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

Abstract

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.

Probiotics Affect One‐Carbon Metabolites and Catecholamines in a Genetic Rat Model of Depression

“…The probiotic and vehicle solutions were freshly prepared just before administration by dissolving the respective weight of the powder in tap water (vehicle: 6 g in 9 mL water, daily dose per rat: 0.2 g; low‐dose probiotics: 0.4 g in 6 mL water, daily dose per rat: 0.02 g; high‐dose probiotics: 4 g in 6 mL water, daily dose per rat: 0.2 g). Rats received the intervention dose dissolved in a total volume of 0.3 mL administered via syringe‐feeding (i.e., consuming the probiotics directly from a syringe held into their cage) once daily toward the end of the active phase (2 p.m. ± 1 h) over the 10‐week treatment period. Animal weight as well as water and food intake (per 100 g bodyweight) were recorded throughout the study.…”

Ingestion of probiotic (Lactobacillus helveticus and Bifidobacterium longum) alters intestinal microbial structure and behavioral expression following social defeat stress

“…Hamsters received either the probiotic intervention or placebo for 14 days prior to the behavior experiment and throughout testing for a total treatment length of 21 days. Each day, hamsters were given 0.3 mL of the appropriate solution by syringe feeding 69 , which all animals readily ingested, at the start of the active phase of the daily activity cycle.…”

Minocycline-induced microbiome alterations predict cafeteria diet-induced spatial recognition memory impairments in rats

“…Minocycline hydrochloride (Chemlin, China; 40 mg/kg/ day) was delivered via daily syringe feeding 31,32 . Minocycline was suspended in vehicle (golden syrup; CSR Sugar, Australia; diluted to 20-35% sucrose solution with water) immediately before administration.…”