Effect of Supplementation of Quercetagetin on the Antioxidant Function, Liver Mitochondrial Function and Gut Microbiota of Broilers at High Stocking Density

This study investigates the effects of quercetagetin (QG) supplementation on the antioxidant capacity, liver mitochondrial function, and cecal microbiota of broilers raised under high-density conditions. A 2 × 2 factorial design with 144 one-day-old WOD168 broilers, which were allocated to two stocking densities (LD: 4 birds per cage, equivalent to 11.1 birds per square meter; HD: eight birds per cage, equivalent to 22.2 birds per square meter) and two levels of dietary supplementation of QG (0 and 20 mg/kg). At the conclusion of day 21, broilers of similar body weights were randomly allocated into four groups (22 to 42 d): control (CON), QG treatment (QG), high stocking density (HSD), and high stocking density with QG supplementation (H_QG). The results demonstrated that HD groups significantly reduced broiler growth performance, including body weight (BW), average daily gain (ADG), and average daily feed intake (ADFI) (p < 0.05). Additionally, HD groups increased serum stress hormone levels (CORT and ACTH), pro-inflammatory cytokines (IL-1β and IL-6) (p < 0.05), while decreasing liver antioxidant enzyme activities (GSH-Px, T-SOD), serum CAT and T-SOD activities, and mitochondrial function (GSH, complex I-III, ATP contents) (p < 0.05). However, dietary supplementation with 20 mg/kg QG significantly alleviated the negative effects induced by HSD, restoring growth performance, stress hormone levels, immune parameters, and liver antioxidant and mitochondrial function. Moreover, QG supplementation markedly improved cecal microbiota composition, enhancing gut health. Correlation analysis revealed a strong association between microbial composition and overall broiler health, indicating that gut microbiota plays a critical role in mediating these beneficial effects. In conclusion, QG exhibits protective effects against oxidative stress, mitochondrial dysfunction, and gut microbiota imbalance induced by high-density rearing, suggesting its potential as a functional feed additive to improve broiler health under intensive farming conditions.