Immunochemical Studies on Gastric and Intestinal Digestion of Soybean Glycinin and β-Conglycinin in Vivo

Two experiments were conducted to study gastric and small intestinal digestion of soybean glycinin and β-conglycinin in preruminant calves fed milk replacers containing a mixture of skim milk powder and antigenic heated soybean flour. In experiment 1, duodenal passage of immunoreactive β-conglycinin lasted for a much longer time after the morning meal than that of glycinin. Western blotting revealed the early abomasal outflow of glycinin subunits that associated nearly intact basic polypeptides to partially degraded acidic polypeptides. Intact β-conglycinin was evidenced at most sampling times. In experiment 2, intact basic glycinin (M r = 21000) associated with partially digested acidic glycinin (7000 < M r < 25000) was demonstrated in ileal digesta up to 8−10 h after the meal. β-Conglycinin immunoreactivity could not be evidenced by Western blotting in ileal digesta. Keywords: Calf nutrition; ELISA; protein digestion; soy globulin; Western blotting