Impact of Feeding 2-Hydroxy-4-(methylthio)butanoic Acid and DL-methionine Supplemented Maize-Soybean-rapeseed Meal Diets on Growth Performance and Carcase Quality of Broilers.

1. This experiment was conducted to compare the effectiveness of DL-2-hydroxy-4-(methylthio)butanoic acid (HMTBA) and DL-methionine (DLM) on growth performance and carcase quality of broilers in a 2 x 3 x 2 factorial experimental design including two methionine (Met) sources, three equimolar levels of Met supplementation and two sexes. 2. No difference was observed between the two Met sources in growth performance and muscle deposition from 10 to 49 d. With increasing Met levels, average daily gain was increased in the starter, grower and overall phases, average daily feed intake was increased in the starter phase, and feed:gain ratio was decreased in the grower and overall phases. Met supplementation increased breast muscle content and decreased abdominal fat content. Broilers given HMTBA had breast and thigh muscle coloration that was characterised as superior to those fed DLM. 3. These results indicated that Met supplementation improved growth performance and carcase quality irrespective of the Met sources. Compared to DLM, HMTBA has the same molar bioefficacy for improving the growth performance and carcase quality; however, HMTBA-fed birds had superior meat colour to DLM-fed birds.