Table 2.

A comparative analysis of the microbiota across diverse mammalian species and its influence on reproductive processes.

Aspect	Human	Non-human	Rate	Cattle, Sheep	Horse
Vaginal microbiota	Lactobacillus species dominate, with acidic pH aiding infection defense, while disruptions like bacterial vaginosis affect fertility (Olson et al., 2018).	A more diverse microbiota, less dependent on Lactobacillus, relies on immune adaptations for infection defense (Nuriel-Ohayon et al., 2016).	The vaginal microbiome shifts significantly during the estrous cycle, with reduced Lactobacillus dominance and a greater influence on mating behaviors (Miller et al., 2016).	Lactobacillus is less prevalent, with microbial shifts influenced by reproductive cycles. Infections like metritis reduce fertility (Santos and Bicalho, 2012).	In marsupials, pouch microbiota varies with reproductive architecture, while in horses, vaginal microbiome diversity impacts fertility (Chhour et al., 2010).
Seminal microbiota	A diverse microbiome influences sperm motility, with an overgrowth of bacteria like Enterococcus associated with male infertility (Jendraszak et al., 2024).	The seminal microbiome in non-human primates affects sperm quality, but it is less studied than in humans (Camargo et al., 2017).	Microbial imbalances in seminal fluid are less studied but can similarly affect sperm motility and reproductive success, as in humans (Bicalho et al., 2017).	The seminal microbiome influences sperm quality in animals, with homogeneous compositions linked to higher fertility (Castillo et al., 2015).	Microbial imbalances in horse seminal fluid can impair sperm motility and fertility, despite a diverse seminal microbiota composition (Al-Essawe et al., 2018).
Microbial changes during pregnancy	As gastrointestinal diversity decreases, Lactobacillus dominance in the vaginal microbiome rises. Dysbiosis may lead to preterm birth and preeclampsia (Koren, Goodrich, Cullender, Spor, Laitinen, Bäckhed, et al., 2012).	The vaginal microbiota in pregnancy changes more subtly than in humans, relying on immune system regulation (Weichhart et al., 2015).	Gut and vaginal microbiota shifts during pregnancy facilitate microbial transfer to the child, influencing immune system development (Rautava et al., 2012).	Pregnancy has a smaller impact on livestock microbiota, but reproductive diseases like metritis can be detrimental (Liu et al., 2022).	Marsupials experience unique microbial changes due to the pouch environment, while in horses, microbial stability during pregnancy is crucial for fetal health (Hand et al., 2016).
Microbial transfer to offspring	Vaginal birth introduces beneficial bacteria to newborns, and breastfeeding offers additional microbial exposure, crucial for immune development (Dominguez-Bello et al., 2010).	Similar to humans, though with different bacterial species and less Lactobacillus dominance, breastfeeding still transfers beneficial bacteria (Łubiech and Twarużek, 2020).	Vaginal delivery and breastfeeding support early microbial colonization, aiding the development of the newborn’s immune system (Bäckhed et al., 2015a).	Vaginal delivery and colostrum transfer crucial microorganisms for infant survival, while microbial diversity supports immune priming (Reynolds and Bettini, 2023).	In marsupials, exposure to pouch microbiota is vital for offspring survival, while in horses, similar microbial transfer occurs during birth and nursing (Zhong and Zhong, 2016).
Reproductive cycle and microbial shifts	The microbiota remains largely stable throughout the reproductive cycle, except for pregnancy-related changes that protect the fetus and support reproductive health (Borody and Khoruts, 2011).	Hormonal changes during the reproductive cycle significantly alter microbial composition, directly affecting reproductive success (Antwis et al., 2019).	Microbial composition shifts with the estrous cycle, affecting reproductive behaviors and outcomes (Qi et al., 2021a).	Microbial shifts during the menstrual cycle enhance fertility and help prevent diseases like metritis and vaginitis (Molina et al., 2020).	Microbial changes in seasonal breeders like horses align with hormonal shifts, boosting reproductive success and supporting pregnancy (Yatsunenko et al., 2012).
Impact of dysbiosis on reproduction	Dysbiosis is linked to infertility, premature birth, and bacterial vaginosis. In men, seminal microbiota imbalances reduce sperm motility (Baker et al., 2018).	Dysbiosis leads to reproductive disorders like infertility, though research in this area is less advanced compared to human studies (Markle et al., 2013).	Dysbiosis affects fertility and pregnancy outcomes by disrupting reproductive health and immune system regulation (Morgan, 2015).	Dysbiosis leads to reproductive diseases like metritis, mastitis, and vaginitis, significantly lowering reproductive success (Bicalho and Oikonomou, 2013).	Dysbiosis in marsupials can disrupt pouch microbiota, while microbial imbalances in horses are linked to reduced fertility and reproductive issues (Garcia-Garcia et al., 2022).