Biotechnology Bulletin ›› 2025, Vol. 41 ›› Issue (2): 40-50.doi: 10.13560/j.cnki.biotech.bull.1985.2024-0764

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Research Progress in Ammonia Assimilation and Genetic Evolution in Rumen

WANG Tong1(), XIAO Han-jie1, XIE Hao-jiong1, ZHANG Li-shen2, YAO Xiao-liang3, YAN Hui1(), JI Shou-kun1()   

  1. 1.College of Animal Science and Technology, Hebei Agricultural University, Baoding 071000
    2.Administration of Agriculture and Rural Affairs of Tang County, Baoding 072350
    3.Hebei Tuoyi Biotechnology Co. , Ltd. , Shijiazhuang 051531
  • Received:2024-08-08 Online:2025-02-26 Published:2025-02-28
  • Contact: YAN Hui, JI Shou-kun E-mail:wang2896784183@163.com;yanhuihui@126.com;jishoukun@163.com

Abstract:

The shortage of protein feed resources has severely restricted the sustained and stable development of animal husbandry in China. Ruminants possess the special ability to convert non-protein nitrogen into amino acids or proteins. Adding non-protein nitrogen is an effective approach to alleviate protein feed shortages in ruminants, but rumen ammonia assimilation is the key step limiting its utilization efficiency. Therefore, improving the nitrogen assimilation efficiency of ruminants is an important means of alleviating the shortage of protein feed. Ammonia assimilation refers to the process of free ammonia merging into the carbon skeleton to form nitrogen-containing organic compounds. Rumen microorganisms may assimilate free ammonia into microbial protein (MCP), providing 49%-98% of metabolizable protein for ruminants. Rumen ammonia assimilation can be carried out through four pathways: ① the glutamate dehydrogenase (GDH) pathway: ammonia and α-ketoglutarate undergo aminification catalyzed by GDH to produce glutamate; ② the glutamine synthetase-glutamate synthase (GS-GOGAT) pathway: ammonia and glutamate are catalyzed by GS to form glutamine;③ the alanine dehydrogenase (ADH) pathway: alanine can be produced by ammonia and pyruvate through the ADH pathway; ④ the asparagine synthetase (AS) pathway: aspartate and ammonia can form asparagine through the AS pathway. This article explores the process of ammonia assimilation pathway reaction in rumen microorganisms and reviews these four ammonia assimilation pathways of rumen microbes, their key enzymes, microorganisms involved, and influencing factors. By constructing phylogenetic trees to explain the evolutionary relationships of key genes, theoretical support for the utilization of ammonia nitrogen in ruminants is provided.

Key words: ruminants, non-protein nitrogen, ammonia assimilation pathway, GDH pathways, GS-GOGAT pathways