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The quest to reduce dependency on fish‐ or vegetable‐based oil resources has prompted aquaculture experts to intensify their search for a suitable and sustainable alternative for aquafeed production. Based on this reality, the current study was designed to evaluate the dietary influence of African palm weevil oil (PWO) on the growth performance, serum biochemistry, lipid peroxidation products, antioxidant enzyme response, and organ integrity of African catfish (Clarias gariepinus) juveniles. Four diets were formulated, wherein the control diet was prepared using soybean oil (SO) as the main dietary oil source and was replaced with PWO in the treatment diets at 50% (PWO‐50), 75% (PWO‐75), or 100% (PWO‐100). A total of 180 African catfish (average weight: 18.76 ± 0.043) were randomly stocked at 15 fish per 50‐L tank in triplicate and hand‐fed to apparent satiation twice daily for 45 days. The results showed that the highest weight gain (WG), specific growth rate (SGR), and thermal growth coefficient (TGC) were found in control (SO)‐fed fish, which is similar to the PWO 50% but differs significantly from others (p < 0.05). The feed conversion ratio (FCR) and protein productive value (PPV) showed linear and quadratic trends, with a significantly lowest and highest value recorded in fish‐fed control and PWO 50%, respectively, compared to other dietary groups (p < 0.05). The protein efficiency ratio (PER) value decreases linearly (p < 0.001) as the level of PWO increases. The highest total immunoglobulin (TIG) and superoxide dismutase (SOD) activity were recorded in fish fed PWO‐50%, while PWO‐75% registered the highest lysozyme activity (LA). There was no statistically significant difference (p > 0.05) in the physiological parameters such as total cholesterol (TC), triglyceride (TG), low‐density lipoprotein cholesterol (LDL‐C), high‐density lipoprotein cholesterol (HDL‐C), alanine aminotransferase (ALT), C‐reactive protein (CRP), and lipid peroxidation index (malondialdehyde [MDA]) among the groups. The fish fed PWO‐100% had the lowest recorded values of villus height, area of absorption, and cryptal depth (p < 0.05). In summary, the current finding shows that oil extracted from African palm weevils appears promising at a 50% dietary level without impairing the growth performance, liver, or intestinal health of African catfish. [ABSTRACT FROM AUTHOR]

The shortage of lipid sources has been a limiting factor of the aqua‐feed industry. Lysophospholipid (LPL) is a highly efficient lipid emulsifier, which may help improve lipid utilization efficiency and thus spare the dietary lipid. This study aimed to evaluate the effects of LPL on growth performance, fatty acid composition, and lipid metabolism of juvenile Litopenaeus vannamei (averagely, 2.4 g). Five diets were prepared: a control diet with 6.5% lipid, the control diet supplemented with 0.05% or 0.1% LPL (0.05% LPL and 0.1% LPL), a moderately low‐lipid (MLL) diet supplemented with 0.05% LPL (0.05% LPL‐MLL), and an extremely low‐lipid (ELL) diet supplemented with 0.1% LPL (0.1% LPL‐ELL). Each dietary group had triplicate tanks (30 shrimp in each tank). The feeding experiment lasted 8 weeks. Compared with the control group, the addition of 0.05% LPL promoted the growth by 9.95%; diet 0.05% LPL‐MLL resulted in a comparable growth to the control, but diet 0.1% LPL‐ELL tended to adversely affect the growth. Dietary LPL had little effect on the whole‐body proximate composition. The content of 18:2n−6 and 18:3n−3 was significantly higher in the 0.05% LPL group compared to the control. The 20:5n−3 content was the highest in the 0.05%LPL‐MLL group. In addition, the 0.05% LPL and 0.1% LPL group increased the plasma high‐density lipoprotein‐cholesterol content. Meanwhile, all LPL groups reduced the low‐density lipoprotein‐cholesterol content. The addition of LPL significantly regulated the messenger RNA (mRNA) expression of genes related to cholesterol homeostasis, such as ldlr, srb1, abca1, and abcg8. In conclusion, dietary supplementation with 0.05% LPL tended to promote shrimp growth and can spare 15% dietary lipid. However, when the dietary lipid content decreased from 6.5% to an extremely low level of 4.8%, dietary LPL was ineffective to spare lipids. This was the first study to validate the lipid‐sparing effect of dietary LPL in shrimp. [ABSTRACT FROM AUTHOR]

The dietary lipid level is closely associated with ovarian maturation of broodstock. However, optimal lipid requirements during broodstock gonad development for aquatic animals remain limited. In order to assess the impact of dietary lipid levels (6%, 8%, 10%, 12%, and 14% lipid, denoted as L6%, L8%, L10%, L12%, and L14%) on the ovarian maturation, antioxidant status, and messenger RNA (mRNA) expression of genes involved in the lipid metabolism of Macrobrachium rosenbergii broodstock (initial weight 10.53 ± 1.97 g), this study carried out an 8‐week feeding experiment. The findings showed that while there was no significant difference in the survival rate across the groups (p > 0.05), the weight gain observed in prawns fed the 8% lipid‐level diet was significantly higher than those fed other diets (p < 0.05). The hepatosomatic index and the gonadosomatic index showed a significant increase with the rise in dietary lipid level (p < 0.05). More ovaries from M. rosenbergii broodstock reached stages Ⅲ and Ⅳ after being supplemented with dietary lipid levels between 8% and 14%. Serum glucose content did not show any significant difference among all groups (p > 0.05), but serum triglyceride and total cholesterol content increased followed by a decreasing trend with increasing levels of dietary lipids, both peaking in the prawns fed a 10% lipid‐level diet. Furthermore, the progesterone (PROG) and 17β‐estradiol (E2) content of prawns fed the 10% and 12% lipid‐level diets were significantly higher compared to other groups (p < 0.05). Based on serum E2 and PROG content, the optimal lipid level needed for maximal ovarian maturation was determined to be 11.79% and 10.88%, respectively. Moreover, there were more endogenous vitellogenic oocytes in prawns fed 8% and 10% lipid‐level diets, with a more compact arrangement compared to the less tightly arranged structure of the ovarian tissue in prawns fed other diets. With the increase in dietary lipid levels, there was a significant increase in the activity of superoxide dismutase. The activities of total antioxidant capacity and glutathione peroxidase initially increased and then decreased significantly, peaking at prawns fed 8% and 10% lipid‐level diets, respectively (p < 0.05). The malondialdehyde content reached its lowest point in prawns fed a diet containing 10% lipid. In addition, the mRNA expressions of hepatopancreatic diacylglycerol acyltransferase and acetyl‐CoA carboxylase showed the highest values in prawns fed a 10% lipid diet. Conversely, there was a significant decrease in the mRNA expression of carnitine palmitoyltransferase‐1a in the hepatopancreatic as dietary lipid levels increased. The highest mRNA expression of fatty acid‐binding proteins was observed in prawns fed an 8% lipid diet. In conclusion, dietary lipid levels ranging from 8% to 11.79% are beneficial for ovarian maturation and health of M. rosenbergii broodstock. [ABSTRACT FROM AUTHOR]

This study investigated the effect of dietary lipid levels on growth performance, lipid metabolism, antioxidant capacity, digestive enzyme activity, and metamorphosis rate of bullfrog (Aquarana catesbeianus) tadpoles. A total of six isonitrogenous diets were prepared, each containing 4.46% (L5), 6.95% (L7), 9.10% (L9), 10.90% (L11), 12.34% (L13), and 15.00% (L15) crude lipid content. The experimental diets were administered to triplicates of tadpoles (stage 25, 0.007 g) twice daily for 75 days with a daily feeding rate of 6.50% of their body weight. Weight gain (WG), specific growth rate (SGR), crude protein content of the whole body, apparent digestibility of dry matter and gross energy, intestinal lipase (LPS) capacity, lipoprotein lipase (LPL), and carnitine palmitoyltransferase‐I (CPT‐I) and contents of growth hormone (GH) and insulin‐like growth factor‐1 (IGF‐1) in the liver, high‐density lipoprotein cholesterol (HDL‐C) content in the serum, and metamorphosis rate at stages 40 and 41 increased as the dietary lipid level increased from 4.46% to 12.34% and then decreased. As the dietary lipid level increased from 4.46% to 10.90%, the protein efficiency ratio (PER), protein deposition rate (PDR), lipid deposition rate (LDR), crude lipid content and gross energy of the whole body, apparent digestibility of the crude lipid, superoxide dismutase (SOD), catalase (CAT) activities in the liver, and the intestinal trypsin (TPS) activity all increased and then decreased. According to the second‐order polynomial regression analysis of the WG and metamorphosis rate at stage 41 to the dietary lipid level, the ideal dietary lipid content for tadpoles was 11.08% and 10.72%, respectively. Overall, the appropriate dietary lipid level for bullfrog tadpoles was found to be 10.72%–11.08% of the diet. [ABSTRACT FROM AUTHOR]

Dietary docosahexaenoic acid (DHA) is crucial for the optimal (Opt) growth of bivalves, but the precise dietary DHA requirement remains undetermined in bivalves. Our study identifies the optimal dietary DHA requirement for razor clam Sinonovacula constricta and demonstrates its effects on fatty acid profiles and gene expression related to inflammation and detoxification. Microencapsulated feeds with different DHA levels (DHA1–6 groups: 1.68, 4.85, 9.49, 12.6, 15.59, and 16.95 mg g−1 dry matter) were prepared using spray drying. Razor clams (initial wet weight: 3.8 ± 0.6 mg) were fed these microcapsules for a period of 20 days. The present study showed that the clams in the DHA1 group exhibited significantly lower weight and shell length gain rates compared to those in the DHA3, DHA4, DHA5, and DHA6 groups. Based on the shell length gain rate, the Opt dietary requirement of DHA for clam is approximately 6.42 mg g−1 dry matter. The clams in the DHA2 group had significantly higher crude lipid content compared to those in the DHA1 and DHA6 groups, while the clams in the DHA1 group had the highest ash content, significantly higher than that in the DHA4 and DHA6 groups. The DHA levels in the clams increased with the increase in DHA content in the microcapsules, while the levels of total n‐6 polyunsaturated fatty acids (PUFAs), linoleic acid (LA), and alpha‐linolenic acid (ALA) decreased. The mRNA levels of cyclooxygenase-2 (cox2) and 5-lipoxygenase type 2 (5-lox-2) were higher in the DHA1 and DHA6 groups compared to other microcapsule groups. As dietary DHA levels increased, the mRNA levels of nuclear factor kappa B (nfκb) and nuclear factor erythroid 2-related factor 2 (nrf2) decreased. Additionally, the mRNA levels of glutamate-cysteine ligase catalytic subunit (gclc) and glutathione S-transferase (gst) were highest in the DHA1 group. This is the first study to determine the Opt DHA requirement for juvenile razor clams using microcapsules with different DHA levels, and this study further reveals that dietary DHA can help reduce inflammation and oxidative status in clams. [ABSTRACT FROM AUTHOR]

Simple Summary: Intermittent and chronic hypoxia are common and harmful to marine animals. The tiger puffer is a representative species of the family Tetraodontidae, which has only slit-like gill openings and is susceptible to hypoxia stress. Both intermittent and chronic hypoxia decrease the growth and visceral weight of tiger puffer but increase the feed conversion ratio and blood hemoglobin content. Chronic hypoxia but not intermittent hypoxia promoted protein synthesis and the glycolysis pathway. Intermittent hypoxia but not chronic hypoxia decreased lipid synthesis and monounsaturated fatty acids content but increased n-3 polyunsaturated fatty acids levels. These changes promoted the adaption of tiger puffer to intermittent and chronic hypoxia. Intermittent and chronic hypoxia are common stresses to marine fish, but the different responses of fish to intermittent and chronic hypoxia have not been well-known. In this study, tiger puffers were farmed in normoxia conditions (NO, 6.5 ± 0.5 mg/L), intermittent hypoxia (IH, 6.5 ± 0.5 mg/L in the day and 3.5 ± 0.5 mg/L in the night), or choric hypoxia (CH, 3.5 ± 0.5 mg/L) conditions for 4 weeks, after which the growth, nutrient metabolism and three hifα isoforms expression were measured. Both intermittent and chronic hypoxia decreased the fish growth and visceral weight but increased the feed conversion ratio and blood hemoglobin content. Chronic hypoxia but not intermittent hypoxia promoted protein synthesis and whole-fish protein content by activating mtor gene expression and promoted the glycolysis pathway by activating gene expression of hif1α and hif2α. Intermittent hypoxia but not chronic hypoxia decreased the hepatic lipid synthesis by inhibiting fasn and srebf1 gene expression. Meanwhile, intermittent hypoxia reduced the monounsaturated fatty acid content but increased the n-3 polyunsaturated fatty acids percentage. The results of this study clarified the adaptive mechanism of tiger puffer to intermittent and chronic hypoxia, which provides important information about mechanisms of hypoxia adaption in fish. [ABSTRACT FROM AUTHOR]

The polychaeta Neanthes japonica is a common by-product in mariculture ponds. It is rich in essential nutrients, but has not been well-explored. Therefore, this 56-day experiment investigated the effects of substituting N. japonica meal for dietary fishmeal on juvenile tiger puffer (15.49 ± 0.02 g, n = 450 fish). The control diet (CON) contained 40% fishmeal. Freeze-dried N. japonica meal (FNM) was supplemented into CON at the levels of 3% (FNM3), 6% (FNM6), and 9% (FNM9), replacing fishmeal. The fifth diet contained 6% oven-dried N. japonica meal (ONM6), replacing fishmeal. The results indicated that no significant difference was observed in growth, feed efficiency, and somatic index among all the treatment groups. The feed intake of the FNM6 group was significantly higher compared to CON. No significant difference was detected in fish proximate composition, as well as the fatty acid composition, amino acid composition, and muscle texture. The supplementation of N. japonica meal decreased the activities of intestinal lipase and α-amylase. The addition of freeze-dried N. japonica meal significantly up-regulated the expression of the intestinal amino-glycine transporter pat1. It was concluded that adding 9% N. japonica meal to the feed had no significant effect on the growth performance and body composition of juvenile tiger puffer. [ABSTRACT FROM AUTHOR]

Palm oil, with its higher production, lower prices, and higher levels of palmitic acid and oleic acid, may have great potential for use in the aquafeed industry. In this study, with an 8‐week feeding experiment, the efficacy of palm oil as a substitute for fish oil in tiger puffer feeds was comprehensively evaluated. The control diets (FO group) contained 8% marine fish oil as the main lipid source, while in the treatment diets, the added marine fish oil was replaced with palm oil at 25%, 50%, 75%, and 100%, respectively, which was named 25PO, 50PO, 75PO, and 100PO, respectively. Juvenile tiger puffers with an initial weight of 15.0 ± 0.04 g were used, with three replicate tanks of 30 juvenile fish tiger puffer for each dietary group. The fish oil replacement by palm oil did not have an adverse effect on fish growth and feeding, but the weight gain decreased by 17.3% in group PO100. Palm oil had no significant effects on fish proximate composition and muscle texture. The effects of dietary palm oil on muscle fatty acid composition were not significant, with DHA and EPA significantly lowered only in the 100PO group. In contrast, the changes in liver and intestinal fatty acid compositions in response to diets were more significant than those in the muscle. In the intestine, the replacement of more than 50% fish oil by palm oil significantly downregulated the gene expression associated with peroxisomal fatty acid β‐oxidation and triglyceride hydrolysis, while upregulated the expression of cholesterol biosynthetic genes. In the liver, the replacement of more than 75% fish oil also significantly upregulated the cholesterol synthesis. In conclusion, palm oil can replace 75% of added marine fish oil in tiger puffer diets and does not adversely affect the growth performance, feed utilization, muscle composition, and muscle texture. [ABSTRACT FROM AUTHOR]

Aquaculture has become the largest source of seafood consumption, leading to increased research in aqua-nutrition. A survey of publications on aqua-nutrition topics was conducted, revealing that feed additives are the most studied area due to the need for alternatives to antibiotics. Plant extracts and microbial agents are popular feed additives, with a focus on natural and green options. Research on alternative protein and lipid sources, such as insects and microalgae, is also prominent. The study emphasizes the importance of considering the demands of the aquaculture industry and market in aqua-nutrition research. [Extracted from the article]

The starry flounder Platichthys stellatus, an economically important benthic fish species widely distributed throughout the North Pacific Ocean, exhibits poor heat tolerance, resulting in frequent adult mass mortality in aquaculture settings. Heat stress disrupts the energy metabolism of P. stellatus, elevating blood glucose and implying its sensitivity to rising water temperatures. In particular, the survival of adult fish in aquaculture settings during the summer season is less than that of larvae or juveniles. This study aimed to understand the heat stress‐associated survival of adults by focusing on the molecular pathways of glycolysis/gluconeogenesis using comparative transcriptome analysis. Transcriptomes were obtained by RNA sequencing of P. stellatus livers of adults exposed to 16 and 28°C, together with juveniles at the same conditions. A total of 16,121,503–18,774,222 raw paired‐end reads were obtained after trimming. The assembled unigenes (39,489 out of 127,460) were annotated in the nr, Clusters of Orthologous Groups (COG), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Swiss‐Prot databases. A total of 6,858 differentially expressed genes were found in juveniles and adults at control (16°C) and high (28°C) water temperatures. Juveniles and adults had 1,856 genes downregulated and 1,548 genes upregulated at the 16°C control water temperature and 1,055 genes downregulated and 1,231 genes upregulated at 28°C, overall involving at least 47 KEGG pathways. When raising the water temperature and comparing the DEGs of juveniles and adults, respectively, we found that both groups showed similar upregulation patterns for the major heat shock protein (HSP) genes under temperature‐increasing conditions, indicating a conserved response mechanism. Additionally, both juvenile and adult fish showed similar upregulation of ER stress‐related genes, including endoplasmic reticulum chaperone BiP (BiP) and homocysteine‐responsive endoplasmic reticulum‐resident ubiquitin‐like domain member 1 (HERP), suggesting consistent transcriptional changes associated with ER stress under heat stress conditions. However, notable differences were observed in the expression of inflammation and immune response‐related genes, and juvenile P. stellatus showed upregulation of immune costimulatory protein B7‐H3 (B7H3) and immunoglobulin superfamily member 9 (IGSF9), while adults showed upregulation of high‐affinity immunoglobulin epsilon receptor subunit gamma (FCER1G), V‐type immunoglobulin domain‐containing suppressor of T‐cell activation (VSIR), and immunoglobulin superfamily DCC subclass member 3 (IGDCC3). Especially, phosphoglucomutase (PGM), glucose‐6‐phosphatase catalytic subunit (G6PC), phosphofructokinase (PFK), and bisphosphoglycerate mutase (BPGM), the enzymes involved in the glycolysis/gluconeogenesis pathway, showed significantly higher FPKM in adult P. stellatus than in juveniles. Overall, this study provides valuable insights into the transcriptional responses of P. stellatus to heat stress, which differ with age and may inform the development of strategies to improve the survival and productivity of this economically important fish species in aquaculture. [ABSTRACT FROM AUTHOR]

Astaxanthin (AST), functioning as an efficient antioxidant and pigment, is one of the most expensive additives in shrimp feeds. How to improve the uptake efficiency of dietary astaxanthin into farmed shrimp is of significance. The present study investigated the effects of lysophosphatidylcholine (LPC), an emulsifier, on dietary astaxanthin efficiency, growth performance, body color, body composition, as well as lipid metabolism of juvenile Pacific white shrimp (average initial body weight: 2.4 g). Three diets were prepared: control group, the AST group (supplemented with 0.02% AST), and the AST + LPC group (supplemented with 0.02% AST and 0.1% LPC). Each diet was fed to triplicate tanks, and each tank was stocked with 30 shrimp. The shrimp were fed four times daily for eight weeks. The AST supplementation improved the growth of white shrimp, while LPC further promoted the final weight of shrimp, but the whole-shrimp proximate composition and fatty acid composition were only slightly affected by AST and LPC. The LPC supplementation significantly increased the astaxanthin deposition in the muscle. The LPC supplementation significantly increased the shell yellowness of both raw and cooked shrimp compared to the AST group. Moreover, the dietary LPC increased the high-density lipoprotein-cholesterol content but decreased the low-density lipoprotein-cholesterol content in the serum, indicating the possible regulation of lipid and cholesterol transport. The addition of astaxanthin significantly up-regulated the expression of npc2 in the hepatopancreas compared to the control group, while the addition of LPC down-regulated the expression of mttp compared to the AST group. In conclusion, the LPC supplementation could facilitate the deposition of dietary astaxanthin into farmed shrimp and further enlarge the beneficial effects of dietary astaxanthin. LPC may also independently regulate shrimp body color and cholesterol transportation. This was the first investigation of the promoting effects of LPC on dietary astaxanthin efficiency. [ABSTRACT FROM AUTHOR]

Simple Summary: With the rapid development of aquaculture, searching for alternative lipid sources to fish oil has become an important task for the aqua-feed industry. Lard is regarded as a valuable alternative lipid source. Basa fish (Pangasius bocourti) offal oil also has a large annual production and high potential to be used in fish feeds. Evaluation of the efficacy of lard and Basa fish offal oil in fish feeds will provide useful information for their application in aquaculture. Both lard and Basa fish offal oil have high levels of saturated fatty acids and monounsaturated fatty acids. The "n-3 LC-PUFA sparing effects" of saturated fatty acids and monounsaturated fatty acids in fish feeds have been observed in many fish species. The present study was also aimed at validating the "n-3 LC-PUFA sparing effects" of saturated fatty acids and monounsaturated fatty acids in lard and Basa fish offal oil. Moreover, the effects of dietary lard and Basa fish offal oil on fish body composition and muscle quality were also evaluated. Lard (LD) and Basa fish offal oil (BFO) have similar fatty acid profiles, both containing high contents of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA). The present study aimed to investigate the efficacy of partial or complete replacement of marine fish oil (MFO, herring oil) by LD or BFO in the diets of tiger puffer. The control diet contained 49.1% crude protein and 9.28% crude lipid content including 6% added MFO. In other diets, 1/3, 2/3, and 3/3 of the added MFO was replaced by LD or BFO, respectively. Each diet was fed to triplicate tanks of juvenile fish (initial body weight, 13.88 g). A 46-day feeding trial was conducted in a flow-through seawater system. Each diet was fed to triplicate 200-L rectangular polyethylene tanks, each of which was stocked with 30 fish. Fish were fed to satiation three times a day. The complete replacement of added MFO (replacing 65% of the total crude lipid) had no adverse effects on fish growth performance in terms of survival (>94%), weight gain (360–398%), feed intake (2.37–3.04%), feed conversion ratio (0.84–1.02), and somatic indices. The dietary LD or BFO supplementation also had marginal effects on fish body proximate composition, biochemical parameters, muscle texture, and water-holding ability, as well as the hepatic expression of lipid metabolism-related genes. Partial (2/3) replacement of added MFO by LD or BFO did not significantly reduce the muscle n-3 LC-PUFA content, indicating the n-3 LC-PUFA sparing effects of SFA and MUFA in LD and BFO. In general, dietary LD or BFO reduced the peroxidation level and led to significant changes in the muscle volatile flavor compound profile, which were probably attributed to the change in fatty acid composition. The results of this study evidenced that LD and BFO are good potential lipid sources for tiger puffer feeds. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of combined replacement of fishmeal (FM) and fish oil (FO) with poultry byproduct meal (PBM) and mixed oil (MO, poultry oil: coconut oil = 1 : 1) on growth performance, body composition and muscle quality of tiger puffer (Takifugu rubripes). Fish with an average initial body weight of 14.29 g were selected for the feeding experiment. FM accounting for 0%, 5%, and 10% of the diet was replaced by PBM. For each grade of FM replacement, 5% FO or MO was used as added oil. The six experimental diets were designated as FO-FM, MO-FM, FO-5PBM, MO-5PBM, FO-10PBM, and MO-10PBM, respectively. Each treatment was performed in triplicate with 30 fish per replicate. The feeding period was 45 days. There was no significant difference in growth performance among the groups. Dietary supplementation of both PBM and MO had marginal effects on whole-fish proximate composition, except that dietary MO supplementation significantly increased the liver moisture content. In serum, there were no significant differences in contents of triglyceride, total cholesterol, total bile acid, and protein carbonyl among groups, but the malondialdehyde content was reduced by MO. The fatty acid composition in fish mirrored those in the diets, but the omega-3 sparing effects of saturated and monounsaturated fatty acid in MO can still be observed. Dietary PBM and MO had marginal effects on free amino acid composition and texture of fish muscle, but exerted complicated effects on the muscle volatile flavor compound composition. In conclusion, combined fishmeal (10% of the diet) and fish oil (5% of the diet) replacement with poultry byproduct and mixed oil (poultry oil + coconut oil) had no adverse effects on the growth performance and body proximate composition of farmed tiger puffer. However, these replacements changed the muscle flavor compound profile. [ABSTRACT FROM AUTHOR]

This study characterized four cholesterol transport-related genes, namely, lcat, acat1, acat2, and mttp, in juvenile tiger puffer in terms of tissue distribution (eye, heart, brain, skin, liver, spleen, muscle, and intestine) and nutritional regulation. Three feeding trials were conducted: (i) using diets with different cholesterol levels (0.11%, 0.65%, 1.10%, 2.32%, and 4.59% of dry matter); (ii) using diets with different lipid levels (8.05%, 12.02%, and 16.36% of dry matter); and (iii) a 1-month starvation experiment with different sampling times (Days 1, 4, 9, 16, and 31). The lcat, acat1, and acat2 were the most abundantly expressed in the liver, while mttp was the most abundantly expressed in the intestine. The lcat had a medium expression level in the muscle and skin but the lowest expression level in the spleen and intestine. The acat1 and acat2 had similar tissue distribution patterns, except that acat2 had a lower expression level in the heart but a higher level in the intestine than acat1. The mttp had medium expression levels in the liver and spleen but had the lowest level in the eye and skin. Different dietary cholesterol levels did not significantly affect the expression of these cholesterol transport genes in the liver and intestine, except that higher cholesterol levels (1.10%–4.59%) significantly downregulated the acat2 expression in the liver. Dietary lipid levels also had a mild influence on the hepatic expression of these genes, except that the diet with 12.02% lipid resulted in significantly higher acat1 expression than the one with 16.36% lipid. The starvation time significantly affected the hepatic expression of these genes. Long-term starvation (16 and 31 days) generally upregulated the hepatic gene expression of lcat, acat1, and mttp but generally downregulated that of acat2. This study provided preliminary knowledge about the tissue distribution and nutritional regulation of cholesterol transport-related genes in marine teleost. [ABSTRACT FROM AUTHOR]

Simple Summary: Enteromorpha prolifera is a type of green marine macroalgae that can cause green tides due to eutrophication. However, aquafeeds demand for E. prolifera meal has gradually exceeded annual E. prolifera production. Therefore, novel extraction methods should be applied to increase the bioactive compounds of E. prolifera at the level of large-scale industrialization to support the efficient utilization of E. prolifera in aquafeeds. According to biological activities of E. prolifera, the growth, feed intake, lipid metabolism, antioxidant, immune parameters and stress resistance were investigated in Pacific white shrimp. It confirmed that bio-products of E. prolifera based on different processing procedures could be used to reduce the amount of E. prolifera in feed without compromising its biological function. It will helpful to improve the application of E. prolifera in aquaculture. A feeding trial was conducted to evaluate the biological activities of Enteromorpha prolifera bio-products in the diets of Pacific white shrimp (Litopenaeus vannamei). Bio-products of E. prolifera included E. prolifera meal, E. prolifera hydrolysate and E. prolifera polysaccharide, which was supplied using different processing procedures. The control diet was supplemented without any E. prolifera bio-products or dietary attractants. Experimental diets were formulated to contain 0.2% and 0.4% of E. prolifera hydrolysate (EPH0.2% and EPH0.4%), 0.03% of E. prolifera polysaccharide (EPP0.03%), 3% of E. prolifera meal (EPM3%), 0.1% of dimethyl-β-propiothetn (DMPT0.1%) and 1% of squid paste (SP1%). Shrimp (~8 g) were randomly distributed in 21 tanks and fed for 44 days. Feed intake showed that 3% of E. prolifera meal and 0.4% of E. prolifera hydrolysate in diets exhibited similar attractant effects as 0.1% of DMPT. Gross qualitative observation showed that the abundance of lipid droplets decreased in hepatopancreas of the EPH0.4% and EPM3% groups, which were supported by hepatopancreas triacylglycerol (TG), where significantly lower concentrations were observed in the EPH0.4% and EPM3% groups compared with the control group. Similarly, TG and low-density lipoprotein cholesterol in serum significantly decreased in the EPH0.4%, EPP0.03% and EPM3% groups compared to the control group. Supplemental E. prolifera bio-products resulted in significantly higher serum glutathione level of EPP0.03% or superoxide dismutase activities of EPH0.4% and EPM3%, but significantly lower serum malondialdehyde level of EPM3%. In addition, tnf-α expression in hepatopancreas was significantly down-regulated in shrimp fed the EPH0.2%, EPH0.4% and EPM3% diets. Based on survival analysis, E. prolifera bio-products improved the resistance of shrimp to hypoxic stresses. Thus, this study confirmed that bio-products of E. prolifera supplied using different processing procedures could be used to reduce the amount of E. prolifera in feed of shrimp without compromising their biological functions. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of imbalanced dietary BCAAs, especially Leu, on the growth and BCAA metabolism in turbot. A control diet was formulated by keeping optimum levels of Leu, Ile and Val. Four experimental diets were prepared by removing supplemental crystalline Leu (deficiency) or supplementing double the amount of Leu, Ile or Val (excess) in the control diet. The growth was not significantly decreased by an excess of Leu, Ile or Val. Fish fed an excess of any particular BCAA significantly increased its postprandial (2 and 6 h) concentration in the plasma, muscles, and liver, but did not decrease the other two BCAA concentrations. The expression of intestinal b0at1 was down-regulated by excessive dietary Leu, Ile or Val. For BCAA catabolism, the mRNA levels of bcat2 in the muscles as well as bckdha and bckdhb in the livers of the Leu-deficient group were the lowest among all the groups, but were up-regulated by excess dietary Leu, Ile or Val. In conclusion, in terms of growth, turbot had high plasticity to an excess of any particular BCAA. Meanwhile, the antagonistic effect caused by an excess of one BCAA were reflected in intestinal amino acid absorption and BCAA catabolism. [ABSTRACT FROM AUTHOR]

Simple Summary: The supply of fish oil, which provides long-chain polyunsaturated fatty acids (LC-PUFA) but is mostly wild-caught, is stagnating, resulting in limited availability and high prices. Therefore, many alternative lipid sources, mainly vegetable oils and rendered animal fats, are increasingly being applied in fish feeds. However, these lipid sources do not contain LC-PUFA, and therefore lower the fillet quality in terms of the LC-PUFA content. Feeding strategies such as alternate feeding between fish oil- and alternative oils-based diets have been applied to maintain the n-3 LC-PUFA contents in farmed fish. The present study validated the relevant efficacy. A 12-week feeding experiment was conducted to evaluate the effects of replacing fish oil (FO) with beef tallow (BT) on the fatty acid composition of farmed tiger puffer (Takifugu rubripes). Two replacement strategies were used: a standard Graded Dietary Replacement of FO with BT (GDR strategy) and Alternate Feeding between FO- and BT-based Diets (AFD strategy). The positive and negative control diets were formulated with 6% FO (FO-C group) or BT (BT-C group) as the sole added lipid source. In the GDR strategy, three experimental diets were formulated, with 25, 50 and 75% of the added FO in the FO-C diet replaced with BT, named 25BT, 50BT and 75BT, respectively. In the AFD strategy, alternated feeding patterns between the FO-C and BT-C diet—namely, 1, 2 and 3 weeks with BT-C followed by 1 week feeding with FO-C (1BT-1FO, 2BT-1FO and 3BT-1FO, respectively)—were applied. Each diet or feeding strategy was assigned to triplicate tanks. The results showed that dietary BT inclusion reduced the contents of long-chain polyunsaturated fatty acids (LC-PUFA) in both the muscle and liver (edible tissues for this species) of the experimental fish, and the liver displayed a more drastic decrease than the muscle. The LC-PUFA content linearly decreased with the decreasing dietary FO levels in the GDR strategy. However, in the AFD strategy, a linear relationship was not observed between the LC-PUFA content and the FO feeding duration. The 3BT-1FO treatment resulted in higher LC-PUFA content than 2BT-1FO. When comparing the two strategies with the same final FO administration level—namely, 50BT vs. 1BT-1FO, and in particular, 75BT vs. 3BT-1FO—the AFD strategy resulted in higher LC-PUFA contents in both the muscle and liver than the GDR strategy. In conclusion, when FO was replaced with BT in the diets, alternate feeding between FO- and BT-based diets resulted in a higher LC-PUFA content than the standard direct replacement. Three weeks of feeding with BT-C followed by one week of feeding with FO-C appeared to be a good alternate feeding pattern. This study provided a promising strategy of FO-sparing in fish farming when the LC-PUFA contents were maintained as high as possible. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the potential effect of graded levels of tryptophan on the growth, cannibalism, and 5-hydroxytryptpamine (5-TH) metabolism in pufferfish (Takifugu obscurus ♀ × Takifugu rubripes ♂). A 63-day feeding trial was performed wherein pufferfish were fed four diets. Three experimental diets were formulated with various levels of tryptophan based on the control diet. Four diets were named as T1, T2, T3, and T4, corresponding to 4.30, 7.80, 14.90, and 23.70 g kg−1 tryptophan of dry diet. Final body weight, weight gain, and specific growth rate were similar between the T1 and T4 groups, but exhibited a significantly increased trend compared to the T2 group. Although survival rate was not affected by various levels of dietary tryptophan, intraspecific cannibalism was significantly reduced in the group fed with highest level of tryptophan (T4). For free amino acid in brain, the concentration of tryptophan was the highest in the T3 group and the lowest in the T2 group, while phenylalanine, tyrosine, and methionine showed an opposite trend between those two groups. The levels of dietary tryptophan not only affected the expression of aromatic amino acid transporter TAT1, but also affected the expression of B0AT1, B0AT2, and 4F2hc in intestine, as well as B0AT1, y+LAT1, and LAT2 in brain. The activity of tryptophan hydroxylase (TPH) in serum increased with the increase of dietary tryptophan, and the expression of TPH1 in brain upregulated in the excessive tryptophan groups (T2, T3, and T4). MAO activity in serum as well as its gene expression in brain and intestine showed a decreased trend in the T4 group. In conclusion, excessive tryptophan (23.70 g kg−1 of dry diet, corresponding to 50.3 g kg−1 of dietary protein) in feed could mitigate cannibalistic behavior of pufferfish and promote the growth, and the reason for this effect might affect the metabolism of 5-TH in vivo. [ABSTRACT FROM AUTHOR]

The fatty acid accumulation in fish tissues are closely related to fish sex, yet the sex differences in fish fatty acids have not been fully known. This experiment investigated the sex differences in fatty acid composition of Chinese tongue sole (Cynoglossus semilaevis), which have typical sexual dimorphism and reversal. Three sexes, namely females, males and pseudomales, were involved in this study. Five batches of fish samples were collected from different fish farms in Shandong Province, China. These fish were identified to be at the gonadal development stage of III–IV. The disparity of fatty acid between sexes (female vs male and pseudomale vs. male) was evaluated by the distance coefficient (Dsex) and multi-variate similarity of percentages analysis (SIMPER). The highest Dsex values between females and males were found in gonad, followed by liver and eye. The fatty acids that differed between females and males were mainly DHA, 16:1n-7, 18:1n-9, and 18:0. The sex difference in DHA and 18:1n-9 contributed significantly to the overall sex difference in fatty acid of brain, eye, and gonad, whereas that in 16:1n-7 contributed significantly in heart, gill, liver, and muscle. The sex difference in 18:0 contributed significantly to the overall sex difference in fatty acid of heart, gill, gut, and skin. The sex differences in fatty acid between pseudomales and males were generally insignificant. In conclusion, at this gonadal development stage (III–IV), the sex differences in fatty acid between female and male Chinese tongue sole have emerged, mainly in the gonad. The testes had higher DHA levels but lower levels of 16:1n-7 and 18:1n-9 than ovaries. In addition, for pseudomales, the phenotypic sex more substantially determined the fatty acid composition than the genetic sex. [ABSTRACT FROM AUTHOR]

Cholesterol has been used as additive in fish feeds due to the reduced use of fish meal and fish oil. In order to evaluate the effects of dietary cholesterol supplementation (D-CHO-S) on fish physiology, a liver transcriptome analysis was performed following a feeding experiment on turbot and tiger puffer with different levels of dietary cholesterol. The control diet contained 30% fish meal (0% fish oil) without cholesterol supplementation, while the treatment diet was supplemented with 1.0% cholesterol (CHO-1.0). A total of 722 and 581 differentially expressed genes (DEG) between the dietary groups were observed in turbot and tiger puffer, respectively. These DEG were primarily enriched in signaling pathways related to steroid synthesis and lipid metabolism. In general, D-CHO-S downregulated the steroid synthesis in both turbot and tiger puffer. Msmo1, lss, dhcr24, and nsdhl might play key roles in the steroid synthesis in these two fish species. Gene expressions related to cholesterol transport (npc1l1, abca1, abcg1, abcg2, abcg5, abcg8, abcb11a, and abcb11b) in the liver and intestine were also extensively investigated by qRT-PCR. However, the results suggest that D-CHO-S rarely affected the cholesterol transport in both species. The protein-protein interaction (PPI) network constructed on steroid biosynthesis-related DEG showed that in turbot, Msmo1, Lss, Nsdhl, Ebp, Hsd17b7, Fdft1, and Dhcr7 had high intermediary centrality in the dietary regulation of steroid synthesis. In conclusion, in both turbot and tiger puffer, the supplementation of dietary cholesterol inhibits the steroid metabolism but does not affect the cholesterol transport. [ABSTRACT FROM AUTHOR]

Simple Summary: In some fish farming practices, cholesterol has been used as a feed additive for growth stimulation. Therefore, it is important to increase our knowledge and experience about dietary cholesterol effects on fish. This study provides useful information for the application of cholesterol in fish diets by analyzing the muscle lipidomics changes in turbot and tiger puffer in response to dietary cholesterol supplementation. Exogenous cholesterol has been supplemented into aqua-feeds due to the reduced proportions of fishmeal and fish oil. This study aimed to investigate the effects of dietary cholesterol supplementation on the muscle lipidomics of two marine fish species, turbot and tiger puffer. A 70-day feeding trial was conducted, where two low-fishmeal diets supplemented with 0 or 1% cholesterol were used. The lipidomic analysis with targeted tandem mass spectrometry showed that, in turbot, a total of 49 individual lipids exhibited significant differences in their abundance in response to dietary cholesterol, whereas the number was 30 for tiger puffer. Dietary cholesterol up-regulated the abundance of cholesterol and cholesterol ester in both species. In turbot, the dietary cholesterol also increased the abundance of triacylglycerol and acylcarnitine, whereas in tiger puffer, it primarily regulated the abundance of phospholipids and BMP. This was the first time the responses of marine fish muscle lipidomics to dietary cholesterol supplementation have been investigated. [ABSTRACT FROM AUTHOR]

Simple Summary: There have been reports on alternate feeding between diets based on different lipid sources, but how the intestinal microbiota of fish responds to alternate feeding strategies and its relevant roles in the host's health have not been reported. The present study provides novel results in this area. The main objective of the study was to assess how the intestinal microbiota of fish responds to alternate feeding between diets based on different lipid sources. Foremost, the juvenile turbot accepted alternate feeding between diets based on different lipid sources with no negative effects on survival or growth performance. Additionally, novel results were observed regarding the different bacterial compositions, microbial co-occurrence networks, and functional predictions among the different alternating feeding strategies. The results of this study indicate that a more comprehensive evaluation should be conducted from the perspective of intestinal microorganisms when a new feeding strategy is applied in aquaculture practices. These results will contribute to the nutritional regulation of aquatic animals from the perspective of microorganisms. A nine-week feeding trial was conducted to investigate changes in the intestinal microbiota of turbot in response to alternate feeding between terrestrially sourced oil (TSO)- and fish oil (FO)-based diets. The following three feeding strategies were designed: (1) continuous feeding with the FO-based diet (FO group); (2) weekly alternate feeding between soybean oil (SO)- and FO-based diets (SO/FO group); and (3) weekly alternate feeding between beef tallow (BT)- and FO-based diets (BT/FO group). An intestinal bacterial community analysis showed that alternate feeding reshaped the intestinal microbial composition. Higher species richness and diversity of the intestinal microbiota were observed in the alternate-feeding groups. A PCoA analysis showed that the samples clustered separately according to the feeding strategy, and among the three groups, the SO/FO group clustered relatively closer to the BT/FO group. The alternate feeding significantly decreased the abundance of Mycoplasma and selectively enriched specific microorganisms, including short-chain fatty acid (SCFA)-producing bacteria, digestive bacteria (Corynebacterium and Sphingomonas), and several potential pathogens (Desulfovibrio and Mycobacterium). Alternate feeding may maintain the intestinal microbiota balance by improving the connectivity of the ecological network and increasing the competitive interactions within the ecological network. The alternate feeding significantly upregulated the KEGG pathways of fatty acid and lipid metabolism, glycan biosynthesis, and amino acid metabolism in the intestinal microbiota. Meanwhile, the upregulation of the KEGG pathway of lipopolysaccharide biosynthesis indicates a potential risk for intestinal health. In conclusion, short-term alternate feeding between dietary lipid sources reshapes the intestinal microecology of the juvenile turbot, possibly resulting in both positive and negative effects. [ABSTRACT FROM AUTHOR]

Booming fish farming results in a relative shortage of fish oil (FO) supply, meaning that alternative oils are increasingly used in fish feeds, which leads to reduction of long-chain polyunsaturated fatty acids (LC-PUFAs) and other relevant changes in fish products. This study investigated the efficacy of an FO-finishing strategy in recovering the muscle quality of farmed tiger puffer. An eight-week feeding trial (growing-out period) was conducted with five experimental diets, in which graded levels (0 (control), 25, 50, 75, and 100%) of added FO were replaced by poultry oil (PO). Following the growing-out period was a four-week FO-finishing period, during which fish in all groups were fed the control diet. Dietary PO significantly decreased the muscle LC-PUFA content, whereas in general, the FO-finishing strategy recovered it to a level comparable with that of the group fed FO continuously. The recovery efficiency of EPA was higher than that of DHA. Dietary PO also led to changes of volatile flavor compounds in the muscle, such as butanol, pentenal, and hexenal, whereas the FO-finishing strategy mitigated the changes. In conclusion, the FO-finishing strategy is promising in recovering the LC-PUFA and volatile-flavor-compound composition in farmed tiger puffer after the feeding of PO-based diets. [ABSTRACT FROM AUTHOR]

The fish oil finishing (FOF) strategy, that is, re-feeding fish with fish oil (FO)-based diet after a certain period of feeding with alternative lipid source-based diets. On tiger puffer, the present study investigated the response of intestinal microbiota to FOF. Fish were fed four diets based on FO, soybean oil, palm oil and beef tallow as lipid sources, respectively, firstly for 50 days (growing-out period), and then fed the FO-based diet for 30 more days (FOF period). The results showed that dietary terrestrially sourced oils impaired the intestinal function in the growing-out period. However, the activities of amylase, trypsin and anti-oxidative enzymes (SOD, CAT, T-AOC), as well as gene expression of inflammatory cytokines (IL-1β, TNF-α, TGF-β) and tight junction protein (Claudin4, Claudin7, Claudin18, JAM, ZO-1) in the intestine were significantly recovered by FOF. The 16S rDNA sequencing analysis showed that FOF improved the similarity of bacterial community among the groups. The MetaStat analysis confirmed that FOF regulated the abundance of butyric acid-producing bacteria (Lachnospiraceae, Eubacterium, Butyricicoccus, Clostridium and Roseburia) and bacteria related to digestion and absorption (Sphingomonas, Romboutsia and Brevibacillus). In conclusion, FOF can recover the intestine function. The intestinal microbiota probably participated in and played a key role in the recovery process. [ABSTRACT FROM AUTHOR]

This study investigated the sex difference in fatty acid (FA) composition of six wild marine fish species, namely, Cleisthenes herzensteini, Platichthys bicoloratus, Pseudosciaena polyactics, Platycephalus indicus, Alosa sapidissima and Scomberomorus niphonius. The coefficient of distance value between sexes (Dsex) and multi‐variate similarity of percentages analysis (SIMPER) revealed universal existence of sex difference in FA composition, particularly in gonad, intestine and liver. Nonetheless, this sex difference was highly dependent on fish species. In general, DHA, 18:1n‐9, 16:1n‐7, 16:0 and EPA appeared to be the TOP FAs differentially abundant between sexes. [ABSTRACT FROM AUTHOR]

Myostatin (MSTN), a member of the transforming growth factor‐β (TGF‐β) superfamily, has retained the function of inhibiting muscle growth in fish. Turbot Scophthalmus maximus possesses two MSTN paralogs (MSTNa and MSTNb), but their respective response to dietary nutrients is still unclear. To clarify the effects of fish protein hydrolysate (FPH) on MSTNa and MSTNb, their mRNA levels were quantified in the muscle using the fasting–refeeding experiment and long‐term feeding trial. Gene expressions in various tissues showed that MSTNb but not MSTNa was expressed mostly in the muscle. After 2 weeks of starvation, MSTNa expression was up‐regulated in the muscle by refeeding FPH diet at 3 h and 6 h, while MSTNb expression was affected from 3 h to 3 days. Moreover, changes in MSTNb expression over time showed that significant reduction was observed at 3 h in fish refed optimal levels of FPH, but at 6 h in fish refed excessive levels of FPH. The expressions of two MSTN paralogs and related gene expressions of TGF‐β/SMAD‐dependent signalling pathway were not significantly altered by graded levels of FPH after 7 days of refeeding, while the expressions of MSTNb as well as the upstream FMODa and downstream SMAD4 were significantly affected after the long‐term feeding trial (8 weeks). In conclusion, FPH mainly modulated the expression of MSTNb in the muscle, whereas MSTNa was only affected in the early stage of refeeding. Furthermore, during the refeeding period, optimal levels of FPH in diets may regulate MSTNb more rapidly to initiate compensatory growth. [ABSTRACT FROM AUTHOR]