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Simple Summary: With the development of the breeding industry, the production of fishmeal will not be able to meet the needs of feed production in the future. Clostridium autoethanogenum protein meal (CAP) is a by-product of people using carbon monoxide exhaust from the steel industry to produce ethanol, with a potential to become a substitute ingredient for fishmeal to alleviate the shortage of fishmeal. This study was conducted on pearl gentian grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂), an economic fish species widely cultured in Southeast Asia. After using different concentrations of CAP to replace fishmeal in the feed for eight weeks, respectively, we found that it could replace 45% of fishmeal in the pearl gentian grouper feed through growth performance, various physiological and biochemical indexes analysis experiments, but a 60% replacement level would significantly affect health and growth. These findings provide a reference for the promotion and further research of CAP as a new environmentally friendly ingredient, which is positive for the sustainable development of the farming industry and even for the utilization of waste gas from the steel industry. In this study, we present data from an eight-week growth trial with pearl gentian grouper fed either a reference diet (FM) with a fishmeal level of 50%, or test diet wherein 15% (CAP15), 30% (CAP30), 45% (CAP45), and 60% (CAP60) fishmeal was replaced by Clostridium autoethanogenum protein meal (CAP). Results showed that the weight gain and daily feed intake ratio of CAP60 were significantly lower than the FM group. In the serum, compared to the FM group, the content of malondialdehyde (MDA), the activities of alanine aminotransferase in CAP60 and CAP45 groups, and acid phosphatase in the CAP60 group were significantly higher, while the content of total cholesterol in CAP60 and CAP45 groups was significantly lower. In the liver, compared to the control group, the content of MDA in the CAP60 group was significantly higher. 3-hydroxy-3-methylglutaryl coenzyme A reductase in CAP30 to CAP60 groups and farnesoid X receptor in CAP60 were significantly upregulated. In distal intestines, the activities of trypsin and superoxide dismutase of CAP30 to CAP60 groups were significantly lower than the FM group. In conclusion, for pearl gentian grouper, CAP could replace up to 45% of the fishmeal in the feed, while a 60% replacement level will affect cholesterol bile acid metabolism and health. [ABSTRACT FROM AUTHOR]

Fishmeal is an important protein source for largemouth bass (Micropterus salmoides). However, the production of fishmeal is decreasing each year and the price of fishmeal is rising. Therefore, it is necessary to find new high-quality and suitable protein sources. This study used a mixed animal protein source (chicken meal:blood meal:shrimp meal:brewer's yeast = 50:12.5:25:12.5) to replace fishmeal. Using a 48 % fishmeal group as the control, five diets with different fishmeal levels (FM48, FM44, FM40, FM36, FM32) were established to determine the effects on largemouth bass growth performance, liver health and intestinal health. There were no significant differences in the percentage weight gain, specific growth rate, feed conversion rate, and condition factor of largemouth bass, but the hepatosomatic and viscerosomatic indexes were significantly decreased when the dietary fishmeal level was reduced to 40 %. The content of taurine, glycine, and histidine was significantly reduced in the muscle of largemouth bass fed the FM32 diet compared with those fed the FM48 and FM44 diets. Mixed protein feed reduced the total bile acid content and increased the low-density lipoprotein cholesterol content in the plasma of largemouth bass. The replacement of fishmeal with the mixed protein source inhibited the expression of tnf-α and caspase 3 and enhanced the expression of apoa1 in the liver, as well as enhancing the protein expression of FXR and SREBP and inhibiting the protein expression of P-PPARA in the liver. The intestinal pparα expression was suppressed when dietary fishmeal was replaced. When dietary fishmeal decreased, the mucosal folds height and muscle layer thickness also decreased. In conclusion, partial replacement of fishmeal with the mixed protein source did not affect the growth performance, while lipid metabolism and intestinal health were negatively affected when dietary fishmeal levels were below 36 %. [Display omitted] • Dietary replacement of fishmeal had no significant impacts on the growth performance of largemouth bass. • Dietary replacement of fishmeal would affect the cholesterol and bile acid metabolism of largemouth bass. • Excessive replacement of fishmeal (FM36 and FM32) could cause oxidative stress and intestinal damage in largemouth bass. [ABSTRACT FROM AUTHOR]

The aim of the present experiment was to evaluate the effects of Schizochytrium limacinum supplementation on the immune response, gut microbiota, and health of Penaeus monodon fed a low fish-meal (FM) diet. A diet containing 25% FM was used as a control (Diet A), and three other diets were formulated to contain 15% FM and supplemented with 0, 0.75, and 1.5% S. limacinum (Diet B, C, and D, respectively). The experiment was carried out in quadruplicates (30 shrimp per replicate, average weight 1.01 ± 0.01 g), and the shrimps were fed the test diets to apparent satiation three times daily for 8 weeks. Shrimp fed diet B and D showed lower weight gain than those fed diet A. Supplementation of 0.75% S. limacinum enhanced expression of antioxidative genes (superoxide dismutase and catalase) and immune-response-related genes in hepatopancreas but could not affect the gene expression of immune deficiency in hepatopancreas and Tube in the intestine. A low FM diet induced endoplasmic reticulum swelling of the intestinal epithelial cells, which was alleviated by S. limacinum supplementation. Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry was employed to analyze the changes of hemolymph metabolomics, 49 significantly different metabolites were identified, and lysoPCs, deoxyinosine, inosine, and highly unsaturated fatty acids were lower in fish fed with low FM diets. Intestinal microbial diversity was lower in shrimp fed Diet B than those fed the control diet. Dietary supplementation of 0.75% S. limacinum increased intestinal microbial diversity of shrimp and decreased the ratio of pathogenic bacterium (Thalassotalea and Tenacibaculum). These results indicated that supplementing S. limacinum into a low FM diet improves the growth performance, immune response, and intestinal health of P. monodon. The optimum inclusion level of seems to be 0.75% of diet. [ABSTRACT FROM AUTHOR]

Dietary fish meal (FM) and fish oil (FO) replacement are crucial for the sustainable development of aquaculture. An eight weeks feeding trial was conducted to evaluate the potential replacing FM with soy protein concentrate, and the suitable FO level for a low FM diet of Penaeus monodon. A diet containing 25% FM was used as the control (C diet), and three other diets were formulated to contain 15% FM, and supplemented with 3%, 2%, 1% FO [high FO (HF), medium FO (MF) and low FO (LF), respectively]. The experiment was conducted in quadruplicates (30 shrimp per replicate, average weight 1.00 ± 0.01 g). The results indicated that besides the final body weight, there were no differences in weight gain, feed efficiency and survival rate observed among the four groups. The results of the acute salinity stress showed that shrimp fed the C and MF diets showed a similar survival rate, which was significantly higher than those fed a LF diet. Shrimp that were fed HF, MF and LF diets showed a lower level of fatty acid transport-related mRNA expression in the hepatopancreas, compared with those fed the C diet. Shrimp fed HF, MF and LF diets showed lower expression levels of superoxide dismutase, endoplasmic reticulum protein 57 and immune deficiency (IMD) in the hepatopancreas than those fed the C diet. Shrimp that were fed a LF diet showed the lowest expression levels of inhibitor of apoptosis proteins, Toll and tumor necrosis factor receptor associated factor 6 (TRAF6) in the hepatopancreas, as well as the highest expression levels of Toll, extracellular signal-regulated kinase, Relish and TRAF6 in the intestine among four groups. Intestinal microstructure damage was observed in shrimp that were fed a LF diet, and intestinal endoplasmic reticulum (ER) swelling was observed in shrimp fed MF and LF diets. In conclusion, these results indicated that the growth performance of shrimp was not affected when the FM and FO contents decreased, whereas a low content of FM negatively influenced the immune response in shrimp by modulating IMD and ER stress related gene expression. Under low FM conditions, a suitable dietary FO level would benefit to the lipid transport, hepatopancreas and intestine health, as well as the immune response of shrimp. • Reduce the dietary FM level from 25% to 15% had no negative effect on growth performance of P. monodon. • Low dietary fish oil reduced the acute salinity stress resistance of P. monodon fed low FM diet. • Low dietary fish oil impaired the immune response of shrimp through the IMD and Toll signaling pathways. [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]

• Legal aquaculture dose of SMX increased weight gain of Micropterus salmoides. • SMX increased the malformation rate of Micropterus salmoides. • SMX increased oxidative stress and inflammation of Micropterus salmoides. Antibiotics have been widely used (mainly mixed with feed) in aquaculture, while few studies have evaluated the interactions between feed composition and antibiotics. Sulfamethoxazole (SMX) is a fat-soluble antibiotic, an eight weeks feeding trial was conducted to investigate the interactions between dietary lipid levels and chronic exposure of legal aquaculture dose of sulfamethoxazole in juvenile largemouth bass Micropterus salmoides , and evaluated the possible human health risk. Six practical diets were formulated to three levels of crude lipid (11, 14.5, 18 %) and two levels of SMX (0 and 0.3 %), namely low fat (LF), moderate fat (MF), high fat (HF), low fat and SMX (LFS), moderate fat and SMX (MFS), high fat and SMX (HFS), respectively. Each diet was assigned to three tanks (20 fish per tank, average weight 30.65 ± 0.02 g). Growth and organ indices were increased by SMX. Higher malformation rate and lower hypoxia stress resistance were found in fish exposed to SMX than those not exposed. Cholesterol and bile acid synthesis related gene expressions were down-regulated by SMX exposure. Oxidative stress, inflammation and apoptosis were increased in fish exposed to SMX. Significant interactions between dietary lipid levels and SMX on renal immune response of fish were observed. Remarkable damage of intestinal histology was observed in fish fed the diet HFS. In addition, dietary SMX exposure increased pathogen susceptibility of largemouth bass and induced dysbiosis of gut microbiota. The concentrations of SMX in muscle of fish fed diets containing SMX were higher than those fed other diets, and close to the maximum residue limit (MRL) in China and international organizations. Although chronic legal aquaculture dose of dietary SMX also increased the target hazard quotient (THQ) and estimated daily intake (EDI), there is no health risk in adults and children consuming fish filet. [ABSTRACT FROM AUTHOR]

An 8-week feeding trial was conducted to evaluate the effects of chenodeoxycholic acid (CDCA) on growth performance, body composition, lipid metabolism, and intestinal health of juvenile white shrimp, Litopenaeus vannamei fed a low fishmeal diet. Four practical diets were formulated: HFM (25% fishmeal), LFM (15% fishmeal), LB1 (LFM + 0.04% CDCA), LB2 (LFM + 0.08% CDCA). Each diet was assigned to four tanks with forty shrimp (initial weight 0.33 ± 0.03 g) per tank. The results indicated that the growth performance of shrimp were similar between the four groups; the crude lipid content of shrimp fed the LB2 diet was significantly lower than those fed the HFM diet (P < 0.05). The lipase activity content in hepatopancreatic were significantly higher in the two CDCA supplemented groups than that in LFM group; the contents of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol in hemolymph were significantly lower in LFM group, LB1 group and LB2 group than that in HFM group (P < 0.05). The shrimp fed LB1 diet was significantly decreased the intestinal expression levels of tube than those fed in HFM diet; the intestinal gene expression of imd and toll were significantly lower in LB2 group than those in HFM group (P < 0.05). The results of hepatopancreas gene expression suggest that shrimp fed the LFM diet showed significantly upregulated expression levels of sterol regulatory element-binding protein (srebp), acetyl-CoA carboxylase (acc), and carnitine palmitoyltransferase 1 (cpt-1) than those fed the HFM diet; shrimp fed the LB1 diet showed significantly upregulated expression levels of srebp , acc , and AMP-activated protein kinase (ampk) than those fed the HFM diet; shrimp fed the LB2 diet had higher expression levels of srebp , acc , and cpt-1 than those fed the HFM diet (P < 0.05). In the hepatopancreas, the shrimp fed the LFM diet shown significantly up-regulated the expression levels of beclin1 compared to those fed HFM diet; the expression levels of autophagy-related protein13 (atg3) , autophagy-related protein 12 (atg12) of in shrimp fed the LB1 diet were significantly higher than those fed the HFM diet; and the expression levels of autophagy-related protein13 (atg13), beclin1 , atg3 , atg12 , autophagy-related protein 9 (atg9) of shrimp fed LB2 diet were significantly higher than those fed the HFM diet (P < 0.05). The atg3 in intestine of shrimp fed the LB2 diet were significantly higher than those fed the HFM diet (P < 0.05). Intestinal mucous fold were damaged, hepatic tubules were disorganized and B cells appeared to be swollen in LFM group. The fold height and width of shrimp fed the diets supplemented with CDCA increased significantly than those fed the LFM diet (P < 0.05), the hepatic tubules were neatly arranged, and R cells increased. In conclusion, supplementary CDCA in a low fishmeal diet promoted lipid metabolism, enhanced autophagy of shrimp, also improved the health of the intestine and hepatopancreas. • Dietary chenodeoxy cholic acid supplementation improved the health of the intestine and hepatopancreas. • Lipid metabolism was affected by dietary chenodeoxycholic acid supplementation. • Cellular autophagy and non-specific immunity were enhanced by dietary chenodeoxycholic acid supplementation. [ABSTRACT FROM AUTHOR]

Plant protein sources are the main alternative to fish meal (FM), but excessive substitution can induce inflammatory responses and oxidative stress in aquatic animals. In this study, the antioxidant capacity, endoplasmic reticulum stress (ERS), apoptosis and intestinal health of Litopenaeus vannamei at the different stages of feeding trial were evaluated after replacing FM with soy protein concentrate (SPC). Two diets were designed: HF diet (25% FM) and LF diet (15% FM + 10% soy protein concentrate), respectively. The samples were collected at 7d, 14d, 28d, 42d, 56d of the feeding trial. The results showed that the antioxidant capacity of the hepatopancreas of shrimp fed the LF diet gradually decreased after 28d. The glutathione peroxidase (GSH-PX) activity, superoxide dismutase (T-SOD) activity and total antioxidant capacity (T-AOC) showed a decreasing trend with the went on of the feeding trial and were lower than those of shrimp fed a HF diet. The length of microvilli and height of mucosal folds in shrimp fed the LF diet were significantly lower than those fed the HF diet after 42d (P <0.05), and the endoplasmic reticulum and mitochondria were swollen, and the mitochondrial matrix showed irregular structure and even almost complete dissolution at 56d. The expression of hepatopancreatic endoplasmic reticulum stress (ERS)-related genes was highest at 14d, and the hepatopancreatic endoplasmic reticulum-related genes were overall higher in shrimp fed the LF diet than those fed the HF diet after 28d. The expression of apoptosis-associated genes in hepatopancreatic cells showed an overall decreasing trend. However, the relative expression of intestinal ERS and apoptosis related gene was in the opposite trend. ERS was enhanced and apoptosis was inhibited in shrimp since 7d of the feeding trial when the dietary FM level was reduced. In conclusion, the antioxidant capacity and immune response of shrimp would be reduced as the feeding trial went on, ERS and apoptosis in the intestine of shrimp fed a LF diet would be earlier to be induced compared to those fed the HF diet. • Soy protein concentrate reduces the antioxidant capacity of shrimp hepatopancreas. • Soy protein concentrate causes stress in the intestinal endoplasmic reticulum. • Soy protein concentrate causes apoptosis of intestinal cells. [ABSTRACT FROM AUTHOR]

Methanotroph (Methylococcus capsulatus , Bath) bacteria meal is a kind of bacterial protein meal (BPM) with an excellent nutrition profile. This study evaluated the effects of replacing fish meal (FM) with BPM on growth, antioxidant capacity, intestinal morphology, and gut microbiota of Pacific white shrimp (Litopenaeus vannamei). A basal diet was formulated to contain 25% FM, then 15, 30 and 45% of FM was replaced with BPM, which were identified FM, BPM15, BPM30, and BPM45 diets, respectively. Triplicate groups (40 shrimp per replicate) of shrimp (0.88 ± 0.01 g) were fed the test diets to apparent satiation four times daily for 7 weeks. There were no significant differences in growth performance among four groups. Malondialdehyde content and anti-oxidative enzymes activity in hepatopancreas were significantly increased with increasing BPM levels. For intestinal histology, the circular muscle layer thickness was significantly increased in BPM45. The mucosal folds height of shrimp fed BPM45 was significantly higher than those fed BPM15. The width of mucosal folds in BPM15 and BPM30 was significantly reduced comparing with FM. Transmission electron microscopy results showed that intestinal microvilli was impaired and endoplasmic reticulum stress was present in shrimp fed BPM45 diet. However, dietary BPM improved the diversity of intestinal microbiota, and more beneficial microbiota such as Pseudoalteromonas , Ruegeria , and Lactobacillus , as well as less harmful microbiota such as Vibrio were found in the gut of BPM45. A 12-day challenge study with Vibrio parahaemolyticus showed that shrimp fed diet BPM15 had a significantly lower mortality throughout the challenge trial. To conclude, BPM replacement of fish meal did not affect growth performance and feed utilization of shrimp. The high dietary inclusion of BPM increased the oxidation level in the hepatopancreas of shrimp and BPM was able to increase the height of the mucosal folds, improve the gut microbiota structure and increase the disease resistance of shrimp. • Replacement of 45% fish meal by BPM would not significantly affect the growth performance of L. vannamei. • High dietary inclusion of BPM increased the oxidation level in the hepatopancreas of shrimp and modified the intestinal microvilli length. • BPM addition increased the height of the mucosal folds, improved the gut microbiota structure and increased the disease resistance of shrimp. [ABSTRACT FROM AUTHOR]