Spatial heterogeneity of rumen development in lambs: morphological characteristics, growth associations, and...

Rumen development shows clear spatial specificity, with distinct tissue morphology and proliferation patterns across regions. This heterogeneity likely results from region-specific transcriptional regulation. Identifying key genes and signaling pathways underlying these spatial differences is helpful for understanding the molecular basis of rumen development. This study investigated the morphological characteristics of different rumen regions in lambs, analyzed their associations with growth performance and fermentation parameters, and explored the underlying transcriptomic profiles. Histological observations revealed pronounced regional variation in rumen morphology. The ventral sac exhibited longer and denser papillae and a thicker keratinized layer than the blind sacs. Correlation analysis showed that papilla length and density were positively associated with growth performance traits such as body weight and average daily gain. Transcriptomic analysis revealed the highest number of differentially expressed genes (DEGs) between the ventral and caudoventral blind sacs. Functional enrichment indicated that DEGs were enriched in focal adhesion, ErbB signaling, and cytoskeletal remodeling pathways. Members of the KLK family and other keratinization-related genes, together with ITGA, SHC, PAK3, and MAPK10, may coordinately regulate these pathways, contributing to the region-specific development of the rumen ventral sac. In conclusion, this study demonstrates distinct morphological and transcriptional patterns among rumen compartments, highlighting the ventral sac as the principal site for volatile fatty acid absorption and epithelial renewal. These findings provide new insights into the spatial regulation and molecular basis of rumen compartmental development.