Nutritional Value And Risk Assessment Of Toxic Heavy Metals Of Selected Fish Species From Freshwater Ecosystems In Ethiopia

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One of the traditional sources of animal protein of the developing world is through livestockrnrearing. Unfortunately, the livestock production is under increasing pressure from the combinedrneffects of human population growth, shortage of grazing land and expantion desertification.rnTherefore, it is important to look for fish, which is the cheap source of animal protein andrnan important source of high quality protein as it contains large amounts of essential amino acids.rnIn addition, fish contains crude lipids, which supply the body with energy as well as omega-3 fattyrnacids- the healthy fats that playa role in regulating blood cholesterol and supporting proper brainrnfunctioning. Moreover, fish is rich in iron, zinc, magnesium, and copper. Despite this fact,rnbiochemical composition and toxic metal accumulation of different fish species from variousrnfreshwater ecosystems had gained little emphasis in Ethiopia. Therefore, the present study wasrnconducted to evaluate the nutritional quality, health benefits and toxic heavy metal risk assessmentrnof selected fish species collected from four freshwater ecos ystems in Ethiopia.rnIn this study, a total of 80 (40 females and 40 males) fish samples of two freshwater fish species,rnnamely African catfish and Nile tilapia (C gariepinus and 0. niloticus) were collected from fourrnfreshwater bodies of Alwero River, Abay River, Lake Hawassa and Lake Ziway found in Ethiopia.rnThe fish samples were transported to the Center for Food Science and Nutrition, Addis AbabarnUniversity for further analysis. Proximate analysis of the fish samples was done by Association ofrnOfficial Analytical Chemists (AOAC) method. Minerals in fish samples were determined byrnAtomic Absorption Spectrophotometry (AAS). Heavy metals were determined by inductivelyrncoupled plasma optical emission spectrometry (ICP-OES) with following a microwave digestionrnprocedure.rnThe analysis of the proximate composition of both fish species (male and female) from all sampledrnsites for maximum and minimum dry matter content for male and female were respectively 7.96%rnand 11.76% (p < 0.05); 7.06% and 12.00% (p0.05) effect on dry matter content, female fish had higher (7.06 - 12.00% dryrnweight (DW) as compared to male fish (7.96 - 11.76%). The dry matter contents in the gill tissuesrnof 0. nilolicus and C gariepinus male fishes were in the range of 6.62 to 10.66% and for femalernfishes were in the range of6.80 to 9.11 % in DW and sex has no significant (p>0.05) effect on dryrnmatter content of gill tissues from all sampled sites.The results on the proximate composition of 0. niioticlIs fish muscle from all sampled sites for thernmaximum and minimum protein, fat, ash and carbohydrate contents were 15.22% and 12.44%rn(p < 0.05); 2.76% and 2.15% (p > 0.05); 106% and 0.65% (p > 0.05); 5.47% and 1.55% (p< 0.05).rnFor C. gariepinlls maximum and minimum protein, fat, ash and carbohydrate contents werern20.23% and 10.75% (p< 0.05); 4.62% and 2.11% (p < 0.05); 1.55% and 109% (p > 0.05); 2.53%rnand 0.28% (p< 0.05) , respectively.rnThe analysis of the proximate composition revealed that fat and ash content of the fish speciesrnranged from 2.69 to 4.60 and 0.65 to 152 g/IOOg wet weight (WW), respectively. The lowestrnmoisture was detected in C. gariepinlls from Lake Ziway (71.11 %) with high fat content (4.62 %).rnThe protein content ranged from 12.44 - 15.22% and 10.75 - 20.23% for 0. niloticlIs and C.rngariepinus from all fresh water bodies, respectively. The difference in fat content was the majorrncause for the change in caloric values for C. gariepinus fish tissue ranged from a 6199 -12206rnkcalllOOg (260.36-512.65 kJ) followed by 0. niloticus ranged from 69.75-82.16 kcal 1l00grn(292.95-345.07 kJ) from all fresh water bodies. Sexes were not significant (P > 0.05) influence inrnterms of the four proximate compositions (protein, fat, ash and caloric values) measured in musclerntissues of 0. niloticlIs and C. gariepinus collected from all sample sites.rnFive essential mineral elements Fe, Ni, Cu, Mn, and Zn and seven toxic heavy metals (Hg, Sn, Pb,rnAs, B, Cd and Cr) were analyzed for each of the fish species in muscle and gill tissues from fourrndifferent freshwater bodies. Iron, zinc, copper, nickel and manganese contents were in the rangernof33.54 to 122.29 mg/kg, 20.21 to 47.43 mg/kg, 0.75 to 10.87 mg/kg, 0.16 to 1.16 mg/kg and 2.48rnto 69.82 mg/kg DW, respectively. The result showed that iron and z inc were the most abundantrnminerals detected in gill and muscle tissues.rnToxic heavy metal concentration were assessed in gill and muscle tissues of C. gariepinlls and 0.rnniloticlis collect from Alwero River, Abay River Lake Hawassa and Lake Ziway. In gill tissue, thernhighest accumulated heavy metals were Cd (0.58 mg/kg DW) and Pb (4.56 mg/kg DW) and werernobserved in 0. niloticlIs species in all water bodies. The highest concentrations of Sn (222.89rnmg/kg DW) and Hg (14.52 mg/kg DW) were observed in gills and muscle of 0. niioticlIs fromrnLake Ziway and Alwero River, respectively, while the highest concentrations ofCr (4.95 mg/kgrnDW) and As (30.92 mg/kg DW) were observed in gills and muscle of C. gariepinlls from LakernZiway, respectively. A surprisingly too high As content was 30.92 mg/kg DW in muscle tissue ofC. gariepinus from Abay River and Hg content was 14.52 mglkg DW in muscle tissue of 0.rnniloticlIs from Lake Ziway, may be due environmental contaminants from municipal, agriculturalrnand industrial sources may enter the food chain, accumulate in fish muscles. Those two fish speciesrnfrom Abay River and Lake Ziway are limiting its consumption for infant and pregnant women.rnHowever, the estimated daily intakes of all metals were below the acceptable daily intake (ADI)rnand oral reference dose (RID) set by international guideline. The target hazardous quotient (THQ)rnand hazard index (HI) values were «1) for all examined metals in both species in all sampled sites.rnThere are no risk for consumptions of 0. niloticlIs and C. gariepinlls muscle meat for consumers.rnTherefore muscles of studied both fish species should be safe for utilization in human diet fromrnthose regions in Ethiopia.

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Nutritional Value And Risk Assessment Of Toxic Heavy Metals Of Selected Fish Species From Freshwater Ecosystems In Ethiopia

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