Changes in host liver transcriptome and rumen microbiota community in fattening goats fed different type of forages

Background: To explore the effects of different forages on rumen flora and expression of genes related to liver metabolism in fattening goats, Boer crossbred male goats were fed three experiment diets lasts for 97 days, including an adaptation period of seven days. The diets were composed of same commercial concentrate, but supplemented with different forages (Hemarthria altissima (HA), Pennisetum sinese (PS), or forage maize (FG)). The liver transcriptome changes along with its correlation with the rumen microbiome changes were investigated in these animals. Results: Transcriptome results revealed a total of 73 differentially expressed genes (DEGs) between FG and HA groups, and biological pathways enriched by these DEGs included circadian regulation of gene expression, transforming growth factor beta receptor signaling pathway, lipid metabolic process, and multiple KEGG pathways related to energy metabolism, such as AMPK signaling pathway, Choline metabolism in cancer, Insulin resistance, cAMP signaling pathway, and Insulin signaling pathway. Furthermore, our 16S rRNA gene sequencing results revealed a remarkable difference in rumen microbiota composition due to different dietary treatment, and the correlations between the relative abundances of bacteria at the genus level and the expression levels of DEGs were analyzed. By which, nine bacteria genera exhibited at least a strong correlation to at least one of these DEGs. Among these bacteria genera, the Muribaculaceaewas reported with involvement in fat metabolism, which exhibited the highest number of associations overall with 18 strong correlations with DEGs, implying the direct relationship between rumen Muribaculaceaeabundance and liver gene expression changes. Conclusions: Our study provides insight into the physiological axis linking the rumen microbiome and liver genes to forage utilization in goats, which may facilitate future studying the underlying molecular mechanism of how forages lead to the improvement of the nutritional value through the microbiota-gut-liver axis in ruminants.