Sulfur Amino Acid Requirement of Broiler Chickens from 3 to 6 Weeks of Age

Abstract

Two experiments were conducted to determine if the TSAA level suggested by the National Research Council (NRC) in 1984 was adequate for optimum performance of 3 to 6-wk-old broilers, and to assess the effect of added copper on the TSAA requirement. A 2 × 3 × 2 factorial arrangement involving two copper (0 and 240 ppm) and three TSAA levels (.72, .78 and .84%) and two sexes was used in each experiment. Copper sulfate (CuSO4·5H2 O) and DL-methionine were the dietary supplements to pelleted diets. There were four groups of 20 males or 20 females in each experiment, housed in floor pens.Methionine supplementation significantly improved body weight gain and feed efficiency in males but not in females. A significant copper × methionine interaction was observed, with methionine supplementation improving feed efficiency more in the presence of copper than in its absence. Abdominal fat per unit of body weight was significantly reduced by both methionine and copper in females but not in males. In a second experiment, methionine significantly improved body weight gain in males fed no added copper and significantly reduced abdominal fat per unit of body weight. Methionine supplementation improved body weight gain in males more in the absence than in the presence of copper (significant TSAA × copper interaction). Methionine supplementation had no significant effects on performance of females in the second experiment, but copper supplementation significantly improved feed efficiency.Combined data from the two experiments showed that in males body weight gain and feed efficiency were significantly increased and abdominal fat significantly decreased, whereas in females, only body weight gain was significantly increased and abdominal fat significantly decreased by increasing the dietary TSAA level. The TSAA requirement of .72% recommended by the NRC for 3 to 6-wk-old broilers appears inadequate; a minimum requirement of .78% is suggested.