Early solid diet supplementation influences proteomic of rumen epithelium in goat kids

Background: Rumen is an important organ for nutrient absorption and metabolism in goats, and its constant development is a prerequisite for the healthy growth of goat kids. Previous studies have shown that the intake of solid feed in early life can significantly promote the development of rumen tissue morphology and metabolic function in young ruminants. However, the expressed proteome in rumen epithelium of goats supplemented solid diet is still limited. In this study, 24 pairs of twin goats were randomly divided into milk replacer group (MR) and milk replacer with supplemented solid diets group (SS) using proteomic analysis based on ITRAQ technique, which allow to further analyze potential biological mechanism. Results: Significant increased papilla length and width, epithelium thickness as well as muscle layers thickness were observed in SS group. A total of 6003 differentially expressed proteins were detected in the SS group compared to the MR group by analyzing the rumen protein expression of six biological replicates, of which 251 proteins were up-regulated and 750 proteins were down-regulated. According to Gene Ontology, the differential expressed proteins (DEPs) were significantly enriched in functions related to cell development and biosynthesis. The networks of KEGG pathways demonstrated that most of the 30 significantly enriched pathways involved in cellular metabolism, signal transduction and immunity. Conclusions: The supplementation of solid feed promoted the growth of rumen epithelial cells, improved the rumen's immune function, and activated lipid metabolism. Our findings provided new insights into the molecular mechanisms underlying rumen developmental differences in goat kids caused by solid feed.