title: 2-keto-4-(methylthio)butyric acid (keto analog of methionine) is a safe and efficacious precursor of L-methionine in chicks.
abstract: Relative bioefficacy and toxicity of Met precursor compounds were investigated in young chicks. The effectiveness of DL-Met and 2-keto-4-(methylthio)butyric acid (Keto-Met) to serve as L-Met precursors was quantified using Met-deficient diets of differing composition. Efficacy was based on slope-ratio and standard-curve methodology. Using L-Met as a standard Met source added to a purified diet, DL-Met and Keto-Met were assigned relative bioefficacy values of 98.5 and 92.5%, respectively, based on weight gain. Relative bioefficacy values of 98.5 and 89.3% were assigned to DL-Met and Keto-Met, respectively, when chicks were fed a Met-deficient, corn-soybean meal-peanut meal diet. Thus, both DL-Met and Keto-Met are effective Met precursor compounds in chicks. Additionally, growth-depressing effects of L-Met, DL-Met, and Keto-Met were compared using a nutritionally adequate corn-soybean meal diet supplemented with 15 or 30 g/kg of each compound. Similar reductions in weight gain, food intake, and gain:food ratio were observed for each compound. Subjective spleen color scores, indicative of splenic hemosiderosis, increased linearly (P < 0.01) with increasing intakes of each compound, suggesting a similarity in overall toxicity among these compounds. Because conversion of Keto-Met to L-Met in vivo merely requires transamination, Keto-Met may prove to be a useful supplement not only in food animal production, but also as a component of enteral and parenteral formulas for humans suffering from renal insufficiency.
authors.affiliation: Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Ryan N
authors.initials: RN
authors.lastname: Dilger
authors.forename: Christoph
authors.initials: C
authors.lastname: Kobler
authors.forename: Christoph
authors.initials: C
authors.lastname: Weckbecker
authors.forename: Dirk
authors.initials: D
authors.lastname: Hoehler
authors.forename: David H
authors.initials: DH
authors.lastname: Baker
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002645:Chickens / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D004305:Dose-Response Relationship, Drug; D008715:Methionine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology
chemical_list: C014632:2-keto-4-methylthiobutyric acid; D008715:Methionine