arbor acres chickens, feed efficiency, intestinal morphology, low-protein diet, nutrient digestibility, protease supplementation, Animal culture, SF1-1100

This experiment was conducted to study the effects of low-protein diet supplemented with exogenous protease on performance and intestinal health of broilers. A total of 560 one-day-old male Arbor Acres broiler chickens were randomly divided into 5 treatments with 8 replicates (12 birds per replicate) in a completely randomised design. The treatments were as follows: (1) maize-soybean meal basal diet (CON); (2) negative control with crude protein being 1% lower than in CON (NCON); (3) NCON + 12 000 U/kg coated alkaline protease (NCAP); (4) NCON + 16 000 U/kg alkaline protease (NAP); (5) NCON + 16 000 U/kg keratinase (NKA). The remaining 80 birds (10 replicates, 8 birds per replicate) were randomly assigned to endogenous indicator measurements. The results indicated that the NCON diet resulted in a higher feed-to-gain ratio and reduced protein digestibility, ileal amino acid digestibility, and intestinal morphological parameters (P