Variations in the Digestible Sulfur Amino Acid Requirement of Broiler Chickens Due to Sex, Growth Criteria, Rearing Environment, and Processing Yield Characteristics

Abstract

Four experiments (Exp.) were conducted with Cobb 500 chicks to evaluate variations in the estimated digestible sulfur amino acid (DSAA) requirement of broilers due to rearing environment, sex, or growth performance during the starter period (7 to 19 d), and live performance response and carcass yield characteristics during the grower period (21 to 42 d). In the first 3 experiments conducted during the starter period, chicks were allocated to battery or floor pens, and in the fourth experiment birds were reared in floor pens. For Exp. 1, 2, and 3 a sulfur amino acid deficient corn-soybean meal-corn gluten meal basal diet and for the grower experiment a corn-soybean meal-peanut meal basal diet was formulated to be isocaloric and isonitrogenous within experiment. Graded levels of DSAA ranged from 0.54 to 0.94% in Exp. 1, 0.53 to 1.03% in Exp. 2, 0.49 to 0.89% in Exp. 3, and 0.43 to 0.83% in Exp. 4. True digestibility of the diets was determined using the precision-fed rooster assay. The DSAA requirements were estimated using 1-slope broken-line methodology. During the starter period, the average DSAA requirement of males and females was similar when based on the gain to feed ratio (G:F; 0.71 and 0.71%, respectively) and BW gain (BWG; 0.67 and 0.67%, respectively). In Exp. 3 involving battery and floor pens, males and females had similar DSAA requirement estimates, but the DSAA requirement based on maximal G:F (0.68%) was higher than the maximal BWG requirement (0.61%). In the grower period, the estimated DSAA requirement for males based on G:F was higher than that based on BWG, but the BWG and G:F requirements were similar for females. The DSAA requirement estimates were similar for males and females based on BWG (0.55%), but the DSAA requirement based on G:F was higher for males than females. The DSAA requirement for maximum breast meat yield was similar for males (0.55%) and females (0.56%), and the requirement for maximal breast meat yield was similar to that for maximal BWG. The DSAA requirements were similar based on sex, rearing environment, or both; however, there was a difference in the estimated DSAA requirements between growth and carcass responses.