Growth Of Bass Research Articles

Effects of dietary protein levels with cottonseed protein concentrate inclusion on growth, feed utilization, liver health and intestinal microbiota of juvenile largemouth bass (Micropterus salmoides)

An 8-weeks growth trial was conducted to evaluate the effects of dietary protein levels mainly based on cottonseed protein concentrate (CPC) meal on growth performance, protein metabolism, liver health and intestinal microbiota of largemouth bass (Micropterus salmoides) juveniles. Five isolipidic (100 g/kg) diets were prepared with protein levels ranging from 400 to 560 g/kg, with CPC of 155 g/kg, 214 g/kg, 272 g/kg, 330 g/kg, 390 g/kg to obtain five experimental diets with gradient protein levels (399.9 g/kg, 428.0 g/kg, 462.8 g/kg, 503.5 g/kg and 541.5 g/kg, respectively (CPC1, CPC2, CPC3, CPC4 and CPC5)). 300 fish (initial body weight: 14.71 ± 0.50 g) were randomly assigned into 15 tanks (3 tanks per diet). The results showed that, the fish of CPC5 group had the highest specific growth rate (SGR), weight gain (WG) and feed efficiency (FE) (P < 0.05). Increased dietary protein up-regulated most liver key genes of mTOR pathway (akt, tor, s6k, 4ebp1, s6) while down-regulated atf4 at medium dietary protein (P < 0.05). The expression of fas was down-regulated with increased dietary protein, while dgat1 was higher at CPC5 group (P < 0.05). The genes related to lipolysis were up-regulated with increased dietary protein (P < 0.05). The key genes of apoptosis including bcl2, casp9, casp3 (apoptosis) oxidative stress and endoplasmic reticulum stress were significantly up-regulated at high dietary protein (P < 0.05), which reduced the antioxidant and anti-stress capacity of the liver. Dietary 462.8 g/kg protein could maintain the normal composition and metabolic function of intestinal microbiota. In summary, dietary protein requirement using CPC as main protein source was estimated to be 463 g/kg to 510 g/kg for liver health or best growth of largemouth bass juveniles.

The impact of crowding stress on growth and intestinal integrity in largemouth bass (Micropterus salmoides): Insights into ER stress, autophagy and apoptosis

Crowding stress is a common abiotic stressor in intensive aquaculture that negatively impacts fish species, leading to growth depression. This study primarily explored the effects of crowding stress on the growth and intestinal integrity of largemouth bass (Micropterus salmoides). A 10-week feeding experiment was conducted with two groups: a control group (0.55 kg/m³) and a crowding stress group (1.10 kg/m³). The results showed that crowding stress significantly impaired fish growth and compromised intestinal integrity. To further elucidate the underlying mechanisms, we investigated the effects of crowding stress on endoplasmic reticulum (ER) stress, autophagy and apoptosis. Our findings revealed an increased proportion of terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL)-positive cells and ER swelling in the intestines of stressed fish, along with a higher number of autophagosomes. Furthermore, there was a significant upregulation in the mRNA expression of genes related to ER stress, autophagy and apoptosis, including GRP78, eIF2α, IRE1, atg3, LC3-2, ulk1α, P62, and caspase-8. In conclusion, crowding stress negatively affects fish growth and intestinal integrity, potentially through the induction of apoptosis and autophagy associated with ER stress-mediated unfolded protein response (UPR). These findings provided critical insights into how intensive aquaculture disrupts intestinal integrity and inhibits growth in fish, offering a valuable reference for future research aimed at enhancing stress resistance in fish under intensive aquaculture conditions.

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.

A superior chitin product: Black soldier fly larvae chitin, beneficial to growth performance, muscle quality and health status of largemouth bass Micropterus salmoides, in comparison to shrimp chitin

We appraised the effects of black soldier fly larvae chitin (BSFC) with four levels (0.4 %, 0.8 %, 1.2 % and 1.6 %) and shrimp chitin (SC) with three levels (0.4 %, 0.8 % and 1.6 %) in diets on the growth performance, nutrient composition and health status of largemouth bass (8.00 ± 0.29 g) fed for 56 days. The results showed that the dietary 0.4 % BSFC distinctly increased the specific growth rate and weight gain rate of fish (P < 0.05), and evidently promoted the deposition of C22:1n-9, C24:1n-9 and increased total monounsaturated fatty acid content in the muscle (P < 0.05). BSFC and SC distinctly stimulated the secretion of β-N-acetylglucosaminidase in the hindgut (P < 0.05). The antioxidant status of fish was improved by BSFC and SC, which was attributed to the decreased malonaldehyde contents in the muscle and midgut and the increased total superoxide dismutase and catalase activities in the midgut. The 1.2 %–1.6 % BSFC and 0.8 %–1.6 % SC enhanced the non-specific immunity of fish, which was attributed to the marked promotion of lysozyme, acid phosphatase and alkaline phosphatase activities by BSFC and the distinct enhancement of lysozyme activity by SC in the serum or midgut (P < 0.05). BSFC and SC notably reduced the abundance of potential pathogenic bacterium Vibrio and Photobacterium (P < 0.05), and 0.4 %, 1.2 %, 1.6 % BSFC and 0.4 % SC markedly increased the abundance of probiotic bacterium Cetobacterium (P < 0.05), and the BSFC and SC of 0.8 % significantly increased the abundance of the probiotics Bifidobacterium and Bacillus respectively (P < 0.05). The increase of acetic acid, propionic acid, butyric acid and valeric acid concentrations in the hindgut might be related to the increase of intestinal probiotics, and 0.8 %–1.6 % BSFC and 0.4 % SC obviously increased the total short-chain fatty acid levels in the hindgut (P < 0.05). BSFC and SC remarkably reduced muscle fiber area and diameter (P < 0.05), while fiber densities were significantly increased under 0.4 %, 0.8 % BSFC and 0.4 % SC supplementation (P < 0.05), which was accordant with increased mRNA expression levels of myod, myf-5, smad-2, tgf-β1 and decreased mRNA expression levels of myos in the muscle. Collectively, BSFC and SC had no negative effect on the growth of largemouth bass, and improved the health status of fish. The dietary 0.4 % BSFC supplementation was beneficial to fish growth and muscle quality, and BSFC was a superior chitin product in comparison to SC.

Multiple effects of dietary supplementation with Lactobacillus reuteri and Bacillus subtilis on the growth, immunity, and metabolism of largemouth bass (Micropterus salmoides)

Probiotics play an essential role in the largemouth bass (Micropterus salmoides) aquaculture sector. They aid the fish in sickness prevention, intestinal structure improvement, food absorption, and immune system strengthening. In this experiment, Bacillus subtilis (BS, 107 CFU/g) and Lactobacillus reuteri (LR, 107 CFU/g) were added to the feed and then fed to M. salmoides for 35 days. The effects of two probiotics on the growth, immunity, and metabolism of M. salmoides organisms were studied. The results revealed that the BS group significantly increased the growth rate and specific growth rate of M. salmoides, while both the BS and LR groups significantly increase the length of villi M. salmoides intestines. The BS group significantly increased the levels of AKP, T-AOC, and CAT in the blood of M. salmoides, as well as AKP levels in the intestine. Furthermore, the BS group significantly increased the expression of intestinal genes Nrf2, SOD1, GPX, and CAT, while significantly decreasing the expression of the keap1 gene. M. salmoides gut microbial analysis showed that the abundance of Planctomycetota was significantly different in both control and experimental groups. Analyzed at the genus level, the abundance of Citrobacter, Paracoccus, Luedemannella， Sphingomonas, Streptomyces and Xanthomonas in the both control and experimental groups were significantly different. The BS group's differentially expressed genes were predominantly enriched in oxidative phosphorylation pathways in the intestine, indicating that they had a good influence on intestinal metabolism and inflammation suppression. In contrast, differentially expressed genes in the LR group were primarily enriched in the insulin signaling and linoleic acid metabolism pathways, indicating improved intestine metabolic performance. In conclusion, B. subtilis and L. reuteri improve the growth and health of M. salmoides, indicating tremendous potential for enhancing intestinal metabolism and providing significant application value.

Effects of Dietary L-glutamic acid on the Growth Performance, Gene Expression Associated with Muscle Growth-Related Gene Expression, and Intestinal Health of Juvenile Largemouth Bass (Micropterus salmoides)

The present research examined the impact of L-glutamic acid (Glu) supplementation on the growth performance, muscle composition, gene expression correlated with muscle growth, and intestinal health of largemouth bass. There were 525 fish in total, which were distributed randomly into five groups. Each group had three replicates, and each replicate consisted of 35 fish. Groups with control and experimental diets were assigned glutamic acid amounts of 0.2%, 0.4%, 0.6%, and 0.8%. The findings demonstrated that glutamic acid supplementation enhanced growth performance, feed intake (FI), and condition factor (CF), with the best value being attained at 0.4% Glu. The mean muscle fiber area was increased and the muscle fiber density was decreased in the 0.6% Glu group. The levels of total amino acids and specific amino acids, such as glutamic acid, aspartic acid, leucine, valine, alanine, and glycine, were shown to be higher in the 0.6% Glu group. In the 0.6% Glu group, the mRNA expression levels of atrogin-1, murf-1, foxo3a, and 4e-bp1 were decreased compared to the control group. Conversely, the mRNA expression levels of myf5, myog, myod, s6k1, tor, akt, and pi3k were increased in the 0.6% Glu group compared to the control group. The 0.4% Glu group had higher intestinal amylase, lipase, and protease activities and greater villus height, villus width, and muscle thickness. In summary, Glu can support largemouth bass growth, muscular development, intestinal digestion, and absorption.

Increasing levels of fishmeal replacement by defatted black soldier fly larvae meal reduced growth performance without affecting fillet quality in largemouth bass (Micropterus salmoides).

A 90-day feeding trial was conducted to evaluate the effects of replacing dietary fishmeal (FM) with defatted black soldier fly larvae meal (BSFL) on the growth performance and fillet quality of largemouth bass (Micropterus salmoides). The largemouth bass was divided into six groups (BSFL0, BSFL15, BSFL30, BSFL45, BSFL75, and BSFL100) and fed six isonitrogenous(CP 50%, 508 g/kg) and isolipid (CL 9%, 124 g/kg) diets, in which 0, 15%, 30%, 45%, 75%, and 100% of the fishmeal was replaced with BSFL, respectively. The results showed that the final body weight (FBW) and specific growth rate (SGR) of the largemouth bass decreased with increasing BSFL content, and they were significantly lower in BSFL75 than in BSFL0. The weight gain rate (WGR) decreased with increasing BSFL content and the feed conversion ratio (FCR) of largemouth bass increased with increasing BSFL content. The saturated fatty acids (SFAs) and n-3 polyunsaturated fatty acids (PUFA) contents of the largemouth bass fillet significantly decreased, and the n-6 PUFA content of the largemouth bass fillets significantly increased with increasing dietary BSFL. The fillet b* significantly decreased with increasing BSFL content. The biological parameters, fillet proximate nutrient composition, fillet amino acid composition, skin color, and fillet texture of the largemouth bass were not affected by the replacement of BSFL. Transcriptomic analysis revealed that BSFL replacement of FM affects the immune system and metabolic processes of largemouth bass through signaling pathways such as complement and coagulation cascades, the PPAR signaling pathway, cholesterol metabolism, and fat digestion and absorption. In conclusion, a replacement level lower than 45% BSFL was suggested for the overall growth and fillet quality of largemouth bass.

Effects of exercise training on growth and physiology of large-mouth bass (Micropterus salmoides) reared in a recirculating aquaculture system

Large-mouth bass originally lived in rivers and lakes and now is often raised in recirculating aquaculture systems (RAS). However, the shortcoming of RAS is that there is very limited space for swimming fish in a high-density culture environment, thus leading to a lack of exercise. To investigate the effects of exercise training on growth performance, digestive enzymes, stress, and antioxidant capacity of large-mouth bass in a RAS, three training water flow velocities with three replicates were used in the present study: low water velocity: 0.5 body length per second (bl/s) (LV); medium water velocity: 1 bl/s (MV); and high water velocity: 1.5 bl/s (HV). 270 large-mouth bass (average initial body weight 47.51 ± 1.44 g, initial body length 12.71 ± 0.06 cm) were randomly divided into nine tanks (30 fish per tank). After 27 days experiment, the results showed that the growth performance of large-mouth bass, including feed intake, weight gain rate, and specific growth rate, in the HV group was significantly higher compared to the other groups. On the physiological level, the lipase and amylase activities were significantly increased in the HV group compared to the other groups. For the stress response parameters, the cortisol, glucose and lactate concentrations in the HV group were significantly increased, which may indicate higher stress in the HV group. Regarding the antioxidant enzyme activities, the activities of catalase (CAT) and glutathione peroxidase (GSH-PX) in the LV group were significantly higher than those in the HV group, which indicated that fish suffered higher oxidative stress in the LV group. Regarding the immune-related parameters, LZM and ACP activities had no significant differences among the groups, while AKP activities in the MV and HV groups were significantly higher than that in the LV group. Overall, the results demonstrated that exercise training had significant effects on the growth, digestion, stress, and immune response of large-mouth bass. It is suggested that exercise training with 1.5 bl/s can enhance fish growth, however, it also presents a potential risk of inducing stress in fish. Therefore, in rearing large-mouth bass in RAS, the setting of water flow velocity should not only focus on the growth of large-mouth bass but also consider its welfare.

Impact of organic and nanoparticle-selenium fortified larval weaning diet on survival, growth, gastrointestinal, and (GPx) activity of European Sea Bass (Dicentrarchus labrax) Larvae

The study involved three groups of six broodstock with a 1:1 male-to-female ratio. They were injected with 13 µg/kg LHRHa to stimulate spawning. We fed the broodstock three diets: a control diet without selenium, a diet containing 0.3 mg of nano-selenium /kg (N-Se), and a diet containing 4 mg of organic selenium /kg (O-Se). The broodstock diet consisted of equal parts of dry feed (45% protein), sardines, and squid. After being laid, the eggs were obtained from the collection ponds at the General Authority for Fisheries Development's fish hatchery and incubated until hatching. The larvae were given a micro diet containing 51.7% crude protein and live food (Rotifer and Artemia). Rotifer density increased from 5/ml to 15/ml by day 22 dph, Artemia nauplii increased from 0.2 to 4 ind./ml, from 7 to 35 dph then decreased to 0 at 55 dph, and micro-diets increased from 100-200 µ at 16 dph to 200-400 µ at 23-40 dph to 300-500 µ at 55 dph, and 500-1000 µ until the experiment ended. Three different diets in three replicates were tested: A micro diet free of selenium as a control diet (C), A micro diet with 0.3 mg of nano selenium (N-Se) kg-1, and A micro diet supplemented with organic selenium 4 mg (O-Se). Each group was taken from the three Broodstock groups respectively. Sixteen days after hatching, the three experimental micro diets were introduced to the larvae and continued for 76 days post-hatch. Larvae (260,000 per tank) were placed in fiberglass tanks with 4 m3 of water at a temperature of 19±2°C for optimal conditions. The larvae fed the N-Se diet had significantly better survival rates (75.0 ± 1.2 %), final body weight (240.0 ± 5.8 mg), weight gain (239.00 ± 5.8 mg), average daily gain (3.98±0.1mg), total length (39.0±0.06 mm), specific growth rate (9.133±0.04 %/day), feed intake (471.67±0.01 mg), and better feed conversion ratio (1.97±0.01) than the other groups (P < 0.05). The group provided with N-Se also had the highest levels of glutathione peroxidase enzyme (GPx) content in the whole larval body, whereas the control diet without Se supplementation recorded the lowest value of (14.8 ± 0.1 U/mg protein). The number and length of folds in the stomach and esophagus of sea bass post-larvae fed on diets fortified with selenium in both forms, nanoparticles or organic, showed a significant (P < 0.05) enhancement on the larval gastrointestinal (GI) tract. Moreover, selenium has an anti-inflammatory action in sea bass post-larvae. This study concluded that using N-Se as an antioxidant supports the growth and survival of European seabass D. labrax, gastrointestinal development and antioxidant efficacy during critical weaning.

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.

Growth, Antioxidant Capacity, and Liver Health in Largemouth Bass (Micropterus salmoides) Fed Multi-Strain Yeast-Based Paraprobiotic: A Lab-to-Pilot Scale Evaluation.

A multi-strain yeast-based paraprobiotic (MsYbP) comprising inactive cells and polysaccharides (β-glucan, mannan oligosaccharides, and oligosaccharides) derived from Saccharomyces cerevisiae and Cyberlindnera jadinii could ensure optimal growth and health in farmed fish. This study assessed the impact of an MsYbP on the growth, immune responses, antioxidant capacities, and liver health of largemouth bass (Micropterus salmoides) through lab-scale (65 days) and pilot-scale (15 weeks) experiments. Two groups of fish were monitored: one fed a control diet without the MsYbP and another fed 0.08% and 0.1% MsYbP in the lab-scale and pilot-scale studies, respectively (referred to as YANG). In the lab-scale study, four replicates were conducted, with 20 fish per replicate (average initial body weight = 31.0 ± 0.8 g), while the pilot-scale study involved three replicates with approximately 1500 fish per replicate (average initial body weight = 80.0 ± 2.2 g). The results indicate that the MsYbP-fed fish exhibited a significant increase in growth in both studies (p < 0.05). Additionally, the dietary MsYbP led to a noteworthy reduction in the liver function parameters (p < 0.05), such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (AKP), and hepatic nuclear density, indicating improved liver health. Furthermore, the dietary MsYbP elevated the antioxidative capacity of the fish by reducing their malondialdehyde levels and increasing their levels and gene expressions related to antioxidative markers, such as total antioxidant ca-pacity (T-AOC), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), catalase (CAT), nuclear factor erythroid 2-related factor 2 (nrf2) and kelch-1ike ech-associated protein (keap1) in both studies (p < 0.05). In terms of hepatic immune responses, the lab-scale study showed an increase in inflammation-related gene expressions, such as interleukin-1β (il-1β) and transforming growth factor β1 (tgf-β1), while the pilot-scale study significantly suppressed the expressions of genes related to inflammatory responses, such as tumor necrosis factor α (tnfα) and interleukin-10 (il-10) (p < 0.05). In summary, our findings underscore the role of dietary multi-strain yeast-based paraprobiotics in enhancing the growth and liver health of largemouth bass, potentially through increased antioxidative capacity and the modulation of immune responses, emphasizing the significance of employing yeast-based paraprobiotics in commercial conditions.

Effects of varied exercise intensities on growth, muscle quality and volatile compounds in largemouth bass (Micropterus salmoides) cultured in recirculating aquaculture system

To explore the impact of different exercise intensities on the growth, muscle quality, and volatile compounds of largemouth bass, this study involved 270 fish with an initial weight of 96.05 ± 18.87 g. They were divided into three groups: a control group (CG) exposed to a constant current speed of 0.30 cm/s for 24 h/day; an interval exercise group (IE) exercising at a rate of 2 body lengths per second (bl/s) for 8 h/day; and a sustained exercise group (SE) exercising continuously at 2 bl/s for 24 h/day. The experiment was conducted in a recirculating aquaculture system over a period of 90 days. Results revealed that SE exhibited remarkably greater body mass and condition factor (CF), with higher weight gain rate (WGR) and specific growth rate (SGR) compared to IE and CG (P < 0.05). SE exhibits superior growth performance. No significant differences was observed among the three groups in terms of centrifugal loss, drip loss, liquid loss, stored loss, and cooked rate. However, in terms of frozen leakage, the IE was considerably lower than the CG and SE (P < 0.05).In terms of raw meat texture, the hardness, chewiness, and shearing of the SE were notably greater than the CG (P < 0.05), and the SE were superior in hardness compared to the IE (P < 0.05). Regarding cooked meat texture, the SE exhibited significantly superior hardness, chewiness, springiness, and shearing compared to both the CG and IE (P < 0.05). The IE demonstrated higher levels of chewiness, springiness, and shearing compared to the CG (P < 0.05). With respect to nutritional indicators, the crude protein content of both the SE and IE was significantly higher than that of the CG. In terms of volatile substances, the CG had relatively high levels of carboxylic acid compounds and alcohol compounds in this experiment. The ketone compounds in the IE were significantly higher than those in the CG and SE. 2-Methylbutanoic acid methyl ester had the highest content in the SE. The results show that interval swimming exercise training and sustained exercise training can effectively improve the sensory quality of fish muscle, effectively remove the irritating smell in the muscle, and produce aromatic odor. Consequently, exercise training at varying intensities has been demonstrated to significantly enhance the growth and muscle quality of largemouth bass, offering potential strategies for improving fish product quality in the aquaculture industry. This contributes to increased efficiency and sustainability in fish farming practices and provides valuable insights for regulating the nutritional quality of fish muscle in future recirculating aquaculture system models.

Microorganism-mediated denitrogenation of aquaculture systems provoked by poly-β-hydroxybutyrate (PHB)

The biodegradable polymer poly-β-hydroxybutyrate (PHB) is a promising carbon source for biological mitigation of nitrogen pollution, a significant problem in aquaculture that physical and chemical methods have not provided a comprehensive solution. Here we investigated the impact of PHB on the zero-water-change largemouth bass culture by 30- and 40-day experiments. PHB loaded into the filter circulation pump at 4 g L−1, optimum value determined by the first experiment, significantly reduced the levels of nitrate by 99.65%, nitrite by 95.96%, and total nitrogen by 85.22% compared to the control without PHB. PHB also significantly increased denitrifying bacteria (e.g., Proteobacteria and Fusobacteria) and expression of denitrification genes (e.g., nirK and nirS) in the microbial community, improving growth and health parameters of largemouth bass. While the impact may vary in other culture systems, PHB thus demonstrated its remarkable utility in aquaculture, highlighting ecological assessment and application to larger aquaculture operations as future considerations.

Exploring the relationship between dietary rapeseed meal, condensed tannin and growth, nutrive metabolism in largemouth bass (Micropterus salmoides)

This study evaluated the effects of rapeseed meal (RM) and condensed tannin (CT) on the growth and nutritional metabolism of largemouth bass (Micropterus salmoides), and speculated whether there was interaction between anti-nutritional factors in RM. Eight diets were formulated for 55-day feeding trial, six of which were practical diet groups, including control group (CG), five RM inclusive groups with graded RM levels of 5% (RM5), 10% (RM10), 15% (RM15), 20% (RM20) and 25% (RM25) partially replacing fishmeal, and the other two were semi-purified diets with 0.062% CT (CT5) ≈ the CT content in the RM5 and 0.31% CT (CT25) ≈ the CT content in the RM25. The results of the experiments on replacing fishmeal with RM demonstrated that with the increase of RM substitution level, the weight gain rate (WGR), survival rate (SR) and specific growth rate (SGR) of largemouth bass showed a downward trend. High levels of RM led to the inhibition of digestive enzyme activity in largemouth bass, as well as the manifestation of abnormal markers related to protein, fat, and carbohydrate metabolism in both plasma and liver. RM reduced muscle protein and fat content, although the effect was not statistically significant at 5% RM level. The results of CT concentration experiments showed that the addition of 0.31% CT significantly reduced WGR, SGR, SR, protein efficiency ratio (PER) and gastrointestinal digestive enzyme activity, and significantly increased the feed coefficient ratio (FCR), plasma ammonia (PA), plasma glucose (PG), and hepatic glycogen (HG) and liver triglyceride (TG). The addition of 0.062% CT significantly reduced PG and HG. Supplementation of CT significantly reduced muscle fat. Among the groups of CT supplementation and RM, CT5 exhibited superior WGR, PER and FCR compared to RM5, along with enhanced intestinal trypsin, amylase activity, liver glutamic pyruvic transaminase (GPT) activity and decreased content of HG and liver TG; CT25 exhibited decreased activities of gastric lipase (LPS), enteric trypsin and pepsin, and increased content of total cholesterol (T-CHO) and glucose in plasma in compariosn to RM25, accompanied with no significant change in growth performance. Therefore, largemouth bass exhibited tolerance to a 5% inclusion of RM in the feed without compromising their growth, digestion and metabolic functions. The incorporation of 5% RM, equivalent to a supplemental 0.062% CT, had regulatory effects on the digestion and metabolism of largemouth bass while improving feed utilization. There was an interaction among anti-nutritional factors in RM, with synergistic effect being evident at low RM levels, whereas antagonism more promient at high levels of RM.

Beneficial effects of the butanoic acid derivative tributyrin on the growth, immunity and intestinal health of large mouth bass (Micropterus salmoides)

Tributyrin (TB) is a novel butanoic acid derivative with potent bioactive functions. In this study, an eight-week feeding trial aimed to investigate the effects of dietary TB on the growth, immunity and intestinal health of large mouth bass (Micropterus salmoides). Five experimental diets containing 0, 0.5, 1.0, 1.5 or 2.0 g/kg tributyrin were formulated and were regarded as TB0 (control), TB0.5, TB1.0, TB1.5 and TB2.0, respectively. Quadruplicate groups (four tanks per group, 30 fish per tank) of juvenile M. salmoides (initial weight: 20.00 ± 1.00 g) were fed to apparent satiation two times daily. After the feeding trial,Aeromonas hydrophila challenge tests were conducted and the A. hydrophila strains were subsequently sampled. As a result, the weight gain rate (WGR) was increased in the TB supplementation groups, and the TB1.5 group obtained the highest value. Furthermore, TB administration improved immune function. The content of serum complement 4 in the TB1.5 group was significantly higher than that in the control group. Increase of lysozyme activity and immunoglobulin M were significant in TB1.0 group than the control group. After A. hydrophila injection, TB1.0, TB1.5 and TB2.0 groups presented markedly higher survival rates than did the control group. Additionally, TB markedly enhanced the activities of amylase and lipase in the gut. Moreover, 16S rRNA sequencing revealed that TB could affect the intestinal microflora composition. Compared to those in the control group, the abundance of Fusobacteria were lower in the TB1.0 and TB1.5 groups. In conclusion, this study demonstrated that TB can improve the growth, immunity and intestinal health of M. salmoides, and the optimal dietary level of TB is determined to be 0.15%.

Estimating Age and Growth of Largemouth Bass in Southwestern Reservoirs by Using Otoliths and Scales

Abstract Age and growth data are frequently used to monitor and manage important North American sport fishes such as Largemouth Bass Micropterus salmoides. Continental and regional growth standards have been developed for this species to assess fish growth over time and across space. However, Largemouth Bass age and growth data are infrequently collected in Arizona and the reliability of age estimates derived from typical structures (e.g., scales, otoliths) in the Southwest is uncertain. Our objectives were to 1) compare precision and bias of age estimates from scales with those from otoliths and 2) estimate Largemouth Bass growth in several southwestern warmwater reservoirs by using otoliths. We collected Largemouth Bass from three Arizona reservoirs—Alamo, Peña Blanca, and Roosevelt—by boat electrofishing in spring 2021. We removed scales and sagittal otoliths from fish and then prepared and independently aged them three times. We compared differences in precision and bias between scales and otoliths using reader agreement percentages, confidence ratings, average coefficients of variation, and age-bias plots. We used age estimates from Largemouth Bass otoliths to calculate mean lengths-at-age at capture and relative growth indices based on published growth standards in each reservoir. Largemouth Bass scale age estimates were less precise, overestimated ages of younger fish, and underestimated age of older fish compared with those of otoliths. Growth was lower in Peña Blanca Lake than in the other two reservoirs according to mean length-at-age estimates, and relative growth indices suggested that Largemouth Bass growth in all three reservoirs was above average at younger ages, but less so at older ages. The results from this study add to a growing body of literature supporting the use of otoliths for estimating age and growth of Largemouth Bass.

Pleurotus eryngii root waste and soybean meal co-fermented protein improved the growth, immunity, liver and intestinal health of largemouth bass (Micropterus salmoides)

The present study aimed to evaluate the effect of king oyster mushroom (Pleurotus eryngii) root waste and soybean meal co-fermented protein (CFP) on growth performance, feed utilization, immune status, hepatic and intestinal health of largemouth bass (Micropterus salmoides). Largemouth bass (12.33 ± 0.18 g) were divided into five groups, fed with diets containing 0 %, 5 %, 10 %, 15 % and 20 % CFP respectively for 7 weeks. The growth performance and dietary utilization were slightly improved by the supplementation of CFP. In addition, improved immunoglobulin M (IgM) content and lysozyme activity in treatments confirm the enhancement of immunity in fish by the addition of CFP, especially in fish fed 20 % CFP (P < 0.05). Furthermore, CFP significantly improved liver GSH (glutathione) content in groups D10 and D15 (P < 0.05), and slightly improved total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity while slightly reduced malondialdehyde (MDA) content. Simultaneously, the upregulation of lipolysis-related genes (PPARα, CPT1 and ACO) expression and downregulation of lipid synthesis-related genes (ACC and DGAT1) expression was recorded in the group D20 compared with the control (P < 0.05), which were consistent with the decreased liver lipid contents, suggests that lipid metabolism was improved by CFP. In terms of intestinal structural integrity, ameliorated intestinal morphology in treatments were consistent with the upregulated Occludin, Claudin-1 and ZO-1 genes expression. The intestinal pro-inflammatory cytokines (TNF-α and IL-8) expression were suppressed while the anti-inflammatory cytokines (IL-10 and TGF-β) were activated in treatments. The expression of antimicrobial peptides (Hepcidin-1, Piscidin-2 and Piscidin-3) and intestinal immune effectors (IgM and LYZ) were slightly up-regulated in treatments. Additionally, the relative abundance of intestinal beneficial bacteria (Firmicutes) increased while the relative abundance of potential pathogenic bacteria (Fusobacterium and Proteobacteria) decreased, which indicated that the intestinal microbial community was well-reorganized by CFP. In conclusion, dietary CFP improves growth, immunity, hepatic and intestinal health of largemouth bass, these data provided a theoretical basis for the application of this novel functional protein ingredient in fish.

Natural zeolite for heavy metal, ammonia removal, and physiological responses in European sea bass (Dicentrarchus labrax) juveniles tanks with different densities.

The present study aims to investigate the influence of zeolite usage and stocking densities on various parameters, including ammonia removal from water, accumulation of heavy metals in fish organs, water quality, growth performance, feed efficiency, muscle composition, as well as hematological and biochemical parameters in European seabass (Dicentrarchus labrax) over a 90-day duration. A total of 2400 D. labrax with an initial weight of 9.83 ± 2.02 g and initial length of 9.37 ± 0.32 cm were distributed among 24 tanks. The research involved six distinct treatment groups, with two different zeolite levels (0 and 15 ppt) and three stocking density levels (50, 100, and 150 fish/m3), each replicated four times. The results of the research demonstrate a statistically significant improvement (p < 0.05) in water quality measures with the introduction of zeolite. The successful implementation of this amendment mitigated the adverse effects of fish density on water quality parameters. Higher stocking density negatively impacted European sea bass growth, feed utilization, and hemato-biochemical indicators. Zeolite use effectively alleviated these adverse effects, particularly on performance, feed utilization, hematological, and biochemical parameters. The study's results indicate that the utilization of zeolite has shown to be efficacious in mitigating the accumulation of heavy metals in both water and fish organs, while concurrently augmenting fish attributes. However, the increase in density led to a significant decrease in the accumulation of heavy metals in both water and fish organs. The present study highlights the capacity of natural zeolites to mitigate the negative consequences associated with water quality concerns. The efficiency of these zeolites in limiting the accessibility of heavy metals in polluted water is shown, hence minimizing their accumulation in fish organs. In addition, the improvement of fish performance has the capacity to have a beneficial influence on both the well-being and efficiency of fish in aquaculture. Additional research is essential to fully understand the complex molecular pathways involved in utilizing natural zeolite under different fish densities.

Development and characterization of 40 InDel markers from the major histocompatibility complex genes of largemouth bass (Micropterus salmoides).

The genetic improvement in growth and food habit domestication of largemouth bass (Micropterus salmoides) have made breakthroughs in past decades, while the relevant work on disease resistance were rarely carried out. Major histocompatibility complex (MHC) genes, which are well known as their numbers and high polymorphisms, have been used as candidate genes to mine disease-resistant-related molecular markers in many species. In present study, we developed and characterized 40 polymorphic and biallelic InDel markers from the major histocompatibility complex genes of largemouth bass. The minor allele frequency, observed heterozygosity, expected heterozygosity and polymorphic information content of these markers ranged from 0.0556 to 0.5000, 0.1111 to 0.6389, 0.1064 to 0.5070, and 0.0994 to 0.3750, respectively. Three loci deviated significantly from Hardy-Weinberg equilibrium, while linkage disequilibrium existed at none of these loci. These InDel markers might provide references for the further correlation analysis and molecular assisted selection of disease resistance in largemouth bass.

Effects of dietary D-mannose supplementation on growth performance, intestinal digestive capacity, gut microbiota, and ammonia tolerance of largemouth bass Micropterus salmoides

To investigate the effects of D-mannose on the growth performance, intestinal digestion capacity, intestinal microbiota composition, and ammonia tolerance of largemouth bass, experiments were conducted using largemouth bass fry with an average body weight of 7.41±0.05 g. Three experimental groups were designed, with 3 replicates per group and 30 fish per replicate. The fish were fed with feed containing different concentrations of D-mannose (0.00%, 1.00%, and 2.00% - Control, 1% mannose, 2% mannose) and were given full satiation twice a day for 56 days. The results indicated that the addition of 2% D-mannose in the feed enhanced the growth performance of the largemouth bass while reducing the feed conversion ratio. The addition of D-mannose in the feed increased the activity of digestive enzymes in the intestines (lipase, α-amylase, pepsin, alkaline phosphatase, Na+/K+ATPase, gamma-glutamyl transpeptidase, and creatine kinase). It also led to an increase in intestinal villi height and intestinal wall thickness; Adding D-mannose reduced the abundance of Staphylococcus and Achromobacter in the gut microbiota, while increasing the abundance of Aurantimicrobium. After being subjected to ammonia stress for 96 hours, the addition of D-mannose in the feed resulted in a decrease in mortality rate and neuronal nitric oxide synthase activity, while simultaneously enhancing the activity of liver argininosuccinate synthetase, argininosuccinate lyase, arginase, ornithine transcarboxylase, and inducible nitric oxide synthase. Adding D-mannose to the feed promotes the growth of largemouth bass, enhances their digestive capacity, and has a positive impact on their intestinal microbiota composition. Furthermore, it has been demonstrated that it can enhance the tolerance of largemouth bass to ammonia.