Effects of feeding carnitine and ractopamine on rainbow trout (Oncorhynchus mykiss, Walbaum 1972)

L-carnitine is required for the transfer of long-chain fatty acids from the cytosol to the mitochondrial matrix for 13-oxidation of them and ractopamine, beta adrenergic agonists, have potential stimulating lipolysis and altering rates of protein degradation and synthesis. Present study was carried out to improve lipid body oxidation and protein-sparing action of fish through addition of L-carnitine and ractopamine to diet of rainbow trout, Oncorhynchus mykiss, Walbaum 1972. An eight-week feeding trial was carried out to evaluate the effects of supplementation of tree levels of L-carnitine tartrate (0, 1 and 2 g/kg) and two levels of ractopamine hydrochloride (0 and 10 ppm) on growth performance, fillet muscle fatty acid compositions and blood biochemical parameters in 288 juvenile rainbow trout (130 g) at 3X2 factorial experimental design. Ractopamine and 1 g/kg carnitine improved the specific growth rate, feed conversion ratio, protein efficiency ratio and weight gain at the end of experiment. The protein and lipid contents of fillet muscle were affected by the inclusion of 10 mg/kg ractopamine in the diet, increasing crude protein and reducing crude fat (P<0.05) of fish fillet muscle. The highest protein and lowest fat contents of fish fillet were observed in diet that contains 2 g/kg carnitine plus ractopamine. Ractopamine and carnitine increased levels of albumin, total protein and globulin in fish blood serum, but carnitine increased triacylglycerol and cholesterol. Fatty acids compositions of fish fillet were also affected by ractopamine and carnitine. All fatty acids except for eicosapentaenoic acid and docosahexaenoic acid, were increased by dietary supplementation of ractopamine. Total saturated fatty acids were not affected by carnitine. Supplementation (P>0.05). However, total n-3 poly unsaturated fatty acids were reduced by carnitine supplementation. A significant interaction was observed between ractopamine and carnitine supplementation regarding the saturated (P<0.01) and n-3 poly unsaturated fatty acid (P<0.001) of fish fillet. This study shows that supplementation of 1 g/kg carnitine and 10 ppm ractopamine could improve performance of juvenile rainbow trout and their combination in diet results in protein increment, fat reduction and change in profile of fatty acids in fillet muscle.

The possible identification and introduction of metallothionein in Persian Sturgeon (Acipenser persicus)

Due to anthropogenic activities, toxic metals still represent a threat for various marine organisms. Metallothionein (MT) and cadmium concentration in gills, liver, and kidney tissues and cadmium partitioning in soluble (cytosol) and insoluble fractions of mentioned tissues of Persian sturgeon (Acipenser persicus) were determined following exposure to sub-lethal levels of waterborne cadmium (Cd) (50, 400 and 1000 μg L-1) after 1, 2, 4 and 14 days. The increases of MT from background levels in comparison to controls were 4.6-, 3-, and 2.8-fold for kidney, liver, and gills, respectively after 14 days. The matallothionein concentration in liver was in the range of 56.89-168.44 μgL-1 and for kidney and gills, 39.78-189.30 and 28.15-91.20 μgL-1, respectively. The results showed that MT level change in the kidney is time and concentration dependent. Also, cortisol measurement revealed elevation at the day 1 of exposure and that followed by MT increase in the liver. Cd concentrations in the cytosol of experimental tissues were measured and the results indicated that Cd levels in the cytosol of liver, kidney, and gills increased 240.71-, 32.05-, and 40.16-fold, respectively 14 days after exposure to 1000 μgL-1 Cd. The accumulation of Cd in cytosol of tissues is in the order of liver > gills > kidney. Spearman correlation coefficients showed the MT content in kidney is correlated with Cd concentration, the value of which is more than in liver and gills. Thus, kidney can be considered as a tissue indicator in Acipenser persicus for waterborne Cd contamination. Also, tissue metal accumulations (gills, liver, kidney and muscle) in Persian sturgeon (Acipenser persicus) were compared following exposure to sublethal levels of waterborne Cd (50, 400 and 1000 μg L-1) after periods of 1, 2, 4 and 14 days. Meanwhile, the trends of Cd concentration increase in different tissues during the exposure periods and concentrations were modelled as equations. The obtained results indicate that at the end of 4 and 14 days of exposure, total tissue cadmium concentration followed the pattern: liver> gill> kidney> muscle. Calculation of bioconcentration factor (BCF) after 14 days exposure showed that at low and high concentrations, highest BCFs were found in kidney and liver, respectively. According to the results, the accumulation capacity of muscle was the lowest at all exposure concentrations. The hematological parameters including osmolarity, total protein, cortisol and glucose of plasma were measured, too. Total protein of plasma was in the range of 416.90-1068.10 mg dl-1 plasma.Total protein decreased not significantly (P≥0.05) after exposure to Cd. Cortisol increased after 1 day exposure that followed by significant (P≤0.05) elevation of glucose. The range of cortisol was very vast and it was determined between 0.03 to 16.21 ng mL-1. The content of plasma osmolarity was in the range of 282.33-294.20 mOsmol L-1.Osmolarity of treated fish plasma showed no significant decrease (P≥0.05). Total protein in gills, liver, and kidney showed that at high concentrations of metal, protein content decreased significantly (P≤0.05) in the liver after 4 and 14 days exposure. Thus, total protein of liver and glucose of plasma can be used as general biomarkers of exposure to Cd. Also, the metallothionein and cadmium were measured in gills, kidney and liver of 8 wild Persian sturgeon caught in coast of Guilan Province. According to the results, the concentration of metallothionein was in the range of 45.87-154.66 microgram per liter with the maximum and minimum concentrations in liver and gills, respectively. The trend of cadmium concentration in cytosol of tissues was: liver> kidney> gills. The results of Spearman correlation test showed that there was a significant positive correlation between metallothionein and cadmium in cytosol of liver (r2= 0.850, p≤ 0.01). In the kidney, the correlation between cadmium and metallothionein was significantly positive (r2= 0.731, p≥ 0.05). But there was not such significant correlation in the gills (p≥ 0.05).