COMBINED EFFECT OF AMPICILLIN, COLISTIN AND DEXAMETHASONE ADMINISTERED INTRAMUSCULARLY TO DAIRY-COWS ON THE CLINICOPATHOLOGICAL COURSE OF E-COLI-ENDOTOXIN MASTITIS

The effects of a single intramuscular injection of a drug product cont aining ampicillin, colistin and dexamethasone, as a suspension in a di ester of propylene glycol of medium-chain fatty acids, on the clinico- pathological course of experimental Escherichia coli-endotoxin mastiti s was examined in 30 dairy cows. Cows were divided into five groups, s ix cows per group, and 24 of them were infused with E. coli endotoxin into two quarters of their udders. The drug product was injected at 25 000 IU colistin sulphate, 10.0 mg ampicillin anhydrate and 0.025 mg d examethasone acetate.kg(-1) body weight as follows: Group 2 cows, imme diately post-endotoxin infusion (PEI); Group 3 cows, 2 h PEI and, Grou p 4 cows, 4 h PEI. Group 1 cows were not treated with the product and served as a positive (endotoxin only) control while Group 5 cows were not challenged with endotoxin and were not treated with the product. A clinical mastitis score (CMS) was developed to quantitatively assess the degree of inflammation. Blood biochemistry and hematological param eters were used to monitor the immediate effects of treatment on sever al conventional inflammatory markers. Milk somatic cell counts (MSCC), milk electrical conductivity and daily milk production were among the parameters used to monitor systemic and local inflammatory reactions. Administration of the drug product immediately PEI and 2 h PEI clearl y nullified some of the most severe early systemic reactions to inflam mation but the effect of therapy on the local inflammatory markers was not as obvious. Notewhorthy, however, were the effects of the treatme nt on reducing the duration of elevated quarter MSCC and the increase in the speed of return to pre-endotoxin challenge daily milk productio n levels. (C) Inra/Elsevier, Paris.