The study aimed to investigate the dose tolerance of enzymatically degraded feather meal (EFM) in diet, and effect two-stage fermented on growth performance amino acid digestibility broilers. In trial 1, 160 one-day-old broilers were randomly assigned into 0, 10, 15, 20% EFM groups. 2, control, 10% EFM, Bacillus subtilis var. natto N21 + B. coagulans L12 (BBEFM), Saccharomyces cerevisiae Y10 (B...