Dietary Tea Polyphenols Improve Growth Performance, Physiological Health and Economic Efficiency in Nile Tilapia (Oreochromis niloticus)

Abstract

Tea polyphenols (TPs) are natural bioactive compounds extensively used in aquaculture diets as a functional supplement because of their antioxidant, antimicrobial and immunomodulatory potential. Four isonitrogenous diets (crude protein: 30%) were designed with incorporating TPs at levels of 0% (control, TPs-0), 0.025% (TPs-1), 0.05% (TPs-2) and 0.075% (TPs-3) and fed to Nile tilapia for 60 days. The final weight, per cent weight gain (WG), specific growth rate, live WG, feed conversion ratio and protein efficiency ratio were significantly improved (p < 0.05) with increasing dietary TPs supplementation. Visceral–somatic index and hepatosomatic index were significantly greater (p < 0.05) in the TPs-0 treatment. Nile tilapia fed with TPs-supplemented diets revealed significant variations (p < 0.05) of different haemato-biochemical parameters. Dietary TPs also improved gut morphology, including villi height, villi width and goblet cell distribution, with the most pronounced effects found in the TPs-3 group. Fish fed the TPs-0 diet exhibited a higher number of vacuoles, decreased nuclei and cytoplasm, and degenerative hepatocytes. Economic efficiency was significantly (p < 0.05) upgraded in the TPs-3 diet, evidenced by greater farm raw margin, increased revenue, enhanced return on investment and lower farm feed cost. These findings suggest that the ameliorative roles of TPs on growth, health and economic performance are dose-dependent, and the most effective dose could be 0.075%.