Hypocalcemic effect of aminoglycoside antibiotics in the dairy cow

The effect of the parenteral administration of aminoglycoside antibiotics on the blood calcium concentration in dairy cows was investigated. Gentamicin was tested in vitro in blood drawn from cows, dihydrostreptomycin was tested in nonlactating cows and neomycin was tested in postpartum cows. The total and bound calcium fractions were significantly reduced by all three antibiotics. No change occurred in the unbound calcium fractions. Caution is advised in the use of these drugs in postpartum cows, especially those with a history of milk fever.