# Proline dipeptides in the rumen linked to higher nitrogen use efficiency in 30 dairy cows

- Published: 2026-11-07 20:50 UTC
- Section: Life & Health › Agritech & food
- Tags: nitrogen utilization efficiency, proline-containing dipeptides, rumen microbiome, S15 peptidyl-peptidase, dairy cows, metagenome-assembled genomes, small peptide metabolism, precision nutrition, milk nitrogen
- URL: https://realtech.media/news/rt-f4fa7972ad8025ecd6e43b19_proline_dipeptides_in/

**Researchers linked proline-containing dipeptides and an S15 peptidase of rumen bacteria to higher milk nitrogen efficiency, a possible target for feeding strategies.**

![Proline dipeptides in the rumen linked to higher nitrogen use efficiency in 30 dairy cows](https://realtech.media/media/2026/11/c6d921dcbdaeba65.jpg)
*Leroy Anderson, Wikimedia Commons, Public domain*

A research team reported in Nature Communications a genome-resolved map of small-peptide metabolism in the rumen microbiome. They combined chemical isotope-labeling metabolomics with metagenomics in 30 dairy cows. Among 349 detected small peptides, proline-containing dipeptides were associated with higher nitrogen utilization efficiency (NUE), together with an S15 peptidyl-peptidase that generates Xaa–Pro dipeptides. [1]

## Why nitrogen use matters in dairy

NUE is the share of dietary nitrogen recovered in milk (milk N/intake N). Reported values vary among individual cows from about 14% to 45%. [1] Livestock systems account for roughly one-third of global anthropogenic nitrogen emissions, and the ruminant supply chain contributes 71% of that (about 46 Tg N per year), according to the cited estimate. [1]

In the rumen, 60–80% of dietary protein is degraded into peptides and amino acids. Peptide-bound nitrogen makes up about half of total ruminal nitrogen. When breakdown exceeds microbial needs, ammonia is absorbed, converted to urea and mostly excreted in urine, which lowers NUE. [1]

## Peptidases in rumen genomes

The map is based on the Bovine Gastro Microbial Genome Map. Of 5978 high-quality metagenome-assembled genomes (MAGs), 3731 (62.4%) encoded peptidases annotated for small-peptide degradation, and 64.6% of these carried a single such gene. [1] Another 1820 MAGs encoded peptidyl-peptidases with a predicted role in generating small peptides; 72.3% of them carried two or more such genes. [1]

Degradation capacity was assigned mainly to Bacteroidota (45.5%) and Bacillota_A (38.4%), while generation capacity was 96% Bacteroidota. [1] Signal-peptide prediction showed that 76% of the generating peptidyl-peptidases carry a signal peptide, whereas 98% of the degrading peptidases lack one. [1]

## Experimental checks

In vitro rumen fermentation, metatranscriptomics and targeted quantification showed that proline-dipeptide accumulation coincided with transcriptional patterns consistent with nitrogen assimilation and amino acid biosynthesis. [1] Bacterial incubation and heterologous expression confirmed that the S15.001 peptidase hydrolyzed Xaa–Pro substrates. [1]

The authors describe this as a microbial proline-dipeptide axis associated with NUE and as a basis for precision nutrition that targets ruminal peptide metabolism. The data are associations from 30 cows plus laboratory experiments; feeding interventions were not tested in this work. [1]

## Sources

1. [Nature Communications](https://doi.org/10.1038/s41467-026-78994-9)

---

Source: RealTech, realtech.media — https://realtech.media/news/rt-f4fa7972ad8025ecd6e43b19_proline_dipeptides_in/