# Liver and Skeletal Muscle Metabolome Characterization in Peripartal Dairy Cows Fed Rumen-Protected Methionine or Rumen-Protected Choline

## TL;DR

This study explores how adding methionine and choline to dairy cow diets affects liver and muscle metabolism during early lactation.

## Contribution

The study reveals how methyl-donor supplements modulate hepatic metabolic pathways in transition cows using untargeted metabolomics.

## Key findings

- Rumen-protected methionine and choline modulated glucose, lipid, and redox-related pathways in the liver.
- Network analysis identified nine hepatic co-expression modules linked to dietary treatments.
- Muscle showed limited metabolic discrimination among treatment groups, with a strong temporal effect.

## Abstract

This study used untargeted metabolomics of liver and muscle to explore the effects of rumen-protected methionine and choline during the periparturient period in dairy cows. During the physiological challenges of early lactation, these methyl donors were associated with changes in metabolites involved in the glucose, lipid, and redox-related pathways, particularly in the liver. Network-based analyses identified groups of correlated metabolites potentially linked to dietary treatments, providing insights into tissue-specific metabolic responses. Overall, these findings contribute to a better understanding of how targeted nutritional strategies may influence metabolic adaptation in transition cows, with possible implications for animal health and production efficiency.

The transition period in dairy cows involves profound metabolic adaptations that challenge energy balance and liver function. This study evaluated the effects of rumen-protected methionine (RPM) and choline (RPC) on hepatic and skeletal muscle metabolism. Twenty-one multiparous Holstein cows from a 2 × 2 factorial design (CON, RPM, RPC) underwent liver and semitendinosus biopsies at −10, +7, and +20 d relative to parturition. Untargeted LC-MS metabolomics detected 2288 and 1454 molecular features in liver and muscle. Data were analyzed using mixed-model ANOVA (FDR ≤ 0.05), complemented by multivariate approaches including sparse PLS-DA and PERMANOVA to assess global metabolic variation. Metabolite annotation was performed using HMDB (±0.005 Da). Dietary supplementation significantly affected 105 hepatic metabolites, whereas time influenced 552 metabolites, generally reflecting increases or decreases in concentration from the prepartum to early postpartum periods. Network analysis identified nine hepatic co-expression modules associated with RPM and RPC. Hub metabolites included glucose-6-phosphate, mannose-6-phosphate, and sphingomyelins, indicating modulation of carbohydrate and lipid metabolism. In muscle, treatment effects were modest, with PERMANOVA and PLS-DA confirming limited discrimination among groups and a predominant temporal effect. Overall, RPM and, to a lesser extent, RPC modulated key hepatic metabolic pathways, supporting energy and redox homeostasis during early lactation. These findings highlight the potential of methyl-donor supplementation to enhance metabolic resilience at the tissue level in transition cows.