Influence of Calcium Chloride on Systemic Acid-Base Status and Calcium Metabolism in Dairy Heifers

¹ Department of Animal Science, University of Kentucky, Lexington 40546

Twenty heifers (12 Holsteins and 8 Jerseys) ranging from 15 to 22 mo of age (SD = 2.2 mo) and weighing 271 to 486 kg (SD = 72 kg) were offered diets containing 0, .5, 1, and 1.5% CaCl₂ for 3 wk followed by a 1-wk readjustment period to evaluate the effect of CaCl₂ on acid-base status, diuresis, and Ca metabolism. These evaluations were conducted under conditions simulating changes in dietary cation-anion balance that potentially can be utilized as prophylaxis for parturient paresis during transition from dry cow period to lactation. Free proton concentration in blood increased and blood bicarbonate decreased with increasing dietary CaCl₂. Plasma protein and blood hematocrit were unaffected by dietary CaCl₂. Plasma Ca and urinary hydroxyproline excretion also were unaffected, but urinary Ca excretion rose with increasing dietary CaCl₂, possibly reflecting either increased bone mobilization or intestinal absorption of Ca. Elevating dietary Cl increased both plasma Cl and urinary Cl excretion. During the readjustment period, all differences caused by CaCl₂ disappeared. Based on the responses of acid-base status and Ca metabolism to the different dietary concentrations of CaCl₂, we suggest that feeding 1% CaCl₂ to dry cows for 3 wk prepartum could be a suitable method to prevent parturient paresis without causing detrimental acid-base disturbances.

Key Words: calcium chloride • calcium • metabolism • acid-base status

Submitted on September 10, 1990
Accepted on November 19, 1990