Transcriptomic insights of mammary gland involution and colostrogenesis in cattle, sheep and goats

Abstract The mammary gland undergoes extensive structural and molecular remodeling from involution until late gestation, establishing the foundations for colostrum synthesis. This review integrates transcriptomic studies across dairy cattle, sheep, and goats to describe the regulatory pathways controlling such transition. Mammary gland involution is marked by downregulation of milk‑synthesis genes and activation of pathways associated with epithelial apoptosis, autophagy, immune recruitment, and extracellular matrix remodeling, mediated by regulatory genes such as IGFBP5. As gestation progresses, metabolic and proliferation pathways like mTOR and PI3K–AKT are activated, which trigger the upregulation of genes supporting protein and lipid synthesis and nutrient transport. Simultaneously, immune‑related pathways, including complement system, cytokine signaling, and immune cell migration become upregulated, likely contributing to tissue remodeling and the enrichment of colostrum with bioactive compounds. Although the transcytosis mediated by the neonatal Fc receptor (FcRn) is considered the main mechanism for IgG transfer, transcriptomics evidence suggests additional mechanisms contributing to this process, namely immune‑cell recruitment, and increased epithelial permeability. Collectively, findings indicate that colostrogenesis results from the combination of metabolic, endocrine, and immune processes, yet the molecular links between these pathways and colostrum quality remain unclear. Future transcriptomics research must focus on addressing such knowledge gaps by integrating longitudinal and cross‑species approaches to identify specific molecular markers of colostrum synthesis.