Dynamic DIA proteomics of mare’s milk reveals distinct colostrum signatures and stage-specific lactation profiles.

Research Overview

• The study analyzed how protein content in mare’s milk changes from colostrum through later stages of lactation using advanced mass spectrometry techniques.
• It identified distinct protein profiles at different lactation stages, highlighting unique functions of colostrum and mature milk proteins.

Objective and Methodology

• Goal: To characterize the dynamic changes in the milk proteome of mares across the entire lactation period (days 1-120).
• Samples: Milk collected from three mares at seven time points spanning colostrum (day 1) to mature milk stages.
• Technique: Data-independent acquisition (DIA) proteomics, an unbiased method enabling comprehensive protein quantification.
• Validation: Parallel reaction monitoring (PRM)-based targeted quantification was used to confirm key DIA proteomic findings.

Key Findings on Colostrum vs. Mature Milk

• Colostrum (Day 1):
  • Distinct protein profile revealed by principal component analysis (PCA), indicating it is markedly different from milk at later stages.
  • High abundance of immune-related proteins: immunoglobulins IgG, IgM, IgE.
  • Presence of proteins linked to rapid energy supply and neurodevelopment such as AGPAT1 (involved in lipid metabolism), NPVF (neuropeptide VF precursor), and CAMK2G (calcium/calmodulin-dependent protein kinase II gamma).
  • Highlights colostrum’s key roles in newborn immune defense, energy provision, and early neural development.
• Mature Milk (Later Lactation Stages):
  • Proteins involved in sustained nutrient metabolism and cellular homeostasis are enriched compared to colostrum.
  • Slower but steady increases in concentrations of key functional proteins such as lactoferrin (iron-binding and antimicrobial activity) and lysozyme (antibacterial enzyme).
  • These features support ongoing growth, metabolic regulation, and immune functions for the foal as lactation progresses.

Significance and Contributions

• Provides a refined definition and molecular characterization of mare’s colostrum based on proteomic signatures.
• Demonstrates that milk protein composition is not static but dynamically shifts to meet the changing nutritional and immunological needs of the foal.
• Improves understanding of the functional roles of milk proteins across lactation stages, which may inform mare and foal health management and nutrition strategies.
• Showcases the power of advanced proteomic approaches (DIA and PRM) for detailed longitudinal studies of milk composition in non-human mammals.