GROWTH PERFORMANCE, FEED EFFICIENCY AND BLOOD PARAMETERS IN NILE TILAPIA EXPOSED TO MERCURY TOXICITY AND ITS REDUCTION BY USING DIETARY SUPPLEMENTATION OF ESSENTIAL OILS

Abstract

A 112-day feeding trial was performed to investigate the toxic effects of mercury on Nile tilapia (Oreochromis niloticus) and attempt to detoxify these drastic effects by using dietary supplementation of citronella (Cymbopogon nardus) and geranium (Pelargonium graveolens) (GEO) essential oils. Fish were divided into four groups, each group was stocked into 3 aquaria, each one contains 10 fish. The first group was fed on basal diet without mercury, the second group was fed on basal diet containing 50 ppm mercury as mercuric chloride (HgCl2), each of third and fourth group was treated with 50 ppm HgCl2 and supplemented with 400 mg/kg diet citronella or geranium oils, respectively. Live body weight at 16 week was significantly increased by 40.76%, 22.64 and 12.41%, respectively in each of fish group fed diets without mercury (basal diet), fish group fed a diet contaminated with mercury and supplemented with citronella oil and fish group fed a diet contaminated with mercury and supplemented with geranium oil when compared with those fed diet contaminated with mercury. Also, daily weight gain at 0-16 weeks significantly increased by 51.38, 28.44 and 15.60%, respectively. Feed conversion at 0-16 weeks significantly improved by 29.56, 16.92 and 14.27%, in fish group fed diets without mercury (basal diet), fish group fed a diet contaminated with mercury and supplemented with citronella oil and fish group fed a diet contaminated with mercury and supplemented with geranium oil, respectively, when compared with those fed diet contaminated with mercury. Serum total protein and albumin significantly increased, while serum ALT, AST, urea-N and Createnine were decreased in fish groups fed diets without mercury. Also serum total protein increased in fish groups fed diet contaminated with mercury and treated with citronella or geranium oil than those fed diet contaminated with mercury. Residual of mercury significantly decreased (P<0.001) by 29.53 and 31.49 in liver and muscles of fish group fed a diet contaminated with mercury and supplemented with citronella oil, respectively. Also in fish group fed a diet contaminated with mercury and supplemented with geranium oil decreased by 41.45 and 47.24, respectively. Based on the obtained results it could be concluded that, growth rate and feed conversion improved by dietary essential oils supplementation.