New neutral oligosaccharides from cow colostrum rc-casein were identified and characterized by 500-MHz New neutral oligosaccharides from cow colostrum It-caseinoglycopeptide samples (C-terminal part of cow ic-casein, residues 106 -169, containing all the sugars) obtained 15 min, 18 h and 42 h after calving are described. While only one neutral disaccharide GalP(l-+ 3)GalNAc-01 was identified in mature milk Ic-caseinoglycopeptide which had no blood group I specificity, four neutral oligosaccharides (from di-to pentasaccharide) were characterized by 500-MHz 'H-NMR spectroscopy in cow colostrum It-caseinoglycopeptide. The latter and the tetrasaccharide which it contains inhibited the hemagglutination of I-positive human erythrocytes. Immunological experiments seem thus to rule out the possibility that the short sugar groups observed just after calving are split products arising from longer prosthetic oligosaccharides. MATERIALS AND METHODS IC-Case inogly copep t ide preparationCow colostrum Ic-caseinoglycopeptide was prepared according to [3] from the colostrum of a unique cow obtained