Multienzyme supplementation improves bone strength in nutrient-restricted broilers without altering locomotor ability or pectoral myopathy severity

1. This study evaluated the effects of exogenous enzyme supplementation on bone quality, locomotor ability and pectoral myopathy severity in broilers given nutrient-restricted diets.2. A total of 1,400 one-day-old male Cobb 500 broilers were distributed among seven treatments. These included a positive control (PC); NC1 (reductions of 100 kcal ME/kg, 0.18% available phosphorus and 0.20% calcium); NC2 (reductions of 1.5% crude protein, 0.18% available phosphorus and 0.20% calcium); NC3 (combined reductions of 100 kcal ME/kg, 1.5% crude protein, 0.18% available phosphorus and 0.20% calcium); and their respective enzyme-supplemented diets: NC1 + phytase + carbohydrases (CPNC1), NC2 + phytase + protease (PPNC2) and NC3 + phytase + carbohydrases + protease (CPPNC3).3. Locomotor ability was assessed using gait score, pododermatitis, angular deformities and tibial dyschondroplasia. Bone quality was evaluated using tibial morphometry, Seedor index, ash content and mechanical resistance. Pectoral myopathies (wooden breast and white striping) were assessed.4. Nutrient restriction without enzyme supplementation reduced tibial weight, length, Seedor index and bone strength (p < 0.05). Compared with nutrient-restricted diets, enzyme supplementation increased bone strength, with PPNC2 restoring mechanical resistance to values comparable to those of the PC (p < 0.001). No significant differences were observed in gait score, tibial dyschondroplasia, angular deformities, or wooden breast severity (p > 0.05). Femoral degeneration scores were lower in birds fed nutrient-restricted diets, regardless of enzyme supplementation (p = 0.037). Pododermatitis scores were lower in NC2 and CPPNC3 than in the PC (p < 0.01). White striping severity differed among treatments (p = 0.038), with lower scores in birds fed nutrient-restricted diets without enzyme supplementation, although the magnitude of these differences was small.5. Exogenous multienzyme supplementation improved bone strength in broilers fed nutrient-restricted diets without adversely affecting locomotor ability. However, it did not consistently reduce pectoral myopathy severity, reinforcing the multifactorial nature of these conditions.