Study On The Requirements Of N-3Series Highly Unsaturated Fatty Acids, Vitamin C And Vitamin E For The Swimming Crab, Portunus Trituberculatus

In the present study, feeding trials were conducted to evaluate the requirements of n-3serieshighly unsaturated fatty acid (n-3HUFA), vitamin C(VC) and vitamin E(VE) for juvenile swimmingcrab, Portunus trituberculatus. The results can be briefly summarized as follows:1. An8-week feeding trial was conducted to determine the effects of dietary n-3HUFA on thegrowth and fatty acid composition of the juvenile swimming crab Portunus tribueculatus. Sixisonitrogenous and isoenergetic experimental diets, with n-3HUFA content as0.74%,1.14%,1.55%,1.94%,2.35%,2.76%and DHA/EPA ratio as1.1, were formulated. The juvenile swimmingcrabs (initial weight2.17±0.14g) were cultured in rectangle plastic baskets in outdoor cement for8weeks. Results showed that dietary n-3HUFA contents influenced the weight gain (WG), specificgrowth rate (SGR), feed efficiency (FE) and molt rate (MR) of the crabs significantly. WG, SGR,FE and MR in2.35%treatments were the highest and significantly higher than that of the controlgroup (0.74%, P<0.05). Dietary n-3HUFA has on significant effect on the survival of the crabs(P<0.05).The moisture, crude protein and ash content were not significantly affected by the dietaryn-3HUFA contents (P>0.05). The crude lipid content in the control group was significantly lowerthan those in other treatments (P<0.05). Dietary n-3HUFA contents affected the n-3HUFA contentsin muscle and hepatopancreas significantly (P<0.05), the content of DHA and EPA increased withincreasing dietary n-3HUFA contents. Given all that, the n-3HUFA optimum requirement forjuvenile swimming crab is2.35%of dry matter.2. An8-week feeding trial was conducted to investigate the effects of dietary Vc on growth,humoral immunity, antioxidant function in swimming crab, Portunus tribueculatus (initial averageweight5.65±0.25g). Six iso-nitrogenous and iso-energetic diets were formulated to supply atdosages of1.91,18.89,36.76,78.42,156.49and315.97mg/kg Vc diet, respectively. After feeding8weeks, blood was drew off for biochemical analysis. Results indicated that dietary Vc hadsignificant effect on the weight gain, specific growth rate and feed conservation rate (P<0.05). WGand SGR increased gradually as Vc in diet increased from1.91to156.49mg/kg,. However, WGand SGR did not increased but decreased significantly in315.97mg/kg Vc group (P<0.05); in78.42mg/kg Vc group, FCR was significantly lower than the control group (P<0.05). Dietary Vc had no significant effect on the survival rate and molting rate of the juvenile crab (P>0.05). Vc hadno significant effect on the bodies’crude protein, moisture and ash content (P>0.05), but couldincrease the bodies’crude lipid content significantly (P<0.05). Total protein and glucose in serumwas not affected by the dietary Vc content, but the content of cholesterol, the content of triglyceride,the activity of alanine aminotransferase and the activity of aspartate aminotransferase decreasedwith the increase of dietary Vc content. Lysozyme activity in serum increased with dietary Vccontent increasing from1.91to78.42mg/kg, reached the highest in78.42mg/kg group, and thendecreased; Alkaline phosphatase activity in serum increased with the increase of dietary Vc contentand increased significantly in315.97mg/kg group; SOD activity increased with the increase ofdietary Vc content, MDA content decreased significantly with the increase of dietary Vc content(P<0.05). Given all that, the juvenile swimming crab grew best when the content of Vc in diet was78.42mg/kg of dry matter, and the humoral imuunity and antioxidant function were strong whenthe ontent of Vc in diet was>315.97mg/kg of dry matter.3. An8-week feeding trial was conducted to investigate the effects of dietary vitamin E ongrowth, humoral immunity, antioxidant function in swimming crab, Portunus tribueculatus (initialaverage weight5.94±0.17g). Six iso-nitrogenous and iso-energetic diets were formulated to supplyat dosages of8.9,19.6,27.0,39.7,77.6and156.9mg/kg VEdiet, respectively. After feeding8weeks, blood was drew off for biochemical analysis. Results indicated that VEhad significanteffect on the weight gain, specific growth rate (P<0.05). With the increase of VEin diet, WG andSGR increased gradually within a range; However, WG and SGR did not increased but decreasedin39.7mg/kg VEgroup. VEhad no significant effect on the feed conversion ratio, survival rate andmolting rate of the juvenile crab (P>0.05). VEhad no significant effect on the bodies’crude protein,moisture and ash content (P>0.05), but could decrease the bodies’crude lipid content significantlywithin a range (P<0.05). Total protein, triglyceride and glucose in serum was not affected by thedietary VEcontent. Lysozyme activity in serum increased significantly (P<0.05) and alkalinephosphatase activity in serum increased gradually as the content of VEin diet increased from8.9to39.7mg/kg; lysozyme and alkaline phosphatase activity reached the highest and humoralimmunity function of the juvenile crab was the strongest when the VEcontent in diet was39.7mg/kg. SOD activity was higher, MDA content was lower and the antioxidant function of juvenilecrab was stronger than the control group when the VEcontent in diet was between39.7and156.9mg/kg. Given all that, the juvenile swimming crab grew best, had the strongset humoralimmunity and had strong antioxidant function when the VEcontent in diet was39.7mg/kg.