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Cited by 1,311Ruminant Nutrition and Digestive PhysiologyAnimal Nutrition and PhysiologyAnaerobic Digestion and Biogas Production

Nitrogen metabolism in the rumen

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Bach, A., Calsamiglia, S., Stern, M.D.·2005·Journal of Dairy Science
DOI 10.3168/jds.s0022-0302(05)73133-7
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Abstract

Protein metabolism in the rumen is the result of metabolic activity of ruminal microorganisms. The structure of the protein is a key factor in determining its susceptibility to microbial proteases and, thus, its degradability. Ruminal protein degradation is affected by pH and the predominant species of microbial population. Ruminal proteolytic activity decreases as pH decreases with high-forage dairy cattle-type rations, but not in high-concentrate beef-type rations. Accumulation of amino acid (AA) N after feeding suggests that AA uptake by rumen microorganisms could be the limiting factor of protein degradation in the rumen. In addition, there are several AA, such as Phe, Leu, and Ile, that are synthesized by rumen microorganisms with greater difficulty than other AA. The most common assessment of efficiency of microbial protein synthesis (EMPS) is determination of grams of microbial N per unit of rumen available energy, typically expressed as true organic matter or carbohydrates fermented. However, EMPS is unable to estimate the efficiency at which bacteria capture available N in the rumen. An alternative and complementary measure of microbial protein synthesis is the efficiency of N use (ENU). In contrast to EMPS, ENU is a good measurement for describing efficiency of N capture by ruminal microbes. Using EMPS and ENU, it was concluded that optimum bacterial growth in the rumen occurs when EMPS is 29 g of bacterial N/kg of fermented organic matter, and ENU is 69%, implying that bacteria would require about 1.31 x rumen-available N per unit of bacterial N. Because the distribution of N within bacterial cells changes with rate of fermentation, AA N, rather than total bacterial N should be used to express microbial protein synthesis.

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Authors
Bach, A., Calsamiglia, S., & Stern, M. D.
Affiliations
  • Universitat Autònoma de Barcelona (ES)
  • University of Minnesota (US)
Corresponding author
Stern, M.D.
ORCID
Venue
Journal of Dairy Science
Publisher
American Dairy Science Association
Published
2005-04
Volume
88
Pages
E9-E21
ISSN
0022-0302 (ISSN-L)
DOI
10.3168/jds.s0022-0302(05)73133-7
OpenAlex
W2001088676
Cited by
1,311
References
113
Citations by year
2026: 69 · 2025: 67 · 2024: 55 · 2023: 62 · 2022: 102 · 2021: 79 · 2020: 62 · 2019: 55 · 2018: 45 · 2017: 56 · 2016: 59 · 2015: 60 · 2014: 78 · 2013: 60 · 2012: 65
FWCI
16.39
Type
journal article
Language
en
Open access
Licence
Locations
  • Journal of Dairy Science (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Agricultural and Biological Sciences › Agronomy and Crop Science › Ruminant Nutrition and Digestive Physiology
  • Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Animal Nutrition and Physiology
  • Physical Sciences › Engineering › Building and Construction › Anaerobic Digestion and Biogas Production
Keywords
rumen nitrogen metabolism, rumen protein degradation, rumen pH, amino nitrogen, microbial protein synthesis, rumen fermentation, dairy cattle feed
MeSH terms
Amino Acids, Ammonia, Animals, Bacteria, Energy Metabolism, Fermentation, Hydrogen-Ion Concentration, Nitrogen, Peptide Hydrolases, Proteins, Rumen, Protein Biosynthesis, Carbohydrate Metabolism, Eukaryota

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