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Six anionic salts [MgCl2.6H2O, MgSO4.7H2O, CaCl2.2H2O, CaSO4.2H2O, NH4Cl, and (NH4)2SO4] were evaluated for their effects on dietary DM intake, systemic acid-base balance, and urinary excretion of Ca. Each of the six salts was fed to 12 nonlactating, nonpregnant Holstein cows for 1-wk periods in two replicates of a 6 x 6 Latin square design. All salts were fed at the rate of two equivalents cow-1 d-1. Anionic salt treatments did not decrease DM intake compared with the control diet fed without salts. Blood pH was not affected by any of the salt treatments; however, mild, compensated metabolic acidosis was evidenced by decreased blood bicarbonate concentrations and decreased blood base excess when any of the salts was fed. Urinary pH and urinary base excess also were lowered by all of the salts. Fractional excretion of urinary Ca was increased by all salt treatments. All six anionic salts tested were of similar value in their acidifying effects and in their ability to increase urinary excretion of Ca.

We investigated the suppressive effects of phosphate on calcium determinations with lanthanum-air/acetylene and potassium-nitrous oxide/acetylene methods, and we evaluated the ability of these methods to meet the suggested analytical goals for urine samples. The 20 g/L La-air/acetylene method was the most nearly accurate for predicting the actual calcium concentrations (t-test value = -0.042), followed by the 2 g/L K-nitrous oxide/acetylene method (t-test value = 0.450), 10 g/L La-air/acetylene (t-test value = -0.733), and finally 5 g/L La-air/acetylene (t-test value = -2.446). The dilution used significantly influences the apparent calcium concentration measured with the La-air/acetylene methods.