Choline bioavailability assessment of oilseed meals in chicks

Choline plays an important role in human health via its relationship to homocysteine metabolism, and it is an essential nutrient for young chicks. Our objective was to evaluate choline bioavailability in soybean meal (SBM), canola meal (CM) and peanut meal (PM), using a severely choline-deficient diet containing soy protein isolate and 2-amino-2-methyl-1-propanol, an inhibitor of choline biosynthesis. In Assays 1 to 3, 10-d-old chicks were fed the basal diet for 12-d, and weight gain increased (P < 0.05) in response to choline, but not (P > 0.05) to betaine, methionine, or excess amino acids, indicating that the basal diet was deficient in preformed choline per se. When the basal diet was fortified with adequate choline, weight gain was not affected (P > 0.05) by 10% dietary SBM, CM or PM. Choline bioavailability in oilseed meals was assessed in two 12-d assays. In Assay 4, weight gain of chicks fed the basal diet increased linearly (P < 0.01) with increasing concentrations of crystalline choline, SBM, CM or PM. Using multiple linear regression analysis, bioavailable choline contents for SBM, CM and PM were 1,708, 1,545 and 1,203 mg/kg, respectively. In Assay 5, similar methodology led to bioavailable choline estimates of 2,002, 1,464 and 1,320 mg/kg for SBM, CM and PM. Severe overheating of the oilseed meals did not (P > 0.05) affect bioavailability. Combined estimates from both assays indicated that bioavailable choline levels were 87, 27 and 77% of analytically determined total choline levels in SBM, CM and PM, respectively. The percentage of choline that was bioavailable was similar in SBM and PM, but was much lower in CM.