Editorial: Understanding the Female Reproductive Microbiome in Livestock

Nicholas Wege Dias ^*

• Kansas State University, Manhattan, United States

The current research topic (RT) focuses on the reproductive microbiome and features of the gastrointestinal microbiome that relates to reproduction of livestock species, including the cow, the sow, and the ewe. This RT encompasses the establishment of the reproductive microbiome following artificial insemination, the reproductive microbiome during gestation, and features of the microbiome related to birth complications and the postpartum period. This RT includes a review by Dias et al. exploring the dynamic interactions between the host and the microbiome, providing insights into the role of microbiota in promoting homeostasis and protecting the host from diseases, while highlighting findings from the rich literature on the human vaginal microbiome as template for reproductive microbiome studies and reviewing the literature of the bovine vaginal microbiome, exploring its relationships with fertility and reproductive diseases. Furthermore, it was originally believed that the uterus is a sterile environment and that introduction of microbes in this organ would result in pregnancy complications and reproductive diseases. Such concept of a sterile uterine environment has been challenged by recent studies. Featured in this RT, Moraes et al. explored whether the bovine uterine microbiome is established in virgin heifers following artificial insemination, a commonly used reproductive technology, or naturally by the acquisition of microbiota from the vagina and the cervix. In beef operations, estrous synchronization protocols (ES) are commonly adopted prior to artificial insemination to synchronize ovulations, thus enabling timed artificial insemination (TAI) to be performed on a large group of cows within the same day. Smith et al. explored both the vaginal microbiome composition change, and blood cytokine profile of Bos indicus beef cows during an ES and its relationships with conception rates to TAI. While achieving great conception rates is greatly desirable in livestock systems, pregnancies must be sustained to term, and complications during gestation can lead to pregnancy complications and abortion. In this RT, Cassas et al. longitudinally characterized the ewe vaginal microbiome throughout gestation by 16S rRNA sequencing, and Moraes et al. characterized the microbiome of several sites from the pregnant uterus and fetal membranes in Holstein dairy cows and heifers following slaughter through both sequencing and culture methods.Finally, complications during parturition, such as dystocia, pelvic organ prolapse, as well as postpartum reproductive diseases can compromise the reproductive efficiency of livestock systems, and not only affect offspring and dam survivability, but also the capacity of the dam to rebreed in a timely manner. Featured in this RT, Kiefer et al. categorized pregnant sows according to pelvic organ prolapse risk and characterized the fecal microbiome composition during late gestation and its correlations with vaginal microbiome and pelvic organ prolapse. Furthermore, Liu et al. explored the structure and function of the microbiome in several gastrointestinal sites and its relationship with energy metabolism and blood metabolite composition in dairy cows during the postpartum period, providing insights into temporal changes of metabolism during the postpartum period, which could inform novel dietary and management strategies during the postpartum period. Finally, Guo et al. utilized the lactic acid producing bacteria, Lactobacillus johnsonii isolated from uterine secretions of healthy dairy cows to engineer a recombinant Lactobacillus johnsonii, expressing bovine granulocyte-macrophage colonystimulating factor, and utilized a specific pathogen-free mice model to explore the effects of inoculating these strains during late-gestation in protecting uterine inflammation following an Escherichia coli challenge postpartum.The studies featured in this RT encompass significant scientific contributions from several authors towards the knowledge of reproductive microbiome in livestock species, addressing a myriad of reproductive processes that are relevant for livestock production, and highlighting the complex and important role the microbiome plays in reproductive health and efficiency.