Effects of dietary supplementation of quercetin on performance, egg quality, cecal microflora populations, and antioxidant status in laying hens.

Plant polyphenols, especially flavonoids, are of great interest due to their wide range of biological activities. Quercetin, a ubiquitous flavonoid, is known to have antioxidant and antibacterial effects. In this study, we investigated the effect of quercetin on performance, egg quality, cecal microflora populations, and antioxidant status in laying hens. Two hundred forty 28-wk-old Hessian laying hens, with an average laying rate of lay 85% at the start, were randomly allotted to 4 treatments and fed 1 of 4 diets (negative control, 0.2, 0.4, and 0.6 g of quercetin/kg of diet) for 8 wk. Layer performance responses, egg quality parameters, cecal microflora populations and antioxidant status were measured at the end of the experiment. Results showed that feed conversion decreased as the quercetin level increased. Laying rate had a quadratic correlation with the level of quercetin (P = 0.056) and was maximized by the supplementation level of 0.2 g/kg of diet. However, no significant quercetin effect was observed on egg quality. Regression analysis showed that the population of total aerobes and coliforms decreased and the population of Bifidobacteria increased as the level of quercetin increased. Regression analysis also showed the activities of Cu-Zn-superoxide dismutase increased as the level of quercetin increased (P < 0.05). Results of the study suggest that the appropriate level of supplementation is 0.367 to 0.369 g of quercetin/kg of feed based on the improvement of laying rate (with 88.55 as maximum value) and feed conversion (with 2.0725 as minimum value). Our observations provided further evidence that dietary supplementation of quercetin improved performance by modulation of intestinal environment and liver superoxide dismutase content in laying hens. Quercetin has the potential as functional feed additive in animal production.

Effect of quercetin on performance and egg quality during the late laying period of hens.

1. At the end of the peak laying period for fowl, both performance and egg quality decrease markedly. Counteracting either or both of these could, therefore, have significant positive economic implications. Quercetin, a typical representative of the flavonol compounds, has a variety of biological functions. However, there are no reported findings on its use as a feed additive. 2. In this study, we investigated the effects of quercetin on laying rate, egg quality and blood traits associated with egg quality in laying hens (Hessain) during the late laying period and explored the possibility of using quercetin as a functional feed additive. 3. The laying hens (n = 240; 39 weeks old) were randomly assigned to 4 treatments consisting of 6 replicates (n = 10) and were fed with diets containing quercetin at 0, 0.2, 0.4 or 0.6 g/kg. 4. Results showed that laying rate was increased and feed-egg ratio was decreased significantly by 0.2 and 0.4 g/kg quercetin. Compared with controls, Haugh unit, eggshell strength, eggshell thickness and yolk protein were increased, but yolk cholesterol was decreased by quercetin. 5. In conclusion, quercetin was beneficial in improving performance and egg quality. The recommended concentration of quercetin is 0.4 g/kg of the basal diet. At this concentration, increased laying rate, improved egg quality and reduced yolk cholesterol can be expected.