Effect of treatment of pneumonia and otitis media with tildipirosin or florfenicol + flunixin meglumine on health and upper respiratory tract microbiota of preweaned Holstein dairy heifers

摘要

The objective of this randomized clinical study wasto compare the effect of 2 antimicrobial interventions,tildipirosin or florfenicol + flunixin meglumine, usedfor treatment of pneumonia and extralabel treatmentfor otitis on health parameters and upper respiratorytract (URT) microbiota of preweaned Holstein calves.Housed preweaned Holstein heifers diagnosed witheither otitis or pneumonia were assigned into 1 of 2treatment groups, receiving a single subcutaneous injectionof either 4 mg/kg of tildipirosin (TLD; n = 444)or 40 mg/kg of florfenicol combined with 2.2 mg/kg ofa nonsteroidal anti-inflammatory, flunixin meglumine(FLF; n = 442). Calves were enrolled and treated onthe day of diagnosis of the first case of pneumonia orotitis. If a calf had a recurrent case, the opposite drugwas administered, respecting an interval of 5 d betweendrug injections. Blood samples for leukocyte countswere collected at 0, 2, 4, and 6 d after treatment, andrectal temperature was measured daily during the 5 dafter treatment. Ear scores were observed from calveswith otitis. Additionally, swabs of the URT were collectedfrom a subset of 20 calves in each treatmentgroup at d 0, 3, 6, 9, and 11 following enrollment foranalysis of URT microbiota through next-generationsequencing of the 16S rRNA gene and quantitativePCR. Swabs were also collected from a comparativegroup of 20 healthy calves that did not receive anydrug. No differences were observed between groups forrecurrence risk of either pneumonia (TLD = 32.4%;FLF = 29.7%) or otitis (TLD = 72.7%; FLF = 73.6%).Similarly, no differences were observed for the totalnumber of treatments for pneumonia (TLD = 1.45;FLF = 1.42) or otitis (TLD = 2.96; FLF = 3.07). Onthe other hand, both drugs reduced rectal temperature,ear scores, and leukocyte counts, with FLF calves havinga greater reduction in rectal temperature within4 d after treatment. Both TLD and FLF reducedthe total bacterial load when compared with healthyuntreated calves, but no differences were observed betweentreatment groups. Furthermore, compared withthe untreated group, treated calves had lower meanrelative abundances (MRA) of the genera Mannheimia,Moraxella, and Pasteurella within 11, 9, and 3 d aftertreatment, respectively; however, no significant differenceswere observed between TLD and FLF. On theother hand, MRA of Mycoplasma was not decreased byboth treatments compared to untreated animals, and ahigher MRA was observed in the TLD group during 11d after treatment in comparison to FLF and untreatedcalves. Based on this data, we concluded that bothdrugs used in the study were effective in reducing rectaltemperature, ear scores, leukocyte counts, and MRA ofthe genera Mannheimia, Pasteurella, and Moraxella inthe URT, and calves treated with FLF had a greaterreduction in rectal temperature.