Interrelationships Among Sulfur Amino Acids, Choline and Betaine in the Chicken: Effects on Betaine-Homocysteine Methyltransferase Activity, Homocysteine Utilization and Choline Bioavailability

149 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997.Chick assays (10 to 22-d-old chicks) were conducted to determine choline bioavailability in fluid lecithin (FL), deoiled lecithin (DL), soybean meal (SBM), canola meal (CM) and peanut meal (PM). A basal diet containing soy protein isolate and 2-amino-2-methyl-1-propanol (an inhibitor of choline biosynthesis) was severely deficient in choline, and weight gain of chicks fed this diet responded to choline, but not methionine or betaine. In Assay 1, weight gain of chicks increased linearly $(P0.05)$ affected by severely overheating the oilseed meals. Combined estimates indicated bioavailable choline levels were 87, 27 and 77% of analytically determined total choline levels in SBM, CM and PM, respectively. Three chick assays were conducted to determine effects of dietary changes on hepatic betaine-homocysteine methyltransferase (BHMT) activity. In Assay 1, use of a methionine-deficient purified diet caused a 3-fold increase $(P<0.05)$ in BHMT activity, and addition of choline or betaine further increased $(P<0.05)$ activity. In Assay 2, use of a methionine-deficient corn-peanut meal diet increased $(P<0.05)$ BHMT activity relative to methionine-supplemented chicks, and activity was increased further $(P