Effect of protease inclusion in diets with high antitrypsin activity soybeans on performance, digestibility, and profitability in broiler chickens

Abstract

Introduction: Soybean meal containing elevated levels of trypsin inhibitors (TI) can impair protein digestion and reduce feed efficiency in broiler chickens. Objective: This study evaluated the inclusion of exogenous protease in diets formulated with low-quality soybean meal and its effects on productive performance, ileal digestibility, carcass yield, and economic efficiency. Materials and methods: A total of 240 Ross AP broilers were randomly distributed into six treatments (20 replicates, 2 birds/replicate) and reared for 42 days. Treatments included: (1) Positive control (PC; standard diet), (2) Negative control (NC; −1% crude protein and −50 kcal/kg ME), (3) NC + 1500 ppm protease (AP1500), (4) NC + 2000 ppm (AP2000), (5) NC + 3000 ppm (AP3000), and (6) NC + 18000 U/kg commercial protease (SP18000). Growth performance was evaluated at 21 and 42 days. Ileal digestibility and carcass characteristics were assessed, and economic efficiency was analyzed based on feed cost, profit per bird, and break-even point. Results: Supplementation with exogenous protease produced significant quadratic responses (p < 0.05) in weight gain and feed conversion ratio. Optimal performance was observed between 1400–1950 ppm, with AP2000 yielding the highest crude protein (+2.27%) and dry matter (+0.18%) digestibility at 21 days. Carcass yield improved linearly with increasing enzyme levels, with AP2000 achieving the highest value (2.17 kg). AP2000 also delivered superior economic efficiency, lowering feed cost per kg live weight (USD 2.70), maximizing profit per bird (USD 1.41), and reducing the break-even point (272 birds). Overdosing (AP3000) proved less effective. Conclusion: Inclusion of 2000 ppm of exogenous protease effectively offsets the adverse effects of trypsin inhibitors in soybean meal, improving ileal digestibility, carcass yield, and overall economic efficiency in broiler production.