Inhibition of Babesia divergens in cattle by oxytetracycline

The effects of continuous oxytetracycline administration on the development of parasitaemia of Babesia divergens during both natural and artificial infections were studied. During natural exposure on grazing heavily infested with Ixodes ricinus, seven out of 42 cattle with no previous exposure to tick-borne diseases were injected every four days with a long acting preparation of oxytetracycline at a dose rate of 20 mg/kg. During the six week grazing period 21 untreated cattle developed a patent parasitaemia of B divergens and all became seropositive by the fluorescent antibody test. In contrast, no parasites were observed in treated cattle and antibody titres remained low. Artificial infections were studied with different dose levels of oxytetracycline and their effects on antibody stimulation noted. First, four groups of cows were infected with 10(8) erythrocytes infected with B divergens, three groups being injected every four days with the long acting oxytetracycline formulation at dose levels of 20, 10 and 5 mg/kg, respectively. The highest level completely inhibited parasite replication and antibody formation; the same was observed in one animal dosed at 10 mg/kg but the remainder, plus those treated at 5 mg/kg, developed both low parasitaemia and high antibody titres. The untreated cows developed severe babesiosis. A further untreated control group was added and three weeks after cessation of oxytetracycline treatment all were infected with 10(9) erythrocytes infected with a homologous isolate of B divergens. The controls, plus those in which the previous infection had been completely inhibited, developed severe clinical babesiosis but the remainder were refractory to parasite development.     

Long-acting oxytetracycline prophylaxis to protect susceptible cattle introduced into an area of Kenya with endemic East Coast fever

Two field trials were carried out in successive years at the Ngong Veterinary Farm, Kenya, in which young cattle, previously unexposed to tick-borne diseases, were introduced into an area with endemic East Coast fever while protected by a series of injections of a long-acting oxytetracycline. In 1984, 12 animals which received injections of 20 mg/kg of the drug on days 0, 7, 14 and 21 after introduction, together with 12 untreated controls, were exposed without tick control until clinical disease occurred. All 12 control animals contracted East Coast fever by day 24 and 10 of them died. Five of the 12 injected animals had detectable parasites, and one of them required antitheilerial treatment. In 1985, four groups of 10 calves were introduced. One group received injections of 20 mg/kg of oxytetracycline on days 7 and 14, one group received injections on days 7, 14 and 21, and a third group received injections on days 7, 12 and 17; the fourth group (controls) had no treatment until clinical disease occurred. By day 35 all the control animals had contracted the disease and one had died despite antitheilerial treatment. Three injections of oxytetracycline suppressed the disease so that mild reactions occurred in only four animals in each group, but two injections failed to prevent severe reactions in two animals and mild reactions in four others.(ABSTRACT TRUNCATED AT 250 WORDS)     

Treatment of virulent footrot with lincomycin and spectinomycin

A mixture of lincomycin and spectinomycin was investigated as a treatment for footrot in sheep. In a controlled clinical trial 92.5% of acute and chronic cases of virulent footrot were cured following a single intramuscular injection of a mixture containing 50 mg lincomycin and 100 mg spectinomycin/ml at a dose rate of 1 ml/10 kg bodyweight. No improvement in clinical response was observed in groups of sheep treated on 3 successive days with this dose rate nor in another group treated once at a dose rate 1 ml/3.3 kg bodyweight. Cure effectiveness of each of the 3 treatment groups relative to untreated controls was 89%, 95% and 95%. Efficacy of lincomycin/spectinomycin was compared with that of penicillin/streptomycin in the treatment of footrot on 2 farms in south western New South Wales. Assessments made 14 to 17 d after treatment showed that on one farm all 122 ewes treated with lincomycin/spectinomycin had recovered while 170 of 175 ewes treated with penicillin/streptomycin recovered in the same period. On the second farm 87 of 90 ewes treated with lincomycin/spectinomycin recovered, compared with 184 of 190 sheep in the same flock treated with penicillin/streptomycin. Supportive footbathing did not seem to improve the clinical response in either treatment group and the paring done was sufficient only to establish diagnosis and to remove grossly overgrown horn.     

Successful therapy of balantidiosis of pigs with acetarsol and oxytetracycline

Severe clinical balabtidiosis in 2-month old piglets was treated with acetarsol alone and acetorsol in combination with oxytetracycline. Three groups of 15 animals each were used in this trial. Group 1 received acetarsol at a dose rate of 20 mg/kg body weight orally once daily for 4 days. Group 2 received acetarsol as group 1 plus oxytetracycline at a dose rate of 15 mg/kg body weight orally in feed concentrate twice daily for 4 days. Group 3 animals served as non-treated controls. As judged by clinical and parasitological examinations, acetarsol was found to be 85.7% effective and the combination of acetarsol and oxytetracycline 100% effective. No sign of intolerance or toxicity was observed.     

In vitro action of combinations of antimicrobial agents and EDTA-tromethamine on Pseudomonas aeruginosa

Combinations of EDTA-tromethamine and 7 antimicrobial agents (chloramphenicol, nalidixic acid, oxytetracycline, penicillin, polymyxin-B, streptomycin, and triple sulfa) were tested for synergistic activities against Pseudomonas aeruginosa. Three in vitro tests were used, including minimal inhibitory concentrations of the drugs, a 2-dimensional Microtiter checkerboard technique, and bacterial inhibition studies. A synergistic inhibitory action was observed with combinations of EDTA-tromethamine plus penicillin and EDTA-tromethamine plus oxytetracycline. When chloramphenicol, streptomycin, nalidixic acid, polymyxin-B, or triple sulfa was mixed with EDTA-tromethamine, synergistic action did not occur.     

Pharmacokinetic changes of several antibiotics in chickens during induced fatty liver

The concentrations of five antibiotics (erythromycin, lincomycin, penicillin G, streptomycin and oxytetracycline) were determined in chicken serum before and after induced fatty liver. The pharmacokinetic variables were calculated according to the obtained data. The crossover trial design involved 10 chickens for each antibiotic. The fatty liver was produced by oestradiol-dipropionate injections and monitored by serum malic enzyme activity determinations. Protein binding of the respective antibiotics was determined in vitro in the serum obtained from normal and oestrogen-treated birds. Induction of fatty liver caused several changes in the determined variables. The measured peak concentrations were higher for lincomycin and erythromycin and lower for penicillin and oxytetracycline while streptomycin remained unchanged. The peak concentration of streptomycin appeared earlier and the peak of oxytetracycline later than in the normal chickens. The elimination half-lives were shorter for erythromycin, lincomycin and streptomycin and increased for penicillin and oxytetracycline. The area under the concentration curve (AUC) decreased for erythromycin, penicillin and streptomycin, increased for oxytetracycline and remained unchanged for lincomycin. The body clearance (ClB/f) and the apparent specific volume of distribution (Vd(area'/f) were considerably changed in association with fatty liver induction. Since the fraction of the drug absorbed (f) is not known, it can only be speculated that changes in distribution rather than reduced liver function altered the kinetics. The protein binding was decreased for all the antibiotics, but this did not seem to be the reason for changes in kinetics, except perhaps in the case of penicillin.     

Use of long-acting oxytetracycline against pasteurellosis in lambs

The efficacy of long-acting oxytetracycline in the control of pneumonic pasteurellosis in lambs was tested on seven Scottish farms. After laboratory confirmation of pasteurella-related deaths in lambs, half the lambs in each flock were given long-acting oxytetracycline (20 mg/kg intramuscularly) and half were left untreated. On three farms a single treatment was given and on four farms two doses were administered four days apart. Eighteen of the 878 control lambs died as a result of confirmed Pasteurella haemolytica pneumonia compared with one of the 878 treated lambs. In addition nine of the control lambs were diagnosed clinically to have pasteurellosis which responded to treatment with oxytetracycline. None of the treated lambs were seen to be ill during the trial.     

Efficacy of long-acting oxytetracycline for the prevention of tick-borne fever in calves

Twenty-six calves which had not previously grazed tick-infested pasture were divided into two equal groups. On May 26, 1988 (day 0) they were turned out into a field of rough grazing where cases of redwater fever had occurred the previous spring. Seven, 14, 21 and 28 days after the start of the trial the animals in one group each received an intramuscular injection of 20 mg/kg bodyweight of long-acting oxytetracycline. During the 60 days of the trial the animals received a severe tick-borne fever challenge, in some cases combined with a redwater fever challenge. An unforeseen complicating factor was the presence of animals persistently infected with bovine viral diarrhoea virus, present in almost equal numbers in both groups. At the end of the trial the treated group weighed on average 16 kg more than the control group, a difference which was attributed to the suppression of tick-borne fever by oxytetracycline.     

Factors associated with the effectiveness of antibiotic treatment for ovine virulent footrot

Factors associated with the proportion of sheep cured of virulent footrot after antibiotic treatment were studied in a field trial under dry environmental conditions. From 2 similar flocks, 1091 Merino sheep weighing about 50 kg and infected with virulent footrot received an intramuscular injection of either 12 mL of a mixture of penicillin (250 mg/mL) and streptomycin (250 mg/mL), 6 mL of long acting oxytetracycline (200 mg/mL) or 6 mL of a mixture of lincomycin (50 mg/mL) and spectinomycin (100 mg/mL). Variables that were significantly associated with the proportion of sheep cured were: the type of antibiotic used, the number of feet infected and the flock from which the sheep came. There was an interaction between antibiotic type and number of feet infected and between antibiotic type and flock in association with the proportion of sheep cured. The extent of paring and the occurrence of blowfly strike in footrot lesions treated with diazinon had no significant association with the proportion of sheep cured.     

Single-dose pharmacokinetics of oxytetracycline and penicillin G in tammar wallabies (Macropus eugenii)

McLelland, D.J., Barker, I.K., Crawshaw, G., Hinds, L.A., Spilsbury, L., Johnson, R. Single‐dose pharmacokinetics of oxytetracycline and penicillin G in tammar wallabies (Macropus eugenii). J. vet. Pharmacol. Therap. 34 , 160–167. The pharmacokinetics of oxytetracycline and penicillin G was investigated in tammar wallabies (Macropus eugenii). Groups of eight healthy tammar wallabies were administered i.v. oxytetracycline hydrochloride (40 mg/kg), i.m. long‐acting‐oxytetracycline (20 mg/kg), i.v. sodium penicillin G (30 mg/kg), or i.m. procaine/benzathine penicillin G (30 mg/kg). Plasma concentrations of oxytetracycline were determined using high‐performance liquid chromatography. Pharmacokinetic parameters were comparable to those reported for eutherians of equivalent size and suggest that the practice of adjusting allometrically scaled doses to account for the lower metabolic rate of marsupials may not be valid. Long‐acting oxytetracycline and penicillin G both demonstrated depot effects. However, the plasma concentrations achieved question the therapeutic efficacy of the long‐acting preparations.     

Enrofloxacin is able to control Toxoplasma gondii infection in both in vitro and in vivo experimental models

Currently, toxoplasmosis is treated with sulfadiazine and pyrimethamine. However, this treatment presents several adverse side effects; thus, there is a critical need for the development and evaluation of new drugs, which do not present the same problems of the standard therapy. Enrofloxacin is a fluoroquinolone antibiotic known to control infection against several bacteria in veterinary medicine. Recently, this drug has demonstrated protective effects against protozoan parasites such as Neospora caninum. The present study aimed to determine the effect of enrofloxacin in the control of Toxoplasma gondii infection. For this purpose, human foreskin fibroblast (HFF) cells were infected with T. gondii RH strain and treated with sulfadiazine, penicillin/streptomycin, pyrimethamine, or enrofloxacin. Following treatment, we analyzed the infection index, parasite intracellular proliferation and the number of plaques. Additionally, tissue parasitism and histological changes were investigated in the brain of Calomys callosus that were infected with T. gondii (ME49 strain) and treated with either sulfadiazine or enrofloxacin. Enrofloxacin was able to reduce the infection index, intracellular proliferation and the number of plaques in HFF cells infected by T. gondii in comparison with untreated or penicillin/streptomycin-treated ones. Enrofloxacin was more protective against T. gondii in HFF infected cells than sulfadiazine treatment (P<0.001). In addition, pyrimethamine, enrofloxacin or the associations of sulfadiazine plus pyrimethamine, enrofloxacin plus sulfadiazine or enrofloxacin plus pyrimethamine-treatments were able to reduce the plaque numbers in HFF cells infected by T. gondii when compared to medium, penicillin/streptomycin or sulfadiazine alone. In vivo experiments demonstrated that enrofloxacin diminished significantly the tissue parasitism as well as the inflammatory alterations in the brain of C. callosus infected with T. gondii when compared with untreated animals. Based on our findings, it can be concluded that enrofloxacin is a potential alternative drug for the treatment of toxoplasmosis.     

Antimicrobial resistance in streptococcal species isolated from bovine mammary glands

Streptococcal species isolated from dairy cows with clinical mastitis were obtained from mastitis research workers in Florida, Louisiana, New York, Vermont, Washington, and West Virginia. Seventy-one streptococcal isolates were tested, including 39 strains of Streptococcus agalactiae, 21 strains of S dysgalactiae, and 11 strains of S uberis. The minimal inhibitory concentration of erythromycin, lincomycin, oxytetracycline, penicillin, spectinomycin, streptomycin, and tetracycline was determined for each isolate. Differences were not detected among strains with respect to geographic origin. None of the strains was resistant to penicillin. Lincomycin was the next most effective antimicrobial, with only 2 resistant strains of each streptococcal species. There were no differences among the streptococcal species with respect to resistance to either penicillin or lincomycin. Streptococcus uberis was more likely to be resistant to erythromycin than were S agalactiae and S dysgalactiae (P less than 0.02). Streptococcus agalactiae and S uberis had similar distributions for resistance to oxytetracycline, tetracycline, spectinomycin, and streptomycin. Strains of S dysgalactiae were more likely to have intermediate resistance to oxytetracycline and streptomycin than were strains of S agalactiae and S uberis, which were highly resistant to oxytetracycline and streptomycin (P less than 0.001). Differences were not detected among the streptococcal species with respect to resistance to spectinomycin. Resistance to multiple antimicrobials was observed in all streptococcal species tested. Although S dysgalactiae appeared to have a greater percentage of strains (73%) that were resistant to multiple antimicrobials than did S agalactiae (31%) or S uberis (45%), differences were not statistically significant.     

Efficacy of long-acting oxytetracycline alone or combined with streptomycin in the treatment of bovine brucellosis

Twenty-nine Brucella abortus culture-positive cows were treated with a long-acting oxytetracycline (20 mg/kg of body weight, IM) alone or combined with streptomycin (25 mg/kg, IM or IV) or were re-treated with the same product. There appeared to be a synergism by the 2 drugs. Of 21 courses of treatment with the combined antibiotics, 14 (67%) were considered successful. Only 3 of 14 (21%) were successful using oxytetracycline alone. The period from onset of therapy to cessation of shedding in udder secretions was variable. Four cows that ceased shedding were culture-positive in tissues taken at slaughter. The titers on tube agglutination and complement-fixation tests were of limited value in short-term evaluations of therapeutic regimens.     

Evaluation of the comparative efficacy of a moxidectin plus triclabendazole pour-on solution against adult and immature liver fluke, Fasciola hepatica, in cattle

The objective of this study was to evaluate the efficacy of a pour-on solution containing moxidectin plus triclabendazole (MOX plus TCBZ) against immature and adult stages of the liver fluke in cattle and compare the efficacy with other commercially available preparations. To this end, 104 male Holstein-Friesian calves aged between 3 and 4 months, were randomly allocated to 13 groups of eight animals each, and infected with approximately 500 Fasciola hepatica metacercariae. One group remained untreated, four groups were treated with MOX plus TCBZ at a dose rate of 0.1mL/kg, four other groups were treated with ivermectin (IVM) plus clorsulon injectable at a dose rate of 0.02mL/kg, and the remaining four groups were treated with IVM plus closantel pour-on at a dose rate of 0.1mL/kg. Each treatment was applied to one of the groups at 4 weeks, 6 weeks, 8 weeks and 12 weeks after the experimental infection. At necropsy (99-102 days after infection), all untreated animals were infected with a minimum of 30 flukes. The MOX plus TCBZ treated animals had significantly (P<0.0001) lower fluke counts compared to the untreated control animals at all time points after treatment. Efficacy against 8-week old and adult flukes was >99.5%. For 6-week old immature fluke, the efficacy was 98.0% and for 4-week old immature fluke the efficacy was 90.9%. The IVM plus closantel pour-on treated animals had significantly lower fluke counts compared to the untreated control animals for adult and 8-week old flukes (P<0.0001), and for 6-week old flukes (P=0.002). The efficacy was 26.8%, 68.2%, 90.6% and 99.3% against 4-week, 6-week and 8-week old immature flukes, and adult flukes respectively. The IVM plus clorsulon treated animals had significantly lower fluke counts compared to the untreated control animals for adult (P<0.0001) and 8-week old (P<0.05) flukes. The efficacy was 29.7%, 43.4%, 53.2% and 99.2% against 4-week, 6-week and 8-week old immature flukes, and adult flukes respectively. For treatments at 4, 6 and 8 weeks after infection, the fluke counts were significantly (P<0.0001) lower for the MOX plus TCBZ treatment than for IVM plus closantel or IVM plus clorsulon. The results confirm the high efficacy (>90%) of the MOX plus TCBZ pour-on combination against 4-week old to adult liver fluke in cattle. The IVM plus closantel pour-on combination was effective (>90%) against 8-week old and adult flukes, but had low efficacy against 4- and 6-week old fluke. The IVM plus clorsulon injectable combination was effective (>90%) against adult fluke only.     

Bromocyclen poisoning in the dog.

An 18-week-old male German shepherd dog had a convulsion following the accidental ingestion of bromocyclen two hours previously. The dog then vomited and had a second convulsion. A pulse rate of 150 per minute and a respiratory rate of 54 per minute were recorded. The dog was treated with 2mg acepromazine and 0.6mg atropine administered intramuscularly (im) and repeated every four hours, 10ml of 20 per cent calcium borogluconate administered subcutaneously and 2ml penicillin and streptomycin im. Eighteen hours later, the respiratory rate was in excess of 60 per minute, and penicillin and streptomycin plus 2mg betamethasone were administered im. Only atropine was administered over the next 12 hours and then discontinued. Forty hours after the original convulsion, the respiratory rate had fallen to 30 per minute and the pulse rate to 84 per minute. A day later, the dog had fully recovered.     

'Pink eye' or 'zere oogjes' or keratoconjunctivitis infectiosa ovis (KIO). Clinical efficacy of a number of antimicrobial therapies

In a comparative study the clinical efficacy of five different treatments of keratoconjunctivitis infectiosa ovis (KIO) were tested, namely an intramuscular injection of chloramphenicol base (dosage 15 mg/kg), spiramycin base (Suanovil dosages 10 to 25 mg/kg), oxytetracycline (Engemycine Forte, Terramycin LA, dosages respectively 5 and 10 mg/kg), tiamulin (Dynamutulin, dosage 10 mg/kg) and subcutaneous injection of procaine penicillin G, benzathine penicillin G. and dihydrostreptomycin in the lower eyelid. It appeared from these field trials that spiramycin base, oxytetracycline and tiamulin had a clearly positive effect on the clinical course of 'pink eye', although with tiamulin there was only a temporary effect (high percentage of relapses). In view of the field data the following dosage schemes are, for the time being, advised: spiramycin base (Suanovil), and oxytetracycline (formulation with a good biological availability) both 20 to 30 mg/kg and, if necessary, to be repeated on days 5 and 10 after the first intramuscular injection. The dosage scheme advised for tiamulin is 20-30 mg/kg to be repeated on day 3 and if necessary on days 6 and 9 after the intramuscular injection. In mild cases it is sufficient to rub the eyes with for example oxytetracycline eye-ointment, a few times a day.     

Effect of oxytetracycline therapy on experimentally induced pneumonic pasteurellosis in lambs

Two groups of 10, specific pathogen free lambs were injected with a long acting oxytetracycline preparation at a dose rate of 20 mg/kg either 24 hours before or 24 hours after exposure to an aerosol of Pasteurella haemolytica. When compared with the response of similarly infected but untreated lambs, the effect of pretreatment was to postpone the appearance of clinical signs of pneumonia for four days and the deaths of five lambs for five to six days post infection, by which time seven untreated lambs had died. Treatment 24 hours after infection caused a rapid clinical recovery which persisted until six days after infection but two treated lambs died seven days after infection. Lung lesions in the group treated after infection were significantly less extensive than those in the untreated lambs.     

Persistence of transferable drug resistance in the lactose-fermenting enteric flora of swine following antimicrobial feeding.

Six groups of swine (85 animals) were fed a combination of antimicrobial drugs (sulfamethazine 100 g/ton, chlortetracycline 100 g/ton and penicillin 50 g/ton). After two weeks the antimicronial drugs were removed from the diet of two groups (28 animals). These swine were compared to four groups fed the medicated diet to determine the effect of duration of treatment and degree of animal isolation on the persistence of resistance in lactose-fermenting enteric organisms. The degree of resistance to penicillin, oxytetracycline, dihydrostreptomycin and neomycin as determined by minimum inhibitory concentrations and the incidence of resistant organisms were examined during and after antibiotic feedings. Ninety-two percent or greater of all isolates tested during and after treatment had minimum inhibitory concentrations for oxytetracycline of greater than 100 mug/ml. Thirty-two weeks after cessation of dietary antibiotic, resistance to oxytetracycline and dihydrostreptomycin remained at 100% and 89% respectively. Variation in degree of contact between swine receiving medicated feed and those receiving nonmedicated feed was not sufficient to reduce the incidence of resistance to oxytetracycline or dihydrostreptomycin in all animals. Factors influencing persistence of resistant enteric organisms are discussed. Addition of the antimicrobials to the ration resulted in significantly greater weight gains for treated animals than for the controls but did not alter feed conversion.     

Use of long-acting oxytetracycline in the immunisation of cattle against Babesia bovis and B bigemina

Forty Friesian one-year-old calves were vaccinated simultaneously with live Babesia bovis and B bigemina vaccines. Three groups of 10 calves each were treated with two, three or four doses of 20 mg kg-1 long-acting oxytetracycline (OTC/LA) at six- to seven-day intervals starting from day 6 after vaccination. Ten animals remained untreated. The treated calves showed considerably fewer days of patency and higher packed cell volumes than the vaccinated untreated calves. All calves developed serum antibodies to both parasites following vaccination. Five months later the 40 vaccinated and 30 new calves were challenged with syringe-transferred virulent parasites of both species. The vaccinated calves showed no parasites or clinical manifestations while calves of the new group exhibited severe clinical babesiosis. These results show that when OTC/LA is administered following anti-babesial vaccination, parasitaemia and red blood cell destruction are significantly reduced without, however, inhibiting the development of immunity.     

An evaluation of the relative efficacy of a new formulation of oxytetracycline for the treatment of undifferentiated fever in feedlot calves in western Canada

A field trial was performed under commercial feedlot conditions in western Canada to compare the efficacy of a new formulation of long-acting oxytetracycline (LA 30) to a standard long-acting oxytetracycline formulation (LA 20) and florfenicol (FLOR) for the treatment of undifferentiated fever (UF) in calves that received metaphylactic tilmicosin upon arrival at the feed-lot. Seven hundred and ninety-seven recently weaned, auction market derived, crossbred, beef calves suffering from UF were allocated to 1 of 3 experimental groups as follows: LA 30, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at the rate of 30 mg/kg body weight (BW) at the time of allocation; LA 20, which received intramuscular long-acting oxytetracycline (200 mg/mL formulation) at the rate of 20 mg/kg BW at the time of allocation; or FLOR, which received intramuscular florfenicol administered at the rate of 20 mg/kg BW at the time of allocation and again 48 hours later. Two hundred and sixty-six animals were allocated to the LA 30 group, 265 animals were allocated to the LA 20 group, and 266 animals were allocated to the FLOR group. The relative efficacy of the LA 30 group, as compared with the LA 20 and FLOR groups, was assessed by comparing relapse, chronicity, wastage, and mortality rates. The overall mortality (RR = 0.50) rate in the LA 30 group was significantly (P < 0.05) lower than in the LA 20 group. However, the overall chronicity (RR = 2.56) and overall wastage (RR = 6.97) rates of the LA 30 group were significantly (P < 0.05) higher than in the LA 20 group. There were no significant (P > or = 0.05) differences in UF relapse rates or cause specific mortality rates between the LA 30 and LA 20 groups. In the economic analysis, there was an advantage of $28.59 CDN per animal in the LA 30 group compared with the LA 20 group. The overall chronicity (RR = 2.25) and overall wastage (RR = 2.80) rates of the LA 30 group were significantly (P < 0.05) higher than the FLOR group. There were no significant (P > or = 0.05) differences in UF relapse rates, overall mortality rates, or cause specific mortality rates between the LA 30 and FLOR groups. In the economic analysis, there was an advantage of $12.90 CDN per animal in the LA 30 group compared with the FLOR group. In summary, the results of this study indicate that it is more cost-effective to use a new formulation of long-acting oxytetracycline (300 mg/mL formulation administered at a rate of 30 mg/kg BW) than a standard long-acting oxytetracycline formulation (200 mg/mL formulation administered at a rate of 20 mg/kg BW) or florfenicol for the treatment of UF in feedlot calves that have previously received metaphylactic tilmicosin upon arrival at the feedlot.