Sulfur amino acid requirement of broiler chicks from fourteen to thirty-eight days of age. 1. Performance and carcass yield.

Two experiments were conducted to evaluate increasing dietary levels of methionine and TSAA on broiler performance and carcass yield. In Experiment 1, the corn-soybean basal diet contained .75% TSAA, to which increasing dose levels of DL-methionine were added, providing at the highest supplemental level .95% TSAA. The experimental diets were fed for 20 d, covering the age period of 14 to 34 d. In Experiment 2, a corn-soybean basal diet containing .70% TSAA was used along with DL-methionine supplements to determine TSAA requirement during the age period of 14 to 38 d. The highest supplemental level of DL-methionine in this experiment provided .94% TSAA. The TSAA requirement was found to be higher for maximum efficiency of feed utilization and breast meat yield than for obtaining maximum weight gain. Based on feed conversion efficiency and breast meat yield, the requirement for TSAA was estimated to be at least .88% for the age period of 14 to 34 or 38 d. It was calculated that the estimated TSAA requirement was equivalent to approximately .75% apparent digestible SAA or .78% true digestible SAA.