There is increasing interest in using locally sourced soybeans and soybean meal. Ileal amino acid digestibility (IAAD) of soybean meal from Kentucky-grown soybeans in broiler chickens was evaluated in 9- and 19-day-old broiler chickens. The experiment used 1,080-day-old male by-product Cobb breeder chicks in a randomized complete block design consisting of 6 treatments with 10 replicate cages of 10 (sampled on day 9) and 10 replicates of 8 (sampled on day 19) birds per cage. All birds were fed a standard corn-SBM-based broiler starter diet that met or exceeded nutrient and energy requirements of the birds. The starter diet was fed until the experimental diets (nitrogen-free diet [NFD], NFD+phytase, NFD+phytase+carbohydrase enzymes, semipurified SBM, semipurified diet+phytase, semipurified diet+phytase+carbohydrase enzymes). For birds that were sampled on day 9, the NFD diets were fed for 3 days (day 6 to 9) while birds on the semipurified diets were fed the experimental diets for 5 days (day 4 to 9). Ileal digesta was collected from all birds on day 9. Similar procedures were followed for birds that were sampled on day 19 with the NFD and semipurified diets being fed for 3 and 5 days, respectively. Data were analyzed as a 2 x2 factorial arrangement of treatments (age x diet) for ileal endogenous amino acid losses (IEAAL), apparent IAAD and standardized IAAD (SIAAD). Data from the NFD were used to determine the SIAAD from the apparent IAAD values. Basal IEAAL and nitrogen losses decreased (P < 0.05) with either phytase (Thr) or a combination of phytase and carbohydrase supplementation (Tyr and Trp) while Cys and Trp endogenous losses increased (P < 0.05) with age. Apparent IAAD was improved by phytase supplementation to the semipurified diet compared to the control diet for Asp, Thr, Ser, Glu, Gly, Pro, Cys, and total amino acid. Apparent ileal digestibility for DM and Pro increased (P < 0.05) with age. After correction for basal IEAAL, the effect of enzyme supplementation was not significant for nitrogen and any amino acid except for Cys, which increased (P < 0.05) with enzyme supplementation. Standardized IAAD values for Ser, Pro, and Cys increased (P < 0.05) with age.