Effect of dietary yeast nucleotide on antioxidant activity, non-specific immunity, intestinal cytokines, and disease resistance in Nile Tilapia

The Effect of Short-Term Artificial Feed Domestication on the Expression of Oxidative-Stress-Related Genes and Antioxidant Capacity in the Liver and Gill Tissues of Mandarin Fish (Siniperca chuatsi)

To investigate whether Mandarin fish developed oxidative stress after being domesticated with artificial feed, we conducted a series of experiments. Oxidative stress is an important factor leading to diseases and aging in the body. The liver integrates functions such as digestion, metabolism, detoxification, coagulation, and immune regulation, while the gills are important respiratory organs that are sensitive to changes in the water environment. Therefore, we used the liver and gills of Mandarin fish as research materials. The aim of this study was to investigate the effects of short-term artificial feed domestication on the expression of oxidative stress genes and the changes in oxidative-stress-related enzyme activity in the liver and gills of Mandarin fish. We divided the Mandarin fish into two groups for treatment. The control group was fed with live bait continuously for 14 days, while the experimental group was fed with half artificial feed and half live bait from 0 to 7 days (T-7 d), followed by solely artificial feed from 7 to 14 days (T-14 d). The experimental results showed that there was no difference in the body weight, length, and standard growth rate of the Mandarin fish between the two groups of treatments; after two treatments, there were differences in the expression of genes related to oxidative stress in the gills (keap1, kappa, gsta, gstt1, gstk1, SOD, and CAT) and in the liver (GPx, keap1, kappa, gsta, gstt1, gr, and SOD). In the liver, GPx activity and the content of MDA were significantly upregulated after 7 days of domestication, while in the gills, SOD activity was significantly upregulated after 7 days of domestication and GPx activity was significantly downregulated after 14 days of domestication. These results suggest that artificial feed domestication is associated with oxidative stress. Moreover, these results provide experimental basic data for increasing the production of aquaculture feed for Mandarin fish.

Effects of yeast extract supplemented in diet on growth performance, digestibility, intestinal histology, and the antioxidant capacity of the juvenile turbot (Scophthalmus maximus)

An 8-week feeding experiment was conducted on the juvenile turbot (Scophthalmus maximus) to evaluate the influence of yeast extract (YE) supplementation in the diet on growth performance, feed utilization, body composition, nutrient digestibility, intestinal histology, and antioxidant capacity. Four experimental diets were formulated with graded levels of yeast extract 0 (YE0), 1% (YE1), 3% (YE3), and 5% (YE5) and fed to turbots (initial body weight: 4.2 ± 0.1 g) with three replicates per diet and 200 fish in each replicate, respectively. The results showed that turbots fed with diets YE1 and YE3 displayed a significantly higher specific growth rate and protein efficiency rate than those fed with diets YE0 and YE5, while the feed conversion ratios in YE1 and YE3 groups were lower than those in YE0 and YE5. Fish fed with diets YE3 and YE5 showed higher body crude protein contents than those in groups YE0 and YE1. The highest apparent digestibility coefficients for dry matter and crude protein, digestive enzyme activities (trypsin, lipase, and amylase), and the height of the intestinal fold were observed in the YE3 group. YE3 treatment displayed a significantly higher superoxide dismutase (SOD) activity than the YE0 group, while the malondialdehyde (MDA) content in YE1 was significantly lower than those in YE0 and YE5. No significant difference was observed in serum physiological and biochemical parameters among all treatments. Overall, appropriate dietary supplementation of the yeast extract could improve the growth performance, digestibility, and antioxidant capacity of the juvenile turbot, and the recommended yeast extract level in the feed is 2.47%.

Effects of Red Yeast (Sporidiobolus pararoseus) on Growth, Innate Immunity, Expression of Immune-related Genes and Disease Resistance of Nile Tilapia (Oreochromis niloticus)

The purpose of this study was to evaluate the effects of red yeast (Sporidiobolus pararoseus) produced from crude glycerol, as a by-product of the biodiesel production process, on the growth, innate immunity, expression of immune-related gene, and resistance of Nile tilapia against challenge with Streptococcus agalactiae. Fish were fed diets supplied with different concentrations of S. pararoseus dried cells at 0.0 (control; T1), 5.0 (T2), 10.0 (T3), and 20.0 (T4) g kg-1 diets for 90 days. The results showed that final body weight, weight gain, and average daily gain were significantly higher in fish fed T3 and T4 compared to the control group (p < 0.05). Likewise, significant (p < 0.05) increases in total carotenoid content, liver superoxide dismutase activity (SOD), and serum lysozyme and albumin were observed in Nile tilapia fed S. pararoseus, with the highest (p < 0.05) values displayed in fish fed the T4 diet. Moreover, up-regulation of IL-1β transcription in Nile tilapia spleen and liver was observed in fish feeding group T4. In a challenge test against S. agalactiae, the fish survival rate was significantly higher in fish fed red yeast compared to the control group (p < 0.05). The highest bactericidal activity found in the T4 group (p < 0.05). However, no significant differences were found in hematology, blood chemical, malondialdehyde (MDA), body chemical composition, organosomatic indices, and myeloperoxidase (p > 0.05) in all treatments. The present results suggested that red yeast S. pararoseus (20.0 g kg-1) can be used as a potential supplementation on growth, immune response, and disease resistance of Nile tilapia.

Immunonutrients and intestinal microbiota: a gap in the literature

The human intestinal microbiota is composed of a wide variety of microorganisms that play an important role in intestinal permeability, digestion, and especially, in the maturation of host's immune system. At the same time, effectiveness of immunomodulatory nutrients is known, especially in situations of stress and in strengthening body's defenses. However, the influence of the use of immunonutrients on microbiota's composition and variability is still poorly investigated. Studies indicate that the use of immunomodulators such as omega 3, glutamine, and arginine, can play a role in its modulation, through the immunological enhancement of the hosts. Therefore, this article sought to concentrate the latest evidence on the influence of the use of the main immunonutrients used in clinical practice on human gut microbiota, and their potential benefits.

Effects of yeast hydrolysate supplementation in low-fish meal diets for pikeperch

Plant proteins have been increasingly used as sustainable substitutes for fish meal (FM) in aquafeeds; however, their high inclusion level compromises fish performance. The objective of this study was to examine whether yeast hydrolysate (YH) supplementation can improve the utilisation of high soybean meal (SM) diet and ameliorate its potential deteriorating impacts in pikeperch (Sander lucioperca). A basal diet was formulated using 44% FM, and four additional diets were produced by replacing 30 or 60% of FM with SM with or without the addition of 2% YH (FM, SM30, SM60, SM30 + YH, and SM60 + YH diets). Each diet was fed to three groups of fish (35.3 ± 0.10 g, 150 fish per group) to visual satiety four times daily for 70 days. Fish growth was not impacted by FM replacement level or YH application. However, SM60 group exhibited markedly higher feed conversion ratio and lower survival rate than those fed the FM- and YH-supplemented diets (P < 0.05). The highest and the lowest protein efficiency ratio values were obtained for the SM30 + YH and SM60 groups, respectively. Whole-body lipid content decreased in SM60 and SM60 + YH groups, and muscle lipid decreased in all the replacement groups. Serum triglyceride and glucose concentrations tended to decrease as FM replacement level increased. The highest alanine aminotransferase, aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities were detected in the SM60 group, and YH addition significantly decreased the AST and LDH activities. Serum lysozyme activity decreased in SM30, SM60 and SM60 + YH groups. Serum myeloperoxidase and antiprotease activities decreased in SM60 group, and YH supplementation improved their activities. No effects of diets were observed on serum antioxidant parameters such as catalase activity and malondialdehyde concentration, and gut morphological indices. Number of goblet cells in midgut decreased by increasing the SM inclusion level and a slight improvement was observed by YH application. These findings suggest that YH supplementation has the potential to support the replacement of up to 60% FM with defatted SM in pikeperch feed without deteriorating growth, feed utilisation, and survival rate. Further, YH incorporation mitigated the damaging impacts of high SM diet on liver function and non-specific immune response.

Effects of dietary nucleotide and yeast cell wall on growth performance, feed utilization, anti-oxidative and immune response of grass carp (Ctenopharyngodon idella)

A 70-day feeding trial was conducted to study the effects of dietary nucleotide, yeast cell wall (containing 20% β -glucan) and their combination on growth performance, feed utilization and immune response of grass carp (Ctenopharyngodon idella) with 69.97 ± 0.05 g of initial body weight. Four isonitrogenous (about 38% crude protein) and isolipidic (about 5% crude lipid) diets were established. Based on the control diet (CD), the other three experimental diets were prepared by adding 0.01% of nucleotide (NT), 0.1% of yeast cell wall (YCW) and NT (0.01%) +YCW (0.1%), respectively. Results showed that no significant difference was found in survival of grass carp ranging from 94.44% to 97.78% among all the groups (P > 0.05). Compared with the control group, weight gain rate, muscle crude protein content, serum protein, trypsin and chymotrypsin activities in midgut, lysozyme and immunoglobulin M in serum significantly increased in fish fed the YCW diet (P < 0.05). The significantly highest weight gain rate, villus height and digestive enzyme activities in midgut and innate immune parameters in serum were found in fish fed the NT + YCW diet (P < 0.05). The gene expressions of β-defensin, hepcidin, il-10 and tgf-β1 in the midgut, and tor and s6k1 in liver significantly increased in fish fed the NT + YCW diet. Meanwhile, the gene expressions of il-1β and tnf-α in the midgut decreased significantly (P < 0.05). The liver histology showed the better development in dietary NT and/or YCW supplemented groups than those in the control group. In conclusion, combination of dietary NT and YCW had significantly synergetic improvements on the growth, feed utilization, digestive enzymes, innate immunity and histology of midgut and liver of grass carp.

Nuclease treatment enhanced the ameliorative effect of yeast culture on epidermal mucus, hepatic lipid metabolism, inflammation response and gut microbiota in high-fat diet-fed zebrafish

As a functional feed additive, yeast cultures are rich in nucleotides, and adding extra nuclease can significantly increase the content of nucleotides in yeast culture. In this experiment, the effects on growth, epidermal mucus, liver and intestinal health of zebrafish were evaluated by supplementing the yeast culture or nuclease-treated yeast culture with a high-fat diet (HFD). One-month-old zebrafish were fed four diets: normal diet (NORM), HFD, yeast culture diet (YC), and nuclease-treated yeast culture diet (YC (N)) for three weeks. Results showed that the complement 4 activity of the epidermal mucus in YC (N) group was significantly higher than those in HFD and YC groups (P < 0.05). The YC and YC (N) significantly reduced the content of hepatic triglyceride caused by HFD (P < 0.05). Moreover, compared with the YC group, the YC (N) significantly increased the expression of lipolysis genes, such as PPARα, PGC1α, ACOX3 (P < 0.05). Compared with the YC group, the YC (N) group significantly increased the expression of liver pro-inflammatory factors TNFα, IL-6, IL-1β and anti-inflammatory factors TGFβ, IL-10 (P < 0.05). The diet YC and YC (N) significantly improved the height of the intestinal villus (P < 0.05). Compared with the HFD group, the YC (N) group significantly increased the expression of intestinal pro-inflammatory factors TNFα, IL-6 and anti-inflammatory factors TGFβ, IL-10 (P < 0.05). The YC (N) group significantly decreased the abundance of intestinal Proteobacteria and Acinetobacter, and increased the abundance of intestinal Actinobacteria, Mycobacterium and Rhodobacter (P < 0.05). In conclusion, compared with the supplement of yeast culture, nuclease treated yeast culture can further alleviate the adverse effects of HFD on liver and intestinal health, and be used as feed additives for the nutritional and immune regulation of fish.

Improvement of hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) by enzyme-digested poultry by-product: Growth performance, amino acid and peptide transport capacity, and intestinal morphology

Background

At present, fish meal (FM) resources are in short supply, and competition for food between humans and animals is becoming increasingly critical. Finding non-grain protein sources that can replace FM is the key to solving the rapid development of aquaculture.

Methods

Seven trial diets were prepared with 0 g/kg (EP0), 30 g/kg (EP3), 60 g/kg (EP6), 90 g/kg (EP9), 120 g/kg (EP12), 150 g/kg (EP15), and 180 g/kg (EP18) of enzyme-digested poultry by-product meal (EPBM) by replacing of FM. A total of 630 hybrid groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) were equally portioned into 21 tanks. At 8:00 and 16:00 each day, groupers were fed until they were full for a cumulative period of 8 weeks.

Results

The results showed that 30 g/kg of EPBM significantly increased the rates of weight gain and special growth (P < 0.05). Significantly higher activities of serum glutamic pyruvic transaminase, glutamic oxaloacetic transaminase, catalase, and superoxide dismutase were observed in the EP3 group (P < 0.05). The categories and numbers of the top 10 dominant bacteria in the phylum and genus levels were not significantly influenced by feed (P > 0.05). In the proximal intestine and distal intestine, there were significantly higher expressions of SNAT3, LAAT1, CAT2, and CAT1 in the EP3 group compared with the EP0 group (P < 0.05). In the EP3 group, the expressions of PepT1, LAAT1, B0, +AT, and CAT2 were significantly increased in MI than those in all other groups (except the EP0 group, P < 0.05).

Conclusion

When FM was replaced by 30 g/kg of EPBM, growth performance, antioxidant capacity, and the ability to transport amino acids and peptides of hybrid grouper were significantly improved.

Nuclease-Treated Stabilized Fermentation Product of Cetobacterium somerae Improves Growth, Non-specific Immunity, and Liver Health of Zebrafish (Danio rerio)

High-fat diets (HFD) are harmful to fish health. Probiotics are commonly utilized to improve fish nutrition metabolism, immune response, and health. Nucleic acids of the probiotic bacterium can be hydrolyzed by nuclease to generate nucleotides. The present study aimed to evaluate the effects of stabilized fermentation product of nuclease-treated Cetobacterium somerae XMX-1 [XMX-1 (N)] on growth, non-specific immunity, and liver health of zebrafish (Danio rerio). Compared to the HFD group, 100 g/kg XMX-1 (N) significantly increased weight gain and decreased feed conversion ratio (FCR). However, 5 or 10 g/kg XMX-1 (N) had no influence on zebrafish growth. In addition, supplementation of 100 g/kg XMX-1 (N) significantly increased lysozyme activity and total antioxidant capacity in skin mucus, and the expression of inflammation related genes interleukin 1 beta (IL-1β), interleukin 10 (IL-10), and interleukin 6 (IL-6) in the gut as well as fatty acid oxidation related genes uncoupling protein 2 (UCP2) and proliferator-activated receptor γ coactivator 1α (PGC1α) in the liver, while decreased the content of hepatic triacylglycerol (TAG) in zebrafish. The gene sequencing, 16S rRNA, showed that 100 g/kg XMX-1 (N) enhanced the relative abundance of Firmicutes while lowered Proteobacteria and Actinobacteria. 10 g/kg XMX-1 (N) significantly increased lysozyme activity and complement component 4 (C4) in skin mucus, and intestinal expression of inflammation-related genes. In the 5 g/kg XMX-1 (N) group, however, only an increase in C4 level in skin mucus was observed. Together, these results reveal that dietary supplementation with nuclease-treated C. somerae XMX-1 (N) has a dose-dependent beneficial effect on fish health.

Assessment of chicken intestinal hydrolysates as a new protein source to replace fishmeal on the growth performance, antioxidant capacity and intestinal health of common carp (Cyprinus carpio)

Promoting circular economy by transforming food residues into alternative high-value protein sources for aquaculture feed is a new way to develop alternative raw materials for fishmeal. This study systematically evaluated the effects of chicken intestinal hydrolysates (CIH) on the intestinal immune health of common carp through growth performance, antioxidant capacity, and intestinal immunity analysis in order to replace fishmeal. Five iso-nitrogenous and iso-lipidic experimental feeds were formulated to replace 0% (CIH-0), 25% (CIH-25), 50% (CIH-50), 75% (CIH-75) and 100% (CIH-100) of the fishmeal with CIH. Each experimental diet was fed to triplicate groups of 30 carp for 8 weeks. The results revealed that no significant differences in the final body weight, weight gain rate, feed coefficient radio, feed intake and protein efficiency ratio were found among the CIH-0, CIH-25, and CIH-50 groups, while the final body weight and weight gain rate in the CIH-75 and CIH-100 groups were significantly decreased and the feed coefficient radio was significantly increased. The aspartate aminotransferase of all CIH groups were significantly decrease, and the total protein, albumin did not differ among the CIH-0, CIH-25, CIH-50, and CIH-75 groups. The trypsin content was significantly increased in the CIH-75 and CIH-100 groups. No significant differences in the antioxidant index (catalase, glutathione peroxidase and malonaldehyde) were found among all CIH groups compared with the CIH-0 group. The expression levels of pro-inflammatory cytokines IL-1β and TNF-α were significantly down-regulated in the CIH-50 group and anti-inflammatory cytokines IL-10 and TGF-β2 were significantly up-regulated in the CIH-50 and CIH-75 groups. No significant differences in the expression levels of claudin-1, claudin-7 and claudin-11 were observed between the CIH-0 and CIH-50 groups, while the expression levels of ZO-1, occludin and MLCK were significantly up-regulated in the CIH-50 group compared with the CIH-0 group. The expression level of claudin-1 was down-regulated in the CIH-75 and CIH-100 groups. Hence, the study demonstrated the potential of CIH as a novel protein source for replacing fishmeal, and replacing 50% of fishmeal with CIH did not significantly influence the growth performance, immune responses, and intestinal barrier of common carp (Cyprinus carpio).

Effects of yeast hydrolysate on growth performance, serum parameters, carcass traits, meat quality and antioxidant status of broiler chickens

BACKGROUND

Yeast hydrolysate (YH) has multiple salutary biological activities. Nevertheless, the application of YH in broiler production is limited. This study was conducted to evaluate the protective effects of YH derived from Saccharomyces cerevisiae by exploring growth performance, serum parameters, organs relative weight, carcass traits, meat quality and antioxidant status of broilers.

RESULTS

Supplementing YH linearly and quadratically improved (P < 0.05) body weight gain and gain-to-feed ratio compared to that in the control group. Triglycerides, low-density lipoprotein cholesterol and total cholesterol in serum, the decline in pH and cooking loss of breast muscle, and malonaldehyde concentration in serum and liver were decreased linearly and/or quadratically by YH (P < 0.05), whereas high-density lipoprotein cholesterol in serum, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in serum, GSH-Px activity in liver, glutathione content in serum and liver, eviscerated yield rate and chest muscle yield, and the relative weight of spleen and liver were linearly and/or quadratically increased (P < 0.05). Moreover, YH enhanced the mRNA levels of nuclear factor erythroid 2-related factor 2, heme oxygennase-1 (HO-1), GSH-Px1 and SOD1 (linear and/or quadratic, P < 0.05).

CONCLUSION

Dietary YH beneficially affected growth performance, serum parameters, organ relative weight, carcass traits, meat quality and antioxidant status in broilers, indicating its potential application as a promising feed additive in broiler production. © 2021 Society of Chemical Industry.

Nutritional Modulation of the Immune Response Mediated by Nucleotides in Canine Leishmaniosis

Leishmaniasis is an emerging, uncontrolled, and neglected zoonotic disease. Climate change is contributing to its ongoing global expansion. The dog is the main reservoir; hence the importance of implementing effective treatment, prevention, and control measures in this animal species to protect public health. However, although the standard treatment for canine leishmaniosis (CanL) is effective, it does not provide full parasitological clearance, and side effects and drug resistance have been described. The host's immune system plays a key role in the establishment and evolution of leishmaniasis. Dietary nucleotides modulate the immune response and, given their reported efficacy and safety in sick and clinically healthy Leishmania-infected dogs and because they represent a sustainable option with no associated side effects or resistance, they could be included within the prevention, treatment, and control strategies for leishmaniasis. This article briefly summarizes the scientific literature on CanL management, including unresolved issues, and reviews the scientific evidence on immunomodulatory effects of dietary nucleotides in different animal species. It also proposes a CanL management algorithm, including nucleotides. It is concluded that nutritional modulation of the immune response with nucleotides can contribute to better management of leishmaniasis following a One Health approach, especially in the COVID-19 era.

RNA form baker's yeast cultured with and without lipopolysaccharide (LPS) modulates gene transcription in an intestinal epithelial cell model, RTgutGC from rainbow trout (Oncorhynchus mykiss)

The objective of this study was to evaluate if the intestinal RTgutGC cell line could be suitable for research on dietary ingredients and their function as modulators of inflammation during lipopolysaccharide (LPS) induced stress. The RTgutGC cells cultured together with RNA from baker's yeast, reached confluency after 72 h. The cells were grown in either compete L-15 (CM) or nutrient deprived L-15 (DM). Then, the RTgutGC cells were exposed to LPS or RNA from baker's yeast, either alone, or in combination, in CM or DM. All cultures were harvested following LPS challenge for 48 h and 72 h. LPS induced transcription of Interleukin 1β (IL-1β), Interleukin -8 (IL-8), Toll like receptor 3 (TLR3), interferon regulating factor 3 (irf3), Nuclear factor ĸβ (NFĸβ), one of the multidrug transporters, ABCC2, and glutamine synthase 1 (GLS01) in RTgutGC cells at one or both sampling points (48 h and/or 72 h post LPS challenge). RNA from baker's yeast in culture alone, (cultured 120 h and 144 h with RTgutGC cells and harvested at the respective LPS sampling points) induced transcription of INF1, TNFα and ticam/trif, not induced by LPS. In addition, RNA from baker's yeast affected IL-1β, TLR3, irf3 and NFĸβ, comparable to the responses triggered by LPS. RNA from baker's yeast alone did not affect ABCC2 or GLS01 transcriptions in this set up. So, LPS and RNA from baker's yeast affects distinct but also common gene transcripts in this intestinal cell line. Culturing RTgutGC cells in DM, adding a combination of LPS and RNA from baker's yeast, reduced IL-1β transcription compared to cells grown in CM, 48 h and 72 h post LPS challenge. Also, in RTgutGC cells, grown in DM, the LPS induced transcription of ABCC2 declined, measured 48 h post LPS challenge. Possibly indicating that optimal transcription of IL-1β and ABBC2 in RTgutGC cells, cultured over time, requires access of adequate nutrients under stressful condition. RNA from baker's yeast induced INF1 transcription in the RTgutGC cells, regardless if the medium was complete or deprived of nutrients. However, culturing RTgutGC cells in DM enriched with RNA from baker's yeast for a longer period of time (120 h, 144 h), seemed beneficial for INF1 transcription.

Nano spirulina dietary supplementation augments growth, antioxidative and immunological reactions, digestion, and protection of Nile tilapia, Oreochromis niloticus, against Aeromonas veronii and some physical stressors

The current study evaluated the effects of nano delivery of Spirulina platensis on growth performance, digestive enzymes, and biochemical, immunological, and antioxidative status, as well as resistance to Aeromonas veronii and some physical stressor challenges in Nile tilapia, Oreochromis niloticus. Three experimental fish groups (n = 270) with mean weights of 26 ± 0.30 g and mean lengths of 10 ± 0.5 cm were used; the first additive-free basal diet served as the control group, whereas the following two groups were supplemented with spirulina nanoparticles (SPNP) at 0 (control), 0.25, and 0.5%/kg diet for 4 weeks. Following the feeding trial, fish were challenged with hypoxia, cold stresses, and pathogenic bacteria (A. veronii) infection (9 × 10⁸ CFU/ml). SPNP supplementation, especially 0.5%, (p < 0.05) significantly increased growth performance (specific growth rate % day^-1, feed conversion ratio, and length gain rate %), immunological (plasma lysozyme and liver nitrous oxide) antioxidants (superoxide dismutase, catalase, and glutathione peroxidase in liver), biochemical (aspartate aminotransferase, alanine transaminase, glucose, and cortisol concentrations in plasma) assays, and digestive enzymes (lipase and amylase in plasma). The expression of liver's heat shock protein 70 (HSP70) and interleukin 1, beta (IL-1β) genes showed a significant upregulation outline of 0.5% SPNP > 0.25% SPNP > 0% SPNP compared with the control. Protection in the incorporated fish groups exposed to A. veronii was 100% compared with the control group, which showed 50% cumulative mortalities. In conclusion, dietary SPNP supplementation improved growth performance, antioxidant activity, immune response, digestive enzymes, related gene expression, and resistance of Nile Tilapia to hypoxia, cold, and A. veronii infection. Thus, SPNP could be used as a natural therapy for controlling those stressors.

The effects of dietary yeast hydrolysate on growth, hematology, antioxidant enzyme activities and non-specific immunity of juvenile Nile tilapia, Oreochromis niloticus

The present study was aimed to compare and evaluate the impacts of supplemented diets with different yeast hydrolysate (YH) levels on growth performance, body composition, hematological characteristics, antioxidant enzyme activities, and non-specific immunity (intestinal cytokines) of juvenile Nile tilapia (Oreochromis niloticus). Three isonitrogenous (protein, 33%) and isolipidic (lipid, 6%) experimental diets supplemented graded levels of YH (0% for control; 1% and 3% as tested diets) were fed to juvenile Nile tilapia. A total of 240 fish with initial body weight averaging 3.5 ± 0.02 g were randomly divided into three groups with four replicates per group and 20 fish for each replicate. For apparent satiation, the fish were fed twice daily during eight weeks. The results showed no significant difference in survival among all treatments. The fish fed the diet containing 1% yeast hydrolysate had significantly elevated weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) compared to the control group and lower feed conversion ratio (FCR). The fish fed 1% and 3% YH showed higher glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT) activity and a significantly lower malondialdehyde (MDA) level in the liver than the control group, indicating enhancement of the anti-oxidant status. Serum lysozyme activity was significantly increased in the diet having 1% and 3% yeast hydrolysate supplementation groups, suggesting an improvement influence on the non-specific immune response. The expression of IL-1β, IL-10, TNF-α, TGF-β2, ALP and TLR2 was significantly elevated in fish fed the diet containing 1% YH. In conclusion, dietary supplementation with 1% yeast hydrolysate improves growth performance, and feed utilization enhances the antioxidant status and exerts an adequate stimulus on the non-specific immunity (intestinal cytokines) of Nile tilapia.

Efficacy of purified nucleotide supplements on the growth performance and immunity of hybrid striped bass Morone chrysops x Morone saxatilis

Fishmeal is being increasingly replaced in aquatic animal diets with alternative plant protein feedstuffs such as soybean meal which have lower concentrations of nucleotides; therefore, supplemental sources of exogenous nucleotides in diets could become increasingly important. A 9-week feeding trial was conducted with triplicate groups of juvenile hybrid striped bass (average initial body weight ± standard deviation, 5.6 ± 0.1 g) to determine the effects of supplementing single purified nucleotides on the growth performance and immune parameters. The basal diet, which utilized menhaden fishmeal (25%) and soybean meal (75%) as protein sources, contained 44% protein, 10% lipid and an estimated digestible energy level of 3.5 kcal g^-1. Single additions of 5'- adenosine monophosphate (AMP), 5'- uridine monophosphate (UMP), 5'- cytidine monophosphate (CMP), 5'- guanosine monophosphate (GMP), and 5'- inosine monophosphate (IMP) disodium salts (Chem-Impex International, Wood Dale, Illinois, USA) were evaluated with each nucleotide added to the basal diet at 0.5% of dry weight at the expense of cellulose. A positive control diet in this trial was a diet containing 5'- AMP from Sigma-Aldrich also supplemented at 0.5% by weight. Results showed significantly (P < 0.05) improved weight gain between fish fed AMP-supplemented diets and the basal diet. No statistical significance (P > 0.05) was detected in whole-body proximate composition and protein retention of fish fed any of the dietary treatments. The respiratory burst of whole blood phagocytes also was significantly (P < 0.05) higher in fish fed the AMP Sigma diet compared to the other dietary treatments. Dietary IMP and AMP both significantly (P < 0.05) enhanced the capacity of isolated phagocytes to generate extracellular superoxide anion compared to all other dietary treatments. No significant differences were seen in other innate immune parameters such as plasma lysozyme, total plasma protein, and total immunoglobulin. The ability of isolated B lymphocytes to proliferate prompted by the presence of lipopolysaccharides was significantly (P < 0.05) different among dietary treatments with the highest simulation index observed in fish fed the diets containing AMP Sigma and UMP; however, it was not significantly different from that of fish fed the basal diet. Based on all the measured responses, it is concluded that AMP at 0.5% of diet had the most positive influence on growth performance and innate immunostimulation of hybrid striped bass.

Transcriptome-based evaluation and validation of suitable housekeeping gene for quantification real-time PCR under specific experiment condition in teleost fishes

Quantification real-time PCR (qRT-PCR) is a common method in analysis of gene expression, but the stable reference genes for the normalization analysis have not been appreciated before identifying expression pattern of genes in teleost fishes. In this study, we selected eight candidate reference genes (18S, Actin, EF-1α, 40S, B2M, TUBA, UBCE and GAPDH) basing on transcriptome analysis and the traditional housekeeping genes, and analyzed the stability of the reference genes in spleen, head kidney and head kidney leukocytes (HKL) after pathogen challenge in Schizothorax prenanti (S. prenanti). Three common programs (geNorm, NormFinder and Bestkeeper) were used to evaluate the stability of the candidate reference genes. Two reference genes, Actin and EF-1α presented higher stability, while 18S and GAPDH were the lower stable genes, both in in vitro and in vivo. An important immune gene, toll-like receptor 22a (TLR22a), was selected to validate the stability of the proposed reference genes (Actin and EF-1α) across different experiment treatments. The results reveal that Actin and EF-1α are quite suitable reference genes for the normalization analysis. Otherwise, using the most stable gene Actin to validate the reliable of transcriptome data showed the high correlation between the fold change of transcriptome data and qRT-PCR data. In conclusion, our study not only acquired the suitable reference gene for the qRT-PCR assay under specific experiment condition, but also provided a comprehensive method to evaluate and validate the reference gene based on transcriptome analysis in teleost fishes.

Effects of dietary hydrolyzed yeast (Rhodotorula mucilaginosa) on growth performance, immune response, antioxidant capacity and histomorphology of juvenile Nile tilapia (Oreochromis niloticus)

An 8 weeks feeding experiment was conducted to evaluate the effects of dietary supplementation with hydrolyzed yeast (HY) (Rhodotorula mucilaginosa) on growth performance, hematological parameters, immune response and antioxidant ability of juvenile Nile tilapia. Five isonitrogenous and isolipidic diets (32% protein and 4% lipid) with different levels (0%, 0.125%, 0.25%, 0.5%, 1%) of HY were formulated. Each diet was randomly assigned to quadruplicate groups of fish (initial body weight 19.1 ± 0.01 g). Results indicated that significantly higher specific growth rate (SGR) and lower feed conversion rate (FCR) were obtained in fish fed 1% HY diet than that of fish fed 0% HY diet (P < 0.05). Fish fed 0.25% HY diet showed the lowest value of hepatopancreas somatic indices (HSI) and significantly lower than that of fish fed 0% HY diet (P < 0.05). Meanwhile, protein and ash in the whole-body content of fish fed 1% HY diet was significantly higher than that of fish fed 0%-0.5% HY diets. Serum immunological parameters showed that the lysozyme (LZM) activity and Complement C3 content were significantly increased by dietary supplementation of 0.5%-1% HY (P < 0.05). However, dietary supplementation with 0.125%-1% HY significantly decreased the activity of myeloperoxidase (MPO) (P < 0.05). Antioxidant status in serum and liver was significantly enhanced by dietary supplementation of 0.25%-1% HY through the remarkably improved superoxide dismutase (SOD) activity both in serum and liver, the raised total antioxidative capacity (T-AOC) of serum as well as the notably reduced malondialdehyde (MDA) content in the liver (P < 0.05). However, T-AOC in the liver was not significantly influenced among all diet treatments (P > 0.05). Villi height and intraepithelial lymphocytes (IEFs) of mid-intestine were significantly higher in fish fed 0.5%-1% HY diets (P < 0.05). The challenge test demonstrated the enhanced protection against Streptococcus iniae strain by the obtained higher cumulative survival rate. In conclusion, dietary supplementation of 1% HY could maintain the better growth performance, nutrient composition as well as immune response and antioxidant capacity for juvenile Nile tilapia.

Effects of curcumin on haematological values, immunity, antioxidant status and resistance of rainbow trout (Oncorhynchus mykiss) against Aeromonas salmonicida subsp. achromogenes

The present study was conducted to evaluate the effects of various levels of dietary curcumin on growth performance, haematological values, immunity and protection against Aeromonas salmonicida subsp. achromogenes infection in rainbow trout, Oncorhynchus mykiss. Fish were fed with diets containing different levels of curcumin; 0% (C), %1 (E1), %2 (E2) and %4 (E3), as treatment groups. After 8 weeks of feeding, the growth performance [weight gain (WG), specific growth rate (SGR) and feed conversion ratio (FCR)], haematological values [the red blood cell (RBC) count, haemoglobin (Hb) concentration, haematocrit (Ht) level and erythrocyte indices: mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC)], various immune parameters [white blood cell (WBC) count, oxidative radical production (nitroblue tetrazolium (NBT) assay), phagocytic activity (PA) and phagocytic index (PI), total protein (TP) and immunoglobulin M (IgM) levels, serum bactericidal (BA), lysozyme (LYZ) and myeloperoxidase (MPO) activities] and antioxidant capacity [tissue malondialdehyde (MDA) levels and superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities] were analysed. In addition, fish were challenged by Aeromonas salmonicida subsp. achromogenes and survival rate was recorded for 14 days. The results indicated that the growth performance was significantly influenced by the dietary curcumin levels, the maximal WG and SGR occurred at fish fed the diet containing 2% curcumin. Fish fed the diet containing curcumin had lower FCR than those fed the control diet. The RBC count, Hb concentration, and Ht level increased in the groups fed with curcumin when compared with the control group. However, there were no significant differences in the MCV, MCH and MCHC values among experimental groups. All the chosen immune parameters were enhanced in the groups fed diets containing curcumin. Also, the relative percentage survivals were higher in the groups fed with curcumin, especially in the E2 group, compared to the control. The dietary curcumin stimulated the SOD, CAT and GSH-Px activities in liver, head kidney and spleen as compared to the control group; however, a reverse trend was observed in the MDA levels of tissues. The highest values for haematological, immunological (except TP level of E3 group) and antioxidant parameters were found in the E2 group. These results collectively suggest that curcumin can be used in aquaculture to improve the growth, haematological values, immune responses, antioxidant capacity and disease resistance of rainbow trout, O. mykiss.

Dietary nucleotides can directly stimulate the immunity of zebrafish independent of the intestinal microbiota

In this study, we firstly tested the effects of dietary nucleotides on the disease resistance and innate immunity of zebrafish. Further, we investigated the role of intestinal microbiota in the nucleotides-induced immunostimulatory effect by using a germ-free zebrafish model and microbiota transfer technique. Fish were fed control or nucleotides (NT)-supplemented diets (at 0.05%,0.1%, 0.15% or 0.2%, m/m) for 4 weeks, followed by immersion challenge with Aeromonas hydrophila NJ-1. The results showed that 0.1% NT group enhanced the resistance of zebrafish against A. hydrophila infection. We further observed that the relative expressions of mucin, claudin16, occlusin1, hepcidin, defensin beta-like, myeloperoxidase (Mpo), and serum amyloid A (Saa) increased in the 0.1% NT group compared with control (P < 0.05), indicating that dietary nucleotides enhanced the physical barrier and mucosal immunity in the intestine of zebrafish. Moreover, ROS level in the head kidney was significantly increased in NT fed zebrafish versus control (P < 0.05), indicating enhanced systematic immunity. Furthermore, dietary NT significantly elevated the relative expressions of mpo, saa and the ROS activity in germ-free zebrafish, while germ-free zebrafish colonized with NT-altered microbiota had no significant difference in the relative expressions of mpo, saa and the ROS activity compared with the control microbiota-colonized fish, suggesting that the immunostimulatory effect of dietary NT is mediated by direct action of NT and does not involve the microbiota. Consistently, dietary NT can protect germ-free zebrafish from pathogenic infection, whereas germ-free zebrafish colonized with NT microbiota showed no difference in disease resistance compared with control microbiota colonized counterparts. Together, these results indicated that the immunostimulatory and disease protection effect of dietary nucleotides in zebrafish was mediated by direct action of the nucleotides, and does not involve the intestinal microbiota.

Preventive Effect of YGDEY from Tilapia Fish Skin Gelatin Hydrolysates against Alcohol-Induced Damage in HepG2 Cells through ROS-Mediated Signaling Pathways

According to a previous study, YGDEY from tilapia fish skin gelatin hydrolysates has strong free radical scavenging activity. In the present study, the protective effect of YGDEY against oxidative stress induced by ethanol in HepG2 cells was investigated. First, cells were incubated with YGDEY (10, 20, 50, and 100 μM) to assess cytotoxicity, and there was no significant change in cell viability. Next, it was established that YGDEY decreased the production of reactive oxygen species (ROS). Western blot results indicated that YGDEY increased the levels of superoxide dismutase (SOD) and glutathione (GSH) and decreased the expression of gamma-glutamyltransferase (GGT) in HepG2 cells. It was then revealed that YGDEY markedly reduced the expressions of bax and cleaved-caspase-3 (c-caspase-3); inhibited phosphorylation of Akt, IκB-α, p65, and p38; and increased the level of bcl-2. Moreover, the comet assay showed that YGDEY effectively decreased the amount of ethanol-induced DNA damage. Thus, YGDEY protected HepG2 cells from alcohol-induced injury by inhibiting oxidative stress, and this may be associated with the Akt/nuclear factor-κB (NF-κB)/mitogen-activated protein kinase (MAPK) signal transduction pathways. These results demonstrate that YGDEY from tilapia fish skin gelatin hydrolysates protects HepG2 cells from oxidative stress, making it a potential functional food ingredient.