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Blood Calcium Dynamics after Prophylactic Treatment of Subclinical Hypocalcemia with Oral or Intravenous Calcium
Total serum Ca dynamics and urine pH levels were evaluated after prophylactic treatment of subclinical hypocalcemia after parturition in thirty-tree multiparous Jersey/Holstein crossbreed cows. Cows were blocked according to their calcemic status at the time of treatment (Vetscan 200-1000R, Abaxis) [normocalcemic (8.0- 9.9 mg/dl; n=15), or hypocalcemic (5.0-7.9 mg/dL; n=18)] and randomly assigned to one of three treatments: Control [ no Ca supplementation (n=11)]; intravenous Ca [Ca-IV (n=11), 500 mL of 23% Ca Gluconate (10.7g Ca, Durvet, Blue Springs, MO)]; and oral Ca [Ca-Oral (n=11), one oral bolus (Bovikalc bolus, Boehringer Ingelheim, St. Joseph, MO) containing CaCl2 and CaSO4 [43g Ca] two times 12 h apart]. Total serum Ca levels were evaluated at 0, 1, 2, 4, 8, 12, 16, 20, 24, 36 and 48 h after treatment application (Enzymatic Rate/Automated Chemistry Analyzer method, Marshfield lab, WI) and urine pH at 0, 1, 12, 24, 36, and 48 h (on-farm with Oakton pH Testr 20). Overall, total serum Ca levels did not differ with treatment. But, Ca-IV cows experienced a sharp increase in serum Ca levels after treatment (peak = 11.4 mg/dL at 1 h), followed by a steep decline (nadir = 6.4 mg/dL at 24 h). Total serum Ca levels were higher for Ca-IV than control and Ca-Oral at 1, 2, and 4 h after treatment, but lower than Ca-Oral at 20, 24 and 36 h and control at 36 and 48 h. Treatment, time and treatment by time interaction were significant for urine pH. Mean urine pH was lower for Ca-Oral cows (6.69) than for control (7.52) and Ca-IV (7.19) cows. Urine pH levels at 1 h after treatment were lower for Ca-IV compared to both Control and Ca-Oral. At 12, 24, and 36 h, urine pH levels were lower for Ca-Oral compared to both Control and Ca-IV. This was expected as the oral Ca supplementation used (Bovikalc) is designed as an acidifying agent. Wide fluctuations in blood Ca are observed after prophylactic intravenous Ca supplementation in normo- and subclinical hypocalcemic cows. The implications of these transient changes in serum Ca have still to be determined.
Keywords: hypocalcemia, hypercalcemia, dairy cattle