Effects of experimentally induced Pasteurella haemolytica pneumonia on the pharmacokinetics of erythromycin in the calf

Pneumonic pasteurellosis was produced experimentally in 3- to 4-month-old Holstein bull calves by bilateral intrapulmonary administration of 5 X 10(7) to 10(9) colony-forming units of Pasteurella haemolytica. Of 8 calves, 4 developed minor pulmonary changes, 1 died of an apparent bacteremia within 24 hours, and 3 developed extensive pneumonic changes. At 1 week before (1 dose) and at 48, 60, and 72 hours (3 doses) after Pasteurella administration, the calves were given erythromycin at a dosage of 15 mg/kg, and the pharmacokinetic values were determined. There were statistically (P less than or equal to 0.05) significant increases in the distribution and elimination rates associated with pneumonia. The elimination half life decreased from 132.7 +/- 9.6 minutes in prepneumonic calves to 111.1 +/- 13.8 minutes and 99.7 +/- 2.6 minutes in calves with minor and with moderate pneumonic changes, respectively. There also was a decrease in apparent volume of distribution with pneumonia. Erythromycin tissue concentrations were determined 2 hours after the last dose was given to the calves with pneumonia. Tissue concentrations in the pneumonic lung areas were as high or higher than those in nonaffected lung tissues in the same animals. Because of the increased rate of elimination from serum in pneumonic calves, it may be advisable to use shorter dosage intervals in calves with severe respiratory tract disease.     

Efficacy of sustained release needle-less ceftiofur sodium implants in treating calves with bovine respiratory disease

Three experiments were conducted to determine preliminary efficacy of sustained release needle-less implants in effecting cure in calves with bovine respiratory disease. One hundred and twenty beef calves with a rectal temperature > or = 40 degrees C and shallow or labored respiration and coughing were used in these experiments. Four groups (1-ceftiofur sodium injections [days 1, 2, and 3], 2-ceftiofur sodium needle-less implants [days 1, 2, and 3], 3-ceftiofur sodium needle-less implants [days 1 and 3], and 4-ceftiofur sodium needle-less implants [day 1] were included. All treatments contained 250 mg of ceftiofur sodium and were administered intramuscularly in the neck after diagnosis of bovine respiratory disease. Experiment 1 included 20 calves (group 1-10 calves and group 3-10 calves; 213 to 255 kg) and calves were monitored for clinical efficacy. Experiment 2 included five calves per group (all four groups; 164 to 192 kg) and calves were bled frequently after treatment for desfuroylceftiofur (the primary ceftiofur metabolite) concentrations. Experiment 3 included 20 calves per group (all four groups; 160 to 205 kg) and calves were monitored for clinical efficacy. Blood desfuroylceftiofur concentrations remained above the minimum inhibitory concentration for Pasteurella haemolytica, Pasteurella multocida, and Haemophilus somnus for 24 hours after injection and 72 hours after implantation (P < 0.05). Mortalities and the number of calves with a positive response and relapse response were similar (P < 0.25) among the four groups. In summary, the administration of one-250 mg ceftiofur sodium needle-less sustained release implant was as efficacious in treating bovine respiratory disease as three daily 250 mg injections of ceftiofur sodium.     

Single-dose treatment of neonatal calf pneumonia with the new macrolide antibiotic tilmicosin

Tilmicosin, a new macrolide antibiotic, 20-deoxo-20-(3,5-dimethylpiperidin-l-yl)desmycosin, formerly identified as EL-870, has been evaluated in three experiments as a single subcutaneous injection at dosages of 10, 20 or 30 mg/kg for the treatment of naturally occurring pneumonia in neonatal calves. Male Holstein calves, under five days of age, were shipped from Wisconsin and housed in pens. They were assigned sequentially to a treatment group when their temperature was greater than or equal to 39.7 degrees C for two consecutive days or greater than or equal to 39.7 degrees C and signs of respiratory disease were present. Clinical signs were evaluated daily for 14 days after the tilmicosin treatment. Calves that died and those that survived for the 14 day experimental period were examined post mortem. Treatment with tilmicosin was effective at all dosage levels, as determined by significant (P less than or equal to 0.05) reductions in body temperature within 24 hours, in the number of animals that died, in the incidence and severity of clinical signs, in the number of Pasteurella species found in lung tissue and in the severity of the pneumonic lesions. In two of the three experiments severe outbreaks of cryptosporidiosis resulted in significant mortalities within a few days after the arrival of the calves. Treatment with tilmicosin was effective against respiratory disease even in the presence of this severe concurrent disease.     

Probenecid effect on cefuroxime pharmacokinetics in calves

Cefuroxime pharmacokinetics were studied in unweaned calves. The antibiotic was administered at 10 mg/kg to six calves i.v., to 12 calves i.m. and to ten of the previous 12 calves i.m. at 10 mg/kg together with probenecid at 40 mg/kg. Intramuscular doses of cefuroxime alone at 20 mg/kg were given to seven calves; to five of these calves cefuroxime was also given together with probenecid at 40 mg/kg and at 80 mg/kg. The serum concentration-time data were analyzed using statistical moment theory (SMT). The elimination half-life (t1/2) was 69.2 min (harmonic mean) after i.v. and 64.8 min and 64.9 min following i.m. administration of the lower and higher dose, respectively. Co-administration of probenecid did not affect the t1/2. The mean residence time (MRT) was 80.9 +/- 23.5 min (mean +/- SD) after i.v. and 117.8 +/- 9.3 min and 117.7 +/- 5.4 min after i.m. administration of cefuroxime at 10 and 20 mg/kg, respectively. The MRTi.m. following administration of cefuroxime at 10 mg/kg together with probenecid at 40 mg/kg was 140.0 +/- 8.8 min. The MRTi.m. values were 132.8 +/- 2.3 min and 150.8 +/- 5.1 min after cefuroxime was given at 20 mg/kg together with probenecid at 40 mg/kg or 80 mg/kg, respectively. The total body clearance (ClT) was 3.56 +/- 1.11 ml/min/kg and the volume of distribution at steady state (Vd(ss] 0.270 +/- 0.051 l/kg. The MIC90 values of cefuroxime were 16 micrograms/ml for E. coli and Salmonella isolates, 0.5 microgram/ml for Pasteurella multocida and 2.0 micrograms/ml for P. haemolytica.     

Chloramphenicol, lincomycin and oxytetracycline disposition in calves with experimental pneumonic pasteurellosis

The effects of pneumonia on the pharmacokinetics of chloramphenicol, lincomycin, and oxytetracycline were evaluated in two-month-old calves. Pneumonia was induced by injection of Pasteurella haemolytica cultures directly through the thoracic wall into each lung. Six days prior to induction of pneumonia, the antibiotics were administered in a single i.v. dose. The antibiotics were administered again 48 (i.v.), 60 and 72 h (i.m.) following injection of P. haemolytica. The pharmacokinetics of chloramphenicol (25 mg/kg) and lincomycin (10 mg/kg) were not significantly different in calves with pneumonia. The hybrid rate constant beta for oxytetracycline was increased in calves with pneumonia from 0.0034 +/- 0.0003/min to 0.0048 +/- 0.0007/min between 2 h and 8 h. Thus the elimination half-life in serum was shortened from 212.4 +/- 20.3 min to 149.3 +/- 19.5 min. In addition, there was an apparent but not statistically significant decrease in K12 with pneumonia. These findings accentuate the need for observance of 12-h dose intervals with oxytetracycline.     

Clinical efficacy of diclofenac sodium and flunixin meglumine as adjuncts to antibacterial treatment of respiratory disease of calves

Objective To compare the efficacy of the non-steroidal antiinflammatory drugs, diclofenac sodium and flunixin meglumine as adjuncts to the antibiotic treatment of bovine respiratory disease (BRD). Procedure We randomly allocated 80 Holstein calves with BRD to three groups. All the calves received a dose of 2.5 mg/kg tulathromycin by single subcutaneous injection and two of the groups received, in addition, either 2.5 mg/kg diclofenac sodium as a single intramuscular injection (diclofenac group, n = 30) or 2.2 mg/kg flunixin meglumine as an intravenous injection on the first three consecutive days after tulathromycin administration (flunixin group, n = 30). All calves were given a clinical score prior to initial treatment (day 0) and after treatment (days 1, 2, 3, 7 and 14) by observing appetite, demeanour, rectal temperature, the rate and type of respiration, presence or absence of coughing, and nasal discharge. Results During the first 48 h, improvement of adverse signs of respiratory disease, such as pyrexia and elevated respiratory rate, and of a high clinical index score was significant in the two adjunct groups compared with the calves receiving antibiotic alone. The reduction in pyrexia was greatest in the diclofenac group. There were no statically significant differences between treatment groups with regard to eventual perceived recovery from respiratory disease in 14 days. Conclusion In this trial, a single intramuscular dose of diclofenac sodium was equally effective as three intravenous injections of flunixin meglumine given on consecutive days as adjunctive therapy for BRD.     

Treatment of pneumonia in pigs with long-acting injectable tylosin

A blinded, randomised clinical trial was carried out in Brittany, France on three commercial pig farms with a history of pneumonia. Pigs with clinical signs of respiratory disease were randomly allocated to one of two treatment groups; 100 pigs received a single intramuscular injection of a long-acting formulation of tylosin at a dose rate of 20 mg tylosin/kg bodyweight, and 101 pigs received three consecutive daily intramuscular injections of 10 mg tylosin/kg bodyweight. The pigs' rectal temperatures and other clinical variables were recorded at intervals and a scoring system was used to evaluate the results of the treatments. Relapses were recorded for up to nine days after the treatment. There were no statistically significant differences between the two treatments in terms of clinical scores, rectal temperatures, or cure or relapse rates.     

Pharmacokinetics and bioavailability of ceftriaxone administered intravenously and intramuscularly to calves

Ceftriaxone was administered to Israeli-Friesian male calves by IV and IM routes. The antibiotic was administered IV (10 mg/kg) to 10 calves and IM to 23 calves; 8 were given the antibiotic at the rate of 10 mg/kg of body weight, 5 were given 20 mg/kg, and 10 were given 10 mg/kg, together with probenecid at 40 mg/kg. Serum concentration vs time profiles measured after IV and IM administration were analyzed by use of statistical moment theory. The following mean values +/- SD were found: elimination half-life (t1/2) was 83.8 +/- 8.6 minutes after IV administration and significantly longer 116.8 +/- 20.5 minutes (P less than 0.001) after IM administration at 10 mg/kg. The t1/2 was increased to 141.3 +/- 24.4 minutes by the coadministration of probenecid and to 145.0 +/- 48.2 minutes by doubling the IM dosage to 20 mg/kg. The total body clearance was 3.39 +/- 0.42 ml/min/kg and the renal clearance 2.37 +/- 0.74 ml/min/kg. The specific volume of distribution was 0.2990 +/- 0.0510 L/kg. The average mean residence time (MRT) was 94.0 +/- 12.3 minutes after IV administration and 137.6 +/- 19.9 minutes after IM administration of ceftriaxone at 10 mg/kg. The MRT was increased to 198 +/- 48.8 minutes by the coadministration of probenecid and to 191.0 +/- 59.4 minutes by doubling the IM dose. The former value was significantly different from the MRT after IM administration of the antibiotic at 10 mg/kg. Bioavailability of ceftriaxone after IM administration at 10 mg/kg and at 20 mg/kg was 78% and 83%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of in-feed medication with tylosin for the treatment and control of Mycoplasma hyopneumoniae infections

The efficacy of in-feed medication with tylosin for the treatment of enzootic pneumonia was examined in an experimental Mycoplasma hyopneumoniae infection model. One group of 10 conventional M. hyopneumoniae-free pigs was inoculated intratracheally with a highly virulent field isolate of M. hyopneumoniae; a second group of 10 pigs was inoculated in the same way and after 12 days was given tylosin at 100 mg/kg feed for 21 days; a third group of 10 pigs was inoculated with sterile culture medium, and these pigs were not given tylosin. The pigs were examined daily for clinical signs and each pig was given a respiratory disease score. Thirty-three days after they had been infected the pigs were euthanased, the lung lesions were quantified and samples of lung were processed for immunofluorescence testing for M. hyopneumoniae. The mean (sd) respiratory disease and lung lesion scores were significantly higher (P<0.05) in both the infected groups than in the uninfected group. Between 23 and 33 days after infection the mean respiratory disease score of the pigs treated with tylosin was 0.54 (0.22), significantly (P<0.05) lower than that of the infected pigs which were left untreated, 1.54 (0.46); similarly, their average lung lesion score, 1.72 (1.20), was significantly lower than that of the untreated pigs, 5.27 (3.85).     

Experimentally induced pneumonic pasteurellosis: dose-response relationships and protection against natural reinfection in calves

Calves were inoculated intranasally with 2 X 10(6.2) tissue culture infective doses of infectious bovine rhinotracheitis virus, followed in 7 days by intratracheal inoculations with 1 of 4 challenge doses of pathogenic Pasteurella haemolytica. Severity and duration of the ensuing clinical signs of respiratory tract disease were correlated with the challenge dose of bacteria. Calves given 1 X 10(6) colony-forming units (CFU) of bacteria did not develop reliable clinical evidence of disease, whereas those given 1 X 10(8) CFU or 1 X 10(10) CFU of bacteria developed clinical signs of pneumonic pasteurellosis within 12 to 24 hours of bacterial challenge. Severity of clinical signs was equal at the 10(8) and 10(10) doses of bacteria, but duration of clinical signs was greater in calves given the 10(10) dose. Calves given 1 X 10(12) CFU of bacteria developed relatively severe respiratory tract disease in excess of what was necessary for positive clinical detection. Positive correlations were found between the bacterial challenge dose and the height and duration of increased rectal temperature, amount and duration of increases in ocular and nasal discharges, and the subjective evaluation of depressed attitude and appetite. Correlations were not found between challenge dose and respiratory rate or character, or between challenge dose and complete blood cell count. Convalescent calves were resistant to naturally occurring pneumonic pasteurellosis, which caused severe disease in nontreated calves. Adverse effects of P haemolytica were not observed after the first 4 to 15 days after bacterial administration; however, the bacteria were isolated from nasal secretions of convalescent calves 89 to 116 days after bacterial inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of a florfenicol-tylosin combination after intravenous and intramuscular administration to beagle dogs

A pharmacokinetic study of a commercial florfenicol-tylosin (2:1) combination product was conducted in six beagle dogs after intravenous (IV) and intramuscular (IM) administration at doses of 10 mg/kg (florfenicol) and 5 mg/kg (tylosin). Serum drug concentrations were determined by a validated high performance liquid chromatography (HPLC) using UV detection. A rapid and nearly complete absorption of both drugs with a mean IM bioavailability of 103.9% (florfenicol) and 92.6% (tylosin), prolonged elimination half-life, and high tissue penetration with steady state volume of distribution of 2.63 l/kg (florfenicol) and 1.98 l/kg (tylosin) were observed. Additional studies, including pharmacodynamic and toxicological evaluation are required before recommendations can be made regarding the clinical application of the product in dogs.     

Subarachnoid butorphanol augments lidocaine sensory anaesthesia in calves

To determine the efficacy and safety of subarachnoid butorphanol combined with lidocaine, six calves were studied. Each calf underwent two treatments, at least one week apart, via subarachnoid injection: (1) butorphanol (0.03 mg/kg) plus 2% lidocaine (4 mg/kg) and (2) 2% lidocaine (4 mg/kg) alone. Subarachnoid injections were performed at the lumbosacral space. Analgesia, motor block, sedation, heart rate, arterial blood pressure, respiratory rate, arterial oxygen saturation as measured by pulse oximetry, and rectal temperature were compared before and after subarachnoid administration of drugs. Subarachnoid administration of the butorphanol-lidocaine combination induced bilateral prolonged analgesia extending from the coccygeal to the T11-T13 dermatomes in the calves, with minimal sedation and severe ataxia. Cardiovascular effects were significant in both treatments: heart rate was increased, and there was a minimal decrease in arterial pressure. It was concluded that adding a small dose of butorphanol to subarachnoid lidocaine in calves is effective and safe.     

Clinical pharmacology of cefixime in unweaned calves

Cefixime is a unique third-generation oral cephalosporin. Its in vitro activity and pharmacokinetic properties have been studied to assess its potential for use in the therapy of newborn calf infections due to gram-negative bacteria. The minimum inhibitory concentrations of cefixime for 90% (MIC₅₀) of field isolates of Escherichia coli. Salmonella and Pasteurella were 0.10–0.40 μg/mL. The serum disposition kinetics of cefixime following intravenous and oral administration was evaluated. The elimination half-life of cefixime after intravenous and oral administration was 3.5–4.0 h, the steady-state volume of distribution was 0.34 L/kg and approximately 90% of the drug was bound to serum proteins. Oral absorption was comparatively slow and bioavailability values for single 5 mg/kg doses were 20.2% after the administration of 200 mg of cefixime in capsules, 28.3% after dosing an aqueous solution of cefixime and 35.7% after fasted calves received the solution of cefixime. Mean serum drug concentrations 12 h after the cefixime solution was administered orally (5 mg/kg) were 1.05 μg/mL for the milk-fed calves and 1.76 μg/mL for the fasted calves. Computations showed that mean free drug concentrations equal to the MIC₅₀ of the drug for gram-negative pathogens associated with newborn calf infections can be maintained in tissues by multiple treatments at 5 mg/kg every 12 h or 10 mg/kg every 24 h.     

In vitro antimicrobial susceptibility of Pasteurella haemolytica and Pasteurella multocida recovered from cattle with bovine respiratory disease complex

The antimicrobial susceptibilities of 421 Pasteurella haemolytica and 158 P. multocida isolates recovered from cattle with respiratory disease were determined with a microdilution minimal inhibitory concentration test system. Isolates were analyzed for patterns of resistance to ampicillin, ceftiofur, erythromycin, gentamicin, penicillin, spectinomycin, sulfachlorpyridazine, sulfadimethoxine, tetracycline, and tylosin. All isolates tested were found susceptible to ceftiofur and sulfachlorpyridazine. Pasteurella haemolytica isolates were resistant to ampicillin, penicillin, sulfadimethoxine, tetracycline, and tylosin. Pasteurella multocida isolates were resistant to sulfadimethoxine, tetracycline, and tylosin.     

Pharmacokinetic properties of theophylline given intravenously and orally to ruminating calves

The disposition of theophylline in healthy ruminating calves was best described by a first-order 2-compartment open pharmacokinetic model. The drug had a mean elimination half-life of 6.4 hours and a mean distribution half-life of 22 minutes. Total body clearance averaged 91 ml/kg/h. The mean values for the pharmacokinetic volume of the central compartment, pharmacokinetic volume of distribution during the terminal phase, and volume of distribution at steady state were 0.502, 0.870, and 0.815 L/kg, respectively. Theophylline was readily absorbed after oral administration to the ruminating calf, with a mean fraction of 0.93 absorbed. The plasma concentrations after oral dosing peaked in approximately 5 to 6 hours, with a mean absorption half-life of 3.7 hours. A flip-flop model (rate constant of input is much smaller than the rate constant of output) of drug absorption was not found because the elimination process roughly paralleled that of the study concerning IV administration. In a multiple-dose trial that used a dosage regimen based on single-dose pharmacokinetic values, clinically normal calves responded as predicted. However, diseased calves had higher than expected plasma concentrations after being given multiple oral doses of theophylline at 28 mg/kg once daily. Overt signs of toxicosis were not seen, but this aspect of the drug was not formally investigated. Theophylline can be used as an ancillary therapeutic agent to treat bovine respiratory disease, but not without risk. The suggested oral dose of theophylline at 28 mg/kg of body weight once daily should be tailored to each case.(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of metaphylactic florfenicol therapy during natural outbreaks of bovine respiratory disease

The efficacy of an injectable formulation of florfenicol (300 mg/mL) as metaphylactic control of naturally occurring bovine respiratory disease (BRD) was evaluated in two double‐blind randomly controlled field studies on two Dutch veal calf herds (A and B). Cattle aged not older than 3 months and in the direct presence of calves with clinical respiratory disease were randomly allocated to treatment with 40 mg/kg florfenicol subcutaneously (s.c.) a positive control treatment (12.5 mg/kg tilmicosin p.o. twice daily for five consecutive days in herd A, and 12.5 mg/kg doxycycline p.o. twice daily for five consecutive days in herd B), or a negative control (one placebo saline s.c. administration on D0). The predominant respiratory pathogens present in pretreatment respiratory samples from affected animals were Mycoplasma bovis and Pasteurella multocida in outbreaks A and B, respectively. Metaphylactic administration of florfenicol resulted in a statistically significant weight gain, decreased rectal temperature for five consecutive days after treatment and decreased metaphylactic failure percentages compared with both positive and negative control groups. In summary, these studies demonstrated that a single s.c. injection of florfenicol is effective and practical for control of the bacterial component of BRD in veal calves.     

Effect of parenteral administration of erythromycin, tilmicosin, and tylosin on abomasal emptying rate in suckling calves

OBJECTIVE: To determine the effect of parenteral administration of erythromycin, tilmicosin, and tylosin on abomasal emptying rate in suckling calves. ANIMALS: 8 male Holstein-Friesian calves < 35 days old. PROCEDURES: Calves received each of 4 treatments in random order (2 mL of saline [0.9% NaCl] solution, IM [control treatment]; erythromycin, 8.8 mg/kg, IM; tilmicosin, 10 mg/kg, SC; and tylosin, 17.6 mg/kg, IM). Calves were fed 2 L of milk replacer containing acetaminophen (50 mg/kg) 30 minutes later. Jugular venous blood samples and transabdominal ultrasonographic abomasal dimensions were obtained periodically after suckling. Abomasal emptying rate was assessed on the basis of the time to maximal plasma acetaminophen concentration and ultrasonographic determination of the halftime of abomasal emptying. One-tailed Dunnett post tests were conducted whenever the F value for group was significant. RESULTS: Emptying rate was faster for erythromycin, tilimicosin, and tylosin than for the control treatment, as determined on the basis of time to maximal plasma acetaminophen concentration. Ultrasonography indicated that the half-time of abomasal emptying was significantly shorter for erythromycin than for the control treatment. Tylosin and tilmicosin accelerated the abomasal emptying rate, but not significantly, relative to the emptying rate for the control treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of erythromycin, tilmicosin, and tylosin at the label dosage increased abomasal emptying rate in calves. The clinical importance of an increase in abomasal emptying rate in cattle remains to be determined.     

Comparative disposition kinetics and plasma protein binding of gentamicin sulphate in three juvenile animal species

The pharmacokinetics of gentamicin was studied in lambs, calves and foals, respectively after single intravenous (i.v.) injections of 5 mg kg(-1) body weight. The plasma concentration-time curves of gentamicin sulphate were best fitted to follow a two-compartment open model in calves and foals and a three-compartment open model in lambs. Gentamicin showed high plasma level at 5 min post-injection. Then its concentration decreased gradually until its minimum detectable level at 10 and 12 h post-injection in foals and calves, respectively, was reached. In contrast, the plasma concentrations were much higher in lambs and persisted up to 48 h from the onset of injection. Values of pharmacokinetic parameters for gentamicin sulphate in different animals after i.v. injections were calculated. Pharmacokinetic data in lambs demonstrated a triphasic decline in plasma gentamicin concentration with slow terminal elimination phase (washout phase) with (t(1/2y)) of 7.7 h. Gentamicin showed a small volume of distribution Vd(ss) (80.3 ml kg(-1)) in lambs indicating that the drug is slightly distributed in extra-vascular tissues. The overall rate of total body clearance ClB in lambs was (0.46 ml kg(-1)) slower than in calves (1.5 ml kg(-1)) and foals (2.7 ml kg(-1)). In vitro protein binding per cent of gentamicin sulphate in plasma were 16.80, 11.03 and 7.98% in lambs, calves and foals. The results of this study emphasize the importance of determining the pharmacokinetics of gentamicin in each species of young animals separately.     

Pharmacokinetics of tylosin in broiler chickens

Biological availability and pharmacokinetic properties of tylosin were determined in broiler chickens after oral (p.o.) and intravenous (i.v.) administration at a dose of 10 mg/kg. The calculated bioavailability--F%, by comparing AUC values--p.o. and AUC--i.v., ranged from 30%-34%. After intravenous injection tylosin was rapidly distributed in the organism, showing elimination half-life (t1/2 beta) values of 0.52 h and distribution volume (Vd) of 0.69 L/kg, at a clearance rate (Cl) of 5.30 +/- 0.59 ml/min/kg. After oral administration, tylosin has a similar distribution volume (Vd = 0.85 L/kg), while the elimination half-life t1/2 beta of 2.07 h was four times bigger than after i.v. administration at Cl = 4.40 +/- 0.27 ml/min/kg. The obtained value tmax = 1.5 h for tylosin after oral administration indicates that using this antibiotic with drinking water in broiler chickens is the method of choice. However, a relatively low value Cmax = 1.2 micrograms/ml after oral administration of tylosin shows that dosing of this antibiotic in broiler chickens should be higher than in other food producing animals.     

Oscillatory measurements,blood gas analysis and clinical observations after intravenous clenbuterol administration in healthy and acutely pneumonic calves

The effects of clenbuterol (Ventipulmin, Boehringer Ingelheim) on respiratory functions were investigated in 6 calves aged 4–6 weeks prior to and after experimental infection withPasteurella haemolytica A1. On days 1–3 (prior to infection) and on days 7–9 (after infection), blood gas analysis, monofrequency forced oscillation techniques and clinical examinations (heart rate, respiratory rate) were conducted for 135 min after the intravenous administration of clenbuterol (0.8 µg/kg body weight). In healthy calves prior toPasteurella infection, intravenous administration of clenbuterol induced a mild tachycardia and a reduction in the mean oscillatory respiratory resistance. Using the same dose of clenbuterol in diseased calves after infection, the statistically significant reduction in oscillatory respiratory resistance was more impressive and it was accompanied by a significant increase in the oxygen pressure of the arterialized blood. Heart rate and respiratory rate did not change significantly after the administration of clenbuterol in infected calves.Abbreviations HR heart rate - IV intravenous - MFOT monofrequency forced oscillation technique - PaO₂ arterial oxygen pressure - R_os oscillatory resistance - RR respiratory rate