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The increasing demand for meat and milk products due to the rising population, coupled with limited resources, requires increased efficiency of livestock. The microbiome within the rumen allows ruminant species to convert low-quality forages into volatile fatty acids (VFA) that are absorbed and digested by the animal to be used as an energy source. Understanding the development of microorganisms within the rumen is of interest due to their effects on host health, energy, performance, and efficiency (Flint and Bayer, 2008; Guan et al., 2008). Evidence suggests that colonization of the calf gastrointestinal tract may occur prior to birth due to the presence of bacteria in the meconium (Alipour et al., 2018). In addition, the establishment of the bacterial communities within the rumen occurs sequentially (Jami et al., 2013; Rey et al., 2014); however, little is known about the relationship and influence of the maternal rumen microbiome on subsequent development of the calf rumen microbiome and VFA production. Research in humans (Biasucci et al., 2010) and ruminants (Cunningham et al., 2018) suggests that there is a maternal influence on gut microbiome development, including mode of delivery and nutrition. In addition, microbial populations established early in life have the ability to affect the health and performance of the adult animal, suggesting the potential for programming of the microbiome (Abecia et al., 2013). Thus, we hypothesized that the cow maternal rumen microbiome would influence colonization of the calf rumen microbiome. Our objective was to relate the rumen microbiome of the cow prior to parturition (RFC) and at weaning (RFCw) to the calf’s meconium microbiome (M) and calf rumen microbiome at birth (RFd1), day 2 (RFd2), day 28 (RFd28), and weaning (RFNw).

Simple Summary The purpose of this study was to explore the influence of maternal feed intake restriction on the microbiome of the reproductive tract and its subsequent colonization of the bovine fetal gut microbiome in utero. After sequencing the microbial DNA of the maternal vagina, placental tissues, and fetal gut, our data show the microbiome of the vagina and cotyledon remain relatively unaffected by feed intake restriction and mineral supplementation. The placental microbiome of feed restricted pregnancies was less diverse, and feeding using a mineral supplement did not impact these differences. However, mineral supplementation improved the richness of the fetal gut microbiomes regardless of feeding treatment, substantiating prior evidence that in utero mineral supplementation improves calf performance. The obtained results may offer insight into improving nutrient use of calves born to dams experiencing feed restriction. Abstract Feed intake restriction impacts both humans and ruminants in late gestation, although it is unknown whether this adverse maternal environment influences the microbiome of the reproductive tract, and through it, the colonization of the fetal gut. A 2 × 2 factorial design including a 70% feed intake restriction (feed restricted ‘FR’ or control diets ‘CON’) and mineral supplementation (unsupplemented ‘S−’ or supplemented ‘S+’) was used to analyze these effects in multiparous cows (n = 27). Vaginal swabs were obtained 60, 30, and 10 days prior to the estimated calving date, along with neonatal rumen fluid and meconium. Placental tissues and efficiency measurements were collected. Microbial DNA was extracted for 16S sequencing of the V4 region. Feed restriction decreased the diversity of the placental microbiome, but not the vagina, while mineral supplementation had little impact on these microbial communities. Mineral supplementation did improve the richness and diversity of the fetal gut microbiomes in relation to reproductive microbes. These differences within the placental microbiome may influence individual health and performance. Adequate maternal nutrition and supplementation yielded the greatest placental efficiency, which may aid in the establishment of a healthy placental microbiome and fetal microbial colonization.