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  • Author or Editor: Terry N. TerHune x
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Abstract

Objective—To determine the efficacy of difloxacin, a novel fluoroquinolone antibiotic, in calves experimentally infected with Mannheimia haemolytica (formerly Pasteurella haemolytica).

Animals—Seventy-two 3-month-old Holstein calves.

Procedures—Calves were inoculated with M haemolytica intratracheally; after they developed clinical signs of pneumonic pasteurellosis, they were randomly assigned to 1 of 6 groups (n = 12/group). Calves in each group were treated with 10% difloxacin (2.5 or 5 mg/kg of body weight), 5% difloxacin (2.5 or 5 mg/kg), enrofloxacin (5 mg/kg), or saline (0.9% NaCl) solution (control group), once daily for 5 days, and clinical signs were scored daily. On day 15, calves were euthanatized, and the percentage of diseased lung tissue was calculated. Swab specimens of the lungs were submitted for bacterial culture.

Results—Mortality rate and percentage of diseased lung tissue were significantly higher and cure rate and average daily gain were significantly lower for control calves, compared with calves in the treatment groups; however, no significant differences were found among treatment groups. Mannheimia haemolytica was isolated from the lungs of 10 control calves and from at least 2 calves in each of the treatment groups.

Conclusions and Clinical Relevance—Results suggest that difloxacin and enrofloxacin were equally effective for treatment of calves with experimentally induced pneumonic pasteurellosis. However, treatment of infected calves with difloxacin or enrofloxacin may not eliminate the organism. (Am J Vet Res 2000;61:710–713)

Full access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To evaluate effects of various doses of polyethylene glycol (PEG)–conjugated bovine granulocyte colony-stimulating factor (bG-CSF) on the incidence of naturally occurring clinical mastitis in periparturient dairy cattle.

ANIMALS 211 periparturient Holstein cows and heifers.

PROCEDURES Approximately 7 days before the anticipated date of parturition (day of parturition = day 0), healthy cattle received SC injections of sterile saline (0.9% NaCl) solution (control treatment) or PEG–bG-CSF at 5, 10, or 20 μg/kg. Cattle were commingled and housed in a pen with dirt flooring, which was kept wet to maximize the incidence of naturally occurring clinical mastitis. Within 24 hours after parturition, each animal again received the assigned treatment. Mammary glands and milk were visually scored for abnormalities twice daily for 28 days after parturition. Milk samples were aseptically collected from mammary glands with an abnormal appearance or abnormal milk and submitted for microbial culture. Daily milk production was recorded, and milk composition was assessed on days 3, 5, 7, and 10.

RESULTS Cattle treated with PEG–bG-CSF at 10 and 20 μg/kg had significantly fewer cases of clinical mastitis (9/54 and 5/53, respectively), compared with control cattle (18/53). Administration of PEG –bG-CSF did not significantly affect daily milk production or milk composition.

CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that PEG–bG-CSF was effective for reducing the incidence of naturally occurring clinical mastitis in periparturient dairy cattle. Further investigations of the use of PEG–bG–CSF as a potential preventative intervention should be conducted.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare concentrations of danofloxacin, enrofloxacin, and ciprofloxacin in plasma and respiratory tissues of calves treated after challenge with Mannheimia haemolytica.

Animals—75 calves.

Procedure—24 hours after challenge with M haemolytica, 72 calves with clinical signs of respiratory tract disease were randomly assigned to 1 of 12 equal treatment groups. Three nonchallenged, nontreated calves formed a control group. Challenged calves were treated with danofloxacin (6 and 8 mg/kg, SC) and enrofloxacin (8 mg/kg, SC) once. At 1, 2, 6, and 12 hours after treatment, 6 calves from each treatment group were euthanatized. Antimicrobial drug concentrations were assayed in various specimens. Peak plasma concentration (Cmax)-to-minimum inhibitory concentration (MIC; Cmax-to-MIC) ratios and the area under the concentration versus time curve over a 12-hour period-to-MIC ratios (AUC12h-to-MIC) were calculated.

Results—Danofloxacin and enrofloxacin had MICs of 0.03 µg/mL for the M haemolytica challenge isolate. Danofloxacin administered at doses of 6 and 8 mg/kg resulted in numerically higher geometric mean concentrations of danofloxacin in plasma and all respiratory tissues than geometric mean concentrations of enrofloxacin after treatment with enrofloxacin. Geometric mean concentrations of enrofloxacin were numerically higher than geometric mean concentrations of ciprofloxacin metabolite in plasma and almost all respiratory tissues. Danofloxacin and enrofloxacin achieved Cmax-to-MIC ratios > 10 and AUC12h-to-MIC ratios > 125 hours.

Conclusions and Clinical Relevance— When used to treat pneumonic pasteurellosis in calves, danofloxacin and enrofloxacin can be expected to deliver concentration-dependent bactericidal activity against M haemolytica, the bacteria most commonly associated with bovine respiratory tract disease. (Am J Vet Res 2005;66:342–349)

Full access
in American Journal of Veterinary Research