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ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Microorganisms in Vertebrate Digestive Systems
Volume 16 - 2025 |
doi: 10.3389/fmicb.2025.1441143
Different Lysine-to-Methionine ratio in a low protein diet act on the microbiome and metabolome affecting the jejunal barrier functions of Tibetan sheep
Provisionally accepted
Fengshuo Zhang 
Zhenling Wu 
Yu Zhang Quyangangmao Su Kaina Zhu Xuan Chen Shengzhen Hou 
Linsheng Gui *- College of Agriculture and Animal Husbandry, Qinghai University, Xining, China
The study evaluated the effects of dietary Lys/Met ratio in a low protein diet on short-chain fatty acids (SCFAs) profiles, villus morphology, antioxidant capacity, and immune status of the jejunum in Tibetan sheep. Ninety weaned Tibetan sheep were divided into three treatments with Lys/Met ratios of 3 (LP-H), 2 (LP-M), and 1 (LP-L) in a basal diet containing 10% crude protein. The 100-day feeding trial included a 10-day acclimation period and a 90-day experimental period. LP-L significantly increased villi height, SOD activity, and T-AOC concentration compared to LP-M and LP-H (P < 0.05). LP-H showed lower IL-1β concentration (P < 0.05). Activities of α-amylase, chymotrypsin, and lipase were higher in LP-L than in LP-H (P < 0.05). Bacterial sequencing revealed increased Chao1 and Ace richness in LP-L (P < 0.05), suggesting a connection between species richness and dietary Lys/Met ratio. Decreasing dietary Lys/Met ratio significantly increased the abundance of Romboutsia, Ruminococcus gauvreauii group, Lachnospiraceae NK3A20 group, Ruminococcus 2, and Christensenellaceae R-7 group (P < 0.05) while decreasing Methanobrevibacter abundance (P < 0.05). Several differential metabolites, including beta-alanine, pantothenate, pantothenic acid, phosphoenolpyruvate, cysteine, adenosine 5'-diphosphate, isodeoxycholic acid, glutamate conjugated cholic acid, and 3-dehydrocholic acid, significantly increased in LP-L (P < 0.05). Functional analysis indicated that these metabolites were mainly focused on pantothenate and CoA biosynthesis, ferroptosis, and the tricarboxylic acid cycle. Genes related to barrier function, such as Occludin and Muc-2, were up-regulated in LP-L (P < 0.05), while IL-6 and TNF-α were down-regulated (P < 0.05). The results suggest that dietary Met/Lys ratio could affect jejunal SCFAs concentration by modulating the microbial community and regulating metabolism, thus contributing to jejunal barrier functions. These findings provide a theoretical basis for the application of Lys/Met diet supplementation in the nutritional management of Tibetan sheep when reducing dietary crude protein levels.
Keywords: Lys/Met ratio, microbiome, Metabolome, Jejunum, Tibetan sheep
Received: 01 Jun 2024; Accepted: 20 Jan 2025.
Copyright: © 2025 Zhang, Wu, Zhang, Su, Zhu, Chen, Hou and Gui. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Linsheng Gui, College of Agriculture and Animal Husbandry, Qinghai University, Xining, China
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