Bovine colostrum: Postpartum changes in fat globule size distribution and fatty acid profile

Although "zero waste" valorization concepts are gaining increasing attention, colostrum, a byproduct of milk production, remains underused due to technological challenges. Information about the fat fraction and the size of fat globules is needed to address these challenges, but such information is currently lacking. This study aimed to fill this gap in the knowledge by measuring the size distribution of bovine colostrum fat globules (CFG) and analyzing its relationships with postpartum milkings, parity, and fatty acids (FA) profile. Four sequential postpartum colostrum samples were collected from 44 cows and analyzed for the abovementioned parameters. The results indicated that CFG size increases almost twice during postpartum milkings (from ∼5 to ∼10 µm), whereas lactation has little, if any, effect on CFG size. The FA profile analyses showed that the content of most FA in the fourth postpartum milking was different from the previous milkings. The correlation analyses between CFG size and FA profile also demonstrated that the fourth milking was clearly distinguishable from the first 3 postpartum milkings. For example, the saturated FA content from the first 3 milkings had a positive correlation with smaller CFG (and a negative correlation with larger CFG), whereas the fourth milking demonstrated no correlations. Based on these CFG size and FA profile analyses, the results of this study suggest that the first 3 postpartum milkings can be considered as colostrum, whereas the fourth milking represents transition milk. Information about CFG size distribution enables modification of the FA profile of colostrum products and the ability to create better valorization technologies for colostrum-based food and feed supplements.