Effect of alternative synchronisation treatments on the vaginal microbiota of ewes and their impact on pregnancy rate

Abstract

The low pregnancy rate by artificial insemination in sheep represents a fundamental challenge for breeding programmes. In this species, estrous synchronization is done by manipulating hormonal regimens through the insertion of progestogens in intravaginal sponges, which may alter the vaginal microbiota and the success of artificial insemination. In this study, we analysed the microbiome of 94 vaginal swabs from 47 ewes with alternative treatments applied to the progesterone-releasing intravaginal devices, in two sample periods (before and after removing the devices) using nanopore-based metagenome sequencing. A lower abundance of the genera Neisseria (Proteobacteria) and Oenococcus (Firmicutes) was observed in pregnant compared to non-pregnant ewes. Although differences between treatments were not detected, the progestogen of the synchronization devices seemed to increase the alpha-diversity and decrease the abundance of harmful microorganisms belonging to Gammaproteobacteria and Fusobacteriia classes, suggesting that progestogens may have a beneficial effect on vaginal microbiota favouring the artificial insemination success.