Bovine colostrum casein: Post-partum dynamics of micelle size, content, and associated traits

In milk, casein exists in the form of colloidal casein micelles (CM), which are crucial for various biological functions such as neonatal nutrition, calcium phosphate control, and amyloid fibril suppression. However, bovine colostrum casein has received less attention despite its importance. The objective of this study was to investigate the size of colostrum CM and their relationship with compositional traits during four post-partum milkings. A total of 184 samples (collected at 12 ± 1 h intervals) were obtained from 46 cows over four sequential milkings. The results demonstrated a significant decrease in CM size of colostrum from 227.2 nm to 201.9 nm over the four post-partum milkings. Fat, protein, casein content, and Brix values also declined across milkings and showed a positive correlation with CM size, although the relationships were nonlinear. Understanding CM size can be valuable for decision-making regarding colostrum and transition milk processing due to its significant role.