and its contribution to mastitis, metritis, and displaced abomasum, all of which cause their own welfare harms.