Evaluation of the local tolerance and systemic safety of a novel intravaginal probiotic product in cows.

Since its discovery, the microbiota has been increasingly recognised for its role in maintaining health and contributing to various disease conditions. In the reproductive tract, microbial populations can significantly influence endometrial health, internal homeostasis, and fertility. The preservation or restoration of a balanced microbiota through appropriate probiotic products may support reproductive health; in addition, candidate probiotics must be demonstrated to be safe for use. The aim of this study was to assess the local tolerance and systemic safety of a novel intravaginal probiotic product in cows. Twenty-four animals were enrolled and assigned to four groups: single-dose, three-, and five-fold dose of the test product, and a placebo group receiving excipients only. Physical examination and evaluation of the vaginal mucosa were conducted prior to each treatment, one day after and one and two weeks after the final probiotic administration. Blood and urine samples were collected before treatment and following treatment: one day after the last administration of intravaginal probiotic and again two weeks post-treatment. Blood haptoglobin, serum amyloid A, glucose, non-esterified fatty acids, and beta-hydroxybutyrate were measured to assess inflammatory and metabolic responses, and differences over time and between groups were statistically analysed. No dose-dependent systemic changes were observed; however, transient, time-related alterations were noted across all groups, including controls. The investigational probiotic product was well tolerated both locally and systemically, with tolerability comparable across all groups, including the placebo. These data establish a safety profile in healthy cows and support further investigation of this product in studies focusing on efficacy and microbiome modulation.