(a) The concentration of total Sia (Neu5Ac, Neu5Gc, Kdn) in mouse milk. (b) The concentration of free Sia (Neu5Ac, Neu5Gc, Kdn) in mouse milk. (c) The percentage of free and bound Sia in total milk Sia. Os, oligosaccharides. (d) The concentration of total Sia (Neu5Ac, Neu5Gc, Kdn) in mouse brain. Blue points = male pups, red points = female pups. (e) The percentage of total Neu5Ac, Neu5Gc, and Kdn in mouse brain Sia.