Liu, Guanchen2020-06-232020-06-232019-12Liu_cornell_0058O_10768http://dissertations.umi.com/cornell:10768https://hdl.handle.net/1813/70109113 pagesTwo studies were conducted to investigate effects of supplementing 100 or 130% of the required digestible methionine to corn-soybean meal-based grower and finisher diets (1) as DL-methionine (DL-MET) for broilers housed in a higher density and (2) as either DL-MET or 2-hydroxy-4-(methylthio)butanoate (HMTBA) for broilers exposed to a high ambient temperature. In the first study, the high density impaired (P < 0.05) growth performance in both phases, decreased (P < 0.05) liver and adipose tissue fatty acid concentrations, and increased (P < 0.05) glutathione (GSH) in all assayed tissues except for the liver of the growers. The 130% DL-MET supplementation decreased (P < 0.05) feed intake of the finishers as well as the finisher breast and thigh malondialdehyde (MDA) levels. DL-MET elevated (P < 0.05) GSH in the grower thigh and fatty acid concentrations in the finisher liver. The hepatic expressions of heat shock protein 90 (HSP90) was decreased (P < 0.05) by the extra methionine supplementation. In the second study, the 130% methionine supplementations of both forms enhanced (P < 0.05) hepatic GSH concentrations of the growers and ferric reducing ability of plasma (FRAP) of the finishers. The DL-MET-fed growers had greater (P < 0.05%) muscle GSH and hepatic unsaturated fatty acid concentrations than those fed HMTBA. Expression of inflammation-related genes in the liver of finishers was affected (P < 0.05) by interaction effects of the methionine form and concentration. In summary, extra methionine supplementation showed moderate beneficial effects on tissue antioxidant status and growth performance of broilers under environmental stresses.enBroilerhigh stocking densityHigh temperatureMethionineOxidative stressdissertation or thesishttps://doi.org/10.7298/08d6-wd61