333 Awardee Talk: Navigating the bovine neonatal microbiome: Insights into inoculation, maternal sources, and immunological influence

As research delves into the intricacies of the bovine reproductive tract microbiome, a paradigm shift is occurring, moving away from viewing the microbiome as a detached entity to recognizing it as a dynamic system intricately regulated and fluctuating in tandem with host physiology. This study investigates the effects of physiological insults before parturition on microbial composition and immune responses, with a particular focus on dam-neonate interactions. Authors aimed to elucidate the microbial community composition of the bovine dam vaginal and calf nasal tract post-partum after using betadine lavages (BL). The dam vaginal and calf nasal microbial communities and immune responses were evaluated on 0-, 15-, 30- and 60-d post-partum. Microbiota composition of the dam haircoat, udder, and immunoglobulins (IgG) in the colostrum and calf sera were also evaluated on d 0. The physiological impact of serial BL before parturition did not alter the alpha diversity of the dam vaginal microbiota but had a notable impact (P = 0.03) on the calf nasal microbiota at parturition. Furthermore, dams subjected to BL exhibited increased (P = 0.04) colostrum IgG concentrations compared with control (CON) dams, indicative of an augmented immune response due to the physiological insult of BL before parturition. This finding iterates the plasticity of the reproductive tract microbiome composition, despite a rapid return to a characteristically normal community, physiological effects from the insult were still evident. The beta diversity of the calf nasal microbiota showed differences (P < 0.01) on d 0 compared with all other timepoints. Interestingly, on d 15, the alpha and beta diversity of calves were altered (P > 0.05) compared with d 0, but the community remained similar (P = 0.38) on day 30 post-partum, until undergoing another compositional shift (P < 0.01) on d 60, which was distinct from all other timepoints. The identification of these apparent reinoculation timepoints between 0 to 14 and 30 to 60 d of age suggests a secondary role of timing in shaping neonatal microbial communities, which could be significant for early interventions to alter neonatal microbiome development and health outcomes. The calf nasal microbiota was different from the dam vaginal microbiota at all timepoints post-partum, regardless of treatment. These findings are indicative of a clear divergence in the calf nasal microbiota from the theoretical inoculating community of the dam vaginal tract on d 0. This unexpected finding may be linked to the maturation of the calf immune system. In conclusion, this study reveals the complex interplay between host physiology and microbiome dynamics in beef cow-calf relationships, paving the way for targeted research aimed at optimizing post-partum cow-calf health by investigating the relationship between the existing microbiome, microbial inoculations, and subsequent immune system development in neonates.