Blood Calcium Levels Below 5.5 mg/dl
Cows with clinical hypocalcemia often appear weak, are unable to stand, and can have twitching ears.
The sudden onset of milk and colostrum production before calving causes some cows to have difficulty absorbing enough calcium from their diet or from their bones to maintain adequate blood calcium levels. Elevated levels of potassium and sodium (cations), and low levels of chloride and sulfur (anions) limit the cows' ability to maintain normal blood calcium levels. A cow with total blood calcium below 5.5 milligrams per deciliter (mg/dl) would be considered to have clinical milk fever.