Effects Of Water Salinity, Dietary Fish Oil And Astaxanthin Levels On Fattening Performance, Physiological Metabolism And Nutritional Quality Of Adult Male Chinese Mitten Crab, Eriocheir Sinensis

Exp.1 Effect of different water salinity on gonadal development osmoregulation and physiological metabolism of adult male Chinese mitten crab, Eriocheir sinensisThe current study was conducted to investigate the osmoregulation and physiological metabolism when the adult male E. sinensis was subject to different water salinity, i.e. 0‰, 6‰, 12‰ and 18‰, after 60 days adaption. The results showed that:(1) Water salinity had no significant effects on gonadosomatic index(GSI) and hepatosomatic index(HSI) of male E. sinensis(P>0.05).(2) The osmolality, Na+, Mg2+, and Cl- concentrations in the serum increased significantly with the elevation of water salinity(P<0.05). For all treatments, the serum osmolality of the crabs was significantly higher(P<0.05) than that of its culture brackish water;(3) The posterior gills of 0‰ treatment had the significantly higher Na+/K+-ATPase activity than that of other treatments(P<0.05), while no significant differences were found for the Na+/K+-ATPase activity among the 6‰, 12‰ and 18‰ salinity treatments(P>0.05);(4) For the metabolism indices in the serum, the crab from the 12‰ salinity treatment had the significantly highest triglyceride(TG) level(P<0.05), but the lowest uric acid(UA), glucose(Glu), malondialdehyde(MDA) and superoxide dismutase(SOD) among the four treatments.(5) The lowest contents of MDA and the activity of γ-glutamyltranspeptidase(γ-GT) in the hepatopancreas were detected at salinity 6‰, while the highest activities of acid phosphatase(ACP) and γ-GT in the hepatopancreas were found in the treatment with the salinity of 12‰ treatment(P<0.05).In conclusion, these results suggested that the increasing water salinity would lead to the higher haemolymph osmolality and the concentration of the major serum ions, the lower Na+/K+-ATase activity in the posterior gills of adult male E. sinensis than those of freshwater treatment; most of metabolism indices in the serum and hepatopancreas indicated the crabs from the treatment of 12‰ salinity may had the lower metabolic level, but the better ability for the immunity and anti-oxidation than the other treatments. Exp.2 Effects of fish oil replacement by blending vegetable oils in fattening diets on gonadal development, physiological metabolism and nutritional quality of adult male E.sinensisIn order to investigate the effects of dietary fish oil replacement by blending vegetable oils on gonadal development, lipid metabolism, antioxidant capacity and nutritional quality of adult male E.sinensis), five isonitrogenous(crude protein 39.5%) and equal lipid content(crude lipid 14.0%) experimental diets were formulated to replace 0, 25%, 50%, 75% and 100% of fish oil(Feed 1# ~ Feed 5#, respectively) with blending vegetable oils(soybean oil: rapeseed oil=1:1). Therefore, there were five treatments(defined as T1~T5) in this study and each treatment had four replicates(each replicate with 25 crabs) for the culture of male crabs. The results showed as the followings:(1) Dietary fish oil replacement had no significant effects on GSI and HSI of male E. sinensis(P>0.05).(2) The lowest content of triglyceride(TG) in the hepatopancreas was detected in T4; T2 had the relatively higher lipid serum metabolism indices levels than the other treatments.(3) For the antioxidant indices in the hepatopancreas, T1 had the highest levels of total antioxidant capacity(T-AOC), peroxidase(POD), MDA in the hepatopancras.(4) The higher ALP activity in the serum was detected in T3, but T2 had higher content of serum hemocyanin, T-AOC and SOD activities, lower POD activity and MDA content in the serum than the other treatments(P<0.05).(5) There were no significant differences in the contents of moisture, crude protein and crude lipid in testis among five treatments(P>0.05). The crude lipid of T1 was lower than that of the other treatments. Except for the T1, the crude lipid and ash contents in muscle increased with the elevation of replacement level(P<0.05).(6) The total n-6 polyunsaturated fatty acid(∑n-6 PUFA) contents in testis increased with the increasing replacement level, while the total n-3 polyunsaturated fatty acid(∑n-3 PUFA) contents of testis had opposite changing tendency. T3 had the highest ∑n-3 PUFA and ∑HUFA contents in hepatopancreas. The ∑n-6 PUFA contents in muscle increased when the replacement levels were elevated. In conclusion, fish oil replacement by blending vegetable oils(soybean: rapeseed oil=1:1) in fattening diets have no significant effect on male gonadal development and the moisture and protein of edible parts, and the appropriate levels of diet fish oil or vegetable oils would have no negative effects on lipid metabolism and antioxidant capacity of adult male E. sinensis. Therefore, the appropriate levels of dietary fish oil replacement are around 25~50% for fattening diets of adult male Chinese mitten crabs. Exp.3 Effects of different dietary Haematococcus pluvialis contents on gonadal development, physiological metabolism and nutritional quality of adult male E.sinensis This study was conducted to investigate the effects of dietary supplementation of Haematococcus Pluvialis powder on gonadal development, antioxidant ability and colouration of adult male Chinese mitten crab Eriocheir sinensis, and four isonitrogenous(crude protein 42.4%) and isolipidic(crude lipid 16.3%) experimental diets were formulated to contain 0, 0.2%, 0.4% and 0.6% of Haematococcus pluvialispowder(defined as Diet 1# ~ Diet 4#, respectively). Therefore, there were four treatments(defined as T1~T4) in this study and each treatment had three replicates(25 crabs/replicate). Sixty days culture experiment was carried out in the outdoor experimental ponds. The results showed as the followings:(1) Dietary Haematococcus pluvialiscontents had no significant effects on gonadosomatic index(GSI) and hepatosomatic index(HSI) of male E. sinensis(P>0.05).(2) For the colour indices, the total carotenoids content of carapace and hepatopancreas as well as the redness(a value) of them increased significantly with the elevating contents of dietary Haematoccus pluvialis(P<0.05), while there were no significant differences for “L” value of carapace and hepatopancreas among four treatments(P>0.05).(3) For the antioxidant indices in the serum, T4 had the lowest activitiesof superoxide dismutase(SOD) and peroxidase(POD), but the highest levels of glutathione peroxidase(GSH-Px) and lactic dehydrogenase(LDH) were detected, while the malondialdehyde(MDA) content of serum was significantly decreased with the rising content of dietary supplementation of Haematoccus pluvialis(P<0.05); T1 had the highest levels of SOD, POD and GSH-Px in hepatopancreas, and the changing trend of MDA content in the hepatopancreas was similar to that in the serum.(4) For the non-specific immune indices in the serum, the acid phosphatase(ACP) and γ-glutamyl transpeptidase(γ-GT) levels of T3 and T4 were significantly higher than other treatments(P<0.05), while there were no significant differences among the alkaline phosphatase(ALP), phenoloxidase(PO), nitric oxide(NO) and hemocyanin(Hc) contents of all four treatments; T1 had the highest levels of ACP, ALP, γ-GT and NO in hepatopancreas, while T2 and T3 had the lowest levels of ALP and ACP, respectively. In conclusion, dietary supplementation of Haematococcus pluvialis powder had no significant effects on male gonadal development, but could improve the total carotenoids content of carapace and hepatopancreas, colorness and antioxidant ability. Our results suggested the optimal dietary astaxanthin levels was around 40-80mg/kg for adult male E. sinensis.