In vitro and some animal models have shown that quercetin, a polyphenol derived from plants, has a wide range of biological actions including anti-carcinogenic, anti-inflammatory and antiviral activities; as well as attenuating lipid peroxidation, platelet aggregation and capillary permeability. This review focuses on the physicochemical properties, dietary sources, absorption, bioavailability and metabolism of quercetin, especially main effects of quercetin on inflammation and immune function. According to the results obtained both in vitro and in vivo, good perspectives have been opened for quercetin. Nevertheless, further studies are needed to better characterize the mechanisms of action underlying the beneficial effects of quercetin on inflammation and immunity.

Quercetin, a polyphenolic flavonoid with diverse biological activities including anti-inflammatory and antiviral, inhibits lipid peroxidation, prevents oxidative injury and cell death. The purpose of the research was to investigate the effect of quercetin on productive performance, reproductive organs, hormones and apoptotic genes in laying hens between 37 and 45 weeks of age, because of the structure and oestrogenic activities similar to 17β-oestradiol. The trial was conducted using 240 Hessian laying hens (37 weeks old), housed in wire cages with two hens in each cage. These hens were randomly allotted to four treatments with six replicates, 10 hens in each replicate and fed with diets containing quercetin as 0, 0.2, 0.4 and 0.6 g/kg feed for 8 weeks. The results showed that dietary quercetin significantly increased (p < .05) the laying rate and was higher in group supplemented with 0.4 g/kg, and feed-egg ratio was decreased (p < .05) by quercetin. Dietary quercetin has no effect (p > .05) on average egg weight and average daily feed intake. Compared with control, secretion of hormones, oestradiol (E ) progesterone (P4), follicle-stimulating hormone (FSH), luteinizing hormone (LH), insulin-like growth factors-1 (IGF-1) and growth hormone (GH), was found to be significantly higher (p < .05) in quercetin-supplemented groups. Also ovary index, uterus index and oviduct index were not significantly influenced (p > .05) by quercetin, whereas magnum index, isthmus index, magnum length, isthmus length and follicle numbers were significantly increased (p < .05) with quercetin supplementation. Additionally, expression of apoptotic genes was significantly (p < .05) up-regulated or down-regulated by quercetin. These results indicated that quercetin improved productive performance, and its mechanism may be due to the oestrogen-like activities of quercetin.

No abstract

The present study was designed to alleviate the negative biohazards of high ambient temperature on the productive performance and physiological status of laying hens. A total of 135 Bovans laying hens were distributed into nine groups in a 3 × 3 factorial design experiment. Basal diet was supplemented with vitamin E at levels of 0, 250, and 500 mg /kg diet. Within each dietary vitamin E level, each diet was supplemented with sodium selenite as a source of selenium (Se) to supply 0, 0.25, and 0.50 mg Se/kg diet. Results showed that supplementing layer's diet with 500 mg vitamin E/kg was accompanied with the lowest feed consumption (FC) and feed conversion ratio (FCR). The interaction among vitamin E and Se levels exerted significant effects only on FC and FCR. Insignificant differences were observed in egg quality criteria due to the treatments studied. Increasing vitamin E level was associated with a gradual decrease in basophil count and an increase in monocytes. A gradual decrease in the count of each of heterophils, monocytes, and eosinophils was observed with the elevation in the dietary Se level. The combination among vitamin E and Se levels produced a significant effect on all hematological parameters studied. As vitamin E increased, a marked decrease in serum AST and a gradual increase in total lipids, total cholesterol, and calcium were observed. As the level of dietary Se increased, serum total protein, albumin, T, total cholesterol, and total lipids increased. No significant impacts were detected for the interaction among vitamin E and Se levels on any of blood constituents determined except serum globulin, ALT, and calcium. In conclusion, the combination between vitamin E and Se showed a good ability to alleviate the harmful impacts of heat stress and produced the highest productive performance when compared with the other groups, which exhibit the synergistic effect between the two antioxidants.

No abstract