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