Distribution of bovine milk sialoglycoconjugates during lactation

The sialoglycoconjugate content of human milk has been extensively studied. However, little attention has been paid to the changes occurring in these compounds in bovine milk during lactation. Since sialoglycoconjugates are v ery abundant in milk from the early stages of lactation, they have been sug gested to be important for the nutrition of the newborn during the first mo nths of life. The distribution of sialoglycoconjugates (expressed as glycoc onjugate-bound sialic acid) from four different stages of lactation (colost rum, transitional, mature, and late-lactation milks) was investigated in fo ur Spanish-Brown cows. All the fractions studied (total sialic acids, glyco proteins, oligosaccharides, casein, and gangliosides) showed a similar tren d. We found the highest values in the colostrum, these decreasing in transi tional and mature milks and increasing again in late-lactation milk. We als o found a selective change in the relative contents of glycoprotein- and ol igosaccharide-bound sialic acids. In mature milk, the latter increased up t o 80% (59% in colostrum) and the former decreased to 3.9% (35.3% in colostr um). It would appear that the decrease in oligosaccharide-bound sialic acid is compensated by the increase in glycoprotein-bound sialic acid. From the se results, it is deduced that newborn infants or calves fed with infant fo rmulas or milk replacers, respectively, should be supplemented with sialogl ycoconjugates to approximate the composition of human and cow milk as far a s is practicable.