Background:Several infant formulas are bovine milk-based products. Mature bovine milk has a very low sialoglycoconjugate content compared with human milk from the first phases of lactation.Methods:The present study was undertaken to determine total sialic acid and oligosaccharide, glycoprotein, and ganglioside sialic acid contents of bovine milk-based formulas.Results:Starter formulas, designed for the first days/weeks after birth, have very similar sialic acid contents (233-266 mg/L fresh milk). We found more oligosaccharide-bound sialic acids (167-174 mg/L fresh milk) than those bound to proteins (53-84 mg/L fresh milk) in these formulas. The ganglioside sialic acid contents of starter formulas (952-1135 μg/L fresh milk) vary slightly from formula to formula. However, all the above-mentioned contents are lower than in human colostrum or transitional milk.Conclusions:Infants fed starter formulas have total sialic acid and oligosaccharide, glycoprotein, and ganglioside sialic acid intakes of 36, 28, 50, and 20%, respectively, of those fed human colostrum or transitional milk. By contrast, follow-on formulas, used from 4 to 5 months of age, provide total sialic acid and oligosaccharide, glycoprotein, and ganglioside sialic acid contents similar to those furnished by mature human milk. Since the reference standard for optimal nutrition in the early months of infancy is human milk, a supplementation with sialic acid-containing glycoconjugates of infant formulas recomended for the first daysafter delivery could be advisable when breast-feeding is not possible.