Immunoglobulins are relatively more resistant to gastrointestinal digestion than other milk or colostral proteins. Upon ingestion and entry into the stomach, the caseins form a curd under the influence of the acidic environment and proteolytic activity. As a consequence, casein is retained in the stomach of the neonate longer than the whey proteins, including IgG [201] . In the intestine, the fate for the other major whey proteins is rapid digestion for α-lactalbumin, while β-lactoglobulin is more slowly digested. Intestinal digestion of IgG is among the slowest of the whey proteins and IgG provides the smallest proportion of amino acids to the neonate relative to the other major whey proteins [201] . In vitro incubations of IgA and IgG with small intestinal content of young lambs have shown that IgA is more resistant towards digestion than is IgG [17] .