Core microbiota for nutrient digestion remained and ammonia utilization increased after continuous batch culture of rumen microbiota in vitro

Mengyu Liu; Tong Wang; Lu Wang; Hanjie Xiao; Jinhui Li; Chunhui Duan; Lijie Gao; Yueqin Liu; Hui Yan; Yingjie Zhang; Shoukun Ji

doi:10.3389/fmicb.2024.1331977

Core microbiota for nutrient digestion remained and ammonia utilization increased after continuous batch culture of rumen microbiota in vitro

Front Microbiol. 2024 Jan 24:15:1331977. doi: 10.3389/fmicb.2024.1331977. eCollection 2024.

Authors

Mengyu Liu^#¹, Tong Wang^#¹, Lu Wang¹, Hanjie Xiao¹, Jinhui Li¹, Chunhui Duan¹, Lijie Gao¹, Yueqin Liu¹, Hui Yan¹, Yingjie Zhang¹, Shoukun Ji¹

Affiliation

¹ College of Animal Science and Technology, Hebei Agricultural University, Baoding, China.

^# Contributed equally.

Abstract

Introduction: This study aimed to investigate the digestive function, urea utilization ability, and bacterial composition changes in rumen microbiota under high urea (5% urea in diet) over 23 days of continuous batch culture in vitro.

Methods: The gas production, dry matter digestibility, and bacterial counts were determined for the continuously batch-cultured rumen fluid (CRF). The changes in fermentation parameters, NH₃-N utilization efficiency, and microbial taxa were analyzed in CRF and were compared with that of fresh rumen fluid (RF), frozen rumen fluid (FRF, frozen rumen fluid at -80°C for 1 month), and the mixed rumen fluid (MRF, 3/4 RF mixed with 1/4 CRF) with in vitro rumen fermentation.

Results: The results showed that the dry matter digestibility remained stable while both the microbial counts and diversity significantly decreased over the 23 days of continuous batch culture. However, the NH₃-N utilization efficiency of the CRF group was significantly higher than that of RF, FRF, and MRF groups (p < 0.05), while five core genera including Succinivibrio, Prevotella, Streptococcus, F082, and Megasphaera were retained after 23 days of continuous batch culture. The NH₃-N utilization efficiency was effectively improved after continuous batch culture in vitro, and Streptococcus, Succinivibrio, Clostridium_sensu_stricto_1, p.251.o5, Oxalobacter, Bacteroidales_UCG.001, and p.1088.a5_gut_group were identified to explain 75.72% of the variation in NH₃-N utilization efficiency with the RandomForest model.

Conclusion: Thus, core bacterial composition and function retained under high urea (5% urea in diet) over 23 days of continuous batch culture in vitro, and bacterial biomarkers for ammonia utilization were illustrated in this study. These findings might provide potential applications in improving the efficiency and safety of non-protein nitrogen utilization in ruminants.

Keywords: NH3-N utilization efficiency; ammonia utilization; continuous batch culture; core microbiota; rumen.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by the earmarked fund for CARS-38, Hebei Natural Science Foundation (C2022204232 and C2021204147), Hebei Grass Industry Technology System (HBCT2023160202).