# Effects of Left-Displaced Abomasum on the Rumen Microbiota of Dairy Cows

## TL;DR

This study found that cows with a left-displaced abomasum have distinct gut microbes, which could help detect the condition early.

## Contribution

The study identifies specific microbial markers and functional changes in the rumen associated with left-displaced abomasum in dairy cows.

## Key findings

- LDA-affected cows had fewer microbial species compared to healthy and treated cows.
- LDA cows showed increased Bacteroidota and decreased Firmicutes, with specific genus-level changes.
- Treatment restored microbial and metabolic profiles to levels similar to healthy cows.

## Abstract

In this experiment, the rumen microbiota of healthy cows, cows with left-displaced abomasum (LDA), and cows after 7 days of LDA treatment (LDA_7) were compared to explore the correlation between LDA and the rumen microbiota and identify early warning markers for LDA. Compared with the healthy group and the LDA_7 group, the LDA group exhibited fewer Operational Taxonomic Units (LDA: 21,361; Healthy: 23,231; LDA_7: 23,956; p < 0.05). The results revealed significant differences in community structure between LDA-affected cows and healthy cows, as well as between treated and untreated LDA-affected cows. Specifically, the relative abundance of Bacteroidota significantly increased and the relative abundance of Firmicutes significantly decreased in LDA-affected cows (p < 0.05). At the genus level, the abundances of UCG_002, UCG_010, and Bacteroidales_BS11_gut_group significantly increased (p < 0.01), whereas those of Trichosporon, Chryseomicrobium, and [Ruminococcus]_gauvreauii_group significantly decreased in LDA-affected cows (p < 0.01). Functional prediction analysis indicated that amino acid biosynthesis and glycerol ester metabolism were significantly downregulated in LDA-affected cows (p < 0.01). After treatment, the abundance of key microbial taxa (UCG_002 and Lachnospira) and metabolic functions normalized to levels similar to healthy cows (p > 0.05). These findings suggest that changes in rumen microbiota richness and diversity could serve as early warning markers for LDA detection.