Rumen Epithelial Transcriptome Analysis Revealed the Regulatory Mechanism of Host Adaptation to Nitrogen Source Replacement Diet in Simmental Cattle

Soybean meal, a high-quality protein in ruminant diets, has been explored by farmers and researchers to replace soybean meal with other nitrogen sources to reduce feed costs due to its high price and limited resources. Gelatinized urea is a commonly used substitute for nitrogen source. In this study, RNA sequencing was performed on rumen epithelial tissues of Simmental beef cattle fed the diet that gelatinized urea replace 10% soybean (experimental group, <i>n</i> = 6) as well as Simmental beef cows fed soybean meal normally (control group, <i>n</i> = 4) to explore possible regulatory mechanisms in rumen tissues after nitrogen source substitution. The results showed that after the nitrogen source was replaced, the rumen epithelium may increase the nutrient absorption capacity by decreasing the degree of intercellular connectivity, increasing intercellular permeability, and possibly changing the rumen morphology, and the expression of genes related to lipoprotein synthesis was increased in the rumen epithelial tissues, which suggested that the rumen epithelium may have produced a compensatory mechanism to adapt to the changes of the nutrients in the diets.