Dose-dependent effects of dietary quercetin supplementation on growth performance, nutrient digestibility, meat...

Objectives: This study aimed to determine the optimal dose of quercetin (plant origin) on growth performance, nutrient digestibility, meat composition, shank mineralization, and production costs in broilers. Materials and Methods: A total of 180 day-old, mixed-sex Ross 308 chicks were randomly assigned to four dietary groups, with five replicates of nine birds per group. The corn-soy-based basal diet provided 2998 kcal metabolizable energy (ME)/kg and 22.94% crude protein (CP) in the starter diet and 3120 kcal ME/kg and 21.25% CP in the grower diet. The basal diet was supplemented with quercetin at 0.00, 0.40, 0.80, or 1.20 gm/kg, corresponding to the 0.00Q (control), 0.40Q, 0.80Q, and 1.20Q groups, respectively. Results: Quercetin supplementation at increasing levels improved feed intake and body weight gain, increased conversion ratios (feed, CP, and ME), and increased meat fat content, with the 1.20Q group showing the greatest effects (p ≤ 0.05). However, there were no significant differences among the quercetin-supplemented groups. Moreover, quercetin supplementation had no impact on broiler dressing yield (DY), drip loss, meat components (dry matter (DM), CP, and ash), shank DM, and ash percentages (p > 0.05). Shank dry weight, DM, ash yield, and nutrient digestibility were significantly improved in the 1.20Q group compared to the control and 0.40Q groups (p < 0.05). Quercetin supplementation at increasing levels significantly increased feed and quercetin costs but improved profit and the benefit-cost ratio (BCR), with the 1.20Q group showing the greatest improvement (p < 0.05). Conclusions: Supplementation at 1.20 gm quercetin/kg diet improved growth performance, digestibility, shank mineralization, and BCR, but had no significant effect on DY and meat composition except for fat content.