A study of the potential effect of yellow mealworm (Tenebrio molitor) substitution for fish meal on growth, immune and antioxidant capacity in juvenile largemouth bass (Micropterus salmoides)

Effect of silkworm pupae meal on the growth of Oreochromis niloticus (Cichliformes: Cichlidae) (Order: Cichliformes, Family: Cichlidae) CichliformesCichlidae

Increasing costs and limited supply of fishmeal make fish feed more expensive. Pupa of the silkworm (Bombyx mori L.), a byproduct of the sericulture industry is a cheap and sustainable alternative to fish meal. This study aimed to examine the impact of replacing fish meal with silkworm pupae meal on the growth performance and health profile of Gift Tilapia fingerlings (Oreochromis niloticus). Gift Tilapia fingerlings (3.38 ± 0.23 g) were divided into 4 groups (n = 60 in each group). These fish were reared for 10 wk and fed at the rate of 4% body weight daily at 10 am and 3 pm. The basal standard diet was given to the control. The other 3 experimental diets were prepared with 10% (SWP10), 20% (SWP20) and 40% (SWP40) replacement of fish meal with silkworm pupae meal. The results showed that the values of weight gain, feed efficiency ratio and organosomatic indices were significantly higher (P < 0.05) in the SWP40 group as compared to all other groups. The values of red blood cells, white blood cells, hematocrit, mean corpuscular volume, and hemoglobin concentration were also significantly improved in the SWP40 group. Whole-body crude protein differed non-significantly (P > 0.05) in all the study groups. The fat content was significantly higher in the SWP20 group. It can be concluded that silkworm pupae are a suitable source of protein to be substituted in the feeds of Gift Tilapia replacing 10% to 40% of fish meal for enhanced health profile and promising growth.

Impacts of Substituting Fish Meal With Hydrolyzed Feather Meal on the Growth Performance, Immunity, and Antioxidant Capacity of Juvenile Largemouth Bass (Micropterus salmoides)

An 8-week breeding experiment was conducted to study the impacts of adding different levels (0%, 3.1%, 6.2%, 9.3%, 12.4%, and 15.5%) of hydrolyzed feather meal (HFM) in place of fish meal (FM) in the feed on the growth performance, immune function, and antioxidative ability of juvenile largemouth bass (Micropterus salmoides), with fishmeal substitution levels (FSLs) of 0% (control group; FSL0), 10% (FSL10), 20% (FSL20), 30% (FSL30), 40% (FSL40), and 50% (FSL50), respectively. The findings show that there were no notable differences observed among the different treatment groups when contrasted with FSL0. However, as the substitution level increased, final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) declined, while the feedback coefficient rate (FCR), condition factor (CF), hepatosomatic index (HSI), and viscerosomatic index (VSI) increased. With an increase in the FSL, catalase (CAT) activity increased in all the groups and was significantly higher in the FSL20 and FSL50 groups than the control group; SOD activities in FSL40 and FSL50 significantly increased, and the plasma MDA contents in FSL40 and FSL50 significantly decreased. The gene expression levels of IL-10 and IL-8 in the groups FSL20 to FSL50 significantly decreased. When compared with FSL0, the gene expression levels of CHOP and ATF6 were also significantly lower in the FSL10 to FSL50 groups. The overall expression level of ASK1 was significantly reduced in the FSL20 group. Similarly, the expression level of JNK1 was also significantly reduced in the FSL20 group. To sum up, replacing FM with HFM at 50% did not impact the growth of juvenile largemouth bass. An FSL range of 20%-50% can enhance the antioxidant capacity of largemouth bass, reduce inflammation and stress states, and have beneficial effects on the body. It is beneficial for maintaining the healthy growth of largemouth bass.

Effects of black soldier fly larvae oil on lipid metabolism, liver fatty acid composition, and plasma metabolite profiles in gilthead seabream juveniles

The potential of insects as alternative ingredients in animal feeds is well-established. However, limited information is available on the use of insect oils as alternative lipid sources in aquafeeds. To address this, a study was conducted on gilthead seabream (Sparus aurata) juveniles to evaluate the effects of including black soldier fly (Hermetia illucens) larvae oil (HIO). Diets were formulated to include 4, 7.9, and 9.5 % HIO, replacing a vegetable oil blend at 42, 84, or 100 %, respectively. After 70 days, the effects on liver fatty acid profiles, plasma metabolites, and lipid metabolism gene expression were assessed. The results showed that HIO inclusion led to a linear decrease in plasma lipids and triglycerides, while high-density lipoprotein levels increased. The experimental diets also altered the liver's fatty acid composition without affecting total lipid content. There was an increase in the liver's saturated fatty acid content, like lauric acid, and monounsaturated fatty acids, like oleic acid. In contrast, n-3 and n-6 polyunsaturated fatty acid content was reduced, although EPA and DHA levels remained unaffected. Additionally, the content of C16:0 and C18:0 (% of total fatty acids) was higher in the liver than in the corresponding diets. The inclusion of HIO had minimal impact on the expression of genes associated with fatty acid synthesis, transport, and β-oxidation. However, a downregulation of elongation of very long-chain fatty acids proteins 6 and 1b (elovl6 and elovl1b) was observed with increasing HIO levels. Overall, the study indicates that up to 9.5 % HIO inclusion in diets is well tolerated by gilthead seabream juveniles, with minimal effects on plasma metabolites and key gene expression related to fatty acid metabolism. These findings support the use of HIO as a viable alternative lipid source for juvenile gilthead seabream, contributing to the sustainable development of aquafeeds.

The Significant Enhancing Effect of Vitamin B6-Fortified Feed on the Intestinal Digestive Efficiency, Immunity, and Antioxidant Defense Mechanisms of Juvenile Largemouth Bass (Micropterus salmoides)

A 12-week aquaculture trial was conducted to evaluate the effects of vitamin B6 on the intestinal health of largemouth bass (Micropterus salmoides). Six feeds with a vitamin B6 content of 2.03 (control group), 2.91, 3.30, 6.03, 9.53, and 21.79 mg/kg were prepared. The results were as follows. Regarding digestive efficiency, the 9.53 mg/kg group showed significantly higher activities of AMY, LPS, and TRY compared to the control group; the 6.03 mg/kg group exhibited increased AKP and Na+/K+ ATPase activities. Regarding immunity, the 6.03 mg/kg group had markedly higher relative expressions of zo-1 and occ than the control group; the 9.53 mg/kg group showed significantly higher relative expressions of il-10, tgf-β, igm, and cd83, while il-8 and tnf-α were notably lower, and nf-κb was noticeably decreased in 21.79 mg/kg group. For antioxidant capacity, the 6.03 mg/kg group had markedly higher activities of CAT, SOD, GSH-Px, and T-AOC levels, compared to the control group; the MDA level in the control group was markedly higher than in the other groups. The relative expressions of nrf2, cat, Cu-Zn sod, and gpx were highest in 9.53 mg/kg group and significantly higher than in the control group. In conclusion, an appropriate level of vitamin B6 in the feed is vital for protecting the intestinal health of largemouth bass.

Retrospect of fishmeal substitution in largemouth bass (Micropterus salmoides): a review

With the growth of the population, the demand for aquatic products is increasing. Additionally, the development of the aquaculture industry has led to a heightened demand for fishmeal (FM). FM is a high-protein feed raw material made from one or more types of fish, which has been deoiled, dehydrated, and crushed. The world's major FM-producing countries include Peru, Chile, Japan, Denmark, etc., among which exports from Peru and Chile account for about 70% of the total trade volume. However, in recent years, global warming, environmental pollution, and overfishing have gradually declined marine fishery resources. The shortage of high-quality FM and its rising prices have become a significant constraint to the development of fisheries. Consequently, aquaculture nutritionists are actively seeking solutions to reduce the reliance on FM by either enhancing the utilization rate of existing FM or developing new protein sources as substitutes. The challenge of FM replacement has thus emerged as a significant global issue. Largemouth bass (LMB) is one of the more cultured freshwater fishes in the world and is popular among consumers for its delicious and delicate flesh and rich and diverse nutrition. The protein content in feed is an essential factor affecting LMB growth and feed cost. LMB protein requirement is about 40-50%, and the amount of FM added accounts for about 50% of the protein feed. This article reviews the current research status of alternative protein sources, including plant proteins, livestock and poultry by-product proteins, insect proteins, and single-cell proteins. This research is significant for exploring feed formulation and cost reduction for LMB.

Interactions between feed protein source and feeding frequency on growth performance and health status of largemouth bass (Micropterus salmoides)

In order to evaluate the effects of the interaction between different proteins and feeding frequency on largemouth bass (Micropterus salmoides) and to provide scientific guidance for the application of novel proteins and the corresponding optimal feeding strategy, a two-factorial design (5 × 3) with five protein feeds (fishmeal (FM), Clostridium autoethanogenum protein (CAP), Tenebrio molitor (TM), Chlorella meal (ChM), cottonseed protein concentrate (CPC)), and three feeding frequency (1, 2, and 3 times/d; FF1, FF2, FF3) was designed in culturing largemouth bass (initial weight, 2.98 ± 0.22 g/fish) for 8 weeks. Z-score combined with cluster analysis was used to analyze and compare the effects of different treatments on different indicators, such as growth performance, feed utilization, antioxidant capacity, and immune response to draw a general picture of the relationship among all these massive biomarkers. The results showed that different protein sources and feeding frequencies had significant interactive effects on growth performance, feed utilization efficiency, body lipid, and health status of largemouth bass. Fish fed with ChM feed showed similar performance to that in FM group, implying its potential for complete replacement of fishmeal in largemouth bass. Fish fed with CAP, TM, and CPC feeds showed worse performance compared to FM and ChM groups, characterized by poor growth and feed utilization, enhanced stress, chronic inflammation, and varying symptoms of histological changes in the liver and intestine, which demonstrated the adverse effects of the complete replacement of fishmeal by these three proteins. In terms of feeding frequency, fish fed with FM feed in FF3 group led to liver hypertrophy, fat accumulation, and the risk of fatty liver, while inducing liver inflammation. In addition, the TM and CAP group had the higher expression levels of inflammatory factors at FF3 group, which displayed that the interactions between FM, CAP, TM feeds and feeding frequency at FF3 might aggravate the occurrence of liver inflammation and oxidative damage of hepatocytes. Overall, FF2 had higher feed efficiency, protein efficiency, antioxidant enzyme and lysozyme activities, lower MDA content, and lower gene expression of inflammatory cytokines and could be considered as the optimum feeding frequency for largemouth bass fed with different protein feeds.

Effects of Dietary Cobalt Levels on Growth Performance, Antioxidant Capacity, and Immune Status of Juvenile Largemouth Bass (Micropterus salmoides)

A 9-week experiment investigated the effects of dietary cobalt levels on the growth performance, antioxidant capacity, and immunity of largemouth bass. Six feed groups were designed and each group received different cobalt levels, including 0.129 mg/kg (control group), 0.192 mg/kg, 0.201 mg/kg, 0.233 mg/kg, 0.277 mg/kg, and 0.316 mg/kg. The results show that the control group (0.129 mg/kg diet) had the lowest final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR), and the highest feed conversion ratio (FCR), when compared to the cobalt supplementation groups. Dietary cobalt levels of 0.192 mg/kg increased the body protein content and decreased the body moisture content. Regarding antioxidant capacity, the highest catalase (CAT) activity was found in the 0.277 mg/kg dietary cobalt group, while the malondialdehyde (MDA) content was significantly diminished; the total antioxidant capacity (T-AOC) content and glutathione peroxidase (GSH-Px) activity exhibited the highest values in the 0.192 mg/kg and 0.233 mg/kg dietary cobalt groups, respectively. Regarding gene expression, compared with the control group, the mRNA expression of sod was upregulated in the 0.192 mg/kg, 0.233 mg/kg, and 0.277 mg/kg dietary cobalt groups, while the mRNA expression of gpx was diminished when dietary cobalt levels were below 0.233 mg/kg. In addition, the highest il-10 and tgf-β mRNA expression levels were observed in the 0.201 mg/kg and 0.233 mg/kg dietary cobalt groups, respectively. According to the quadratic regression analysis based on the SGR and FCR, the optimal requirement was 0.24 and 0.26 mg/kg of dietary cobalt, respectively.

Research on Function of Ribosomal Protein S6 Kinases, 1α and β, Based on Molecular Cloning and siRNA-Based Interference in Juvenile Blunt Snout Bream (Megalobrama amblycephala)

The aim of this study was to investigate the effects of S6K1α and β on the expression of glycolysis- and gluconeogenesis-related genes in juvenile blunt snout bream. Two isoforms, α and β, of ribosomal protein S6 kinase 1 in blunt snout bream were cloned and characterized, and their expression patterns were examined in vivo. The sequence analysis showed that s6k1α and s6k1β contain open reading frames of 2217 and 1497 bp, encoding 738 and 498 amino acids, respectively. Both S6K1α and S6K1β consist of an S_TKc domain and an extended S_TK_X domain. s6k1α and s6k1β were abundantly expressed in the heart and gonads. siRNAs were designed, and the experiment showed that α-siRNA inhibited s6k1α and s6k1β expression, but β-siRNA exclusively inhibited s6k1α expression (p < 0.05). α-siRNA upregulated the expression levels of gk and pk, while β-siRNA upregulated pepck and g6p expression (p < 0.05). The expression of g6pdh was found to be downregulated, but the gs mRNA level was overexpressed after treatment with α-siRNA and β-siRNA (p < 0.05). In the present experiment, S6K1α was more intimately involved in the regulation of gluconeogenesis when only S6K1α was inhibited, whereas the inhibition of both S6K1α and S6K1β collectively co-regulated glycolysis.

J. A, Sethupathy A. M, S. S, Alrashdi YBA, Ibrahim AE, El Deeb S. Current Status and Global Research Trend Patterns of Insect Meal in Aquaculture From Scientometric Perspective: (2013-2022)

In the past decade, insect meal has gained popularity in the animal feed industry, particularly in aquafeed, due to rising costs and decreased availability of fish meal (FM) and fish oil. Initially met with skepticism, insect meal is now seen as a promising ingredient because of its high nutrient profile. Research worldwide is exploring its potential as a FM replacement. Insects are abundant, nutritious, and environmentally friendly, as they can be reared on organic waste, minimizing the need for land, water, and energy. This research aims at obtaining a comprehensive and in-depth understanding of the current status and research trend patterns in this research field. To achieve this goal, this study conducts a mini systematic review and scientometric analysis of the global research published from 2013 to 2022 on the usage of insect meal in aquaculture. In the scientometric analysis, a total of 354 papers published by 1800 authors in 124 different journals from the Web of Science (WoS) core collection were analyzed, evaluating the number of publications, most relevant authors, organizations, top cited countries, most globally cited publications, and trending research themes in this field. The result showed that the University of Turin was the leading organization in insect meal research, whereas aquaculture was the leading journal, and author Laura Gasco was the prominent researcher in this field in the studied time frame (2013-2022). Italy was the leading country in Europe, while China dominated Asia in terms of the number of publications. The annual growth rate in insect meal research was found to be positive (23.11%), with 36.95 average citations per document. This study helps practitioners and scholars understand the current state of insect meal in aquaculture and identifies research requirements that can benefit both academia and industry.

Chlorogenic Acid Plays an Important Role in Improving the Growth and Antioxidant Status and Weakening the Inflammatory Response of Largemouth Bass (Micropterus salmoides)

This experiment evaluated the function of chlorogenic acid (CGA) in the growth, health status, and inflammation of largemouth bass (Micropterus salmoides). Over eight weeks, CGA supplementation was designed at five levels: 0, 60, 120, 180, and 240 mg/kg. The 180 and 240 mg/kg CGA-supplemented groups showed significant improvements in the FBW, SGR, and WGR compared to the control group (0 mg/kg) (p < 0.05). All the CGA-supplemented groups exhibited a significant reduction in the FCR (p < 0.05), with the 180 mg/kg CGA group showing the lowest FCR. Nonetheless, there were no appreciable differences in the plasma concentrations of TP, ALT, or AST among the treatments (p > 0.05). Compared to the control group, the 180 mg/kg CGA group exhibited significantly lower TC and TG levels (p < 0.05). The ALP levels showed no significant differences from the control group (p > 0.05). In terms of antioxidant parameters, CGA supplementation considerably reduced the MDA content (p < 0.05) and increased the GSH levels, while decreasing the CAT, SOD, and GPx activity levels Meanwhile, CGA supplementation resulted in reduced mRNA levels of SOD, CAT, Nrf2, Keap1, and NF-κB compared to the control group. In contrast, the mRNA levels of GPx, IL-8, TLR2, and RelA were elevated in the liver. Our findings indicated that CGA supplementation improved the growth performance and antioxidant status and weakened the inflammatory response of largemouth bass. These findings suggest that CGA could be a valuable dietary supplement for enhancing the health and growth of this species.

Evaluation of four novel non-grain protein sources completely replacing soybean meal on growth performance, serum biochemistry, amino acid transport and intestinal health of grass carp (Ctenopharyngodon idella) at different water temperatures

To investigate the effects of non-grain protein source and water temperature on growth and feed utilization differences of grass carp, the effects of different protein sources on the growth performance, serum biochemistry, digestive enzymes, amino acid transport and intestinal health of grass carp were studied at 24 °C, 28 °C and 32 °C. In this study, a total of 1350 grass carp (Ctenopharyngodon idella) (initial weight 5.00 ± 0.02 g) were selected, and Clostridium autoethanogenum protein (CAP), Tenebrio molitor meal (TMM), cottonseed protein concentrate (CPC) and Chlorella powder (CHP) were used as a single protein source to completely replace soybean meal for 56 days. The results showed that the final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER) of grass carp increased significantly with the increasing temperature (P < 0.001). The CHP and SBM groups showed no significant differences in FBW, WGR, SGR and PER (P > 0.05), which were higher than the CAP, TMM and CPC groups (P < 0.001). The alanine transaminase (ALT), aspartate aminotransferase (AST), total protein (TP) and triglyceride (TG) concentrations of grass carp at 32 °C were significantly lower than those at 24 °C and 28 °C (P < 0.001). The acid phosphatase (ACP) activity decreased significantly with the increase of temperature (P = 0.001). The amylase (AMS) activity of the TMM, CPC and CHP groups was significantly lower than that of the SBM and CAP groups (P < 0.001), and the ACP and lipase (LPS) activities in the TMM group were significantly lower than those in the SBM group (P < 0.001). In addition, the interaction between temperatures and protein sources significantly affected the gene expression levels of amino acid transport including solute carrier family 1 member 3 (SLC1A3), solute carrier family 7 member 1 (SLC7A1), solute carrier family 7 member 5 (SLC7A5), solute carrier family 15 member 1b (SLC15A1b), solute carrier family 7 member 7 (SLC7A7), target of rapamycin (TOR), 4E binding protein 1 (4E-BP1) and ribosomal protein S6 kinase 1 (S6K1), intestinal inflammatory including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-8 (IL-8), interleukin-10 (IL-10) and tight junction proteins (occludin, claudin1, claudin3, claudin7 and claudin11) (P ≤ 0.001). Collectively, our results indicated that CHP could be a potential protein source in the case of complete replacement of soybean meal in grass carp.

The Potential of Defatted Yellow Mealworm (Tenebrio molitor) Meal as an Alternative Protein Source for Juvenile Chinese Mitten Crab (Eriocheir sinensis)

This study was aimed to investigate the effects of replacing dietary fish meal (FM) with defatted yellow mealworm (Tenebrio molitor) meal (DYM) on growth performance, intestinal health, serum immune, and antioxidant indexes of juvenile Chinese mitten crab (Eriocheir sinensis). Four hundred juvenile Chinese mitten crabs (4.94 ± 0.08 g) were randomly distributed into five groups in quadruplicate (20 crabs per tank), and each group was fed with diets that replaced FM with DYM at 0% (CON, containing 200 g/kg FM), 25% (DYM25), 50% (DYM50), 75% (DYM75), and 100% (DYM100) for 8 weeks, respectively. The results showed that the growth, serum immune and antioxidant indexes, digestive enzyme activities, intestinal histology, and microbiota composition of DYM25, DYM50, and DYM75 groups all reached the similar level as the CON group. While when 100% fishmeal was replaced, significantly decreased the final body weight (FBW), weight gain (WG), serum alkaline phosphatase (AKP), acid phosphatase (ACP), lysozyme (LZM), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and total superoxide dismutase (T-SOD) activities, hepatopancreas protease activity, mid-intestine folds height and number (P < 0.05), significantly increased the feed conversion ratio (FCR), serum malondialdehyde (MDA) content, and the abundance of intestinal harmful bacteria Shewanella (P < 0.05). Overall, these results suggest that 75% dietary FM (150 g/kg) can be effectively replaced by DYM without negative impact on the growth performance, intestinal health, serum immune, and antioxidant indexes of juvenile E. sinensis.

Effects of Taurine and Vitamin C on the Improvement of Antioxidant Capacity, Immunity and Hypoxia Tolerance in Gibel Carp (Carrassius auratus gibeilo)

To investigate the effects of taurine and vitamin C on gibel carp (Carrassius auratus gibeilo), fish (41.85 ± 0.03 g) were fed three diets with 0% taurine + 0% vitamin C (D0), 0.1% taurine + 0% vitamin C (D1), and 0.1% taurine + 0.1% vitamin C (D2) for 8 weeks. Then 12-hour hypoxic stress test was conducted. The results showed that weight gain rate (WGR), specific growth rate (SGR), and sustained swimming time (SST) were significantly increased in the D2. CAT, SOD, T-AOC, and GSH were increased. GSH-Px and il-6 were decreased in D1 and D2. In hypoxia, CAT and T-AOC were decreased, while GSH, sod, and nrf2 were the highest in D1. Compared to normoxia, GSH-Px was increased, while SOD and MDA were decreased. Il-10 and nf-κb were increased. Vegf, epo, and ho-1 were increased and they all were higher than that in normoxia. The number of gill cell mitochondria and survival rate (SR) of gibel carp had an increasing trend but no significant difference among groups. In conclusion, taurine with vitamin C improved the growth and SST of gibel carp, and taurine and taurine with vitamin C improved antioxidant capacity, immunity, and hypoxia tolerance.

Role of Cholecystokinin (cck) in Feeding Regulation of Largemouth Bass (Micropterus salmoides): Peptide Activation and Antagonist Inhibition

This study investigated the role of cholecystokinin (cck) in the feeding regulation of largemouth bass (Micropterus salmoides) via peptide activation and antagonist inhibition. The results show that the cck gene was expressed in various tissues, with the highest expression level occurring in the brain. Feeding, continuous feeding, and refeeding after fasting could significantly improve the mRNA levels of cck in the brain. Moreover, the activation of cck via injecting an exogenous CCK peptide could inhibit feed intake by regulating the mRNA levels of anorexigenic and feed-promoting factors in the brain and intestine. Furthermore, the CCK peptide reduced feed intake; however, the presence of an antagonist (Ly225910-CCK1R and devazepide-CCK2R) could reverse this effect through regulating the mRNA levels of anorexigenic and feed-promoting factors in the brain and intestine. Treatment with devazepide + CCK (CCK2R) reversed feed intake more effectively than Ly225910 + CCK (CCK1R) treatment. In summary, cck could regulate the feed intake of largemouth bass through regulating feeding-related genes in the brain and intestine. In addition, cck required binding with the receptor to inhibit feed intake more effectively in largemouth bass, and the binding effect of CCK1R was better than that of CCK2R.

Effects of Substituting Tenebrio molitor and Elodea nuttallii as Feed on Growth, Flesh Quality and Intestinal Microbiota of Red Swamp Crayfish (Procambarus clarkii)

This study aimed to evaluate the impact of substituting a portion of feed with Tenebrio molitor (TM) and Elodea nuttallii (EN) on crayfish culture. A total of 270 crayfish (5.1 ± 0.4 g) were fed three different diet combinations (A: 100% feed; B: 80% feed + 10% TM + 10% EN; C: 75% feed + 15% TM + 10% EN) for 12 weeks. The findings demonstrated that group C had an important beneficial impact on the growth performance of crayfish. This was evidenced by a rise in digestive enzyme activity (trypsin, lipase, and cellulase) in the intestinal and hepatopancreas, as well as an upregulation in the expression of growth-related genes (ghsr, igfbp7, mhc, mlc1, mef2, and pax7) in the muscle. Furthermore, the assessment of the flesh quality of crayfish muscle in group C was conducted. The findings indicated a significant increase (p < 0.05) in the energy value (moisture, crude protein, and crude lipid) within the muscle. The levels of delicious amino acids (Glu, Ala, Ser, Gly, and Tyr) and polyunsaturated fatty acids (ARA, DHA) were enhanced, resulting in an improved nutritional profile and flavor of the muscle while maintaining the Σn-3/Σn-6 ratio. The remodeling of the intestinal microbiota (abundance of Proteobacteria and ratio of Firmicutes/Bacteroidota bacteria) also revealed improved growth performance. Additional research is necessary to ascertain whether excessive use of TM or EN feed substitution can have negative effects on crayfish culture.

Excessive Replacement of Fish Meal by Soy Protein Concentrate Resulted in Inhibition of Growth, Nutrient Metabolism, Antioxidant Capacity, Immune Capacity, and Intestinal Development in Juvenile Largemouth Bass (Micropterus salmoides)

This study investigated the effects of replacing 0% (SPC0), 25% (SPC25), 50% (SPC50), 75% (SPC75), and 100% (SPC100) of fish meal (FM) with soy protein concentrate (SPC) on the growth, nutritional metabolism, antioxidant capacity, and inflammatory factors in juvenile largemouth bass (Micropterus salmoides) (17.03 ± 0.01 g). After 56 days of culturing, various growth parameters including FW, WGR, and SGR were not significantly different among SPC0, SPC25, and SPC50 groups; however, they were significantly higher than those in SPC75 and SPC100 groups. Conversely, significantly lower FCR were determined for the SPC0, SPC25, and SPC50 groups compared with that for the SPC100 group; specifically, no significant difference among SPC0, SPC25, and SPC50 groups was found. Moreover, compared with SPC75 and SPC100 groups, a significantly higher FI was observed in the SPC0 group, whereas a significantly lower SR was observed in SPC100 compared with that in SPC0 and SPC25 groups. Compared with the SPC0 group, significantly lower mRNA levels of tor, rps6, 4ebp1, pparγ, and fas were found in SPC75 and SPC100. Additionally, the mRNA levels of cpt were significantly higher in SPC0, SPC25, and SPC50 groups than in SPC75 and SPC100 groups. Moreover, the mRNA levels of scd and acc remained unchanged for all the groups. Replacement of FM with SPC did not significantly affect the mRNA levels of gk, pk, and pepck. Compared with the SPC0 group, significantly decreased activities of CAT were observed in the SPC50, SPC75, and SPC100 groups, and significantly decreased activities of GSH-Px were observed in the SPC75 and SPC100 groups. In addition, significantly lower activity of SOD was observed in SPC100 compared with the other groups. Moreover, compared with the other groups, the SPC75 and SPC100 groups had significantly decreased and increased contents of GSH and MDA, respectively, while significantly lower mRNA levels of nrf2, cat, sod, and gsh-px were found in SPC50, SPC75, and SPC100; however, significantly higher mRNA levels of keap1 were observed in SPC75 and SPC100 groups. Additionally, significantly higher mRNA levels of il-8 and nf-κb were found in the SPC50, SPC75, and SPC100 groups compared with the SPC0 group. Conversely, significantly lower mRNA levels of il-10 and significantly higher mRNA levels of tnf-α were found in the SPC75 and SPC100 groups compared with the other groups. Compared with the SPC0 group, mucosal thickness and villus height were significantly decreased in the SPC75 and SPC100 groups. Collectively, SPC replacing 50% FM did not affect its growth of juvenile largemouth bass. However, SPC replacing 50% or more FM might inhibit antioxidant capacity and immune capacity to even threaten the SR, resulting in impaired intestinal development in replacing FM level of 75% or more.

Black soldier fly larvae meal as a potential modulator of immune, inflammatory, and antioxidant status in gilthead seabream juveniles

This study aimed to evaluate the effects of fish meal (FM) replacement with defatted Hermetia illucens larvae meal (HM) on the hematological profile, immune parameters, intestinal inflammatory status, and antioxidant response in gilthead seabream juveniles. Four diets were formulated, replacing FM with HM at 0%, 22%, 60%, and 100% levels, corresponding to an inclusion level of 15 (diet HM15), 30 (diet HM30), and 45% (diet HM45), respectively. Over 67 days, fish were fed these diets until apparent visual satiation. Results showed no significant differences in immune parameters or hematological profiles, except for a decrease in hemoglobin and hematocrit levels. In the liver, glucose-6-phosphate dehydrogenase and glutathione peroxidase decreased linearly with HM content, especially at 100% replacement. Glutathione reductase activity was also reduced with HM inclusion, being lower in fish fed diet HM30 compared to the control. Fish fed diet HM15 showed lower hepatic superoxide dismutase activity, while catalase activity and lipid peroxidation remained unaffected. In the intestine, antioxidant enzyme activity was not influenced by HM, but lipid peroxidation linearly decreased with HM inclusion, being lower in the HM30 diet compared to the control. The inclusion of HM reduced the expression of intestinal pro-inflammatory genes (interleukin-1β and cyclooxygenase-2) while the expression of transforming growth factor β was higher in fish fed diet HM30 compared to the control and HM45 diets. In conclusion, up to 45% dietary inclusion of HM showed no adverse effects, improving liver antioxidant status, reducing intestinal oxidative stress, and regulating inflammatory gene expression.

Dietary protein, lipid and insect meal on growth, plasma biochemistry and hepatic immune expression of lake whitefish (Coregonus clupeaformis)

Studies are lacking that investigate the dietary nutrient requirements of lake whitefish (Coregonus clupeaformis), a newly farmed fish species in Ontario, Canada. Dietary levels of protein and lipid must be optimized to ensure high growth performance for the commercial success of this species. Additionally, the inclusion of insect meal in the diet may improve growth and immune response. The objective of this study was to evaluate the effects of dietary protein:lipid ratios and insect meal as a feed additive on the growth performance and hepatic immune function of juvenile lake whitefish (301 ± 10 g). A 16-week (112 day) trial was performed with five diets including a commercial control diet (BCC), and four experimental diets with high or low levels of protein (54 and 48%, respectively) and lipid (18 and 12%, respectively). The high protein dietary groups contained 5% of full-fat black soldier fly larvae (Hermetia illucens). Fish weights, viscera, liver, and blood were collected for further analysis. Specific growth rate, thermal growth coefficient and weight gain were significantly higher in fish fed with the BCC and high protein high lipid (HPHL) diets. However, viscerosomatic index was found to be significantly higher in fish fed the BCC diet, thus HPHL is more optimal for non-visceral weight gain. Higher levels of plasma phosphorus, aspartate aminotransferase and potassium indicated poor growth and stress in fish fed low lipid diets. Relative expression of HSP70, involved in cellular repair, was significantly downregulated in fish fed high lipid diets, and no effects were found on the expression of innate immune and oxidative stress genes. Also, IL8 (CXCL8) and catalase were upregulated (non-significant) in fish fed the HPHL diet with the largest weight gain. No effects of insects were found on growth, plasma biochemistry or gene expression, which suggests 5% dietary inclusion was too low. Overall, we recommend a HPHL diet for the cultivation of lake whitefish based on improved growth performance, low viscera weight, improved plasma biochemistry and downregulation of cellular repair genes.

Different Starch Sources Affect the Growth Performance and Hepatic Health Status of Largemouth Bass (Micropterus salmoides) in a High-Temperature Environment

The experiment was designed to investigate the effects of different starch types on the growth performance and liver health status of largemouth bass in a high-temperature environment (33-35 °C). In this study, we designed five diets using corn starch (CS), tapioca starch (TS), sweet potato starch (SPS), potato starch (PS), and wheat starch (WS) as the starch sources (10%). We selected 225 healthy and uniformly sized largemouth bass (199.6 ± 0.43 g) and conducted the feeding experiment for 45 days. The results showed that the WS group had the highest WGR, SGR, and SR and the lowest FCR. Among the five groups, the WS group had the highest CAT activity, SOD activity, and GSH content, while the SPS group had the highest MDA content. Furthermore, oil red O staining of liver samples showed that the TS group had the largest positive region, indicating high lipid accumulation. Lastly, the gene expression results revealed that compared with the WS group, the CS, TS, and SPS groups showed suppressed expression of nrf2, keap1, cat, sod, gpx, il-8, and il-10. Therefore, our results demonstrated the effect of different starch sources on largemouth bass growth performance and hepatic health in a high-temperature environment.

Potential mechanisms of different methylation degrees of pectin driving intestinal microbiota and their metabolites to modulate intestinal health of Micropterus salmoides

Four diets containing 8 % cellulose, low methyl-esterified pectin (LMP), high methyl-esterified pectin (HMP) and MMP (half LMP and half HMP) were designed to evaluate the potential mechanisms by which different esterification degrees of pectin drive intestinal microbiota and their metabolites modulating the intestinal health of Micropterus salmoides. The results showed that both dietary LMP and HMP consistently upregulated intestinal zonula occludens protein 1 (Zo-1), Caludin-1, and Caludin-4, and downregulated intestinal tumor necrosis factor-alpha (TNF-α), interleukin-8 (IL-8), and interleukin-1 beta (IL-1β) gene expression (P < 0.05). Dietary HMP separately upregulated intestinal Occludin, nuclear factor erythroid2-related factor 2 (Nrf2), B-cell lymphoma-2 (Bcl-2), and Bcl-2 associated agonist of cell death (BAD) gene expression, as well as the digesta propionate content, OTUs, Sobs, Shannon, Chao, and ACE indices (P < 0.05), whereas dietary LMP decreased digesta arginine, 4-aminobutyric, L-tyrosine, and phenylalanine contents (P < 0.05). Moreover, dietary HMP decreased plasma lipopolysaccharide and d-lactic acid contents and increased intestinal superoxide dismutase and glutathione peroxidase activities and immunoglobulin (Ig) receptor and IgM levels (P < 0.05). Collectively, dietary HMP improves intestinal health by increasing intestinal flora α-diversity and enhancing intestinal mechanical barrier, anti-inflammatory, antioxidant, and immune functions. On the contrary, the interference of dietary LMP with butyrate, tyrosine, arginine, and 4-aminobutyric acid metabolism is the main reason for its detrimental effects on intestinal health.

Eucommia ulmoides Oliver repairs the disorder of intestinal microflora caused by high starch in Micropterus salmoides and improves resistance to pathogens

Eucommia ulmoides Oliver (EuO) is a natural medicine that can improve the composition of intestinal flora in fish, but more experiments and data are needed to support whether it can effectively improve the changes of intestinal flora and intestinal damage caused by high starch. This study examined the changes in intestinal structure as well as intestinal flora before and after the addition of EuO to high-starch diets and analyzed the effects of such changes on immune and digestive functions. The results showed that EuO reduces mortality during Nocardia seriolae attack and can reduce starch-induced intestinal inflammation. Eucommia ulmoides Oliver supplementation was able to alter the changes of intestinal flora in fatty acid degradation, bacterial chemotaxis, porphyrin metabolism and flagella assembly caused by high starch. By analyzing the abundance and correlation of bacterial communities, three bacterial communities that were significantly related to the intervention effect of EuO were screened. Further analysis revealed that EuO supplementation reduced the increase in abundance of Limnochordaceae, Nitrolancea, Lysinibacillus, and Hydrogenispora induced by high starch, which were negatively correlated with levels of the immunoreactive substance LZM in fish. This study reveals the regulatory effects of EuO on the intestinal flora of Micropterus salmoides fed on high starch diets, and provides a theoretical basis for reducing starch damage to fish in production.

Phenylalanine Plays Important Roles in Regulating the Capacity of Intestinal Immunity, Antioxidants and Apoptosis in Largemouth Bass (Micropterus salmoides)

This experiment was planned to explore the role of dietary phenylalanine levels in intestinal immunity, antioxidant activity and apoptosis in largemouth bass (Micropterus salmoides). Six iso-nitrogen and iso-energy diets with phenylalanine levels of 1.45% (DPHE1), 1.69% (DPHE2), 1.98% (DPHE3), 2.21% (DPHE4), 2.48% (DPHE5) and 2.76% (DPHE6) were designed. Juvenile largemouth bass were fed the experimental diet for 8 weeks. In this study, the DPHE5 group increased the expression of intestinal antioxidant genes in largemouth bass (p < 0.05), and the increase of antioxidant enzyme activities and content of related substances was most concentrated in the DPHE3 and DPHE4 groups (p < 0.05). The results of plasma biochemistry were similar to that of enzyme activity. The expression of genes related to the TOR signalling pathway mainly increased significantly in the DPHE5 group (p < 0.05). Similarly, the expression of inflammatory factors, as well as apoptotic factors, also showed significant increases in the DPHE5 group (p < 0.05). In conclusion, unbalanced phenylalanine in the diet could lead to a decrease in intestinal immune and antioxidant capacity and also cause a decline in the aggravation of intestinal cell apoptosis.

Enzymatically Hydrolyzed Poultry By-Product Supplementation, Instead of Fishmeal, Alone Improves the Quality of Largemouth Bass (Micropterus salmoides) Back Muscle without Compromising Growth

This study was designed to investigate the effects of enzymatically hydrolyzed poultry by-products (EHPB) on the growth and muscle quality of largemouth bass. Different concentrations of EHPB (0.00, 3.10, 6.20, 9.30, and 12.40%) were added to replace fishmeal (0.00 (control), 8.89 (EHPB1), 17.78 (EHPB2), 26.67 (EHPB3), and 35.56% (EHPB4)), respectively, in dietary supplementation. The results revealed that the growth performance and muscle amino acid and fatty acid remained unaltered in EHPB1 (p > 0.05). EHPB1 showed significant reduction in muscle hardness, gumminess, chewiness, and muscle fiber count and exhibited a significant increase in muscle fiber volume. The decrease in muscle hardness, gumminess, and chewiness means that the muscle can have a more tender texture. The expression of protein metabolism-related genes reached the highest levels in EHPB1 and EHPB2 (p < 0.05). The mRNA levels of s6k and igf-1 in EHPB2 and EHPB1 were significantly lower than those in the control group. Compared to the control group, the expression of muscle production-associated genes paxbp-1 was higher in EHPB1, and myod-1, myf-5, and syndecan-4 were higher in EHPB2. The mRNA levels of muscle atrophy-related genes, in EHPB4 and EHPB2, were significantly lower than those in the control group. Therefore, the EHPB1 group plays a role in promoting the expression of genes related to muscle formation. In summary, replacing 8.89% of fishmeal with EHPB in feed has no effect on growth and may improve back muscle quality in largemouth bass.

Substituting Fish Meal with Tubiechong (Eupolyphaga sinensis) By-Product in the Diets of Largemouth Bass (Micropterus salmoides): Effects on Growth, Meat Quality, and Liver Health

A feeding trial was conducted to evaluate the effect of replacing 0% (control), 10% (T10), 20% (T20), 30% (T30), and 40% (T40) fish meal with a Tubiechong (Eupolyphaga sinensis) by-product in largemouth bass (Micropterus salmoides). Triplicate groups of 30 fish (5.36 ± 0.01 g) were fed two times daily to apparent satiation for 60 days. The experimental results showed that the Tubiechong by-product could improve the growth performance of largemouth bass by increasing the FBW, WGR, and SGR until the replacement ratio was 40%. The quadratic regression analysis showed that the proportion of the Tubiechong by-product was 20.79% and 20.91%, respectively, when WGR and SGR were the best. Concurrently, the meat quality in the replacement groups was higher, specifically, the lightness and white values were higher, and the water loss rates were lower (P < 0.05) than that in the control group. Moreover, the changes of the activities of CAT and GSH in the liver and T-AOC and GSH in serum could reveal the antioxidant capacity improvement of fish by the Tubiechong by-product. In the study, the replacement groups had lower T-CHO and HDL-C in serum (P < 0.05), indicating that the Tubiechong by-product had an active role in improving blood lipid and regulating lipid metabolism. Simultaneously, the replacement groups had a normal structure with central hepatocytes' nuclei and deviated from the center partly, while most of the hepatocytes were swollen in the control group with nuclear degeneration. The results showed that the Tubiechong by-product had a positive effect on the liver health of fish. Conclusively, the present study indicated that the partial dietary replacement of fish meal using the Tubiechong by-product (for up to 40% replacement level) in the diet of largemouth bass not only caused no adverse effects on fish health but also improved the growth performance, meat quality, antioxidant capacity, and hepatic health and is conducive to supplying nutritious, high-quality, and healthy aquatic products.

Yellow mealworm (Tenebrio Molitor) enhances intestinal immunity in largemouth bass (Micropterus salmoides) via the NFκB/survivin signaling pathway

This study aimed to elucidate the mechanisms of yellow mealworm (Tenebrio Molitor, YM) in intestinal immunity and health. Largemouth bass, as an enteritis modeling animal, were fed 3 diets containing YM at 0% (YM0), 24% (YM24) and 48% (YM48). The YM24 group had reduced levels of proinflammatory cytokines, while the YM48 group experienced a negative impact on intestinal health. Next, the Edwardsiella tarda (E. tarda) challenge test consisted of 4 YM diets, 0% (EYM0), 12% (EYM12), 24% (EYM24), and 36% (EYM36). The EYM0 and EYM12 groups exhibited intestinal damage and immunosuppression by the pathogenic bacteria. However, the above adverse phenotypes were attenuated in the EYM24 and EYM36 groups. Mechanistically, the EYM24 and EYM36 groups enhanced intestinal immunity in largemouth bass via activating NFκBp65 and further upregulating survivin expression to inhibit apoptosis. The results identify a protective mechanism of YM as a novel food or feed source by improving intestinal health.

Feeding Yellow Worms to Meagre: Effects on Whole-Body Fatty Acid Profile and Hepatic and Intestine Oxidative Status

This study aimed to determine the effects of dietary inclusion of Tenebrio molitor larvae (yellow worms) meal (TM) on meagre fish (Argyrosomus regius) whole-body fatty acids (FA) profile and hepatic and intestine oxidative status. For that purpose, fish were fed for 9 weeks a fishmeal-based diet (control) or diets including 10%, 20%, or 30% TM. With the increase in dietary TM level, whole-body oleic acid, linoleic acid, monounsaturated FA, and n-6 polyunsaturated FA (PUFA) increased while saturated FA (SFA), n-3 PUFA, n-3 long chain-PUFA, SFA:PUFA ratio, n3:n6 ratio, and FA retention decreased. Hepatic superoxide dismutase (SOD), glucose-6-phosphate dehydrogenase (G6PDH), and glutathione reductase (GR) activities increased and catalase (CAT) and glutathione peroxidase (GPX) activities decreased with dietary TM inclusion. Hepatic total and reduced glutathione were lower in fish fed 20% TM. Intestinal CAT activity and oxidized glutathione increased and GPX activity decreased with dietary TM inclusion. Intestine SOD, G6PDH, and GR activities increased and malondialdehyde concentration decreased in fish fed the diets with lower TM inclusion levels. Liver and intestine oxidative stress index and liver malondialdehyde concentration were unaffected by dietary TM. In conclusion, to avoid major whole-body FA changes or antioxidant status imbalances, it is recommended to limit TM to 10% inclusion in meagre diets.

Effects of Yellow Mealworm (Tenebrio molitor) on Growth Performance, Hepatic Health and Digestibility in Juvenile Largemouth Bass (Micropterus salmoides)

This study investigated the effects of yellow mealworm meal (TM) on growth performance, hepatic health and digestibility in juvenile largemouth bass (Micropterus salmoides). The fish were fed with the basic feed and the test feed (70% basic feed and 30% raw materials) containing Cr₂O₃, and feces were collected for digestibility determination. The fish were fed with five isonitrogenous (47% crude protein) and isolipidic (13% crude lipid) diets, in which fishmeal (FM) was replaced with 0% (TM0), 12% (TM12), 24% (TM24), 36% (TM36) and 48% (TM48) TM. The fish were reared in cylindrical plastic tanks in a recirculating aquaculture system for 11 weeks. The apparent digestibility coefficients (ADC), of dry matter, crude protein and crude lipid, in largemouth bass of TM were 74.66%, 91.03% and 90.91%, respectively. The ADC of total amino acid (TAA) of TM in largemouth bass was 92.89%, and the ADC of essential amino acid (EAA) in TM in largemouth bass was 93.86%. The final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) in the TM24 group were significantly higher than those in other groups. Similarly, the highest mRNA expression levels of hepatic protein metabolism genes (pi3k, mtor, 4ebp2 and got) and antioxidant enzyme (glutathione peroxidase, Gpx; catalase, Cat) activities were observed in the TM24 group. Moreover, the expression levels of anti-inflammatory factors (il-10 and tgf) in liver were up-regulated and the expression levels of pro-inflammatory factors (il-8 and il-1β) in liver were down-regulated. Quadratic regression model analysis, based on weight gain rate (WGR) against dietary TM level, indicated that the optimum level of dietary TM replacing FM in largemouth bass diet was 19.52%. Appropriate replacement levels (less than 36%) of FM by TM in the diets can enhance the antioxidant capacity and immunity of largemouth bass. However, high levels of FM substitution with TM (more than 48%) in the feeds can damage the liver health and inhibit the growth of largemouth bass. Notably, largemouth bass has high ADC and high utilization of TM, which indicates that it is feasible to use TM as feed protein source for largemouth bass.

Improving flesh quality of grass carp (Ctenopharyngodon idellus) by completely replacing dietary soybean meal with yellow mealworm (Tenebrio molitor)

In order to find viable alternative protein sources for aquaculture, we evaluated the effect of partial or complete replacement of dietary soybean meal with yellow mealworm (TM) on the flesh quality of grass carp. In this study, 180 grass carp (511.85 ± 0.25 g) were fed 3 experimental diets in which 0% (CN), 30% (YM30) and 100% (YM100) dietary soybean meal was replaced by TM for 90 d. The results showed that growth performance, biological parameters and serum antioxidant capacity of grass carp were not affected by dietary TM (P > 0.05). Both muscle and whole body crude protein were obviously promoted with the increase of dietary TM (P < 0.05), and the concentration of heavy metal in muscle was not influenced (P > 0.05), indicating that food safety was not influenced by TM. Dietary TM improved muscle textural characteristics by elevating adhesiveness, springiness and chewiness in YM100 (P < 0.05). In addition, the muscle tenderness was significantly increased by declining the shear force (P < 0.05). The muscle fiber density in YM30 &YM100 and length of dark bands and sarcomeres in YM100 were obviously increased (P < 0.05). The expression of myf5, myog and myhc exhibited a significant upward trend with the increase of dietary TM (P < 0.05), which promoted fiber density, length of sarcomere and texture of grass carp muscle. According to the results of metabolomics, the arachidonate (ARA) and eicosapentaenoic acid (EPA) were notably elevated in YM30 and YM100, which indicated that the improvement of flesh quality of grass carp may contribute to the dietary TM influence on muscle lipid metabolism, especially the polyunsaturated fatty acids. In conclusion, TM can completely replace dietary soybean meal and improve the nutritional value of grass carp.

The effects of replacing fishmeal by mealworm (Tenebrio molitor) on digestive enzymes activity and hepatopancreatic biochemical indices of Litopenaeus vannamei

Reducing the use of fishmeal (FM) in aquafeed means a significant saving in the amount of FM at the global level and reducing environmental impacts. One of the potential protein sources to replace FM in shrimp diet is the use of insects’ meal. Therefore, the present study aimed to examine the effects of replacing FM with mealworm (MW; Tenebrio molitor) on the growth, digestive enzymes activity and hepatopancreatic biochemical indices of Pacific white shrimp (Litopenaeus vannamei). Shrimp were fed for 60 days with a control diet (T0) and 4 practical diets (T15, T30, T60 and T100) where 15, 30, 60 and 100% of the FM was substituted by MW, respectively. Results showed that there were significant differences in weight gain (WG) and hepatopancreatic index (HPI) among treatments and the lowest and highest values for were observed in T0 and T30, respectively. Our findings indicated a significant increase (P<0.05) in activity of glutathione peroxidase (GPX), catalase (CAT), superoxide dismutase (SOD), total nitric oxide (TNO) and total antioxidant capacity (TAC) and a meaningful decrease (P<0.05) of malondialdehyde (MDA) in hepatopancreas of L. vannamei juveniles fed diets containing MW. The alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in the T0 did not show a significant difference (P>0.05) with other experimental treatments. Protease and lipase indicated an increasing trend with increasing the amount of MW up to 60%. The protease activity showed a significant difference (P<0.05) between the treatments containing MW and the control treatment. These findings indicated that MW could be a feasible candidate for replacing FM in diets of the Pacific white shrimp without any detrimental effects.

Effects of Enzymatic Cottonseed Protein Concentrate as a Feed Protein Source on the Growth, Plasma Parameters, Liver Antioxidant Capacity and Immune Status of Largemouth Bass (Micropterus salmoides)

This study appraised the impact of enzymatic cottonseed protein concentrate (ECP) as a fish meal (FM) substitute on the growth and health of largemouth bass (Micropterus salmoides) (initial weight 14.99 ± 0.03 g). Five diets with equal nitrogen, fat, and energy were designed to replace 0%, 7.78%, 15.56%, 23.33%, and 31.11% FM by adding 0%, 3.6%, 7.2%, 10.8%, and 14.4% ECP, named ECP0, ECP3.6, ECP7.2, ECP10.8, and ECP14.4, respectively. We fed 300 fish with five experimental diets for 60 days. The results revealed that weight gain rate (WGR) and specific growth rate (SGR) did not notably reduce until the addition of ECP exceeded 7.2%. The proximate composition of fish was not affected by the amount of ECP added in diets. Plasma total protein (TP), albumin (ALB), and high-density lipoprotein (HDL) concentrations increased with the increase of ECP dosage, while the triglyceride (TG) and low-density lipoprotein (LDL) concentrations and alkaline phosphatase (ALP) activity showed an opposite trend. For hepatic antioxidant capacity, the hepatic total superoxide dismutase (T-SOD) and catalase (CAT) activities, glutathione (GSH) content, and the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase (SOD), and CAT were increased by ECP, while the hepatic malondialdehyde (MDA) content and the expression of kelch-like-ECH-associated protein 1 (Keap1) were decreased. With regard to inflammation, the expression of nuclear factor-kappa B (NF-κB), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) were inhibited by ECP. In summary, the amount of ECP added to diet can reach 7.2% to replace 15.56% FM without hampering the growth of largemouth bass, and ECP can improve the antioxidant and immune capacity.

Oxidative Stress Response of Meagre to Dietary Black Soldier Fly Meal

This study aimed to assess the effect of Hermetia illucens meal (HM) dietary inclusion on meagre oxidative status. Thus, fish were fed a fishmeal-based diet (CTR diet) and three other diets with increasing levels of HM inclusion, namely 10%, 20%, and 30% (diets HM10, HM20, and HM30, respectively). At the end of the trial, hepatic and intestine superoxide dismutase, catalase, and glucose-6-phosphate dehydrogenase activities and malondialdehyde concentration were unaffected by the diet composition. Liver glutathione peroxidase activity was higher in the fish fed the HM20 diet than in the fish fed the CTR and HM30 diets, and glutathione reductase activity linearly increased with the dietary HM level. The hepatic total glutathione and reduced glutathione contents were significantly lower in fish fed the HM20 diet than in fish fed the CTR and HM10 diets. In the intestine, the oxidized glutathione (GSSG) content and oxidative stress index linearly increased with the increase in dietary HM level, with the GSSG content of fish fed the HM20 diet being significantly higher than of fish fed the CTR diet. In conclusion, 30% HM might be included in meagre diets without negatively affecting hepatic and intestine oxidative status.