Primary Experiments for Determination of Sulfur-Containing Amino Acid Requirement in Female Broilers Affected by Age

The effects of age on sulfur-containing amino acid (SAA) requirement of broilers were studied using body weight gains and feed conversion ratio as main criteria.In Experiment 1, the basal diet contained 20.7% of CP and 3371 kcal/kg of ME. Methionine was added in the range of 0 to 0.5% substituting for the same amount of glutamic acid to make 6 diets with graded levels of SAA. Broiler chicks aged 4 and 24 days old were fed ad libitum the experimental diet and water for 20 days. The body weight and feed intake were recorded on the 10th and 20th days on the experimental diet.In Experiment 2, the basal diet contained 18.6% of CP and 3175 kcal/kg of ME. Methionine was added to make 6 diets with graded levels of SAA by the same method as in Experiment 1. Broiler chicks aged 4 and 21 days old were fed ad libitum the experimental diet and water for 10 days. The body weight and feed intake were recorded on the 10th day.In Experiment 1, the body weight gain increased and then tended to decrease without a significant difference with the increase of methionine addition in all experimental periods. The maximum body weight gain was achieved at 1.14, 1.11 and 1.12% of dietary SAA levels from 4 to 14, 14 to 24 and 4 to 24 days, and 1.03, 0.99 and 1.00% of dietary SAA levels from 24 to 34, 34 to 44 and 24 to 44 days, respectively.The feed conversion ratio at the lowest SAA level did not fit to a linear line. Except this point, it decreased and reached the minimum level at 1.18, 1.08 and 1.10% of dietary SAA levels from 4 to 14, 14 to 24 and 4 to 24 days, and 1.05, 1.02 and 1.03% from 24 to 34, 34 to 44 and 24 to 44 days, respectively.In Experiment 2, the body weight gain and feed conversion ratio showed the same tendency as in Experiment 1. The maximum body weight gain was achieved at 0.97% from 4 to 14 days and at 0.89% from 21 to 31 days. The feed conversion ratio reached the minimum level at 0.97% from 4 to 14 days and at 0.93% from 21 to 31 days.The average requirements determined from body weight gain and feed conversion ratio decreased with increase of age in both experiments.