Illumina Sequencing and Metabolomics Analysis Reveal Thiamine Modulation of Ruminal Microbiota and Metabolome Characteristics in Goats Fed a High-Concentrate Diet.

Yi Ma,Chao Wang,Junhu Yao,Hongrong Wang,Hao Zhang,Daoqing Gong,Li Dong,Lihuai Yu

doi:10.3389/fmicb.2021.653283

Abstract

Long-term supplementation of a high-concentrate diet enhances the accumulation of lactate and decrease in pH in goat rumen, thereby disrupting the composition of microbial community. Studies have shown that incorporation of thiamine in high-concentrate diet increases ruminal pH and decreases rumen lactate concentration. To explore the effects of thiamine supplementation with a high-concentrate diet on alteration of the whole ruminal microbiota and their metabolites, 18 mid-lactating Saanen goats were randomly fed with one of three diets: (1) control diet (CON; n = 6; concentrate:forage 30:70), (2) high-concentrate diet (HG; n = 6; concentrate:forage 70:30), and (3) high-concentrate diet with 200 mg of thiamine/kg of DMI (HGT; n = 6; concentrate:forage 70:30). The goats received experimental diets for 8 weeks. Ruminal samples were collected on the last day of the 8 weeks for 16S rRNA gene sequencing and the liquid chromatograph–mass spectrometer (LC-MS) analysis. The results revealed significant alterations of the ruminal bacterial community structure and diversity in HGT groups compared to HG groups, with an overall dominance of Bacteroidetes at the phylum level and Oribacterium (P < 0.05), Anaerobiospirillum (P < 0.01), and Fibrobacter (P < 0.01) at genus level in the HGT group. The LC-MS analysis revealed that thiamine supplementation resulted in lower levels of propionate (P < 0.05), pyruvate (P < 0.01), lactate (P < 0.05), putrescine (P < 0.05), tyramine (P < 0.05), and histamine (P < 0.01) and higher levels of acetate (P < 0.05), succinates (P < 0.01), oxaloacetic acid (P < 0.01), leucine (P < 0.01), valine (P < 0.05), linoleic acid (P < 0.05), docosahexaenoic acid (P < 0.05), and 4-phenylbutyric acid (P < 0.05) in the HGT group than in the HG group. The decrease in these compounds enhanced homeostasis in the rumen environment and suppressed epithelial inflammation. Correlation analysis revealed the potential relationships between ruminal metabolites and microbial community. These findings demonstrate that thiamine supplementation can alleviate subacute ruminal acidosis (SARA) by stabilizing the microbial community and reducing toxic unnatural compounds.

Highlights

Subacute ruminal acidosis (SARA) is a nutritional metabolic disease that affects the finishing period of feedlot beef cattle, especially during the early and middle lactation periods of dairy cattle
It has been shown that short-chain fatty acids (SCFAs) and lactate generated by fermentation can be fully absorbed, reducing the ruminal pH, which exceeds the adaptability of animals (Kleen et al, 2003)
Rarefaction curves revealed that the curve flattens out as the sequencing deepens, demonstrating that the operational taxonomic units (OTUs) of the highconcentrate diet + thiamine group (HGT) group was higher than that of the high-concentrate diet (HG) group but lower than that of the control diet (CON) group at the same sequencing depth (Figure 1B)

Summary

Introduction

Subacute ruminal acidosis (SARA) is a nutritional metabolic disease that affects the finishing period of feedlot beef cattle, especially during the early and middle lactation periods of dairy cattle. Long-term supply of a high-concentrate diet has been found to affect the structure of the bacterial community and fermentation characteristics in the rumen (Khafipour et al, 2009; Hook et al, 2011). Gram-negative bacteria die and lyse when the structure of the bacterial community changes and pH drops sharply, leading to the formation of endotoxins and histamine, which are absorbed into the blood, forming endotoxemia acidosis (Slyter, 1976; Andersen and Jarlv, 1990; Duffield et al, 2004). Some studies have shown that inoculating lactate-utilizing bacteria can relieve SARA. The addition of thiamine could relieve the inflammatory response by decreasing endotoxin levels in the rumen and inhibit the expression of proinflammatory cytokines in the rumen epithelium (Pan et al, 2017b; Zhang et al, 2019)

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