Vc Synthesis In Vitro And Its Dietary Requirement By Trionyx Sinensis

Vitamin C is of many very important biological functions and is one of the indispensable nutrients to aquatic animals for their maintenance, fast growth, quality breeding and better products-This paper had taken fresh water soft-shelled turtle Trionyx sinensis which has been widely and intensively farmed in China to measure Vc synthesis ability in tissue, to explore the main affecting factors for Vc synthesis in vitro, and aslo to show the minmum amount of Vc requirement for the optimum growth and healthy body condition.In Vc synthesis ability study period, twenty juvenile Taiwan line of Trionyx sinensis with initial body weight 150g were divided into five experimental treatments with 5 replicate groups. Kidney, liver, spleen, lung, heart, intestine, particle in gut, leg muscle, calipesh of the test turtle were taken as the samples. GLO analysis method was followed according to Fracalossi modificated method in 2001. The result showed that kidney is the only organ or tissue be able to synthesis Vc and the GLO activity was 14.31+0.31μg/g kidney tissue/h.In a series of case studies, we have conducted effects of turtle blood lines, growth periods (body weights), gender, dietary Vc contents, farming methods, hiberation and disease infection on Vc synthesis abilities of Trionyx sinensis in vitro. (1) In case of turtle blood lines, five main cultured lines of Trionyx sinensis in China were measured. Based on the result from 18 male turtle from each blood line with body weight 650g per each, it has been known that there was no significant difference among lines on Vc synthesis in vitro (P>0.05). (2) In case of turtle growth periods (body weights), fertlizered eggs, new hatched turtles, growing turtles with body weight 50, 150,450,650 and 750 g were been taken as the samples for tissue or kidney GLO analysis. The results showed that there is no GLO activity in fertlizered eggs and new hatched turtle body. As turtle growth, the GLO activity had been increased significantly (P<0.05). Based on the results of GLO activity and turtle body weight, the equition could be built and showed y= - 0.00007x2+ 0.1086x+0.6777 (R2= 0.9968) with the maxium Vc synthesis ability 42.80μg/g kidney tissue/h when the body weight is about 776 g. (3) In case of gender, eighteen male and eighteen female turtles in body weight 150 g and the same number of body weight 450 g were taken respectively for GLO analysis. The results showed that the GLO of male turtle is about 18.64%higher than female in turtle body weight 150g and about 5.29%higher than female in turtle body weight 450 g respectively (P<0.05). (4) In case of dietary Vc content, seventy two turtles with body weight about 1OOg were divided to 6 groups, and respectively fed the same basal diet with Vc content of 11,189,375,728,1452 and 2889 mg/kg for 60 days. The results showed that the Vc synthesis ability was decreased significantly when dietary Vc content were 1452 mg/kg and higher (P<0.05) comparing to the lower dose of dietary Vc. (5) In case of farming methods, six male turtles with body weight about 450g from dark geenhouse intensive culture with stocking density of 20 turtle/m2 and six turtles with the same gender and body weight from earth pond extensive culture with stocking density of 2 turtle/m2 were taken as the samples for GLO analysis. The results showed that there was no significant difference between two kind of farming methods on kidney GLO activity (P>0.05). (6) In case of hiberation, six turtle with body weight 650g and hiberation for 3 months in about 8-10℃earth pond were taken for GLO analysis. The results showed that the GLO activity of hibemant turtle was significantly lower than that of the turtle grown in dark greenhouse with the water temperature at 30℃(P<0.05), and the GLO activity of the turtle in hiberation was only about 21.34% of the normal turtle. (7) In case of disease infection, six turtle with body weight 650 g and infected by Aeromonas hydrophila for 20 days were taken for GLO analysis. The results showed that the GLO activity of infected turtle is only about 6.97% of the healthy turtle's (P<0.05).A 105-day feeding trial was conducted to study the effects of the different levels of dietary vitamin C on growth, tissue concentrations of Vc in juvenile Taiwan line of Trionyx sinensis. White fish-meal based diet was formulated and Vc were added as the levels of 0,50,100,200, 400,800 mg L-ascorbic acid per kg diets on ascorbic acid equivalent basis in the form of phosphorylated L-ascorbic acid. Three thousand and six hundred soft-shell turtles with initial body weight 55g were divided into six experimental treatments with triplicate groups and cultured in 18 concreted-tanks with water temperature controlled at 31±2℃. This study results showed:(1) The supplementary dietary Vc could improve weight gain and protein efficiency rate, reduce feed conversion rate. (2) Based on turtle weight gain, regression analysis and broken-line analysis, the minimum dietary Vc supplementation for maximum growth of juvenile soft-shell turtle is 184 mg/kg. (3) The Vc concentration in liver linearly increased with dietary Vc supplementation (R2=0.9542), and the dietary Vc supplementation for optimum Vc concentration in liver of juvenile soft-shell turtle is 192 mg/kg. In addition, there is a significant different (P<0.05) between contrast and treatments on Vc concentration in liver. (4) The dietary Vc supplementation could significantly reduce water content (P<0.05) in turtle whole body composition. In addition, there was no any deficiency symptom shown in experimental turtles fed diet without or with low dose of dietary Vc supplementation.In case study of dietary Vc content on anti-stress, anti-oxidation and collagen synthesis functions, seventy two turtles with body weight about 100g were divided to 6 groups, and respectively fed the same basal diet with Vc content of 11,189,375,728,1452 and 2889 mg/kg for 60 days. The results showed that dietary Vc significantly reduced plasma cortisol and glucose contents (P<0.05). It is very necessary to keep Vc higher than 189 to 375 mg/kg in the diet in order to release turtle stress efficiently. As the dietary Vc increased, GSH-Px, SOD, GR, MPO, CAT and LSZ activities were all improved significantly (P<0.05), especially when dietary Vc was not less than 728 mg/kg. In addition, when dietary Vc was not less than 375 mg/kg in diet, the collagen content in leg muscle, calipesh and carapace of Trionyx sinensis would be increased significantly (P<0.05).