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

This experiment was conducted tostudy the effects oflow-protein diet supplemented with exogenous protease onperformance and intestinal health ofbroilers. Atotal of560 one-day-old male Arbor Acres broiler chickens were randomly divided into 5treatments with 8replicates (12birds per replicate) inacompletely randomised design. The treatments were asfollows: (1)maize-soybean meal basal diet (CON); (2)negative control with crude protein being 1% lower than inCON (NCON); (3)NCON+ 12000U/kg coated alkaline protease (NCAP); (4)NCON+ 16000U/kg alkaline protease (NAP); (5)NCON+ 16000U/kg keratinase (NKA). The remaining 80birds (10replicates, 8birds per replicate) were randomly assigned toendogenous indicator measurements. The results indicated that the NCON diet resulted inahigher feed-to-gain ratio and reduced protein digestibility, ileal amino acid digestibility, and intestinal morphological parameters (P<0.05). Supplementation ofdifferent exogenous proteases significantly improved the apparent and true ileal digestibility ofspecific 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.