Treatment of acute Escherichia coli mastitis in cows with enrofloxacin: effect on clinical signs and chemiluminescence of circulating neutrophils

We have studied the effect of treatment with enrofloxacin on local and gene ral clinical signs and chemiluminescence of circulating polymorphonuclear l eucocytes during experimentally induced Escherichia coli mastitis in cows i mmediately after parturition. Twelve cows were infected with 10(4) cfu Esch . coli P4:O32 into both left quarters. Six cows received an intravenous inj ection of 5 mg enrofloxacin/kg at 10 h after infection and a second enroflo xacin treatment administered subcutaneously at 30 h post infection. The oth er six cows were controls that received no treatment. General clinical sign s (fever, tachycardia, loss of appetite, reduced rumen motility and depress ion) were similar in both groups. Local clinical signs, such as swelling, p ain and firmness of the inflamed mammary quarters, were less severe in the treated cows. We saw no difference in the appearance of the milk: fleck and watery or purulent milk were observed in both groups. The beneficial effec ts of treatment with enrofloxacin were mainly on milk production and compos ition. The decline in milk production and the changes in milk concentration s of lactose, Na+ and bovine serum albumin were less pronounced in the trea ted cows. Treatment with enrofloxacin accelerated the clearance of bacteria from the infected quarters, but had no effect on the chemiluminescence res ponse of isolated polymorphonuclear leucocytes. The changes in the number o f circulating leucocytes and the appearance of immature neutrophils in the circulation of the treated cows indicated possible beneficial effects on mi gration of neutrophils into the inflamed glands. Higher milk somatic cell c ounts in the treated cows supported this hypothesis. The results of this st udy indicated that treating cows that have been experimentally infected wit h Esch. coli mastitis after parturition with enrofloxacin reduced the sever ity of the disease, especially the decline in milk production and the chang es in milk composition.