Effects of dietary supplementation with quercetin on broiler immunological characteristics

Quercetin, among other flavonoids, is under investigation as feed additive for poultry due to its antioxidative properties. Quercetin is also known to possess immunomodulatory and in particular anti-inflammatory properties. As uncompromised immune function is important for poultry productivity and welfare this study investigates possible effects of dietary supplementation of broilers with quercetin on their immune function and immune status. We assessed aspects of the chickens cell-mediated and humoral immune response and immune status when fed with diets supplemented with quercetin at 0.5 and 1 g/kg feed compared to control diets. We measured their cellular immune response to the phytohaemagglutinin skin test, their humoral immune response to sheep red blood cells and assessed the status of the birds' lymphoid organs and the cell subset composition of the thymus. We found no differences between dietary treatment groups in cellular immune response or immune status (P>0.05). Interestingly, while total and IgM antibody titers did not differ among treatment groups (P>0.05), IgY antibody titers significantly increased with increasing quercetin supplementation (P-linear<0.05). Therefore, dietary quercetin did not compromise any of the immune parameters tested but on the contrary enhanced IgY antibody production.