Effects Of Dietary Vitamin E And L-carnosine On Growth Performance, Antioxidant Status, Non-specific Immunity In Juvenile Turbot(Scophthalmus Maximus L.)

Turbot(Scophthalmus maximus L.) is a rare low-temperature economic fish and its cultivation is a pillar industry in northern China. Effects of L-carnosine on growth performance, antioxidant status, non-specific immunity and liver tissue structure and the combined utilization effects of vitamin E and L- carnosine in juvenile turbot were discussed in this paper:Part 1 An 8-week feeding trial was conducted to investigate the effects of dietary L-carnosine on growth performance, antioxidant status, non-specific immunity, growth hormone levels and liver tissue structure in juvenile turbot[average initial weight:(14.00 ± 0.02) g]. Graded levels of L-carnosine(0 mg/kg,50 mg/kg,100 mg/kg,150 mg/kg and 200 mg/kg) was added in five iso-nitrogenous and iso-energetic experimental diets, named as D0, D50, D100, D150 and D200 respectively, and each diet was randomly assigned into triplicate tanks with 46 fish per tank in a circulating water system. Results showed that: 1) No significant differences in final body weight, weight gain rate(WGR), specific growth rate(SGR) and protein efficiency ratio(PER) in fish fed 50 mg/kg and 100 mg/kg L-carnosine were observed compared to control group(P>0.05), but significant reduction were observed in fish fed 150 mg/kg and 200 mg/kg L-carnosine than control group(P < 0.05). There was no significant difference of daily food intake(DFI) in all diets compared with the control treatment(P>0.05), but DFI in fish fed 150 mg/kg and 200 mg/kg L-carnosine were significant lower than that in fish fed 100 mg/kg L-carnosine(P<0.05). No significant differences of feed conversion ratio(FCR) were observed in fish fed 50 mg/kg and 100 mg/kg L-carnosine than control group(P>0.05), but FCR in fish fed 150 mg/kg and 200 mg/kg L-carnosine were significant higher than the control(P < 0.05). Condition factor(CF), viscerosomatic index(VSI), hepatosomatic index(HSI) and survival rate(SR) were all not significant affected by increasing L-carnosine levels(P>0.05). 2) No significant difference were observed in whole fish body composition and dorsal muscle moisture and crude lipid among dietary treatments(P>0.05). Crude protein and ash in dorsal muscle were significant affected by dietary L-carnosine(P<0.05), Crude protein in fish fed 50 mg/kg,100 mg/kg and 150mg/kg L-carnosine were significant higher than control group and ash in fish fed 50 mg/kg and 100 mg/kg L-carnosine were significant lower than control group(P < 0.05); 3) Serum superoxide dismutase(SOD), catalase(CAT), glutathione peroxidase(GSH-Px) activities were significantly elevated whereas malondialdehyde(MDA) content was significantly reduced by increasing levels of dietary L-carnosine(P<0.05). Total antioxidant capacity(T-AOC) was significant enhanced by dietary L-carnosine and reached the top when L-carnosine was added 95.50 mg/kg according to the linear regression equation(P < 0.05). 4) Serum complement C3, C4, liver acid phosphatase(ACP)and lysozyme(LZM) were significantly increased by L-carnosine(P<0.05). Liver ACP activities and growth hormone(GH) level in fish fed 50 mg/kg and 100 mg/kg L-carnosine were significant higher than that in control group and GH reached its peak value in 100 mg/kg, 32.38% higher than control group(P<0.05). Ig M in fish fed 50 mg/kg, 100 mg/kg and 150 mg/kg L-carnosine were significantly enhanced compared to the control(P<0.05). Ig M reached its peak value in fish fed 116.75mg/kg L-carnosine according to the liner regression equation. 5) The damage degree trend of liver tissue structure in juvenile turbot was first decrease and then rising with the increasing level of L-carnosine. The liver cell density was increased and fat cell vacuolar degeneration was decreased in fish fed 100 mg/kg L-carnosine. In conclusion, growth performance is not significantly affected by L-carnosine addition, however, antioxidant status and non-specific immunity are significantly enhanced and fatty degeneration was effectively inhibited in juvenile turbot. Analysis by liner regression equations of T-AOC and Ig M indicate that the optimum adding amount is 95.50 to 116.75 mg/kg.Part 2 A 2×4 factorial experiment(2 vitamin E×4 L-carnosine) was conducted to investigate the effects of dietary vitamin E(0 mg/kg and 75 mg/kg) and L-carnosine(0 mg/kg, 50 mg/kg, 100 mg/kg and 200 mg/kg) on growth performance, antioxidant status, non-specific immunity and serum biochemical indices in juvenile turbot(Scophthalmus maximus L.). Eight diets were formulated and randomly allocated into triplicate groups of fish [initial body weight,(14.00 ± 0.02) g] in 24 cylindrical tanks-(H:80 cm×Φ 70 cm, water depth 50 cm) with 46 fish per tank. The feeding trial lasts for 8 weeks. Results show that: 1) Fish weight gain rate(WGR) and specific growth rate(SGR) were significantly enhanced by dietary vitamin E(P<0.05), while no change was observed in fish fed L-carnosine less than 100 mg/kg. However, WGR, SGR and protein efficiency ratio(PER) were depressed whereas feed conversion ratio(FCR) was elevated significantly by 200 mg/kg L-carnosine(P<0.05). 2) Statistical interactions between vitamin E and L-carnosine was observed in serum glutathione peroxidase(GSH-Px), catalase(CAT) activities, malondialdehyde(MDA) content, and liver total antioxidant capacity(T-AOC), superoxide dismutase(SOD) and MDA(P<0.05). GSH-PX activities reached the top in fish fed 50 mg/kg and 100 mg/kg L-carnosine, CAT activities reached the top in fish fed 100 mg/kg and 200 mg/kg L-carnosine and showed no significant difference with fish fed 50 mg/kg(P>0.05), liver T-AOC and SOD activities reached the top in fish fed 100 mg/kg and showed no significant difference with fish fed 50 mg/kg(P>0.05), under the 75 mg/kg vitamin E level. Main effects analysis show that serum T-AOC, SOD and liver CAT activities were significantly elevated by dietary vitamin E(P<0.05), serum T-AOC was significantly elevated by dietary L-carnosine(P<0.05). 3) Statistical interactions between vitamin E and L-carnosine was observed in serum complement C3 and LZM activities(P<0.05). Complement C3 reached the highest value in fish fed 50 mg/kg L-carnosine when vitamin E was added 75 mg/kg(P<0.05). Serum total protein(TP) was not significantly affected by dietary vitamin E and L-carnosine(P>0.05). 4) Serum total cholesterol(TCHO) and triacyglycerol(TG) contents were decreased by vitamin E addition(P<0.05). Comparatively, TG was reduced by dietary L-carnosine and reached the bottom in fish fed 50 mg/kg L-carnosine(P<0.05). Considering growth performance, antioxidant status, non-specific immunity and serum biochemical indices in juvenile turbot [(14.00-39.43) g], 75 mg/kg vitamin E and 50 mg/kg L-carnosine are suggested under the experiment formulation employed here(fish oil 70 g/kg, Soy lecithin 10 g/kg).