Bovine Postparturient Paresis Study Guide

Overview and Clinical Importance

Postparturient paresis (also known as milk fever, hypocalcemia, parturient paresis, or paresis puerperalis) is one of the most important metabolic disorders affecting dairy cattle worldwide. This acute to peracute, afebrile condition is characterized by hypocalcemia occurring at or shortly after parturition, leading to flaccid paralysis, altered mentation, and circulatory collapse if left untreated.

Despite the name "milk fever," affected animals are typically afebrile or hypothermic. The condition occurs when calcium demand for colostrum and milk production exceeds the cow's ability to mobilize calcium from bone and absorb it from the gastrointestinal tract. The annual incidence in dairy herds ranges from 2% to 60%, with an average of 5-10% in high-producing herds.

Etiology and Pathophysiology

Calcium Homeostasis in Cattle

During the dry period, dairy cattle have relatively low calcium requirements of approximately 30 g/day for fetal growth and maintenance losses. At parturition, calcium demands increase dramatically to 50 g/day or more due to colostrum and milk production. This sudden increase in calcium outflow creates a tremendous challenge to calcium homeostasis.