Transcriptome analysis of ruminal epithelia revealed that potential regulatory mechanisms involved in host adaptation to rapid high fermentable dietary transition in beef cattle. Bos taurus

An abrupt transition from high forage to high fermentable diet may induce digestive disorders in the rumen. To date, the host mechanisms regulate the adaption to such dietary transition are largely unknown. To understand the molecular mechanisms involved in such phenomena, RNA-sequencing was performed to identify the changes in the transcriptomes of ruminal epithelia during a rapid high grain transition from 3% to 92% grain. In total, the expression of 11,044, 11,322 and 11,282 genes was detected in ruminal epithelia of beef heifers (n=15) fed 3%, 75% and 92% barley grain diet, respectively. When diet was changed from 75% to 92% grain, a significant difference was observed in the mean ruminal pH change among the individuals with five heifers decreased (DG; pH from 6.30 ± 0.09 to 5.87 ± 0.15, P G) in FABP4 identified between two groups of animals (P < 0.1). The expression of genes involved in regulating lipid transport and fatty acid metabolism varied between DG and UG heifers during rapid 75% to 92% grain transition. The identified genes and SNP could be potential markers and may account for the varied ruminal pH responses between DG and UG heifers, which can be potentially applied in breeding and selecting beef cattle with more tolerance in dietary transition stress. Overall design: Forty five rumen papillae samples were collected from fifteen heathy beef heifers (15 samples were collected when fed 3%, 75% and 92% grain diet, respectively). Using Trizol reagent to extract the total RNA, and the mRNA expression was profiled.