Antioxidant response and bioavailability of methionine hydroxy analog relative to DL-methionine in broiler chickens

This study was designed to compare the effect of methionine (Met) sources (DL-methionine [DLM] and DL-2-hydroxy-4-methylthio-butanoic acid [HMTBa]) and their supplementation levels on broiler growth performance and redox state. A 2 × 2 factorial arrangement was used with 2 sources (DLM and HMTBa) and 2 supplementation levels (0.05% and 0.25%) of Met. A total of 480 one-day-old broiler chicks were randomly divided into 4 treatments with 8 replicates per treatment (15 birds per replicate). The experiment lasted for 21 d. Broiler growth performance, redox capacity, redox-related genes expression, and Met transporters in different tissues were tested. Broilers fed high Met supplementation levels had improved (P < 0.05) body weight (BW), average daily gain (ADG) and feed conversion ratio (FCR). Similarly, broilers fed high Met levels had better (P < 0.05) antioxidant abilities in the serum, small intestine, and liver. Whereas, interactive effects (P < 0.05) were also observed between Met sources and levels. Compared with DLM, birds fed HMTBa diets had decreased (P < 0.05) total glutathione (T-GSH) and oxidized glutathione (GSSG) contents in duodenum, ileum, and liver. Similarly, broilers fed HMTBa supplemented diets had increased (P < 0.05) thioredoxin (Trx) gene expression in the duodenum and ileum, but decreased (P < 0.05) glutaredoxin (Grx), glutathione reductase (GSR), and glutathione synthetase (GSS) genes expression. Furthermore, lower gene expression of Na(+) and Cl(−) dependent neutral and cationic amino acid transporter (ATB(0, +)), and Na(+) dependent neutral amino acid transporter (B(0)AT) in the duodenum brush border, but higher gene expression of diamine acetyltransferase 1 (SAT1) and Na(+)-independent branched-chain and aromatic amino acid transporter (LAT1) in the jejunum and ileum basement membrane along with higher expression of the proton dependent monocarboxylate transporter 1 (MCT1) gene in the ileum were detected in birds fed HMTBa diets. In conclusion, DLM can be effectively used in glutathione synthesis to exert antioxidant functions, whereas HMTBa favors S-adenosylmethionine (SAM) synthesis and thus stimulates antioxidant-related genes expression.