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  • Author or Editor: Valerie K. Shostrom x
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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

Abstract

Objective—To compare effects of an injectable doramectin preparation with those of an injectable ivermectin-clorsulon preparation on control of gastrointestinal nematodes and liver flukes and on growth performance in cattle.

Design—Randomized complete block design.

Animals—60 crossbred calves.

Procedures—Calves (20/treatment group) were treated with doramectin or ivermectin-clorsulon or were not treated. Fecal samples were collected for nematode and Fasciola hepatica egg counts on day 0 and for up to 140 days after treatment. Cattle were weighed before treatment and at 28-day intervals until day 140.

Results—From day 7 through day 49, nematode egg counts for calves treated with doramectin or with ivermectin- clorsulon were significantly lower than those for untreated control calves. As the study progressed beyond day 56, the percentages of cattle with fluke eggs in their feces increased, but differences in regard to these percentages were not detected among the 3 groups. Average daily gain for the doramectin-treated cattle (0.79 kg/d [1.74 lb/d]) was significantly greater than that for the cattle treated with ivermectin-clorsulon (0.71 kg/d [1.56 lb/d]); values for both groups were significantly greater than that for the control cattle (0.62 kg/d [1.37 lb/d]).

Conclusions and Clinical Relevance—Results suggest that doramectin had a greater impact on subclinical gastrointestinal tract parasitism in calves, as demonstrated by growth performance, than did ivermectin- clorsulon. In the Gulf Coast region of the United States, spring-born nursing beef calves may have minimal grazing exposure to F hepatica during the peak fluke transmission period; therefore, mature fluke burdens may be negligible at the beginning of the fall season. (J Am Vet Med Assoc 2001;218: 1465–1468)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To examine effects of danofloxacin and tilmicosin on continuously recorded body temperature in beef calves with pneumonia experimentally induced by inoculation of Mannheimia haemolytica.

Animals—41 Angus-cross heifers (body weight, 160 to 220 kg) without a recent history of respiratory tract disease or antimicrobial treatment, all from a single ranch.

Procedure—Radiotransmitters were implanted intravaginally in each calf. Pneumonia was induced intrabronchially by use of logarithmic-phase cultures of M haemolytica. At 21 hours after inoculation, calves were treated with saline (0.9% NaCl) solution, danofloxacin, or tilmicosin. Body temperature was monitored from 66 hours before inoculation until 72 hours after treatment. Area under the curve (AUC) of the temperature-time plot and mean temperature were calculated for 3-hour intervals and compared among treatment groups.

Results—The AUCs for 3-hour intervals did not differ significantly among treatment groups for any of the time periods. Analysis of the mean temperature for 3-hour intervals revealed significantly higher temperatures at most time periods for saline-treated calves, compared with temperatures for antimicrobial-treated calves; however, we did not detect significant differences between the danofloxacin- and tilmicosin-treated calves. The circadian rhythm of temperatures before exposure was detected again approximately 48 hours after bacterial inoculation.

Conclusions and Clinical Relevance—Danofloxacin and tilmicosin did not differ in their effect on mean body temperature for 3-hour intervals but significantly decreased body temperature, compared with body temperature in saline-treated calves. Normal daily variation in body temperature must be considered in the face of respiratory tract disease during clinical evaluation of feedlot cattle. ( Am J Vet Res 2004;65: 610–615)

Full access
in American Journal of Veterinary Research