Soybean protein concentrate causes enteritis in juvenile pearl gentian groupers (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂)

Substitution of Fishmeal With Soy Protein Concentrate on Growth, Organic Damage, Antioxidant, Transcriptome, and Metabolomics in Macrobrachium rosenbergii

The present study investigated growth performance, body composition, hepatic and intestinal morphology, biochemical indices, transcriptomic responses, and metabolomic profiles in giant freshwater prawn (Macrobrachium rosenbergii) fed six kinds of soy protein concentrate (SPC) diets over an 8-week feeding trial. The six SPC diets were formulated by replacing varying proportions of fishmeal (FM) with SPC, with the final percentage of FM set at 350, 280, 210, 140, 70, and 0 g/kg, respectively, and designated as F35, F28, F21, F14, F7, and F0 diets. Results showed that the final body weight (FBW), weight gain, and specific growth rate (SGR) of prawn fed F35 were greater than those of prawn fed F7 and F0. The crude lipid content of prawn fed F0 was higher than that of prawn fed F28. Notably, increasing SPC substitution levels disrupted hepatopancreas morphology, with structural degradation becoming more pronounced beyond 40% replacement (F21). Compared to F35 group, the F0 significantly decreased the activity of glutathione peroxidase (GSH-PX), and increases the content of malondialdehyde (MDA) and nitric oxide (NO) in hemolymph. Based on the transcriptomics, two differentially expressed genes (DEGs) LOC136825138 and LOC136856310 were consistently observed across all groups. The metabolomics indicated that 77 differentially expressed metabolites (DEMs) across all treatments. A negative correlation was observed between LOC136856310 and eicosapentaenoic acid (EPA), arachidonoyl dopamine, 8Z,11Z-eicosadienoic acid, and vitamin E nicotinate. A comprehensive analysis of both metabolomic and transcriptomic data sets revealed substantial perturbations associated with "alpha-linolenic acid metabolism" and "glycerophospholipid metabolism". In conclusion, elevated levels of dietary SPC had detrimental effects on the growth performance, hepatopancreas health, antioxidant capacity, and immune function of M. rosenbergii. Based on the growth performance, dietary FM level for M. rosenbergii could be reduced to 140 g/kg by using SPC as a sole substitute, with an inclusion of 211 g/kg of SPC in the diet.

Dietary supplementation of Lycium barbarum polysaccharides alleviates soybean meal-induced enteritis in spotted sea bass Lateolabrax maculatus

The aim of this experiment was to investigate the effect of Lycium barbarum polysaccharides (LBP) on alleviating soybean meal-induced enteritis (SBMIE) in spotted sea bass Lateolabrax maculatus. The diet with 44% fishmeal (FM) content was used as a blank control, and soybean meal (SM) was used to replace 50% FM as an experimental control to induce enteritis. Then, on the basis of experimental control, 0.10%, 0.15%, and 0.20% LBP were added as experimental diets. A total of 225 spotted sea bass (44.52 ± 0.24 g) were randomly divided into 5 groups and fed the corresponding diets for 52 d. The results showed that 0.15% LBP decreased serum D-lactic acid (D-LA) content and diamine oxidase (DAO) activity (P < 0.05). In addition, in all LBP supplementation groups, the intestinal tissue morphology was significantly improved (P < 0.05); the intestinal microbial structure gradually recovered to a level close to that without adding SM; and the microbial species richness and diversity were significantly increased (P < 0.05). Through transcriptomic and metabolomic analysis, it was found that the expression of proinflammatory factors such as interleukin-1β (IL-1β), interleukin-12 (IL-12), nuclear factor kappa B subunit 2 (NF-κB2), and Toll-like receptor 2 (TLR2) were significantly down-regulated in the mitogen-activated protein kinase (MAPK) and Toll-like receptor signaling pathways (P < 0.05), and the important tight junction protein gene Occludin was up-regulated (P < 0.05). In addition, LBP down-regulated saponin metabolites and up-regulated amino acid metabolites (P < 0.05). In conclusion, LBP demonstrated a significant alleviating effect on SBMIE of spotted sea bass L. maculatus.

Dietary Lithospermum erythrorhizon ethanol extract alleviates soybean meal-induced enteritis by improving immune tolerance profile of pearl gentian grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂)

The aquaculture industry has a shortage of objected protection against soybean meal-induced enteritis (SBMIE) in carnivorous fish caused by soybean meal feed. Our initial study discovered that Lithospermum erythrorhizon (LE) ethanol extract has potential application value in improving SBMIE. A feeding trial (for eight weeks) was conducted to investigate LE ethanol extract on pearl gentian grouper SBMIE of protection to clarify the influence of LE ethanol extract on the immune tolerance profile. Three hundred and sixty pearl gentian groupers were administered one of three distinct dietary regimes: 1) 100 % fish meal (FM); 2) soybean meal substitution of 50 % fish meal protein (SBM); 3) SBM diet +0.2 % LE ethanol extract (SBMLE). Each treatment included three 1000 L cisterns-each of cisterns with 30 fish. The preliminary weight of the fish varied between 72.01 g and 72.50 g. Growth performance results showed that WGR and SGR were significantly decreased in the SBM group (P < 0.05), while there was no significant difference between the FM and SBMLE groups. There was no significant difference in survival among the three groups. The results showed that SBM-fed fish exhibited enteritis manifested by mucosal fold shortening, lamina propria widening, decreased serum immune markers (IgM, C3, and C4), and up-regulated expression of pro-inflammatory cytokines (il17 and il12) and immune-related gene (tlr3, and tlr9). The addition of 0.2 % LE ethanol extract to the SBM diet, reversed the above symptoms, and anti-inflammatory cytokine (tgf-β1), gene expression increased significantly (P < 0.05). Intestinal transcriptome analysis exhibited that the DEGs between the FM group and the SBM group were mainly enriched in FoxO signaling pathway, while the DEGs between the SBM group and the SBMLE group were enriched in MAPK signaling pathway and FoxO signaling pathway. The RT-qPCR results also revealed changes in MAPK/FoxO signaling pathway-related genes, including Dusp1, jund, Irs2b, fbxo32, and ccng2. Overall, Lithospermum erythrorhizon ethanol extract may alleviate SBMIE by regulating MAPK/FoxO signaling pathway, which would be beneficial for enhancing the immune tolerance and utilization efficiency of pearl gentian groupers to dietary soybean meal.

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.

Intestinal microbiota and gene expression alterations in leopard coral grouper (Plectropomus leopardus) under enteritis

Enteritis poses a significant threat to fish farming, characterized by symptoms of intestinal and hepatic inflammation, physiological dysfunction, and dysbiosis. Focused on the leopard coral grouper (Plectropomus leopardus) with an enteritis outbreak on a South China Sea farm, our prior scrutiny did not find any abnormalities in feeding or conventional water quality factors, nor were any specific pathogen infections related to enteritis identified. This study further elucidates their intestinal flora alterations, host responses, and their interactions to uncover the underlying pathogenetic mechanisms and facilitate effective prevention and management strategies. Enteritis-affected fish exhibited substantial differences in intestinal flora compared to control fish (P = 0.001). Notably, norank_f_Alcaligenaceae, which has a negative impact on fish health, predominated in enteritis-affected fish (91.76 %), while the probiotic genus Lactococcus dominated in controls (93.90 %). Additionally, certain genera with pathogenesis potentials like Achromobacter, Sphingomonas, and Streptococcus were more abundant in diseased fish, whereas Enterococcus and Clostridium_sensu_stricto with probiotic potentials were enriched in control fish. At the transcriptomic level, strong inflammatory responses, accompanied by impaired metabolic functions, tissue damage, and iron death signaling activation were observed in the intestines and liver during enteritis. Furthermore, correlation analysis highlighted that potential pathogen groups were positively associated with inflammation and tissue damage genes while presenting negatively correlated with metabolic function-related genes. In conclusion, dysbiosis in the intestinal microbiome, particularly an aberrantly high abundance of Alcaligenaceae with pathogenic potential may be the main trigger for this enteritis outbreak. Alcaligenaceae alongside Achromobacter, Sphingomonas, and Streptococcus emerged as biomarkers for enteritis, whereas some species of Lactococcus, Clostridium_sensu_stricto, and Enterococcus showed promise as probiotics to alleviate enteritis symptoms. These findings enhance our understanding of enteritis pathogenesis, highlight intestinal microbiota shifts in leopard coral grouper, and propose biomarkers for monitoring, probiotic selection, and enteritis management.

A mixed animal and plant protein source replacing fishmeal affects bile acid metabolism and apoptosis in largemouth bass (Micropterus salmoides)

Chicken meal, shrimp meal, blood meal, and soybean protein concentrate are common alternatives to fishmeal. This study used them to prepare three diets with different levels of fishmeal (FM48, FM40, and FM32) for largemouth bass (Micropterus salmoides). The results found no significant difference in the growth performance of largemouth bass fed different diets. Mixed protein increased the total cholesterol (T-CHO) content in plasma, and reduced the total superoxide dismutase (T-SOD) activity in plasma and liver. Targeted metabolomics analysis found that the low fishmeal diets affected the cholesterol and bile acid metabolism of largemouth bass. Mixed protein inhibited cyp7a1 and enhanced hmgcr and pparγ mRNA levels, as well as enhanced the expression levels of FXR in the liver. The fish-fed FM32 diet showed inhibited fxr, rxrα, and cyp7a1 mRNA levels in the intestine. The results of TUNEL fluorescence staining showed that mixed protein induced apoptosis in largemouth bass. The caspase 3 and caspase 9 mRNA levels in the fish-fed FM40 and FM32 diet significantly increased, as well as the expression levels of CASPASE 3. The experiment also found that it could induce oxidative stress and endoplasmic reticulum stress. In conclusion, the replacement of fishmeal with mixed animal and plant protein diets did not affect the growth performance, but the health and bile acid metabolism of largemouth bass was affected when the fishmeal level was reduced to 32%.

Effects of fermented soybean meal substitution for fish meal on intestinal flora and intestinal health in pearl gentian grouper

This study explored the role of replacing fish meal protein with fermented soybean meal (FSBM) protein on the growth performance and intestinal morphology, immunity, and microbiota of the pearl gentian grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂). Three isonitrogenous and isolipidic diets with increasing levels of FSBM (0%, 20% and 40%; referred to as FM, FSBM20 and FSBM40 diets, respectively) as a replacement for fish meal were selected for this study. The pearl gentian grouper were fed these diets for 10 weeks. The findings revealed that the growth of fish fed the FSBM diets (FSBM20 and FSBM40) were remarkably lower than the fish fed the FM diet. Pathological manifestations of intestinal inflammation, such as shortened intestinal mucosal folds and thickened lamina propria, were observed in the fish fed the FSBM diets. Moreover, the gene expression levels of IL1β, IL12, IL17, and TNFα were remarkably upregulated in fish fed the FSBM40 diet, in contrast to the gene expression levels of IL4, IL5, IL10, and TGFβ1, which were remarkably downregulated (p < 0.05). The FSBM diets significantly affected the stability of the fish gut microbiota. Photobacterium was the dominant phylum in all experimental groups, and the proportion of these bacteria gradually decreased with increasing FSBM substitution. The composition of intestinal flora at the genus level was not the same in the three experimental groups, with a richer composition of intestinal bacteria detected in the FSBM20 and FSBM40 groups (p < 0.05). The correlation between intestinal flora balance and immune gene expression revealed that only Photobacterium was negatively correlated with the above upregulated genes, while other bacteria were positively correlated with these pro-inflammatory factors (p < 0.05). Photobacterium was positively correlated with the above downregulated genes, while other bacteria were negatively correlated with these anti-inflammatory factors (p < 0.05). In conclusion, high levels of substitution of FSBM for fish meal causes intestinal inflammation in pearl gentian grouper. This is likely associated with changes to the intestinal flora. More attention should be paid to the negative role of dietary FSBM on intestinal flora.

Squid industry by-product hydrolysate supplementation enhances growth performance of Penaeus monodon fed plant protein-based diets without fish meal

The poor growth of aquatic animals fed with diets containing high plant proteins has been attributed to low diet acceptability and feed value. Supplementation of protein hydrolysate, with high contents of free amino acids and soluble low molecular weight peptides, may increase the acceptability and feed value of a plant protein-based diet. In the present work, squid processing by-products were enzymatically hydrolyzed and used as a supplement in a plant protein-based diet, without fish meal, of Penaeus monodon to fully maximize the utilization of this marine resource. The hydrolysate was incorporated at 0, 0.5, and 1% levels in P. monodon diets containing 0 and 10% fish meal levels. Growth, digestive enzyme activities, muscle growth-, gut pro-inflammatory and immune-related gene expressions, and muscle morphometric measurements were evaluated as biological indices in an 8-week feeding trial. The squid by-product hydrolysate produced in the present study contains 90.25% protein, 5.84% lipid, and 3.91% ash, and has a molecular weight of 3.76 kDa. Supplementation at 1% hydrolysate in the experimental shrimp diet without fish meal resulted in the highest growth performance associated with increased feed intake, efficient feed and nutrient conversion and retention, enhanced digestive enzyme activities, upregulation of muscle growth- and immune-related genes, and suppression of the gut pro-inflammatory gene. The growth promotion is also linked with a significant increase in muscle mean fiber area, which suggests hypertrophic growth in shrimp. Generally, the supplementation of 1% squid by-product hydrolysate supported the growth of P. monodon fed on a plant protein-based diet without fish meal.