This experiment was conducted to assess the possibility of replacing fish meal (FM) with soy protein peptide (SPP) at different levels—0% (FM), 14.29% (S5), 28.57% (S10), 57.14% (S20), 71.42%(S25)—and its effects on growth, histology, gene expression related to liver lipid metabolism and intestinal immunity in juvenile pompano Trachinotus ovatus (initial mean weight = 39.88 ± 0.15 g). 600 healthy and uniformed-size fish were distributed to five groups of three replicates, each with 40 fish in each floating cage and fed twice daily for 8 weeks. Results showed that no significant difference in the growth was observed with SPP replacing FM (P > 0.05). Serum glutathione peroxidase activity in the S10 group was significantly higher than that in the FM group, and serum malondialdehyde content significantly decreased (P < 0.05). SPP significantly improved intestinal immunity by increasing alkaline phosphatase and lysozyme activities and up-regulating interleukin 10 and complement 4 mRNA levels while simultaneously decreasing triglyceride and total cholesterol content and down-regulating interleukin 1β mRNA expression. Villus length and muscle thickness in the S10 group were significantly higher than those in the FM group (P < 0.05). SPP significantly improved liver fat metabolism by increasing carnitine palmitoyl transferase I mRNA levels, and down-regulating fatty acid synthesis mRNA expression (P < 0.05). In summary, SPP substitution for FM promoted intestinal health, liver lipid metabolism and reduced liver fat accumulation for juvenile pompano T. ovatus, with no significant effect on growth performance. Based on the second-order polynomial analysis model of LYZ activity, the optimal replacement SPP level for juvenile pompano T. ovatus was 11.82%.
Glycerol monolaurate (GML), a representative fatty acid glyceride, was used to promote growth. This study investigated the effects of GML in diets on growth, serum biochemical parameters, antioxidant capacity, liver morphology and lipid metabolism for juvenile pompano Trachinotus ovatus. Six groups of T. ovatus (mean weight = 14.00 ± 0.70 g) were fed with six diets, containing varying GML levels of 0.00% (G0), 0.05% (G5), 0.10% (G10), 0.15% (G15), 0.20% (G20), and 0.25% (G25) for 8 weeks. Fish were reared for in floating cages (length: 1 m; width: 1 m; and height: 2 m). The highest weight gain rate (WGR), specific growth rate (SGR), and protein deposit rate (PDR) were observed in the G15 group (P < 0.05). Hepatic glutathione peroxidase, total antioxidant capacity and superoxide dismutase activities were significantly increased in the G10 and G15 groups compared with the G0 group (P < 0.05), whereas hepatic malondialdehyde (MDA) was significantly reduced in the G10 and G15 groups (P < 0.05). The alkaline phosphatase activity was significantly higher in the G5, G10, G15, and G20 groups than in the G0 group (P < 0.05), and the highest AKP activity was observed in the G15 group. Alanine aminotransferase (ALT) activity was significantly lower in the G10, G15, G20, and G25 groups than in the G0 group (P < 0.05). The addition of GML to the feed significantly reduced triglyceride (TG) content (P < 0.05). In comparison with the G0 group, the G15, G20, and G25 groups had significantly lower total cholesterol content and significantly higher high-density lipoprotein content (P < 0.05). Low-density lipoprotein content was significantly lower in the G5 and G10 groups than in the G0 group (P < 0.05). Serious vacuolation occurred in the G0 group, but the cell boundaries in all added groups were obvious, and the rate of intracellular vacuolization decreased. As the GML level increased, carnitine palmitoyl-transferase Ι mRNA level was significantly up-regulated (P < 0.05). The expression of fatty acid synthesis in the G10, G15, G20, and G25 groups was significantly lower than that in the G0 group (P < 0.05). The expression of sterol regulatory element-binding protein-Ι was significantly lower in the G10, G15, G20, and G25 groups than in the G0 group (P < 0.05). Based on the broken-line model of WGR and PDR corresponding to GML levels, the optimum addition level of dietary GML was 0.14%-0.16% for juvenile T. ovatus. In conclusion, 0.15% GML significantly improved the growth performance, hepatic antioxidant ability, and lipid metabolism and protected the liver for juvenile pompano T. ovatus.
This research aimed to assess effects of fish meal under different storage conditions on growth and antioxidant capacity for juvenile grouper within eight weeks. The healthy fish samples (initial body weight = 18.75 ± 0.05 g) were irregularly distributed to 0.5 m3 barrels with 28 fish per barrel, fed with each diet in the three replicate groups. Fish meals (FMs) were stored at 4°C (experiment 1) and room temperature (30 ± 2°C, experiment 2) for 45, 90 and 135 days, and the data of VBN, HA, AV and TBA were detected. Seven iso‐nitrogenous and iso‐lipidic diets were prepared and denoted as fresh fish meal FFM (control group), 4‐FM45, 4‐FM90, 4‐FM135, RT‐FM45, RT‐FM90 and RT‐FM135, respectively. Prolonged storage time, the volatile base nitrogen, acid value, histamine and thiobarbituric acid contents of FM increased significantly (p < .05). The growth condition and feed utilization of experimental fish were not significantly affected (p > .05). Prolonged storage time, in experiment 1, the catalase (CAT), the superoxide dismutase (SOD) activities and the malondialdehyde (MDA) contents initially increased dramatically and then decreased (p < .05). The reactivity of CAT mRNA in FFM group was significantly higher than that in other treatment groups (p < .05). In experiment 2, CAT activity decreased significantly (p < .05), whereas the MDA contents increased sharply (p < .05). SOD activity and CAT expression in the liver initially increased and then decreased (p < .05). The mRNA level and enzyme activity of trypsin decreased (p < .05) in experiment 1 and 2. In summary, storage of FM (within 135 days) cannot improve the growth and feed utilization of juvenile grouper but weaken the antioxidant capacity of the liver.
Distiller’s dried grains with soluble (DDGS) to replace fishmeal (FM) or other plant protein sources and its effects on an aquatic animal’s growth performance and health system is rarely discussed. In recent times FM use in aquafeed has been a problem for the aquaculture industry because of the depletion of fish resources in the ocean and the high cost of FM. For that reason, researchers are focusing on reducing the cost of aquafeed production by lowering the inclusion of FM in aquafeed. One of the low-cost alternative protein sources to replace FM is DDGS. The present review discusses the compilation of available literature review and other works on the use of DDGS to replace FM in aquafeed and how it improves the growth performance, immune health system, and disease resistance in an aquatic animal. It focuses on the production of DDGS, the nutritional composition of DDGS, the chemical and physical characteristics of DDGS, and the effects of the DDGS inclusion in aquafeed on the aquatic animal. Apart from improving the growth performance of the aquatic animal when included in aquafeed, it also helps improve the immune health system of the animal. It also helps boost the immune system of the aquatic animal to fight diseases and increase disease resistance when included in aquafeed. Furthermore, DDGS also contains some constituents like carotenoids that help improve the meat quality of the animal when included in aquafeed. The current review also discusses the management and use of technology to improve the aquaculture industry, educate farmers on reducing diseases during the culturing periods, and increase productivity and profit in a friendly environment.
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