Studies On The Requirement Of Folic Acid、Biotin And Choline In The Diet To GIFT Tilapia(Oreochromis Niloticus)

Three 12-week, 10-week and 10 week feeding trials were conducted to examine the effects of different dietary folic acid, biotin, choline levels on growth performance、body composition、serum enzyme activities and biochemical indices of GIFT tilapia to detect the suitable requirement of folic acid, biotin and cholide in the diet. Dietary folic acid and biotin requirement experiment of GIFT tilapia was conducted in indoor culture system(Volume 500L). Dietary cholide requirement experiment of GIFT tilapia was conducted in pond cages(1m×1m×1.5m. Results of these studies are presented as follows:1. A 12-week feeding trial was conducted to investigate the dietary folic acid requirement of advanced genetically improved farmed tilapia(GIFT) strain, Oreochromis niloticus. Purified basal diets with six levels(0.04, 0.22, 0.48, 0.96, 2.25, 4.07mg/kg diet) of supplemental folic acid were fed to tilapia(mean initial weight: 60.3±2.6g, means ± SD), reared in a closed re-circulated freshwater system. Each test diet was fed to three replicate groups of 15 fish. Results revealed that the weight gain rate(WGR) of the fish increased linearly with dietary folic acid levels, increasing from 0.04 to 0.40mg/kg, then remaining stable at higher dietary folic acid levels. Hepatic folic acid concentration, whole blood red blood cell counts(RBC), hemoglobin concentration(HB) and hematocrit(HCT) increased with increasing dietary folic acid level. Their values were significantly higher in fish fed with 4.07mg/kg folic acid diet than fish fed with the control diet(P<0.05). With increasing dietary folic acid level, serum aspartate aminotransferase activity(AST) and alanine aminotransferase activity(ALT) significantly decreased(P<0.05). There were no significant differences in serum total protein(TP) and high density lipoprotein cholesterol content(HDL-C) among all the groups(P>0.05). Serum triacylglycerol(TG) and total cholesterol content(T-CHO) reached to the highest level in fish fed diets with 0.96 mg/kg folic acid. Analyses of WGR indicated that the optimal dietary folic acid level for advanced GIFT tilapia was about 0.40mg/kg diet, and 0.7mg/kg for the highest liver folic acid accumulation.2.This study was conducted to investigate the influences of dietary biotin on V growth 、body composition and serum biochemical indices of juvenile GIFT tilapia to detect the suitable requirement of biotin in the diet. Total 270 juvenile GIFT tilapia(Oreochromis niloticus) with initial body weight of(64.04±1.26g)were randomly divided into six groups including 3 replicates(n=15 fish/replicate). Each group was fed a diet containing 0.00(control group) 、0.03 、0.07、 0.31、 0.61 、1.26mg/kg biotin levels for 10 weeks. Weight gain rate(WGR), specific growth rate(SGR), body composition and serum biochemical indices of juvenile GIFT tilapia were detected and analyzed.The supplementary dietary biotin improved Weight gain rate(WGR), feed efficiency(FE), condition factor(CF)(P<0.05). Moisture, crude protein contents of whole body were not affected by the supplemental levels of dietary biotin(P>0.05); but the crude lipid, ash contents were increased in GIFT Tilapia fed the supplementary dietary biotin(P<0.05). The serum total protein(TP), albumin(ALB), globulin(GLO)content in 0.61mg/kg group was significantly higher than that in the control group(P<0.05). Serum total cholesterol(T-CHO)and triglyceride(TG)content in 1.26mg/kg group was significantly higher than that in the control group(P<0.05). The activity of serum superoxide dismutase(SOD)and catalase(CAT)reached to the peak when the fish fed the 0.07mg/kg, 0.31mg/kgdiet biotin levels, and significantly higher than control group(P<0.05). Serum Maleic dialdehyde(MDA)content in 0.03~0.31mg/kg group was significantly lower than the control group(P<0.05). Weight gain analyzed by regression analysis indicated that the requirement for dietary biotin in GIFT tilapia was 0.08mg/kg diet.3. A 10-week feeding trial was conducted to determine the effect of dietary choline chloride supplementation on the growth performance, feed utilization, body composition, serum biochemical indices of GIFT tilapia(Oreochromis niloticus). The basal diet was supplemented with choline chloride(0、300、600、 1200、1800、2400 mg choline per kg food) to formulate six purified diets containing choline of 45.05、308.88、540.54、945.95、1486.49 and 1756.76mg/kg feed. Each diet was randomly fed to four replicates of GIFT tilapia with an initial average weight of(57.4±2.5g) in 24 pond cages. Compared with the control group, the addition of choline to the diet significantly improved weight gain rate, and feed utilization(P<0.05). The liver fat content decreased significantly(P<0.05) in all groups compared with the control. In addition, the liver choline and muscle fat content of all groups increased significantly(P<0.05). Serum total cholesterol(T-CHO)and triglyceride(TG)content among the 945.95 and 1486.49mg/kg groups was significantly higher than that in the control group(P<0.05).Serumaspartate aminotrans-ferase(ALT) and alanine aminotransferase(AST) decreased significantly(P<0.05) with increasing dietary choline content. The choline requirement of GIFT tilapia was 634.07 mg choline per kg food based on the weight gain rate, however, it was 1118.61 mg cholide per kg food based on liver choline concentration.