Syringe-feeding as a novel delivery method for accurate individual dosing of probiotics in rats.

Probiotic administration to rodents is typically achieved using oral gavage or water bottles, but both approaches may compromise animal welfare, bacterial viability, dosing accuracy, or ease of administration. Oral gavage dosing may induce stress, especially when given daily over several weeks, and cannot be performed by inexperienced personnel. Delivery in water bottles does not take multiple co-housed animals into account, leading to inaccurate dosing of individual rats. Moreover, slow consumption of the solutions over several hours may lead to variability in bacterial stability, and potential leftovers or clogging of the bottle further threaten the reliability of this method. To date, no method has been described that can provide non-stressful precise dosing of probiotics or prebiotics in individual rats. In accordance with the 3R principles (replace, reduce, refine), we propose syringe-feeding as a refinement method for simple yet accurate administration of probiotics. Animals hereby voluntarily consume the solution directly from a syringe held into their home cage, thereby enabling controlled dosing of individual animals. This method requires a short training phase of approximately 3 days, but is very fast thereafter, only taking seconds per rat. Since studies using probiotics are usually long-term experiments, we consider syringe-feeding the most appropriate probiotic delivery mode available to date.