Postpartum compositional changes in bovine calf nasal and dam vaginal microbiota and concurrent immune responses following prepartum betadine lavages

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As interest in bovine reproductive tract microbial communities increases, there remains limited information on how the insult of parturition influences postpartum dam reproductive microbiota and early-life microbial development. The objective of this study was to characterize postpartum changes in dam vaginal microbiota and neonatal calf nasal microbiota following transient prepartum disruption of the dam vaginal microbiota using betadine lavages (BLGs), and to evaluate concurrent systemic immune responses in dams and calves. Multiparous beef cows (n = 12) were randomly assigned to either BLG (n = 7) or control (CON; n = 5) 3 wk prior to the expected calving date, and dam vaginal swabs, calf nasal swabs, and blood were collected at 0 (+1), 15 (±1), 30 (±1), and 60 (±1) d postpartum. Samples from Angus cow-calf pairs (n = 12) underwent 16S rRNA gene sequencing with standard contamination controls and QIIME2 processing. Blood samples were analyzed using the D2Dx immunity assay to evaluate systemic humoral immune responses. Microbial alpha diversity (ANOVA), Bray-Curtis beta diversity (PERMANOVA), taxonomic composition (LEfSe), and D2Dx immune responses (repeated-measures mixed model) were analyzed (P < 0.05). In calves, treatment influenced nasal alpha diversity at d 0 (P = 0.03), while nasal beta diversity tended to differ at d 0 (P = 0.08); however, treatment effects were not detected at d 15, 30, or 60 for alpha diversity (P ≥ 0.76) or beta diversity (P ≥ 0.14). Calf nasal communities shifted over time (P = 0.001), with d 0 differing from d 15, 30, and 60, and beta diversity differing over time (P = 0.006). In dams, BLG did not alter vaginal alpha diversity (P ≥ 0.42) or beta diversity (P ≥ 0.14) over time, and time did not affect vaginal alpha diversity (P = 0.60) while vaginal beta diversity tended to shift over time (P = 0.06). Postpartum dam vaginal and calf nasal communities differed compositionally regardless of time (P < 0.05). Systemic immune responses, measured via D2Dx scores, fluctuated postpartum in dams (day effect: P < 0.001) and calves (day effect: P < 0.001), with BLG calves tending toward decreased immune response compared with CON (P = 0.08). Prepartum BLG minimally influenced neonatal nasal microbial diversity at birth and did not alter postpartum dam vaginal community structure, while calf nasal microbiota and D2Dx immune responses changed markedly over the first 60 d of life.

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