Bovine Periparturient Hypocalcemia Study Guide

Overview and Clinical Importance

Periparturient hypocalcemia (also known as milk fever or parturient paresis) is a metabolic disorder of adult dairy cattle characterized by acute hypocalcemia occurring at or soon after parturition. This condition represents one of the most economically significant metabolic diseases in dairy cattle, with clinical incidence ranging from 5-10% of cows calving, though subclinical hypocalcemia affects approximately 50% of multiparous cows. Understanding the pathophysiology, clinical presentation, treatment, and prevention of this condition is essential for NAVLE success and clinical practice.

The term "milk fever" is a misnomer as the disease does not cause elevated body temperature. In fact, affected cows are typically hypothermic in advanced stages. The condition occurs because calcium demand for colostrum and milk production dramatically exceeds the cow's ability to mobilize calcium from bone stores and absorb it from the diet.

Calcium Homeostasis in Dairy Cattle

Normal Calcium Regulation

Calcium homeostasis is maintained through the coordinated actions of three primary hormones acting on three target organs. The normal plasma calcium concentration in cattle is 8.5-10.5 mg/dL (2.1-2.6 mmol/L). Approximately 50% of serum calcium is ionized (biologically active), with the remainder bound to proteins (primarily albumin) or complexed with anions.