Evaluation of bacterial adsorption by ultrapure microporous carbon spheres in dairy cattle: From an in vitro adsorption assay to culture-based assessment of postpartum uterine bacteria.

The study evaluated the bacterial adsorption capacity of microporous carbon spheres (Carb) against E. coli suspension, and their potential to modulate culture-based uterine bacterial populations in postpartum dairy cows. In vitro, Carb reduced by 1-log the recoverable bacteria in the suspension. Dairy cattle were enrolled after calving and assigned to Carb or Control (Ctrl) group. A subset (Carb = 17; Ctrl = 20) was submitted to uterine flush at 14 and 28 days after calving (T14 and T28), for standard microbiology analysis. Three animals received antibiotic due to metritis (1 in Ctrl and 2 in Carb group). No significant difference was found in bacteria frequencies, logCFU counts, or vaginal discharge score (VD) at T14 and T28. A tendency towards lower mesophilic bacterial counts was observed in Carb cows at T14 (P = 0.085). Survival analysis using Cox proportional hazards regression revealed no effect of treatment, VD score or antibiotic administration on calving-to-conception interval (CCI). Likewise, Kaplan-Meier analysis showed no differences in fertility outcomes between groups. Although the adsorption capacity demonstrated in vitro did not translate into measurable microbiological or clinical effects in vivo, no detrimental effects on uterine health, fertility, or incidence of puerperal metritis were observed. These findings indicate that the activated carbon matrix was safe under the conditions tested, but insufficient to meaningfully modulate postpartum uterine bacterial populations. Future studies should focus on optimizing adsorption-based approaches for uterine health management in dairy cattle.