RESUMO
Our recent study demonstrated that diet with blend oil (named BO1) as lipid, which is designed on the base of essential fatty acid requirement of Trachinotus ovatus, achieved good performance. Here, to confirm its effect and investigate the mechanism, three isonitrogenous (45%) and isolipidic (13%) diets (D1-D3) only differing in dietary lipids, which were, respectively, fish oil (FO), BO1, and blend oil 2 (BO2) consisting of FO and soybean oil at 2 : 3, were formulated and used to feed the T. ovatus juveniles (average initial weight: 7.65 g) for 9 weeks. The results showed that the weight gain rate of fish fed D2 was higher than that of fish fed D3 (P < 0.05) and had no significant difference from that of fish fed D1 (P > 0.05). Correspondingly, compared with the D3 group, fish of the D2 group exhibited better oxidative stress parameters such as lower serum malondialdehyde content and inflammatory indexes in the liver such as the lower expression level of genes encoding four interleukin proteins and tumor necrosis factor α, as well as higher hepatic immune-related metabolites such as valine, gamma-aminobutyric acid, pyrrole-2-carboxylic acid, tyramine, l-targinine, p-synephrine, and butyric acid (P < 0.05). Furthermore, the intestinal probiotic (Bacillus) proportion was significantly higher, while the pathogenic bacteria (Mycoplasma) proportion was significantly lower in the D2 group than that in the D3 group (P < 0.05). The main differential fatty acids of diet D2 were close to those of D1, while the levels of linoleic acid and n-6 PUFA, as well as the ratio of DHA/EPA of D3, were higher than those of D1 and D2. These results indicated that the better performance of D2 such as enhancing growth, reducing oxidative stress, and improving immune responses and intestinal microbial communities in T. ovatus may be mainly due to the good fatty acid composition of BO1, which indicated the importance of fatty acid precision nutrition.
RESUMO
An 8-week feeding trial was performed to evaluate the effects of dietary leucine (Leu) and valine (Val) levels on growth performance, glycolipid metabolism and immune response in Oreochromis niloticus. Fish (15.23 ± 0.05 g) were randomly fed four diets containing two Leu levels (1.2% and 2.3%) and two Val levels (0.7% and 1.4%) as a 2 × 2 experimental design (LL-LV, LL-HV, HL-LV and HL-HV). Compared with LL-LV group, the growth parameters (final weight, daily growth coefficient (DGC) and growth rate per metabolic body weight (GRMBW)), feed conversion rate (FCR), the activities of intestinal amylase, lipase, creatine kinase (CK) and Na+, K+-ATPase, liver NAD+/NADH ratio, as well as the expression of SIRT1, GK, PK, FBPase, PPARα, CPT IA, ACO and IL10 all increased significantly in the HL-LV group; however, in the high Val group, final weight, DGC, GRMBW, intestinal enzyme activities, as well as the expression of PEPCK, SREBP1, FAS, IL8 and IL10 of the HL-HV group were significantly lower than those of the LL-HV group, while the opposite was true for the remaining indicators. Significant interactions between dietary Leu and Val were observed in final weight, DGC, GRMBW, plasma IL1ß and IL6 levels, intestinal amylase and CK activities, liver NAD+/NADH ratio, as well as the expression of SIRT1, PK, PEPCK, FBPase, SREBP1, FAS, PPARα, CPT IA, ACO, NF-κB1, IL1ß, IL6 and IL10. The highest values of growth parameters, intestinal enzyme activities and expression of SIRT1, FBPase, PPARα, CPT IA and ACO were observed in the HL-LV group, while the opposite was true for the expression of SREBP1, FAS, PPARα, NF-κB1, IL1ß and IL6. Overall, our findings indicated that dietary Leu and Val can effect interactively, and fish fed with diets containing 2.3% Leu with 0.7% Val had the best growth performance and hepatic health status of O. niloticus.