Importance of the female reproductive tract microbiome and its relationship with the uterine environment for health and productivity in cattle: A review

Abstract

Once thought to be sterile, the reproductive tract microbiome has been characterized due to the transition from culture-dependent identification of bacteria to culture-independent sequencing methods. The urogenital microbiome was first identified in women through the Human Microbiome Project, which led to research in other species such as the bovine. Previous research focused on uterine bacteria associated with postpartum disease, but next generation sequencing methods identified a normal, healthy bacterial community of the reproductive tract of cows and heifers. Bacterial communities are now understood to differ between the uterus and vagina, and throughout the estrous cycle with changes in hormone dominance. In a healthy state, the bacterial communities largely interact with the uterine environment by assisting in maintaining the proper pH, providing and utilizing nutrients and metabolites, and influencing the immunological responses of the reproductive tract. If the bacterial communities become unbalanced due to an increase in potentially pathogenic bacteria, the health and fertility of the host may be affected. Although the presence of a reproductive tract microbiome has become widely accepted, the existence of a placental microbiome and in utero colonization of the fetus is still a popular debate due to conflicting study results. Currently, researchers are evaluating methods to manipulate the reproductive bacterial communities, such as diet changes and utilizing probiotics, to improve reproductive outcomes. The following review discusses the current understanding of the reproductive tract microbiome, how it differs between humans and cattle, and its relationship with the uterine environment.

Exploring the microbiome of two uterine sites in cows

“…There are studies in the female reproductive tract of cattle that showed variation by factors such as age, puberty, menstrual and estrous cycle 11 . In addition, samples were collected from different cows so we could have individual variation between samples and the correlation between UB and UH could be less clear.…”

“…Further studies can use the knowledge of our results that can lead to other analyses related to reproductive features such as the success of embryonic implantation. Furthermore, these studies could consider variables such as estrous cycle, and puberty 11 . As we know, to achieve successful implantation, the uterus should undergo structural and functional remodeling 49 .…”

“…These community dynamics vary throughout the estrous cycle. Understanding these dynamics is crucial for identifying prevention and treatment strategies for reproductive tract-related health issues 11 .…”

Holistic View and Novel Perspective on Ruminal and Extra-Gastrointestinal Methanogens in Cattle

“…However, culture-independent high-throughput sequencing technologies have enabled the identification of commensal microbiota presence in the bovine uterus both during pregnancy and after parturition [100]. The potential role of the uterine microbiome in reproductive health, conception, and embryo development is increasingly appreciated [87,101,102]. Within the bovine uterine microbial community, methanogenic archaeal species have been reported.…”