title: Different ratios of docosahexaenoic and eicosapentaenoic acids do not alter growth, nucleic acid and fatty acids of juvenile cobia (Rachycentron canadum).
abstract: An experiment was performed to study the effect of different ratios of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on the growth, nucleic acid and fatty acids of cobia (Rachycentron canadum) juveniles. The juveniles were fed for 8 weeks using seven treatment diets (D-1-D-7) with the same amount of DHA and EPA (1.50 +/- 0.1% of dried diet), but varying ratios of DHA to EPA (0.90, 1.10, 1.30, 1.50, 1.70, 1.90, 2.10, respectively) and a control diet (D-0, DHA + EPA = 0.8% of dried diet, DHA/EPA = 1.30). At the end of the experiment, the mean body weight (BW) of juveniles fed D-0-D-7 increased significantly (from 6.86 +/- 1.64 in the week 0 to 58.52 +/- 16.45 g at the end of week 8, P < 0.05). The mean RNA amount and RNA/DNA ratio in the muscle (from 39.62 +/- 1.30 microg mg(-1) and 2.29 +/- 0.11 in the week 0 to 272.55 +/- 10.70 microg mg(-1) and 14.54 +/- 1.75 at the end of week 8, respectively) and the mean weight in the liver (from 117.70 +/- 11.15 microg mg(-1) and 3.14 +/- 0.25 in the week 0 to 793.07 +/- 13.38 microg mg(-1) and 13.16 +/- 0.76 at the end of week 8, respectively) of cobia juveniles fed D-0-D-7 were significantly higher at the end of 8-week experiment than initially (P < 0.05). The RNA/DNA ratio in the muscle and liver of cobia juveniles increased with their growth and appeared an obvious positive relationship, especially in the muscle, based on regression analysis. The mean lipid content increased significantly in the liver (from 29.82 +/- 0.99 to 37.47 +/- 3.25% totally) and muscle (from 6.74 +/- 0.25 to 10.63 +/- 0.23% totally) of cobia juveniles (P < 0.05). However, no significant difference was found on the lipid contents of juveniles fed different diets for 8 weeks (P > 0.05). In the muscle and liver of juveniles, EPA decreased with its reduction in the diet; DHA, DHA/EPA ratio and poly unsaturated fatty acids (PUFAs) generally increased with their increment in the diet. The conclusion was drawn that the growth, nucleic acid and fatty acids of cobia juveniles were not significantly affected by different DHA/EPA ratios in our experiments.
authors.affiliation: Institute for Fisheries Sciences, Guangxi University, 100 University Road, 530004 Nanning, Guangxi, China.
authors.forename: Youqing
authors.initials: Y
authors.lastname: Xu
authors.forename: Zhaokun
authors.initials: Z
authors.lastname: Ding
authors.forename: Haizhu
authors.initials: H
authors.lastname: Zhang
authors.forename: Liang
authors.initials: L
authors.lastname: Liu
authors.forename: Shuqi
authors.initials: S
authors.lastname: Wang
authors.forename: John
authors.initials: J
authors.lastname: Gorge
mesh_terms: D000818:Animals; D004032:Diet / Q000662:veterinary*; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D015118:Eicosapentaenoic Acid / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism; D009696:Nucleic Acids / Q000378:metabolism; D010473:Perciformes / Q000254:growth & development*; D012015:Reference Standards
chemical_list: D009696:Nucleic Acids; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid