Reduction in mucosa thickness is associated with changes in immune function in the colon mucosa during the weaning transition in Holstein bull dairy calves.

This study aims to characterize changes in the structure and the molecules related to immune function in the colon mucosa in dairy calves during the weaning transition (weaned at week 6 of age). Colon mucosa thickness, measured at week 5 to 8 and 12 of age, decreased for 2 weeks after weaning, but then recovered. Colon mucosa's transcriptome profiling at week 5, 7, and 12 of age was obtained using RNA-sequencing. Functional analysis showed that pathways related to immune function were up-regulated postweaning. A weighted gene co-expression network analysis identified 17 immune function related genes, expressed higher postweaning, which were negatively correlated with colon mucosa thickness, suggesting that these genes may be involved in colon mucosa inflammation and recovery from mucosa thickness decrement during the weaning transition. As such, it is important to determine the function of immune cells in the colon mucosa during the weaning transition in dairy calves.

Transcriptome profiling revealed that key rumen epithelium functions change in relation to short-chain fatty acids and rumen epithelium-attached microbiota during the weaning transition.

This study aims to characterize the functional changes of the rumen epithelium associated with ruminal short-chain fatty acid (SCFA) concentration and epithelium-attached microbes during the weaning transition in dairy calves. Ruminal SCFA concentrations were determined, and transcriptome and microbiota profiling in biopsied rumen papillae were obtained from Holstein calves before and after weaning using RNA- and amplicon sequencing. Metabolic pathway analysis showed that pathways related to SCFA metabolism and cell apoptosis were up- and down-regulated postweaning, respectively. Functional analysis showed that genes related to SCFA absorption, metabolism, and protective roles against oxidative stress were positively correlated with ruminal SCFA concentrations. The relative abundance of epithelium-attached Rikenellaceae RC9 gut group and Campylobacter was positively correlated with genes involved in SCFA absorption and metabolism, suggesting that these microbes can cooperatively affect host functions. Future research should examine the contribution of attenuated apoptosis on rumen epithelial functional shifts during the weaning transition.