A Combined Metabolomic and Proteomic Study Revealed the Difference in Metabolite and Protein Expression Profiles in Ruminal Tissue From Goats Fed Hay or High-Grain Diets.

Changzheng Guo,Xinfeng Wang,Shengyong Mao,Daming Sun

doi:10.3389/fphys.2019.00066

Changzheng Guo, Xinfeng Wang + Show 2 more

Open Access

https://doi.org/10.3389/fphys.2019.00066

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Abstract

Currently, knowledge about the impact of high-grain (HG) feeding on metabolite and protein expression profiles in ruminal tissue is limited. In this study, a combination of proteomic and metabolomic approaches was applied to evaluate metabolic and proteomic changes of the rumen epithelium in goats fed a hay diet (Hay) or HG diet. At the metabolome level, results from principal component analysis (PCA) and PLS-DA revealed clear differences in the biochemical composition of ruminal tissue of the control (Hay) and the grain-fed groups, demonstrating the evident impact of HG feeding on metabolite profile of ruminal epithelial tissues. As compared with the Hay group, HG feeding increased the levels of eight metabolites and decreased the concentrations of seven metabolites in ruminal epithelial tissues. HG feeding mainly altered starch and sucrose metabolism, purine metabolism, glyoxylate and dicarboxylate metabolism, glycerolipid metabolism, pyruvate metabolism, glycolysis or gluconeogenesis, galactose metabolism, glycine, serine and threonine metabolism, and arginine and proline metabolism in ruminal epithelium. At the proteome level, 35 differentially expressed proteins were found in the rumen epithelium between the Hay and HG groups, with 12 upregulated and 23 downregulated proteins. The downregulated proteins were related to fatty acid metabolism, carbohydrate metabolic processes and nucleoside metabolic processes, while most of upregulated proteins were involved in oxidative stress and detoxification. In general, our findings revealed that HG feeding resulted in differential proteomic and metabolomic profiles in the rumen epithelia of goats, which may contribute to better understanding how rumen epithelium adapt to HG feeding.

Highlights

In modern intensive animal production, feeding high-grain (HG) diets to feedlot goats has become a common practice to meet the energy requirements for the maintenance of the production performance (Penner et al, 2011)
A total of 158 valid peaks were detected by the GC-MS that were unique and non-overlapping in the rumen epithelium
The separation of the two groups in principal components (PCs) 2 revealed significant differences of rumen tissue metabolites in goats fed the HG diet and hay diet, which is apparent in Figure 1B, as analyzed by PLS-DA

Summary

Introduction

In modern intensive animal production, feeding high-grain (HG) diets to feedlot goats has become a common practice to meet the energy requirements for the maintenance of the production performance (Penner et al, 2011). The effect of HG feeding on rumen epithelial morphology (Bannink et al, 2008) and physiological functions (Uppal et al, 2003) have been widely investigated, and the results revealed that HG feeding increased length and surface of rumen papilla (Shen et al, 2004) and impact rumen epithelial absorption, barrier, and immune function (Liu et al, 2013). These findings improved our understanding of the adaptative mechanism of the ruminal epithelium in response to HG diet feeding. To our knowledge, previous studies are only focused on one level (gene, metabolite or morphology) to investigate the response of rumen epithelial function to HG feeding, which is limited to understand the global change in physiological functions of rumen epithelium during HG feeding

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