The Effect of Dietary Metabolisable Energy and Stocking Density on Growth Performance, Blood Metabolites, Nutrient Utilization, and Carcass Traits in Broiler Chicks

This study aimed to evaluate the effects of dietary metabolisable energy (ME) levels and stocking density (SD) on growth performance, carcass traits, blood metabolites, and apparent total tract digestibility (ATTD) of nutrients over a 42-day feeding trial in broiler chicks. A total of 468 one-day-old male Ross 308 broiler chicks were used in a completely randomized design featuring a 3 × 3 factorial arrangement. The experiment included three SDs (10, 13, and 16 birds/m²; SD10, SD13 and SD16, respectively) and three dietary ME levels: 3% lower than the recommendation, recommended for the strain, and 3% higher than the recommendation (recommended-energy, high-energy, and low-energy diets, respectively), with five replicates per treatment. During the starter phase, feed intake (FI) was significantly (<i>p</i> < 0.05) lower in broilers fed high-energy diets compared to those fed low-energy and recommended diets. Additionally, SD16 exhibited higher FI than SD10 and SD13 (<i>p</i> < 0.05). Birds fed recommended and high-energy diets showed greater weight gain (WG) during the finisher and overall experimental periods compared to those fed low-energy diets. WG in SD16 was significantly higher than in SD10 during the starter phase (<i>p</i> < 0.05). The feed conversion ratio (FCR) was significantly increased in birds fed low-energy diets compared to the other two groups. Blood cholesterol, triglycerides, and HDL-C concentrations were significantly higher in the recommended and high-energy diet groups compared with the low-energy group (<i>p</i> < 0.05). ATTD for lipids was notably lower in chicks fed low-energy diets than in those on the other two diets (<i>p</i> < 0.05). Overall, high and recommended energy levels in the diet increased WG and improved FCR, but elevated blood cholesterol concentration. Increasing the stocking density to 16 birds/m² did not negatively impact broilers performance.