Effects of Dietary Sodium Bicarbonate and Calcium Chloride on Physiological Responses of Lactating Dairy Cows in Hot Weather

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Abstract
Lactating cows (24) were assigned randomly to 3 treatments to evaluate responses to large differences of dietary Na+ and Cl-. Treatments were corn-cottonseed meal-corn silage based complete rations with either .23% NaCl (control), control plus 2.28% CaCl2 or control plus 1.70% NaHCO3. Treatment effects were significant for urine pH (7.96, 5.41, 8.18), blood pH (7.50, 7.39, 7.49), partial pressure of O2 (91.2, 99.4, 86.3 mm Hg), partial pressure of CO2 (34.60, 30.57, 32.98 mm Hg), HCO3- (26.20, 18.06, 24.64 meq/l) [eq = equivalent], total CO2 (27.51, 19.18, 25.88 mM/l), base excess (4.50, -4.31, 3.13 meq/l), plasma Cl- (93.4, 102.8, 95.7 meq/l), serum K (3.26, 4.24, 4.14 meq/l) and Pi (7.11, 5.61, 6.80 mg/100 ml). Blood glucose (45.1, 43.0, 55.5 mg/dl) and blood urea N (11.8, 8.7, 11.9 mg/dl) exhibited treatment effects. Respiration rates, 84.8, 61.8, 89.9 per min, and body temperatures, 39.7.degree., 39.0.degree., and 40.0.degree. C were significantly different. Lower intake of the high Cl- diet and higher intake of the HCO3- diet were probably responsible for some of the effects. Dietary electrolytes should receive attention in formation because acid-base status of the animal is determined, in part, by ionic concentration and balance of the diet.