Breed and Early Postpartum Stage Determine Physicochemical Microstructural and Rheological Properties of Indonesian Goat Colostrum

Abstract Colostrum is the first mammary secretion produced after parturition and represents a biologically active fluid essential for neonatal survival, immune maturation, and early growth. Despite its importance, the compositional and functional diversity of goat colostrum across breeds and postpartum stages remains insufficiently described. This study evaluated the physicochemical, rheological, and microstructural properties of colostrum from four Indonesian goat breeds—Kacang, Local Gorontalo, Saanen crossbreed, and Etawa crossbreed—during the first three days postpartum. Analytical approaches included proximate composition, amino acid and fatty acid profiling, sodium dodecyl sulfate–polyacrylamide gel electrophoresis, high-performance liquid chromatography, gas chromatography, particle size and zeta potential analysis, rheometry, and confocal microscopy. Results revealed significant effects of both breed and day. On Day 1, Saanen crossbreeds showed the highest crude protein (16.5 ± 0.3%) and fat (6.7 ± 1.5%), whereas Kacang and Local Gorontalo exhibited higher lactose (3.5 ± 0.3% and 3.7 ± 0.2%). Amino acid analysis demonstrated enrichment of leucine, lysine, and valine in crossbreeds, while indigenous breeds contained greater methionine and cysteine. Fatty acid profiling revealed higher polyunsaturated fatty acids and conjugated linoleic acid in crossbreeds, supporting immune and metabolic health. Rheological data confirmed greater viscosity (1.95 × 10⁵ Pa·s) and yield stress (418 Pa) in crossbreeds compared with indigenous goats (9.8 × 10⁴ Pa·s; 312 Pa). Confocal microscopy further revealed denser protein–fat matrices in crossbreeds and looser structures in indigenous breeds. These findings highlight genetic and temporal influences on goat colostrum quality, offering insights for breeding, neonatal nutrition, and sustainable dairy product development.