Multi-component protease supplementation restores growth performance in broiler chickens fed reduced amino acid density diets achieved by lowering soybean meal or crystalline amino acids

This study evaluated the effects of multi-component protease ( MCP ) supplementation on growth performance, organ weight, and litter characteristics in broiler chickens fed diets with ∼5% reduced standardized ileal digestible ( SID ) amino acid ( AA ) density, achieved by lowering soybean meal ( SBM ) or crystalline amino acids ( CAA ). A total of 1,350 Ross 708 male broilers were randomly allocated to 45 floor pens (30 birds/pen) and assigned to one of five isocaloric dietary treatments from 0 to 56 d of age: (1) positive control (PC) meeting Ross 708 breeder nutrient specifications; (2) negative control 1 (NC1) with reduced SID AA via lowered SBM; (3) NC1 + 250 ppm MCP; (4) negative control 2 (NC2) with reduced SID AA via lowered CAA; and (5) NC2 + 250 ppm MCP. Broilers fed NC1 and NC2 showed reduced BWG and poorer FCR compared with PC during starter (0–14 d; P ≤ 0.05), grower (15–28 d), and finisher 1 (29–42 d) phases (P ≤ 0.05). MCP supplementation improved BWG and FCR in both NC diets, restoring performance to PC levels during 0–42 d. At 42 d, AA reduction source × MCP interactions were observed for body weight, absolute breast weight, and relative liver weight (P < 0.05). Total litter N was lower in SBM-reduced diets than CAA-reduced diets (P < 0.05). In conclusion, MCP effectively mitigated growth performance deficits from 5% SID AA reduction, irrespective of reduction method (SBM or CAA), with benefits limited to pre-42 d.