Effects of cyclical short-term food deprivation and refeeding on compensatory growth and gene expression of SOD, GPX and HSP70 in Schizothorax wangchiachii

Biorefining and biotechnology prospects of low-cost fish feed on Red tilapia production with different feeding regime

This study aimed to decrease the production cost and increase tilapia yield with a feeding regime. The trial was divided into four treatments with three replications followed by the feeding frequency in monosex male Nile tilapia with an average initial weight of 17.86-18.40 g/fish cultured on a net cage in the earth pond for three months. Fish fed with 18% protein supplemented with 5% protein concentrate. The first month was used by 32% protein feed twice per day (T1, control), fish were fed twice per day every other week (T2), fish were fed twice per day per week (T3), and fish were fed twice per day per week (T3). Fish fed twice per day per week are now fed twice per day (T4). These results revealed that T2 fish had the highest growth performance and most protein consumption (P < 0.05). Moreover, fish in T2 has the lowest production cost and highest benefit-cost ratio (B/C ratio) (P < 0.05). The highest percentage of edible meat in T2 was P < 0.05, but the proximate analysis was close for all three groups (P > 0.05). As a result, it is necessary to ensure that Nile Tilapia culture has sufficient protein and nutrition control. This will allow for both high growth and low cost. Fish health and quality were positively affected by a perfect protein-containing feeding regimen. In fish fed with 18% protein and 5% protein concentrate for the first month, followed by 32% protein feed twice every other day and then with 18% protein.

Environmentally relevant concentrations of microplastics modulated the immune response and swimming activity, and impaired the development of marine medaka Oryzias melastigma larvae

Microplastics (MPs), due to their impacts on the ecosystem and their integration into the food web either through trophic transfer or ingestion directly from the ambient environment, are an emerging class of environmental contaminants posing a great threat to marine organisms. Most reports on the toxic effects of MPs exclusively focus on bioaccumulation, oxidative stress, pathological damage, and metabolic disturbance in fish. However, the collected information on fish immunity in response to MPs is poorly defined. In particular, little is known regarding mucosal immunity and the role of mucins. In this study, marine medaka (Oryzias melastigma) larvae were exposed to 6.0 µm beads of polystyrene microplastics (PS-MPs) at three environmentally relevant concentrations (10² particles/L, 10⁴ particles/L, and 10⁶ particles/L) for 14 days. The experiment was carried out to explore the developmental and behavioural indices, the transcriptional profiles of mucins, pro-inflammatory, immune, metabolism and antioxidant responses related genes, as well as the accumulation of PS-MPs in larvae. The results revealed that PS-MPs were observed in the gastrointestinal tract, with a concentration- and exposure time-dependent manner. No significant difference in the larval mortality was found between the treatment groups and the control, whereas the body length of larvae demonstrated a significant reduction at 10⁶ particles/L on 14 days post-hatching. The swimming behaviour of the larvae became hyperactive under exposure to 10⁴ and 10⁶ particles/L PS-MPs. In addition, PS-MP exposure significantly up-regulated the mucin gene transcriptional levels of muc7-like and muc13-like, however down-regulated the mucin gene expression levels of heg1, muc2, muc5AC-like and muc13. The immune- and inflammation and metabolism-relevant genes (jak, stat-3, il-6, il-1β, tnf-а, ccl-11, nf-κb, and sod) were significantly induced by PS-MPs at 10⁴ and 10⁶ particles/L compared to the control. Taken together, this study suggests that PS-MPs induced inflammation response and might obstruct the immune functions and retarded the growth of the marine medaka larvae even at environmentally relevant concentrations.

Cu/Zn Superoxide Dismutase and Catalase of Yangtze Sturgeon, Acipenser dabryanus: Molecular Cloning, Tissue Distribution and Response to Fasting and Refeeding

Superoxide dismutase and catalase are two major antioxidant enzymes in the fish antioxidant defense system, which can remove excess reactive oxygen species and protect fish from stress-induced oxidative damage. The present study aimed to clone the sequences of Yangtze sturgeon, Acipenser dabryanus, Cu/Zn superoxide dismutase (AdCu/Zn-SOD) and catalase (AdCAT), and to explore changes of gene expression in the liver and intestine during fasting and refeeding. A total of 120 fish were exposed to four fasting and refeeding protocols (fasting for 0, 3, 7, or 14 d and then refeeding for 14 d). The coding sequences of AdCu/Zn-SOD and AdCAT encoded 155 and 526 amino acid proteins, respectively, both of which were expressed mainly in the liver. During fasting, when compared to the control group, liver AdCu/Zn-SOD expression was significantly higher in the 3- and 14-d groups, whereas its intestinal expression increased significantly only in the 7-d group. Liver AdCAT expression increased significantly in the 3-, 7-, and 14-d groups. During refeeding, liver AdCu/Zn-SOD expression increased significantly in the 3-, 7-, and 14-d groups compared with those in the control group. Similarly, intestinal AdCu/Zn-SOD expression increased significantly in the 3- and 7-d groups. Moreover, intestinal AdCAT expression was significantly higher in the 3-d group than in the control group, but decreased significantly in the 14-d group. Our findings indicated that AdCu/Zn-SOD and AdCAT play important roles in protecting fish against starvation-induced oxidative stress. Yangtze sturgeon exhibited the potential to adapt to a starvation and refeeding regime.

Alleviation of the Adverse Effect of Dietary Carbohydrate by Supplementation of Myo-Inositol to the Diet of Nile Tilapia (Oreochromis niloticus)

This study investigated the effect of dietary myo-inositol (MI) on alleviating the adverse effect of the high carbohydrate diet in Nile tilapia (Oreochromis niloticus). Six diets contained either low carbohydrate (LC 30%) or high carbohydrate (HC 45%) with three levels of MI supplementation (0, 400 and 1200 mg/kg diet) to each level of the carbohydrate diet. After an 8-week trial, the fish fed 400 mg/kg MI under HC levels had the highest weight gain and fatness, but the fish fed 1200 mg/kg MI had the lowest hepatosomatic index, visceral index and crude lipid in the HC group. The diet of 1200 mg/kg MI significantly decreased triglyceride content in the serum and liver compared with those fed the MI supplemented diets regardless of carbohydrate levels. Dietary MI decreased triglyceride accumulation in the liver irrespective of carbohydrate levels. The content of malondialdehyde decreased with increasing dietary MI at both carbohydrate levels. Fish fed 1200 mg/kg MI had the highest glutathione peroxidase, superoxide dismutase, aspartate aminotransferase and glutamic-pyruvic transaminase activities. The HC diet increased the mRNA expression of key genes involved in lipid synthesis (DGAT, SREBP, FAS) in the fish fed the diet without MI supplementation. Dietary MI significantly under expressed fatty acid synthetase in fish fed the HC diets. Moreover, the mRNA expression of genes related to lipid catabolism (CPT, ATGL, PPAR-α) was significantly up-regulated with the increase of dietary MI levels despite dietary carbohydrate levels. The gene expressions of gluconeogenesis, glycolysis and MI biosynthesis were significantly down-regulated, while the expression of the pentose phosphate pathway was up-regulated with the increase of MI levels. This study indicates that HC diets can interrupt normal lipid metabolism and tend to form a fatty liver in fish. Dietary MI supplement can alleviate lipid accumulation in the liver by diverging some glucose metabolism into the pentose phosphate pathway and enhance the antioxidant capacity in O. niloticus.

Effect of starvation and refeeding on growth, gut microbiota and non-specific immunity in hybrid grouper (Epinephelus fuscoguttatus♀×E. lanceolatus♂)

Environmental changes can lead to food deprivation among aquatic animals. The main objective of this present research was to assess the effect of starvation and refeeding on growth, gut microbiota and non-specific immunity in a hybrid grouper (Epinephelus fuscoguttatus♀×E. lanceolatus♂). A total of 120 fish with an average weight of 74.16 ± 12.08 g were randomly divided into two groups (control group and fasted-refed group). The control group was fed until satiation for 60 days, while the fasted-refed group was fasted for 30 days and then fed to satiation for 30 days. The results showed that starvation led to a significantly decreased growth performance parameters [weight gain rate (WGR) and specific weight gain rate (SGR), while the feeding rate (FR) ] increased during the refeeding, non-specific immunity was significantly improved (p < 0.05) during the first 15 days of starvation, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), lysozyme (LYM) and catalase (CAT). However, non-specific immunity decreased at 30 days of starvation, the expression of genes related to immunity, such as TNF-α, was upregulated (p < 0.05) during starvation, while the expression levels of IL-17 and IFN-γ was reduced (p < 0.05). The expression of IFN-γ and IL-1β peaked during refeeding. Starvation led to significantly decreased abundance and diversity of intestinal microflora, with a higher abundance of Vibrio and a lower abundance of Brevibacillus, Bifidobacterium, Alloprevotella in the fasted-refed group during refeeding than in the control group. The above results reveal that starvation stimulates changes in growth, non-specific immunity, and the gut microbiota, providing new insights for the study of fish habitat selection and adaptability to environmental changes.