This study investigated the effect of different supplements of Zn on the growth performance, antioxidant, lipid metabolism, and element deposition of hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus). A total of 180 juvenile groupers (bodyweight
10.02
±
0.01
g) were divided into three groups of 20 fish each and fed with ZnSO4, nanozinc oxide (Nano-ZnO), and dihydromyricetin-Zn (DMY-Zn) for 8 weeks(the content of Zn were 123,122.11, and 120.72 mg/kg). The findings revealed that DMY-Zn had a substantial impact on growth, feed conversion ratio, and protein efficiency ratio, whereas Nano-ZnO had a significant impact on feed conversion ratio and protein efficiency ratio. Furthermore, DMY-Zn had a positive effect on the high-density lipoprotein (HDL) content and significantly upregulated the lipid synthesis gene expression (FASN and ACACA) in the liver. The fish fed DMY-Zn had larger levels of catalase (CAT) in both the serum and liver, as well as Cu/Zn-superoxide dismutase (SOD) enzymes in muscle. In terms of antioxidant-related gene expression, the DMY-Zn treatment upregulated the expression of SOD1, Keap1b, and Mt2. Moreover, DMY-Zn also had a prominent effect on element deposition, increasing the concentration of Fe and Zn in the fish liver and muscle and Cu only in the fish muscle. The results revealed that a fish-fed diet enriched with DMY-Zn had significantly higher antioxidant and lipid metabolism activities than a ZnSO4-fed diet. In conclusion, dietary DMY-Zn treatment appears to be effective in increasing hybrid grouper growth, element deposition, antioxidant activity, and lipid metabolism.
The aim of this study was to evaluate the nutritional value of cottonseed protein concentrate (CPC) as a single dietary protein source and the optimal protein level for grass carp (Ctenopharyngodon idellus). An 8-week feeding trial was conducted by feeding juvenile grass carp (initial body weight: 4.68 ± 0.01 g) with six experimental diets containing graded levels of protein provided by CPC. The results showed that the optimal CPC level (CPC4) improved the growth performance and health status of grass carp. The optimal dietary protein level was estimated to be 38.61 and 38.66% based on specific growth rate (SGR) and feed efficiency (FE), respectively. The CPC4 group significantly increased the total antioxidant capacity (T-AOC) content and glutathione peroxidase (GSH-Px) activity in the hepatopancreas (p < 0.05). In addition, the CPC4 group increased the muscle T-AOC and glutathione (GSH) content and improved muscle hardness, and the gene expression of MRFs, fgf6a, myhc-7, myhc-1, myhc-4, igf-II, and tor was upregulated while mstn gene expression was downregulated (p < 0.05). Correlation analysis revealed that the optimal dietary CPC level promoted grass carp growth, health, and flesh quality by regulating the relative abundance of intestinal microbes. Furthermore, CPC6 upregulated the ko00480 (Glutathione metabolism) and ko00620 (Pyruvate metabolism) pathways compared to CPC1 (p < 0.05), possibly indicating that low dietary CPC levels adversely affected amino acid metabolism in the intestinal microbiota of grass carp, while a high level of CPC will meet the metabolic needs of the body by increasing the utilization of energy.
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