# Bacterial and Fungal Dynamics of the Uterine Microbiota in Postpartum Beef Cows Supplemented with Grape Pomace

## TL;DR

This study shows that giving grape pomace to beef cows after calving can help maintain a healthier uterine microbiome, reducing the risk of infections and reproductive issues.

## Contribution

The study demonstrates that grape pomace supplementation modulates both bacterial and fungal uterine microbiota in postpartum beef cows.

## Key findings

- Grape pomace supplementation reduced harmful bacteria like Fusobacterium necrophorum and Trueperella pyogenes.
- Supplemented cows showed greater fungal community stability and lower opportunistic fungal genera.
- Uterine microbiota in unsupplemented cows shifted toward potentially pathogenic bacteria by week nine postpartum.

## Abstract

After calving, the cow’s uterus is exposed to many microorganisms that can affect recovery and future fertility. In the past, the uterus was thought to be sterile, but it is now known to contain a complex community of bacteria and fungi that changes over time. An imbalance in these microorganisms can increase the risk of uterine diseases and reduce reproductive performance. The aim of this study was to examine how the uterine microbial community changes during the weeks after calving in beef cows and to determine whether a natural dietary supplement made from grape byproducts could help maintain a healthier microbial balance. Angus cows were either given a slow-release grape pomace supplement or left unsupplemented, and uterine samples were collected early and later after calving. The results showed that harmful microorganisms became more common later after calving, especially in cows that did not receive the supplement. In contrast, cows given the grape pomace supplement showed a more stable microbial community and fewer microorganisms linked to uterine infections. These findings suggest that grape pomace, a natural and sustainable feed supplement, may help support uterine health and reduce the risk of reproductive problems in beef cows, which could improve animal welfare and productivity.

The bovine uterus, once considered sterile, is now recognized as a dynamic microbial ecosystem that undergoes substantial changes during the postpartum period and plays a critical role in reproductive health. This study investigated the composition and temporal dynamics of the uterine bacterial and fungal microbiota in postpartum Angus cows and showed that dietary grape pomace bolus supplementation was associated with temporal shifts in microbial community composition, including changes in selected bacterial taxa and increased fungal community stability. A total of 19 cows were allocated to control (n = 10) or treatment groups (n = 9), with treated animals receiving slow-release grape pomace boluses administered every three weeks from 21 days prepartum until 60–70 days postpartum. Uterine lavage samples were collected during the first (days 4–12) and ninth (days 63–70) postpartum weeks and analyzed using amplicon-based sequencing targeting the bacterial 16S rRNA (V3–V4) region and the fungal ITS2 region. The uterine microbiota exhibited pronounced temporal changes, with Firmicutes predominating in the early postpartum period and an increased abundance of potentially pathogenic Fusobacteria and Bacteroidetes observed by week nine postpartum, particularly in control cows. Grape pomace supplementation was associated with a more favorable bacterial profile, including a reduced relative abundance of key uterine pathogens such as Fusobacterium necrophorum and Trueperella pyogenes. The uterine mycobiome was dominated by Ascomycota across all groups; however, supplemented cows showed greater fungal community stability and a lower prevalence of opportunistic genera, including Candida spp. In conclusion, dietary grape pomace supplementation may beneficially modulate both bacterial and fungal uterine microbiota during the postpartum period, suggesting its potential as a natural strategy to support uterine microbial homeostasis and reproductive health in beef cows.