Transcriptomics reveals the molecular mechanisms by which micronutrient premix and concentrate supplementation levels affect rumen function in pregnant Hulunbeier sheep under alpine conditions

The nutritional requirements of pregnant Hulunbeier sheep are difficult to be met under traditional feeding management. Increasing the nutritional level by adding micronutrient premixes and increasing concentrate supplements to their diets is bound to affect the physiological function of the rumen, and the molecular mechanisms behind this are unknown. We aimed to analyze the molecular mechanisms underlying the physiological effects of micronutrient premix and concentrate supplements on the rumen of pregnant Hulunbeier sheep with the help of RNA-seq, focusing on thermogenesis, immunity and VFA utilization. The top 3000 genes co-expressed in all three groups were mainly enriched in biological processes related to protein synthesis. Compared with LF, 32 genes were up-regulated and 33 genes were down-regulated in FF, and the differentially expressed genes were mainly enriched in KEGG pathways related to steroid synthesis, chemical carcinogenesis and signal transduction. Compared with FF, 96 genes were up-regulated and 908 genes were down-regulated in FS, and the differentially expressed genes were mainly enriched in KEGG pathways like Focal adhesion, cGMP-PKG signaling pathway, Vascular smooth muscle contraction, Proteoglycans in cancer, and so on. In addition, we statistically analyzed 15, 8 and 11 differentially expressed genes found to be associated with rumen thermogenesis, immunity and VFA utilization, respectively. Formulated concentrates supplemented with micronutrients can increase resistance to toxicants and enhance rumen epithelial function by enhancing rumen epithelial steroid biosynthesis, while decreasing rumen epithelial productivity and VFA utilization efficiency, compared with local concentrates. In addition, excessively high levels of concentrate addition will reduce the efficiency of rumen epithelial cells and even induce inflammation.