Effects of low-protein diet supplemented with exogenous protease on growth performance and intestinal health of broiler chickens

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 < 0.05). Supplementation of different exogenous proteases significantly improved the apparent and true ileal digestibility of specific amino acids, enhanced jejunal chymotrypsin activity, and promoted intestinal morphological development, including increased villus height and villus height-to-crypt depth ratio (P < 0.05). Our findings suggested that the addition of exogenous protease improved the intestinal morphology of broilers.