Effect of dietary supplementation with quercetin or rutin on the growth performance, meat quality and cecal microbiota of broilers under high stocking density.

This study aimed to investigate the effects of quercetin and rutin (the glycoside form of quercetin) on growth performance, organ indices, meat quality, serum biochemistry, intestinal morphology, and cecal microbiota of broilers under high stocking density, and compared their differential effects. A total of 480 one‑day‑old male Cobb500 broilers were randomly allocated to 6 treatment groups (6 replicates per group): a control group reared at 14 broilers/m², a high stocking density group at 20 broilers/m², and four high stocking density groups fed diets supplemented with 400 ppm or 800 ppm quercetin or rutin, respectively. The results of this study show that, compared with the control group, high stocking density, as well as supplementation with 400 ppm quercetin, 400 ppm rutin, and 800 ppm rutin, significantly reduced FI and BWG throughout the entire trial period. However, supplementation with 800 ppm quercetin showed a trend toward alleviating the reduction in FI and BWG caused by high stocking density. Supplementation with quercetin significantly increased the meat color of the pectorales at 45 min postmortem, whereas rutin supplementation significantly reduced drip loss of the pectorales at 24 h postmortem. Furthermore, quercetin and rutin supplementation significantly increased the chao1 index, enriched the beneficial intestinal bacteria