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  • Author or Editor: G. D. Mechor x
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A milking herd consisting of 55 Holstein cows had experienced abortions in several cows, as well as congenital malformations in 1 newborn calf. Bovine viral diarrhea virus was isolated from blood mononuclear cell samples obtained from several cattle, documenting 1 acute infection and 8 persistently infected carriers identified by clinical appearance and laboratory testing. Initial suspicion of persistently infected status in some, but not all animals, was facilitated by poor growth rates in some calves. Virus isolation was performed on transtracheal wash fluid obtained from acutely and persistently infected cattle with respiratory tract infection. We describe the measures taken to identify and characterize the infecting virus strain, and the series of actions taken to identify and eliminate persistently infected carriers in a herd experiencing several related problems that were shown to be caused by bovine viral diarrhea virus.

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in Journal of the American Veterinary Medical Association


To compare the effect of a single parenteral injection of tilmicosin with that of a single dose of a long-acting oxytetracycline as treatment in the early stages of naturally acquired undifferentiated respiratory tract disease in young dairy calves.


Prospective clinical trial, randomized block design.


40 dairy calves.


78 calves from 5 farms were examined weekly until 3 months old. When respiratory tract disease was diagnosed by a veterinarian, the calf was assigned to 1 of 2 treatment groups. Transtracheal wash samples were acquired to characterize the pathogens. The veterinarian, who was unaware of treatment assignments, examined calves for 3 days after treatment and evaluated severity, using a scoring system. Growth rates were measured.


On the basis of response to initial treatment, relapse rates, and effect on growth rates, the antibiotics were determined to be equally effective. Severity of clinical disease was significantly (P < 0.03) less for the tilmicosin-treated calves on days 2 and 3 after treatment. Findings from analysis of transtracheal wash samples indicated Pasteurella multocida (25/40), P haemolytica (4/40), Haemophilus somnus (4/40), Actinomyces pyogenes (3/40), and Aspergillus sp (2/40). Mycoplasma was isolated in association with bacterial isolates in 22 calves.

Clinical Implications

Tilmicosin and oxytetracycline are effective in treatment of respiratory tract disease in young calves, even when Mycoplasma spp are involved. Tilmicosin is more effective in resolving clinical signs. Early treatment of dairy calves with respiratory tract disease may decrease detrimental effects on growth.

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in Journal of the American Veterinary Medical Association


A double-blinded randomized prospective clinical trial was designed to evaluate the effectiveness of flunixin meglumine and phenylbutazone for treatment of acute toxic mastitis in dairy cows. All cows were treated 4 times at 12-hour intervals by intramammary infusion of gentamicin (150 mg). A total of 45 dairy cows with toxic mastitis were randomly assigned to 1 of 3 treatment groups: group 1 (control), saline solution, iv; group 2,1 g of flunixin meglumine, iv; or group 3, 4 g of phenylbutazone, iv. Physical examination and udder variables were assessed at initial examination and 24 hours later. Milk production was recorded at regular intervals from 1 week before until 10 weeks after development of mastitis.

Rear quarters (34/45) were more commonly affected than front quarters. Thirty-five cows returned to the herd, 9 cows were culled, and 1 cow died. There were no significant differences among treatment groups in the need for further treatment or outcome. Klebsiella spp (18/45) and Escherichia coli (16/45) were the most common pathogens isolated by culture of milk from affected quarters. The overall bacteriologic cure rate on days 7 and 14 was 64 and 75%, respectively.

At the time of initial examination, cows of the control group had higher rectal temperature than did cows of the flunixin group. At the examination 24 hours later, the rectal temperature of cows in all treatment groups was lower than the temperature at initial examination; at that time (24 hours), however, there were no significant differences in temperature among the treatment groups.

Adjusted for stage of lactation, calving season, and parity, mastitic cows, compared with nonmastitic cows from the same herd, had lower milk production in the 10 weeks after development of mastitis, particularly during the week of onset. In repeated measures models, the loss of milk associated with mastitis was not significantly different among the 3 treatment groups.

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in American Journal of Veterinary Research


Objective—To determine associations between in vitro minimum inhibitory concentrations (MICs) of tilmicosin against Mannheimia haemolytica and Pasteurella multocida and in vivo tilmicosin treatment outcome among calves with clinical signs of bovine respiratory disease (BRD).

Design—Observational, retrospective, cohort study.

Animals—976 feeder calves with clinical signs of BRD enrolled in 16 randomized clinical trials.

Procedures—Records of clinical trials from October 26, 1996, to November 15, 2004, were searched to identify calves with BRD from which a single isolate of M haemolytica or P multocida was identified via culture of deep nasal swab samples prior to treatment with tilmicosin (10 mg/kg [4.5 mg/lb], SC) and for which MICs of tilmicosin against the isolate were determined. The MICs of tilmicosin against recovered isolates and response to tilmicosin treatment were evaluated.

Results—Tilmicosin resistance among M haemolytica and P multocida isolates was uncommon (6/745 [0.8%] and 16/231 [6.9%], respectively). Treatment outcome, defined as success or failure after tilmicosin treatment, did not vary with the MIC of tilmicosin against recovered isolates. The proportion of treatment failures attributed to M haemolytica isolates categorized as resistant (MIC of tilmicosin, ≥ 32 μg/mL) or not susceptible (MIC of tilmicosin, ≥ 16 μg/mL), was 0.2% and 0.5%, respectively.

Conclusions and Clinical Relevance—Recovery of tilmicosin-resistant M haemolytica or P multocida isolates was rare, and no association was detected between MIC of tilmicosin and treatment response.

Full access
in Journal of the American Veterinary Medical Association