Comparative analysis of red deer milk proteins throughout lactation using quantitative proteomics

Red deer milk is known for its high nutritional quality, containing elevated levels of protein, fat, and essential minerals compared with other ruminant milks. This study investigates the protein profile of red deer milk across various lactation stages, using advanced liquid chromatography-MS/MS techniques to enhance understanding of its nutritional composition. In this study, milk samples were collected from 120 lactating does at 8 distinct points during the lactation period, ensuring consistent dietary conditions. Through this comprehensive approach, a total of 73 proteins were identified, with 9 previously known in deer milk. Significant variations in protein concentrations were observed, highlighting 27 proteins with substantial changes throughout lactation. These proteins are crucial for supporting the physiological needs of the fawn. Key findings revealed the roles of specific proteins, such as osteopontin and lactotransferrin, in immune function, alongside transport proteins involved in nutrient delivery, reflecting the dynamic requirements during lactation. Bioinformatics analysis indicated significant quantitative changes in protein expression, with regression analysis confirming these findings. Gene Ontology analysis was conducted; however, limitations in genomic data for red deer necessitated reliance on related species for functional annotation. The results underscore the complex biochemical changes in deer milk, establishing a foundational understanding of its unique proteome. In conclusion, despite identifying fewer proteins than observed in studies of other ruminants, this research represents the most thorough analysis of proteins in red deer milk to date. It emphasizes the dynamic nature of milk composition throughout lactation and its implications for nutritional and functional attributes in cosmetic products and food, thereby contributing valuable insights into the dairy potential of red deer.