Effect of metaphylactic administration of tildipirosin on the incidence of pneumonia and otitis and on the upper respiratory tract and fecal microbiome of preweaning Holstein calves

The objectives of this study were to evaluate the effect metaphylactic use a semi-synthetic long-acting macrolide (tildipirosin) on prevention pneumonia and otitis in preweaning Holstein calves, as well its effects microbiome their upper respiratory tract (URT) feces. Newborn healthy heifers, collectively housed, randomly allocated 1 2 treatment groups: (TRT; n = 932) or control (CTR; 927). Calves TRT group received single subcutaneous injection 4 mg/kg tildipirosin (Zuprevo, Merck Animal Health) at 7 ± d life. CTR no drug injection. All enrolled calves evaluated from 63 3 life (weaning age) monitored daily for any adverse health events during period. Daily physical examination was performed diagnose otitis, body weight measured weekly all animals. From selected subset 217 blood samples biochemical variables analysis swabs collected URT rectum nasal fecal microbiome, respectively, via next-generation sequencing 16S rRNA gene. Total bacterial load using quantitative PCR. In addition, another 26 more intensive sampling investigate short-term administration microbiome. We general mixed linear models logistic regression analyze continuous binary outcomes, respectively. Tildipirosin metaphylaxis reduced incidence (CTR 47.03%; 37.55%) tended reduce 20.71%; 17.38%) overall mortality risk 6.69%; 4.94%). observed significant differences between groups due 0.86%; 0.97%) 2.05%; 1.39%). had higher average gain than group. Furthermore, total load, genus, phylum groups. However, microbiota, we decrease compared week after decreased mean relative abundance genera Mannheimia, Moraxella, Pasteurella but significantly increased Mycoplasma. Although positive Mycoplasma, it important pathogenic bacteria otitis. can be suitable strategy farms with high prevalence disease.