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Effects Of Melamine, Oxidized Fish Oil And Lipid On Growth And Skin Colour Of Darkbarbel Catfish

Posted on:2012-10-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:J P XueFull Text:PDF
GTID:1113330338965686Subject:Aquatic biology
Abstract/Summary:PDF Full Text Request
The skin colour of cultured darkbarbel catfish (Pelteobagrus vachelli) was studied, and the lutein content in the dorsal and ventral skin and muscle were also determined by HPLC. Based on previous studies on protein and fat requirements for darkbarbel catfish, feeding trials were conducted to determine the effects of melamine (MEL), oxidized fish oil, dietary lipids source, dietary lipid level and vitamin E on the skin colour of darkbarbel catfish. The aim of this paper was to provide theoretical supports for skin colour improvement of darkbarbel catfish. The results were as follows:1. The lightness L* of the dorsal and ventral skin of cultured darkbarbel catfish (135.0±16.4 g) was 28.95 and 74.37, respectively; the redness a* of the dorsal and ventral skin of cultured darkbarbel catfish was -1.09 and 1.25, respectively; and the yellowness b* of the dorsal and ventral skin of cultured darkbarbel catfish was 11.41 and 25.25, respectively. By HPLC, the carotenoids in the skin of darkbarbel catfish was lutein, and the content of which in the dorsal and ventral skin was 490.01 and 267.42 mg kg-1 skin, however, the lutein content in the liver or muscle was undetectable.2. A feeding trial was conducted to investigate the effects of dietary MEL on the growth, skin colour, dorsal skin melanin content and tyrosinase activity of darkbarbel catfish (initial body weight 14.30±0.10 g) with 4 dietary treatments for 8 weeks. The results showed that, dietary MEL supplementation could significantly suppress the specific growth rate (SGR) of darbarbel catfish (P<0.05); with 0.5% or 1% MEL in the diet, the black colour of the dorsal skin vanished, meanwhile, the melanin content decreased significantly (P<0.05), but the tyrosinase activity of the dorsal skin was not significantly affected (P>0.05).3. A feeding trial was conducted to investigate the effects of oxidized fish oil and vitamin E on the growth, skin colour, dorsal skin melanin content and tyrosinase activity of darkbarbel catfish (initial body weight 1.47±0.02 g)for 8 weeks. The POV of fish oil was 0.6, 75, 150 and 300 meq kg-1, respectively, and the supplementation of VE was 80 and 300 IU kg-1, respectively. There were 8 dietary treatments. The results showed that, oxidized fish oil, vitamin E or both of them could supress the SGR of darbarbel catfish. And oxidized fish oil could affect the L* of the dorsal skin of the dabarbel catfish, as the POV of fish oil increased, the L* of the dorsal skin of the dabarbel catfish decreased accordingly.4. A feeding trial was conducted to investigate the effects of different dietary lipid source (fish oil, soybean oil, linseed oil, and mixture of them at a ratio of 1:1:1) on the growth, skin colour, skin and muscle lutein content, lipoproteinlipase (LPL), hepatic lipase (HL) and lipase activity of darkbarbel catfish (initial body weight 6.74±0.07 g) for 8 weeks, the control diet was formulated with fish oil without lutein and the experimental diets was prepard with four oil mentioned above (supplemented with 200 mg kg-1 lutein), and there were 5 treatments. The results showed that, SGR of darkbarbel catfish fed the diets with fish oil was significantly higher than other treatments (P<0.05), while luntein didn't affect the SGR of darkbarbel catfish fed with fish oil (P>0.05). The SGR of darkbarbel catfish fed the diets with linseed oil or mixed oil was the lowest. It is important to add lutein in the diets, since b* of the dorsal and ventral skin of darkbarbel catfish fed the control diet was significantly lower than those fed the experimental diets (P<0.05). And b* of the dorsal and ventral skin of darkbarbel catfish fed fish oil or soybean oil was significantly higher that that fed linseed oil or mixed oil (P<0.05), meanwhile, b* of the ventral skin of darkbarbel catfish fed soybean oil was significantly higher that that fed fish oil (P<0.05). Lutein content in the skin varied by the similar way of b* value, and no lutein was detected in the muscle of darkbarbel catfish by HPLC. So fish oil or soybean oil seemed to be appropriate for the optimal growth of darkbarbel catfish and normal skin colour as well. LPL, HL or lipase were not significantly affected by different dietary lipid source (P>0.05).5. A feeding trial was conducted to investigate the effect of dietary lipid level (6%, 9%, 12%, 15%, 18% and 21%) on the growth, skin colour, skin and muscle lutein content, LPL, HL and lipase activity of darkbarbel catfish (initial body weight 7.14±0.09 g) with 6 dietary treatments (supplemented with 200 mg kg-1 lutein) for 8 weeks. The results showed that, as the level of dietary lipid increased, the SGR of darkbarbel catfish increased first and then decreased, SGR of the fish fed the diet with 9% crude lipid was significantly higher than other treatments (P<0.05). Though the skin lutein content of the darkbarbel catfish fed the diets with 9% crude lipid was significantly lower than that of the 15% or 18% dietary lipid treatment (P<0.05), the b* of the ventral skin was not significantly different among them. No lutein was detected in the muscle of darkbarbel catfish by HPLC. And 9% dietary lipid seemed to be appropriate for the optimal growth of darkbarbel catfish and normal skin colour as well. As dietary lipid increased, LPL activity tended to increase, LPL activity in the fish fed the diet with 21% crude lipid was significantly higher than those fed the diets with 6%, 9%, 12% and 15% crude lipid (P<0.05), but not significantly different from that fed the diets with 18% crude lipid (P>0.05); howerer, HL activity was not significantly affected by dietary lipid level (P>0.05). The lipase activity of darkbarbel catfish increased as the dietary lipid level increased, and that of darkbarbel catfish fed with 6% or 9% crude lipid level were significantly lower than other treatments (P<0.05).6. A feeding trial was conducted to investigate the effect of dietary lipid level (12% and 21%) and vitamin E supplementation (0, 80 and 800 IU kg-1) on the growth, skin colour, skin and muscle lutein content, LPL, HL and lipase activity of darkbarbel catfish (initial body weight 6.93±0.00 g) with 6 dietary treatments (supplemented with 200 mg kg-1 lutein) for 8 weeks. The results showed that, dietary lipid level, vitamin E supplementation and both of them had an effect on the growth of darkbarbel catfish (P<0.05), as high dietary lipid level or high vitamin E supplementation woud suppress the growth of darbarbel catfish. Interaction of dietary lipid level and vitamin E would significatly affect the b* value of the dorsal skin of darkbarbel catfish (P<0.05). Too high level of dietary lipid level or vitamin E supplementation would be adverse for the skin colour of darkbarbel catfish. No lutein was detected in the muscle of darkbarbel catfish by HPLC. So the dietary lipid level and vitamin E supplementation should be controlled at a range (<21% crude lipid and 80 IU kg-1 vitamin E supplementation) to ensure the normal skin colour of darkbarbel catfish. LPL, HL or lipase activity were not significantly different among dietary treatments (P>0.05).
Keywords/Search Tags:darkbarbel catfish (Pelteobagrus vachelli), nutrition, growth, skin colour, lutein
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