Interacción in vitro de la microbiota vaginal en ovejas y la viabilidad espermática del semen ovino fresco

Abstract

The vaginal microbiota plays a fundamental role in maintaining the homeostasis of the reproductive tract and fertility in animals. In sheep, its composition differs from that described in other widely studied species in which lactobacilli are abundant, which is associated with particular physiological characteristics of sheep, such as a near-neutral vaginal pH. Despite its importance, available information on the ovine vaginal microbiota, particularly its in vitro interaction with male ovine germplasm, remains limited. This non-experimental and exploratory study aimed to determine the technical conditions required to establish an in vitro interaction between the vaginal microbiota of ewes and the sperm viability of fresh ram semen. Based on this approach, an anaerobic isolation protocol using MRS medium was developed to recover native vaginal microbiota with potential applications in reproductive biotechnologies involving semen handling. Furthermore, the use of alternative extenders, such as coconut water and UHT milk, together with seminal extenders, was shown to simultaneously preserve bacterial and sperm viability under the experimental conditions evaluated. Finally, phenotypic characterization confirmed the isolation of native strains from the vaginal microbiota, while evaluation using the CASA system showed that the interaction between the microbiota and semen did not compromise sperm quality. Overall, these findings provide a methodological basis for future research on microbiota–semen interactions in reproductive biotechnology protocols in sheep. Keywords: Coconut water; CASA; UHT milk; eubiotic vaginal microbiota; MRS