Chick responses to dietary arginine and methionine levels at different environmental temperatures.

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Abstract
1. Two experiments were conducted with broiler chicks in battery brooders from 1 to 21 d to determine the broiler chicks' responses to arginine (Arg) and methionine (Met) combinations at control (22 to 25 degrees C) and warm (32 to 35 degrees C) temperatures. 2. In Experiment 1, two levels of Arg (15.2 and 25.2 g/kg of the diet) and two levels of Met (3.5 and 5.5 g/kg) of a maize-soy based diet were fed at two temperatures, 22 or 32 degrees C. Results of Experiment 1 were similar to those of Experiment 2, but most treatment differences were not significant. 3. In Experiment 2, chicks were randomly allotted to 9 dietary treatments: 3 levels of Arg (15.2, 25.2 and 35.2 g/kg of the diet) x 3 levels of Met (3.5, 5.5 and 7.5 g/kg of the diet) at 25 or 35 degrees C. At the warmer temperature, chick growth depression from supplemental Arg was not as severe as at the control temperature (significant Arg x temperature interaction); neither were growth increases as large from supplemental Met (significant Met x temperature interaction). 4. Kidney and breast muscles were collected for arginase activity and creatine analysis, respectively. Remaining chicks were fasted for 10 h and re-fed. Excreta from the next 24 h were collected for total creatine and creatinine analysis. There were no effects of either Arg or Met on muscle creatine concentration at either control or warm temperatures. Chicks raised at 25 degrees C excreted more creatine and creatinine than those raised at 35 degrees C. 5. These results confirm that temperature affects responses to dietary Arg and Met and suggest that the higher temperature slowed the Arg metabolism of chicks through the creatine synthesis pathway.