Impact of flavonoids as functional food additives on the health of Nile tilapia, Oreochromis niloticus

Flavonoids, with their diverse bioactive properties, are a group of over 4,000 naturally occurring phenolic compounds found in plants. They are mainly categorized into six classes: flavanones, flavones, flavonols, isoflavonoids, anthocyanins, and flavans. This study evaluates the effects of three flavonoids (catechin, quercetin, and hesperidin) on growth, feed utilization, hematological parameters, serum biochemistry, immune responses, and Nile tilapia, Oreochromis niloticus , resistance to bacterial challenges. Two dietary levels (0.1% and 1.0%) of each flavonoid and a control diet were offered twice daily to three replicate groups of tilapia (initial weight 11.5g) for 8 weeks. High levels (1%) of both quercetin and catechin resulted in reduced weight gain and feed consumption. At 1% inclusion levels, hesperidin significantly enhanced serum complement activities, while catechin increased serum globulin levels. However, catechin reduced erythrocyte count, hemoglobin concentration, and hematocrit at this concentration, whereas quercetin decreased liver size and lipid content. Both dietary hesperidin and catechin concentrations (0.1% and 1.0%) significantly improved survival rates following a challenge with Streptococcus iniae compared to the control group. In conclusion, hesperidin can be used effectively as a functional feed additive in tilapia diets at concentrations up to 1%. It enhances immunity and offers better protection against S. iniae . Similarly, lower concentrations of catechin (<1%) can also be beneficial for protecting against S. iniae .