Four serum protein components are present at birth: α-, β- and γ-globulins and albumin.

The preferential transfer of γ rather than β-globulin, which occurs both prenatally and postnatally in this species, is reflected in the initial amounts of these proteins present at birth and in the relatively rapid increase in the concentration of γ-globulin which occurs postnatally. By five weeks of age seven protein components are discernible in the serum, which is comparable in this respect to adult serum.

The albumin/globulin ratio changes from about 1.5 at birth to about 0.3-0.4 in the active adult.