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Simple Summary: The application of more inedible ingredients in aquafeeds will contribute to sustainable development and alleviate food security. The rising prices and declining yields of traditional aquafeed protein sources such as fishmeal and soybean meal are hindering the development of aquaculture. Therefore, in this study, bovine bone meal, dephenolized cottonseed protein, and blood cell meal were utilized to replace dietary fishmeal in the form of compound protein. Culture trials were conducted on the economically farmed fish, juvenile golden pompano, and the feasibility and suitable ratio of non-grain proteins for application in aquafeeds were evaluated by indicators such as growth performance and muscle quality. The results of this study provide data support for the development of new aquafeeds with less fishmeal and high efficiency, which can help alleviate the shortage of aquafeed feedstuff, and provide theoretical and data references for the study of securing a sustainable food supply. In the context of human food shortages, the incorporation of non-grain feedstuff in fish feed deserves more research attention. Here, the feasibility and appropriate ratio of non-grain compound protein (NGCP, containing bovine bone meal, dephenolized cottonseed protein, and blood cell meal) for dietary fishmeal (FM) replacement were explored in golden pompano (Trachinotus ovatus). Four isonitrogenous (45%) and isolipidic (12%) diets (Control, 25NGP, 50NGP, and 75NGP) were prepared. Control contained 24% FM, whereas the FM content of 25NGP, 50NGP, and 75NGP was 18%, 12%, and 6%, respectively, representing a 25%, 50%, and 75% replacement of FM in Control by NGCP. Juvenile golden pompano (initial weight: 9.71 ± 0.04 g) were fed the four diets for 65 days in sea cages. There was no significant difference between the 25NGP and Control groups in terms of weight gain, weight gain rate, and specific growth rate; contents of crude protein, crude lipid, moisture, and ash in muscle and whole fish; muscle textural properties including hardness, chewiness, gumminess, tenderness, springiness, and cohesiveness; and serum biochemical indexes including total protein, albumin, blood urea nitrogen, HDL cholesterol, total cholesterol, and triglycerides. However, the golden pompano in 50NGP and 75NGP experienced nutritional stress, and thus some indicators were negatively affected. In addition, compared to the Control group, the expression levels of genes related to protein metabolism (mtor, s6k1, and 4e-bp1) and lipid metabolism (pparγ, fas, srebp1, and acc1) of the 25NGP group showed no significant difference, but the 4e-bp1 and pparγ of the 75NGP group were significantly upregulated and downregulated, respectively (p < 0.05), which may explain the decline in fish growth performance and muscle quality after 75% FM was replaced by NGCP. The results suggest that at least 25% FM of Control can be replaced by NGCP, achieving a dietary FM content of as low as 18%; however, the replacement of more than 50% of the dietary FM negatively affects the growth and muscle quality of golden pompano. [ABSTRACT FROM AUTHOR]

To investigate the effects of dietary vitamin C on growth, flesh quality and antioxidant capacity of juvenile golden pompano Trachinotus ovatus, a 56‐day feeding trial with five graded levels of dietary VC (D1: 11.69, D2: 34.89, D3: 59.10, D4: 114.26 and D5: 227.93 mg VC per kg of diet) was performed on 375 fish (triplicate groups of 25 fish per diet, initial weight 13.57 ± 0.09 g). Results showed that fish of D3 group exhibited the maximum specific growth rate (SGR) and the highest liver enzymatic activities of catalase (CAT) and glutathione peroxidase (GSH‐PX), which were consistent with the expression levels of cat and gsh‐px. Besides, the D3 group also showed higher contents of protein and lipid, and lower cooking loss, drip loss and malondialdehyde content in muscle than D1 group. The docosahexaenoic acid proportion in muscle increased with increasing dietary VC levels. Furthermore, the lowest expression levels of carnitine palmitoyltransferase1 (cpt1) and peroxisome proliferator‐activated receptor α (pparα) were detected in livers of D3 group. The optimum dietary VC level was 49.73 mg/kg from the broken‐line analysis based on the SGR, in which better growth performance, antioxidative ability and flesh quality were observed in T. ovatus juveniles. [ABSTRACT FROM AUTHOR]

To investigate the effects of dietary n-3 highly unsaturated fatty acids (HUFA) levels on growth, lipid metabolism and innate immunity in juvenile golden pompano Trachinotus ovatus , a marine carnivorous teleost, a total of 450 fish (average body weight: 14.84 g) were randomly distributed into 18 cages at sea, each dietary group with three cages and respectively fed six diets (D1-D6) with 2.30% (D1), 0.64% (D2), 1.00% (D3), 1.24% (D4), 1.73% (D5), or 2.10% (D6) n-3 HUFA. Here, D1 with fish oil as lipid source was set as control, while D2-D6 used a mixed vegetable oil as lipid source and supplemented with docosahexaenoic acid- (DHA) and eicosapentaenoic acid- (EPA) enriched oils to adjust the n-3 HUFA levels. After 8 weeks feeding, the daily growth coefficient (DGC), specific growth rate (SGR) and feed efficiency ratio (FER) showed no significant difference among the six dietary groups (P > 0.05). The levels of EPA and DHA in serum and liver increased with the dietary n-3 HUFA levels. The activity of total superoxide disumutase (T-SOD) in serum of fish fed D4 and D5 were significantly higher than that of the other groups, whereas the opposite was true for serum IL-1β and IL-6 levels as well as liver malondialdehyde (MDA) content. The mRNA levels of genes related to hepatic lipid metabolism including sterol regulatory element-binding protein-1 (srebp-1), fatty acid binding protein 1 (fabp1), peroxisome proliferators-activated receptor alpha (pparα), elongase of very long-chain fatty acids 5 (elovl5) and fatty acyl desaturase 2 (fads2) were down-regulated in fish fed the diets with high n-3 HUFA levels, while those of apolipoprotein b 100 (aprob 100) and carnitine palmitoyl transferase 1 (cpt1) increased significantly as increasing n-3 HUFA levels up to 1.73% (D2-D5), but decreased in the 2.10% n-3 HUFA group (D6). In addition, the expression levels of genes related to innate immunity including interleukin-10 (il-10) and transforming growth factor β1 (tgf-β1) increased significantly when dietary n-3 HUFA increased from 0.64% to 1.73%, whereas the opposite was true for the expression levels of nuclear factor kappa-B (nf-κb), interleukin-1β (il-1β), interleukin-6 (il-6) and interleukin-8 (il-8). Overall, the results indicated that dietary n-3 HUFA at 1.24–1.73% (D4-D5) can effectively improve fatty acid profiles, lipid metabolism, antioxidant capacity and immune response of golden pompano. Dietary supplementation of n-3 HUFA at 1.73% can effectively improve fatty acid profiles, lipid metabolism and immune response. And, dietary supplementation of n-3 HUFA at 1.24–1.73% enhanced hepatic antioxidant capacity of juvenile golden pompano. Image 1 • Dietary n-3 HUFA levels significantly influenced the fatty acid profiles and lipid content in the liver of golden pompano. • Dietary n-3 HUFA at 1.24% and 1.73% enhanced antioxidant capacity in the liver of golden pompano. • Dietary n-3 HUFA at 1.73% improved hepatic immune response by down-regulating the expression of pro-inflammatory cytokines. [ABSTRACT FROM AUTHOR]