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Simple Summary: There have been few studies on the effects of compound feed attractants on the growth mechanism and health of aquatic animals. This study aimed to investigate the effects of compound feed attractants on the growth performance, feed utilization, intestinal histology, protein synthesis, and immune response of Litopenaeus vannamei. Seven diets were formulated, and shrimp (0.71 ± 0.00) g were distributed to seven groups of four replicates and fed for 7 weeks. In this study, diet supplemented with squid visceral powder, fish soluble, squid paste, and shrimp paste, and a diet supplemented with yeast extract, squid visceral powder, squid paste, and shrimp paste promoted the feed intake and growth performance and enhanced the antioxidative ability of L. vannamei. The combination of squid visceral powder, fish soluble, squid paste, and shrimp paste not only increased the protein synthesis, but also promoted the hepatopancreas and intestinal response of shrimp. Conversely, the diet supplemented with yeast extract, squid visceral powder, fish soluble, and shrimp paste may have some negative effects on the hepatopancreas and intestine of L. vannamei. To investigate the effects of compound attractants on the growth performance, feed utilization, intestinal morphology, protein synthesis, and immune response of Litopenaeus vannamei, the following seven diets were formulated: a positive control (P), a negative control (N), and five diets with compound attractants which were labeled as A, B, C, D, and E, each with four of five tested attractants (yeast extract, squid visceral powder, fish soluble, and squid paste, shrimp paste), respectively. Shrimp (0.71 ± 0.00 g) were distributed to seven groups of four replicates and fed for 7 weeks. Results showed that the final body weight, feed intake, specific growth rate, and weight gain of shrimp in the B and D groups were the greatest. Hemolymph total antioxidant capacity of shrimp in the B, D, and E groups reached the highest level. In the hepatopancreas, the activity of total nitric oxide synthase, malondialdehyde content, the expression levels of sod, myd88, eif4e2, and raptor in shrimp fed the B diet were the highest, and the highest levels of dorsal and relish were observed in the C group. In the intestine, intestinal muscle thickness and expression levels of toll and eif2α in the C group were the highest, while the highest expression level of sod and relish occurred in the B group. In summary, the B and E diets promoted the feed intake, growth performance and the antioxidant enzyme activity of L. vannamei. The C diet enhanced the protein synthesis of shrimp. Regression analysis indicated that the WG and FI of shrimp were increased as the dietary inclusion levels of squid paste and shrimp paste increased, while they were decreased as the dietary inclusion levels of yeast extract and fish soluble increased. [ABSTRACT FROM AUTHOR]

A nutritional feeding experiment was conducted to evaluate the effects of shrimp paste on feeding attractiveness, growth performance, digestive enzyme activities, immune-related genes and intestinal morphology in hybrid snakehead (Channa maculata ♀ × Channa argus ♂). Two diets were formulated with or without shrimp paste supplementation (D1:0% and D2: 3%) to feed fish for 8 weeks. Results showed that growth performance (FBW, WG and SGR) and feed intake (FI) significantly increased with shrimp paste supplemented (P < 0.05), while FCR and SR of hybrid snakehead fed diets supplemented with shrimp paste or not showed no significant difference (P > 0.05). Gut lipase and amylase activities were significantly higher in diet supplemented with shrimp paste than that in control one (P < 0.05). Hepatic antioxidant statuses of hybrid snakehead fed dietary shrimp paste or not showed no significant differences in total antioxidant capacity, malondialdehyde and superoxide dismutase of fish (P > 0.05). Results showed that fish fed diet with shrimp paste supplemented did not show significant difference in expression of GR, IκB, P65 and IL8 than that in control group (P > 0.05). There are significantly more goblet cells in shrimp paste supplemented diet than that in control diet (P < 0.05). However, villi length and muscle thickness showed no significant difference compared to control diet (P > 0.05). The results indicated that dietary 3% shrimp paste supplementation improved the growth performance of hybrid snakehead by enhancing feed intake (FI) while made no difference to antioxidant capacity and immunity. [ABSTRACT FROM AUTHOR]

An 8‐week feeding trial was conducted to evaluate the effects of replacing fishmeal by concentrated dephenolization cottonseed protein (CDCP) on growth, feed utilization, body composition, haemolymph indexes and antioxidative ability of juvenile white shrimp Litopenaeus vannamei, Boone. Six practical diets CDCP0, CDCP50, CDCP100, CDCP150, CDCP200 and CDCP250, containing a gradient of CDCP 0g/kg, 50g/kg, 100g/kg, 150g/kg, 200g/kg and 250 g/kg) to substitute (50g/kg, 90g/kg, 130g/kg, 170g/kg, 210g/kg and 250 g/kg) of fishmeal, diets were fed to four replicate groups. Amino acids were supplemented in the low fishmeal diet to obtain similar amino acid profile as the control diet. The results indicated that shrimp fed the CDCP20 and CDCP25 diet had poor growth performance and feed utilization compared with the CDCP0 group. No difference was observed in body composition among all the treatments. Total cholesterol (T‐CHO), high‐density lipoprotein cholesterol (HDL‐C) and low‐density lipoprotein cholesterol (LDL‐C) concentrations in haemolymph were significantly lower in high‐CDCP groups. The digestibility of protein decreased significantly with increasing CDCP levels. When shrimp fed the CDCP250 diet had the significant lower total antioxidant capacity (T‐AOC) and catalase (CAT) activity than control diet. In conclusion, fishmeal can be reduced from 250g/kg to 130 g/kg by CDCP. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to evaluate the effect of dietary macro-algae in diet of juvenile Pacific white shrimp, Litopenaeus vannamei. The five macro-algae ingredients, including Saccharina japonica, Porphyra dioica, Gracilariopsis lemaneiformis, Ulva lactuca, and Undaria pinnatifida, were used for test diets, named SJD, PDD, GLD, ULD, and UPD, respectively. A reference diet (RD) and five test diets (30% test ingredients and 70% RD) were formulated. Each diet was randomly assigned to triplicate groups of 40 shrimp (initial body weight, 2.00 ± 0.01 g) and the shrimp were hand fed four times a day to apparent satiation. During the last 2 weeks, the fecal samples were collected by siphoning. The results showed that among five test diets, shrimp fed the SJD had the highest weight gain and the lowest feed coefficient, shrimp fed the SJD and GLD shared the same survival ratio and were significantly higher than shrimp fed the PDD and UPD (p < 0.05). For the composition of whole body, shrimp fed the SJD had the highest protein and lipid content compared with the shrimp fed other test diets. Apparent dry matter digestibility from high to low was: P. dioica, S. japonica, G. lemaneiformis, U. lactuca, and U. pinnatifida. Apparent protein digestibility of five macro-algae was highest in U. pinnatifida and lowest in G. lemaneiformis. Additionally, the highest apparent digestibility of gross energy was found in P. dioica. Apparent digestibility of total phosphorous in five ingredients was generally low and highest in S. japonica which was significantly higher than other ingredients (p < 0.05). These results indicated that S. japonica is more suitable for feed ingredient than other four kinds of macro-algae. [ABSTRACT FROM AUTHOR]

A 10-week experiment was conducted to evaluate the effects of dietary lysine levels on growth performance, lipid metabolism, anti-oxidant capacity, mitochondrial biogenesis and immune response of grass carp, Ctenopharyngodon idella. Fish (mean initial weight 51.01 ± 0.17 g) were fed seven diets containing graded levels of lysine (1.69 %, 1.79 %, 1.91 %, 2.01 %, 2.11 %, 2.24 % and 2.31 %). Results showed that fish fed the control diet (1.69 %) showed lower weight gain (WG) and higher feed conversion rate FCR than those fed 2.01–2.31 % lysine (P < 0.05). Viscerosomatic index decreased when dietary lysine increasing from 1.69 % to 2.11 % (P < 0.05). Suitable dietary lysine levels enhanced the lipolysis and mitochondrial biogenesis of grass carp. Total antioxidant capacity (T-AOC) in the liver was higher in fish fed 2.24 % dietary lysine than those fed diets containing 1.69 % and 1.79 % lysine (P < 0.05). The malonaldehyde (MDA) contents in liver decreased when dietary lysine increased from 1.69 % to 2.01 % (P < 0.05). Relative mRNA levels of glutathione peroxidase and catalase in liver and intestine were affected by dietary lysine levels (P < 0.05). B-cell lymphoma 2 (Bcl-2) mRNA level in liver was up-regulated and inhibitor kappa B kinase β (IKKβ) mRNA level in the intestine was down-regulated by increasing dietary lysine levels (P < 0.05). Second-order regression based on WG indicated the suitable level of lysine in feed of grass carp was 2.24 % (6.19 % protein). • Dietary deficiency of lysine would impair the growth performance and feed utilization of grass carp. • The protein synthesis, lipolysis and mitochondrial biogenesis of grass carp might be enhanced by lysine. • Immune response and anti-oxidant defense system of grass carp might be affected by dietary fish lysine levels. [ABSTRACT FROM AUTHOR]

Bile acid (BA) has been reported to improve growth performance and play an important role in lipid metabolism of fish. Five diets were formulated to investigate the effects of dietary bile acid (chenodeoxycholic acid) supplementation on growth performance, antioxidant capacity, lipid metabolism and intestinal health of juvenile largemouth bass (Micropterus salmoides). Fish (18.35 ± 0.05 g) were randomly fed five diets: the positive control diet (10.87% lipid, C), high fat diet (18.08% lipid, HF), and HF diets supplemented with 300, 600 and 900 mg/kg chenodeoxycholic acid (HFC1, HFC2 and HFC3, respectively). After 9 weeks of feeding experiment, the weight gain (WG) and special growth rate (SGR) were significantly lower in the fish fed diet HF compared with those fed diet C (P < 0.05). Compared with the group C, there were no significant differences in WG and SGR of fish fed high fat diet with 900 mg/kg chenodeoxycholic acid (P > 0.05). Viscerosomatic index (VSI) and intraperitoneal fat ratio (IPF) were significantly higher in fish fed high fat diets than those fed the control diet (P < 0.05). The crude lipid and protein contents in muscle showed no significant differences among fish fed diets with high dietary lipid (P > 0.05), while the crude lipid of muscle significantly decreased in HFC2 group (P < 0.05). Triglyceride (TG), malondialdehyde (MDA) in plasma and MDA in liver were higher in HF group than control group, addition of BA could decrease those contents effectively and increase the gene expression of SOD and GSH-Px. Lipidprotein transport and cholesterol synthesis related mRNA levels were significantly increased in fish fed high fat diets containing BA. The supplementation of 900 mg/kg BA significantly increased the gene expression of apolipoprotein B (ApoB-100), sterol 26-hydroxylase (CYP27α) and liver X receptor (LXR) (P < 0.05). High-fat diet significantly increased the pro-apoptotic gene expression, while anti-apoptotic gene B-cell lymphoma-2 (Bcl-2) and B-cell lymphoma-xl (Bcl-xl) mRNA levels were significantly increased with the increasing dietary BA (P < 0.05). In addition, supplemental BA in high-fat diet increased the height of intestinal fold and decreased lipid accumulation in liver. These results suggested that dietary BA supplementation could improve the digestion and absorption of lipids, antioxidant capacity and intestinal health, thereby attenuating the adverse effect induced by high fat diet of largemouth bass. • Dietary bile acid could attenuate the adverse effects induced by high-fat diet on growth performance of largemouth bass. • Dietary bile acid could enhance lipid metabolism and reduce the oxidative stress induced by high fat diet in largemouth bass. • Bile acid supplementation could decrease hepatic apoptosis induced by high fat diet and improve intestinal morphology of largemouth bass. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was proceeded to assess the effects of yeast and yeast extract on growth performance, anti-oxidant ability and intestinal microbiota of Litopenaeus vannamei. Five diets supplemented with 0% (Control), 3% beer yeast (Y), 0.5% yeast extract (YE0.5), 1% yeast extract (YE1) and 2% yeast extract (YE2) respectively were assigned to L. vannamei (four replicates per diet, 30 shrimp in each replicate, initial body weight 1.38 ± 0.01 g). The results showed higher weight gain and specific growth rate in shrimp fed diet YE2 compared with those fed the Control (P <.05). Both dietary yeast and yeast extract increased condition factor of shrimp (P <.05). Whole body moisture was significantly lower in shrimp fed yeast and yeast extract than those fed diet Control (P <.05). Shrimp fed yeast extract showed higher total antioxidant capacity compared to Control group (P <.05). Shrimp fed diet YE2 obtained higher catalase and glutathione peroxidase activities than those fed diet Control, YE0.5 and YE1 (P <.05). The main phyla in intestine of shrimp were Tenericutes, Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria. With the increasing dietary yeast extract supplementation, the relative abundances of Ruegeria , and its belonging Rhodobacteraceae, Rhodobacterales, Alphaproteobacteria, Proteobacteria in intestine increased gradually, which were significantly higher than those fed diet Control and Y (P <.05). Moreover, yeast and yeast extract significantly increased the Shannon indexes of intestinal microbiota (P <.05). Overall, dietary 2.0% yeast extract supplementation significantly increased growth performance and antioxidant ability of shrimp, also enhanced microbial diversity and microbiota structure in intestine of L. vannamei. • The first time to reveal the effect of yeast extract on intestinal microbiota of L. vannamei. • 2% yeast extract supplemented improved growth performance and anti-oxidative ability of L. vannamei significantly. • Both yeast and yeast extract enhanced the stability of bacterial community in intestine of shrimp. • Yeast extract optimized microbiota structure by the increase of beneficial bacteria and decrease of pathogenic bacteria. [ABSTRACT FROM AUTHOR]

Feed intake is a crucial factor in promoting aquatic animals' robust and accelerated growth. Recently, plant protein has been used extensively as a replacement for fishmeal in aquaculture diets, potentially causing adverse effects on both feed palatability and animal health. However, incorporating suitable quantities of feed attractants into the diet can enhance feed palatability, stimulate the appetite of aquatic animals, and potentially augment both growth and overall health. A study was conducted to assess the efficacy of various feeding attractant combinations on Penaeus monodon. In this study, these seven diets were formulated consisting of a positive control (labeled as P) based on commercial feed, a negative control (labeled as N) with a low level of feed attractants, and five diets (labeled as A, B, C, D, and E) containing 8% compositional feed attractants. Each of the five attractants (yeast extract, squid visceral powder, fish soluble, squid paste, and shrimp paste) was added in equal amounts to A-E diets. The results showed that compared to the E diet, the A diet significantly improved the final body weight, specific growth rate, weight gain, and feed intake of shrimp and upregulated the expression of pi3k , eif4ela , and raptor in hepatopancreas. Compared to the P diet, the C diet feed significantly increased the activities of glutamate oxaloacetate transaminase and acid phosphatase and upregulated the expression of pi3k , myd88 , and tor in the intestine. In comparison to the N diet, the D diet feed increased the activity of alkaline phosphatase in hemolymph, total superoxide dismutase activity in hepatopancreas, and malondialdehyde content. Additionally, it upregulated the expression of myd88 , pi3k , tor , and ror. Compared to the control group, the feed in the E diet increased the total superoxide dismutase activity in the hemolymph and upregulated myd88 , pi3k , tor , and imd expression levels. Furthermore, C, D, and E diets increased the width of the shrimp's intestinal folds. Regression analysis showed that the weight gain and feed intake increased with the increasing amount of squid paste in the feed and decreased with the addition of shrimp paste. Feed intake increased with the addition of fish-soluble protein and decreased with the addition of yeast extract in the feed. In conclusion, adding attractants (yeast extract, squid viscera powder, fish soluble, and squid paste) to the feed is beneficial for the growth and feeding of shrimp, and it can promote the expression of shrimp intestinal immune-related genes and histological changes, thus promoting shrimp intestinal health. [Display omitted] • The effect of combined feed attractants on growth performance, feed utilization, intestinal organization and immunity of Penaeus monodon. • Dietary A (yeast extract+squid visceral powder+fish soluble+squid paste) positively influenced feed intake and protein synthesis of shrimp. • The addition of squid paste to the diet increased weight gain rate and feed intake, while increasing shrimp paste additions decreased these. [ABSTRACT FROM AUTHOR]

Fish oil oxidation is a common phenomenon in aquaculture and produces harmful substances that can cause oxidative stress to aquatic animals. However, the metabolic mechanism of oxidized fish oil in the liver of hybrid groupers (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus) is still unclear. In this study, a rearing experiment was conducted for 65 days with diets containing 0, 3, 6, and 9% oxidized fish oil (referred to as R, L, M, and H respectively) to investigate the effect of oxidative stress on growth performance, liver antioxidant status, biochemical index in serum, liver fat accumulation and hepatic metabolism profile of juvenile hybrid groupers. The results showed the oxidized fish oil inhibited the growth performance of grouper, and the growth performance became worse as the proportion of oxidized fish oil in the diet increased. Meanwhile, oxidized fish oil caused oxidative stress in the liver by reducing antioxidant enzyme activity and increasing the content of malondialdehyde. In addition, oxidative stress disrupted lipid metabolism by lowering low-density lipoproteins and increasing elevated-density lipoproteins in serum, and promoted the formation of fatty livers. To explore the mechanism of oxidative stress in the liver, the samples in the fresh fish oil group and the highest oxidized fish oil group were selected for non-targeted metabolome analysis. The differential metabolites in the livers were mainly phosphatidylcholines, phosphatidylethanolamines, and lysophosphatidylchoines with an upregulated status under oxidative stress. The liver responded to oxidative stress through the glycerophospholipid metabolism and choline metabolism in cancer pathways. In conclusion, oxidized fish oil inhibited growth in hybrid grouper and caused oxidative stress and fat accumulation in the liver. This oxidative stress, in turn, changed the hepatic metabolism profile. • The oxidized fish oil inhibited the growth performance. • The oxidized fish oil caused oxidative stress in liver. • The oxidized stress induced fat droplet accumulation in liver. • The oxidized stress changed hepatic metabolism profile. [ABSTRACT FROM AUTHOR]