Tocopherol and tocotrienol deposition in the tissues of red hybrid tilapia, oreochromis sp., fed diets with different vegetable oils.

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Date
2009-05
Authors
Kuan Shern, Lee
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Abstract
In Experiment 1, a 45-day feeding trial was carried out to evaluate the benefits and nutritive value of different dietary oils as endogenous source of vitamin E for red hybrid tilapia, Oreochromis sp., using four isonitrogenous and isoenergetic semi-purified diets. The four vegetable oils investigated were canola oil (CO), coldpressed soybean oil (SBO), wheat germ oil (WGO) and palm fatty acid distillates (PFAD) with vitamin E concentrations in the diet amounting to 34.18, 39.15, 285.79 and 216.65 mg/kg diet, respectively. All four diets were fed to triplicate groups of tilapia fingerlings (initial mean weight: 14.82 ± 0.05 g). Deposition of a-tocopherol (a-T) was the most in all tissues regardless of diets except for liver of fish fed the SBO diet which had more gamma-tocopherol (y-T) deposited in the liver. Fish fed the PF AD diet was the only treatment that had higher a-T deposited in the muscle (9.78 J.Lg/g) compared to the initial fish. a-T3 was deposited in fish adipose tissue of all treatments, with fish fed the PF AD diet having significantly higher (P<0.05) concentrations at 27.31 J.Lg/g. However, y- and o-T3 were only found in fish fed the PF AD diet (18.14 and 0.59 J.Lg/g, respectively). The concentrations of thiobarbituric acid-reactive substances (TBARS) in the muscle of fish fed the CO diet was the lowest while fish fed the SBO diet was the highest (17.71 and 40.83 nmol MDA/g tissue, respectively). TBARS for fish liver however, was the inverse with fish fed the SBO diet having the lowest values and fish fed the CO diet having the highest values (94.15 and 164.79%, respectively). There were no significant differences in fish percent weight gain, feed conversion ratio and protein efficiency ratio among fish given the various experimental diets (P>0.05). In Experiment 2, an eight-week feeding trial was conducted to investigate the effects of dietary vitamin E source on fish growth, lipid peroxidation and distribution of tocopherols and tocotrienols in various tissues of red hybrid tilapia. Three semipurified isonitrogenous and isoenergetic diets were investigated with .crude palm kernel oil (CPKO) used as the sole lipid source. No vitamin E was added to the control diet while the other two diets were supplemented with synthetic a-tocopheryl acetate (ToAc) or a natural tocotrienols-rich fraction (TRF) with total vitamin E concentrations of 1.17, 97.98 and 100.42 mg/kg diet, respectively. All three diets were fed to triplicate groups oftilapia fingerlings (initial mean weight: 15.38 ± 0.01 g). There were no significant differences in fish percent weight gain, feed conversion ratio and protein efficiency ratio among fish given the various experimental diets. We observed that tilapia tissues varied in their ability to accumulate tocotrienols with the highest composition found in adipose tissues accounting for 48.3% of total vitamin E for fish fed the TRF diet, followed by eyes (34.6%), liver (30.8%), muscle (24.6%), skin (23.2%), brain (20.2%) and ovaries (12.2%). Only fish fed the ToAc diet had higher deposition of a-T in the liver compared to the initial fish. The concentrations of TBARS in muscle and liver of tilapia fed the CPKO diet without any vitamin E supplementation were significantly higher (P<0.05) than in the tissues offish fed the TRF diet. Results obtained from the present studies indicated that palm tocotrienols supplementation could markedly enhance the tocotrienols concentration in various tilapia tissues and provide higher protection of these tissues against lipid peroxidation, which ultimately would translate to longer shelf-life for seafood products.
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Keywords
Tocotrienol deposition , Red hybrid tilapia , Oreochromis sp., fed diets , Vegetable oils
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