Late Gestation Maternal Feed Restriction Decreases Microbial Diversity of the Placenta While Mineral Supplementation Improves Richness of the Fetal Gut Microbiome in Cattle

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.