# Metagenomic Insights into the Modulatory Effects of Thiamine Supplementation for Treating Subclinical Ketosis Dairy Cows

## TL;DR

Thiamine supplementation helps reduce subclinical ketosis in dairy cows by improving rumen microbes and increasing milk yield.

## Contribution

This study demonstrates thiamine's novel ability to modulate rumen microbiota and alleviate subclinical ketosis in dairy cows.

## Key findings

- Thiamine reduced BHBA content, milk CFUs, and somatic cell counts in SCK cows.
- Thiamine increased milk yield, milk fat, and acetate levels while improving the A/P ratio.
- Thiamine altered rumen and fecal microbial communities, increasing Proteobacteria and decreasing Firmicutes, Spirochaetes, and Cyanobacteria.

## Abstract

Subclinical ketosis (SCK) is commonly induced in the early lactation period due to severe negative energy balance (NEB) and the accumulation of β-hydroxybutyrate (BHBA), which disrupts the rumen microbial ecosystem and decreases milk yield. This research thoroughly investigates the alleviative effect of thiamine on SCK and its modulatory effects on rumen microbial communities. The results indicate that thiamine significantly decreased BHBA content, milk colony-forming units (CFUs), and somatic cell counts (SCCs), while it significantly increased milk yield, milk fat, acetate content, and the A/P ratio (p < 0.05). The microbial community results revealed that thiamine-treated cows exhibited a significantly increased relative abundance of ruminal and fecal Proteobacteria and significantly decreased ruminal Firmicutes (p < 0.05) and fecal Spirochaetes and Cyanobacteria (p < 0.05), compared with SCK cows. These findings provide a theoretical basis and a practical method for alleviating SCK in early-lactation dairy cows and increasing the milk yield of SCK cows.

(1) Background: The objective of this study was to investigate the modulatory effects of thiamine on BHBA metabolism, milk yield, and the rumen microbial ecosystem. (2) Methods: A total of 24 SCK dairy cows with similar body conditions were selected and randomly allocated to SCK (SCK) or SCK with thiamine supplement (SCKT) treatment. Twelve healthy dairy cows served as the control (CON) treatment. Milk yield, milk quality, ruminal fermentability parameters, rumen and fecal microbial communities were further measured. (3) Results: Thiamine significantly decreased BHBA content, milk CFUs, and somatic cells, while significantly increasing milk yield, milk fat, acetate, and the A/P ratio (p < 0.05). Thiamine-treated cows exhibited significantly increased ruminal and fecal Proteobacteria but significantly decreased ruminal Firmicutes (p < 0.05) as well as fecal Spirochaetes and Cyanobacteria (p < 0.05), compared with SCK cows. Functional analysis showed that differential rumen bacteria exhibited high energy metabolism, nucleotide metabolism, and glycan biosynthesis and metabolism, while the metabolism of terpenoids and polyketides were the primary functional pathways of differential fecal microbiota. (4) Conclusions: Thiamine supplementation in SCK cows effectively alleviated subclinical ketosis by reducing BHBA content, enhancing ruminal fermentability, and proliferating rumen microbial communities, leading to improved milk yield in the early-lactation period.