Inclusion of Pediococcus acidilactici as probiotic candidate in diets for beluga (Huso huso) modifies biochemical parameters and improves immune functions

Feeding Strategies with Multi-Strain Probiotics Affect Growth, Health Condition, and Disease Resistance in Asian Seabass (Lates calcarifer)

A 16-week feeding trial was done to examine the impacts of continuous feeding (CF) or pulse-feeding (PF) of multi-strain probiotics on Asian seabass (Lates calcarifer, 30.0 ± 0.1 g) juveniles. In this study, three different multi-strain probiotic mixtures were added to a basal diet, including (I) a mixture of different strains of Lactobacillus plantarum, (II) a mixture of the first probiotic (I) + L. delbrueckii sub bulgaricus, L. rhamnosus and L. acidophilus, and (III) a mixture of the second probiotic (II) + two quorum quenching (QQ) bacteria (Bacillus thuringiensis QQ1 and B. cereus QQ2). CF (every day) or PF (every two weeks) strategies were applied for using the abovementioned probiotics to design seven experimental groups including C (control, without probiotics), CF-I (continuous feeding of fish with the probiotic mixture I), CF-II (continuous feeding of fish with the probiotic mixture II), CF-III (continuous feeding of fish with the probiotic mixture III), PF-I (pulse-feeding of fish with the probiotic mixture I), PF-II (pulse-feeding of fish with the probiotic mixture II), and PF-III (pulse-feeding of fish with the probiotic mixture III). Four hundred and twenty fish were stocked into 21 circular polyethylene tanks with 220 L volume (20 fish/tank). Each dietary treatment had three replicates. Tanks were supplied with seawater (temperature = 30.5 °C, salinity = 45 g L-1) in a flow-throw system. Fish in CF-I, CF-II, and CF-III had higher growth rate (ca. 113-145%) and better feed conversion ratio than fish fed C and PF-I (P < 0.05). Fish in the CF-III group had the highest protease activity. Continuous feeding strategy resulted in a higher amount of glutathione and catalase activities in both the liver and plasma as well as higher superoxide dismutase activity in the liver of fish. Pulse-feeding strategy resulted in lower plasma lactate dehydrogenase and aspartate aminotransferase levels than the CF strategy. Regardless of feeding strategy, different probiotic mixtures significantly enhanced blood hemoglobin and hematocrit levels compared to the control. Continuous feeding with the multi-strain probiotics resulted in a higher survival rate against Vibrio harveyi than the PF method. Continuous feeding induced higher mRNA transcription levels of granulocyte-macrophage colony-forming cells and interleukin 10 genes in the gut of fish than PF strategy. In conclusion, continuous feeding with multi-strain probiotics is better than pulse-feeding on growth, feed utilization, antioxidant capacity, and the gut's immune-related genes and led to higher resistance of L. calcarifer in challenge with V. harveyi.

Fructooligosaccharide and Bacillus subtilis synbiotic combination promoted disease resistance, but not growth performance, is additive in fish

Species diversification from major to minor carps for their sturdiness and initial higher growth, and also a quest for antibiotic-free aqua farming in the subcontinent, mandates search for and evaluation of alternatives. An experiment was performed to investigate the potential of fructooligosaccharide (FOS) and Bacillus subtilis (BS) (alone or as synbiotics) in promoting growth and immunity against infections in Labeo fimbriatus fingerlings. Six iso-nitrogenous and iso-lipidic diets containing combinations of two levels of FOS (0% and 0.5%) and three levels of BS (0, 104, 106 CFU/g feed) were fed to fish for 60 days. At the end of the feeding trial, twenty-four fish from each group were injected intra-peritoneally with pathogenic strain of Aeromonas hydrophila O:18 to test the immunoprotective efficacy of the supplements against bacterial infection. BS, but not FOS, significantly improved (P < 0.05) growth and feed utilisation attributes like percentage weight gain (PWG), specific growth rate (SGR) and feed conversion ratio (FCR). There were interactive effects of FOS and BS on PWG, SGR and FCR; however, the effects were not additive in nature. These beneficial effects of BS, alone or in combination with FOS, were corroborated by increased protease activity, microvilli density and diameter and number of goblet cells. Overall beneficial effects of FOS and BS included improved erythrocyte (RBC), hemoglobin (Hb), total protein and globulin levels. Total leucocyte (WBC) count and immunological parameters like respiratory burst activity of leucocytes (NBT reduction), lysozyme activity, albumin: globulin ratio and post-challenge survival were significantly improved by both FOS and BS, and their dietary combination yielded the highest improvement in these parameters. Synergistic effects of FOS and BS as dietary supplements indicate that a combination of 106 CFU/g BS and 0.5% FOS is optimal to improve growth, feed utilisation, immune functions, and disease resistance in L. fimbriatus fingerlings.

Combined effects of Spirulina platensis and Pediococcus acidilactici on the growth performance, digestive enzyme activity, antioxidative status, and immune genes in zebrafish

The combined effects of Spirulina platensis (SP) and Pediococcus acidilactici (PA) on growth performance, digestive enzyme activity, antioxidative status, and immune genes in zebrafish were investigated in the present study. Four experimental diets were designed: control and three test diets mixed with SP at 2.5%, PA at 107 CFU/g, or a combination of 2.5% SP and 107 CFU/g PA. After 56 days, fish treated with PA and SP mixture had higher final weight, weight gain, SGR, and lower FCR than fish fed the control and SP diets (P<0.05). The results also illustrated that fish fed PA, SP, and their mixture had higher (P<0.05) protease and amylase activities than the control. The lipase activity was significantly higher in fish treated with PA or the mixture of PA and SP than in the control (P<0.05). The alternative complement pathway (ACH50) and lysozyme activity in the mucus samples of fish treated with PA or both PA and SP were significantly higher (P<0.05) than in fish treated with the control and SP diets. The total immunoglobulin level in the skin mucus was significantly higher (P<0.05) in fish fed PA than in control. In the body homogenates samples, the lysozyme activity and immunoglobulin levels were markedly higher (P<0.05) in fish treated with the mixture of PA and SP than in the control. The dietary PA and SP diet mixture improved the glutathione peroxidase, superoxide dismutase, and total antioxidative capacity. The expression of IL-1β and IL-8 genes in fish treated with PA or the mixture of PA and SP was significantly higher (P<0.05) than in fish treated with the control or SP diets. Fish treated with PA, SP, or both PA and SP had marked (P<0.05) upregulation of the lysozyme gene expression. In conclusion, the mixture of S. platensis and P. acidilactici is more effective than using each individually for improving the growth performance, digestive enzyme activity, and the immune and antioxidative capacity of zebrafish.

Meta-analysis and health risk assessment of toxic heavy metals in muscles of commercial fishes in Caspian Sea

Heavy metals from contaminated seafood can have serious consequences for human health. Several studies on the amount of heavy metals in Caspian Sea fish have been conducted to ensure their food safety. This meta-analysis aimed to investigate the levels of five toxic heavy metals; Lead (Pb), Cadmium (Cd), Mercury (Hg), Chromium (Cr), and Arsenic (As) in muscles of commercial fishes of the Caspian Sea with assessing their health risk of developing oral cancer in terms of fish collection place and fish type. A systematic search was performed, and the random effect model was applied for meta-analysis. Finally, 14 studies with 30 different sets of results were included. Our results showed that the pooled estimates for Pb, Cd, Hg, Cr, and As were 0.65 mg/kg (0.52, 0.79), 0.08 mg/kg (0.07, 0.10), 0.11 mg/kg (0.07, 0.15), 1.77 mg/kg (1.26, 2.27), and 0.10 mg/kg (- 0.06, 0.26) respectively. The levels of Pb and Cd were higher than their (FAO/WHO) maximum limits. The Estimated Daily Intake (EDI) of Pb and Cd in Mazandaran, and Hg in Gilan were more than Total Daily Intake (TDI) limits. The consumers' non-carcinogenic risk (THQ) for Hg in Mazandaran and Gilan, and As in Gilan, was unsafe. Carcinogenic risk (CR) for Cr and Cd in all three provinces, and for As in Mazandaran and Gilan, was greater than 1*10 - 4 and was unsafe. The lowest and highest risk levels of oral cancer were for Rutilus kutum and Cyprinus carpio respectively.

Assessing the Influence of Dietary Pediococcus acidilactici Probiotic Supplementation in the Feed of European Sea Bass (Dicentrarchus labrax L.) (Linnaeus, 1758) on Farm Water Quality, Growth, Feed Utilization, Survival Rate, Body Composition, Blood Biochemical Parameters, and Intestinal Histology

The probiotics are being used as ecofriendly and bioremediation tools for developing sustainability to aquaculture. The present study was conducted to explore the practical capability of using dietary lactic acid bacteria (Pediococcus acidilactici) probiotics and see how its dose variation affected the water quality, growth performance, survival rate, body composition, blood biochemical parameters, and intestinal histology of European sea bass (Dicentrarchus labrax L.). A total of 120 fingerlings with an initial weight of $9\pm 0.2$  g were divided into four groups, each with three replicates. The feeding experiment lasted for 60 days. In addition to the control (without probiotics) (T0), fish were fed diets containing (T1) 2.0, (T2) 2.5, and (T3) 3.0 g of probiotics per kg of diet twice a day. When compared to the control, sea bass fed probiotic-supplemented diets had significantly higher growth parameters, fish body “crude lipid,” and villi height ( $p<0.05$ , $p<0.01$ , and $p<0.001$ ). The P. acidilactici probiotic treatments improved survival rate, feed conversion ratio, body composition, and blood biochemical markers, but not statistically significant ( $p>0.05$ ). Also, in regard to water quality, P. acidilactici drastically reduced ammonia and pH levels. In this experiment, fish fed with a dosage of 3.0 g of this commercial probiotic per kg of probiotics performed better. The study found that including probiotics in the diets of European sea bass improved growth, body composition, survival rate, blood biochemical markers, intestinal histology, and some water quality parameters.

The Effect of Lactococcus lactis subsp. lactis PTCC 1403 on the Growth Performance, Digestive Enzymes Activity, Antioxidative Status, Immune Response, and Disease Resistance of Rainbow Trout (Oncorhynchus mykiss)

The effect of Lactococcus lactis subsp. lactis strain PTCC 1403 as a potential probiotic was investigated on the growth, hematobiochemical, immune responses, and resistance to Yersinia ruckeri infection in rainbow trout. A total of 240 fish were distributed into 12 fiberglass tanks representing four groups (× 3 replicates). Each tank was stocked with 20 fish (average initial weight: 11.81 ± 0.32 g) and fed L. lactis subsp. lactis PTCC 1403 at 0 (control, T0), 1 × 10⁹ (T1), 2 × 10⁹ (T2), and 3 × 10⁹ (T3) CFU/g feed for 8 weeks. The results showed enhanced protein efficiency ratio and reduced feed conversion ratio in the fish-fed T2 diet. Further, fish-fed T2 and T3 diets showed a significantly higher survival rate than the control (p < 0.05). Trypsin, lipase, and protease activities were increased in fish-fed L. lactis subsp. lactis PTCC 1403 compared to the control (p < 0.05). Fish fed with a T2 diet showed significantly (p < 0.05) lower glucose content than other groups. The blood lysozyme activity and IgM showed significantly (p < 0.05) higher values in fish-fed T2 and T3 diets than in other groups. The antioxidative responses were increased in fish-fed T2 and T3 diets (p < 0.05). After 7 days post-Y. ruckeri challenge, the cumulative mortality rate showed the lowest value in fish fed with T1 and T2 diets, while the highest value was recorded in the control group. In conclusion, the results revealed beneficial effects of L. lactis subsp. lactis PTCC 1403 on the feed efficiency, immune response, and resistance to Y. ruckeri infection in rainbow trout.

Scope of Archaea in Fish Feed: a New Chapter in Aquafeed Probiotics?

The outbreak of diseases leading to substantial loss is a major bottleneck in aquaculture. Over the last decades, the concept of using feed probiotics was more in focus to address the growth and health of cultivable aquatic organisms. The objective of this review is to provide an overview of the distinct functionality of archaea from conventional probiotics in nutrient utilization, specific caloric contribution, evading immune response and processing thermal resistance. The prime limitation of conventional probiotics is the viability of desired microbes under harsh feed processing conditions. To overcome the constraints of commercial probiotics pertaining to incompatibility towards industrial processing procedure, a super microbe, archaea, appears to be a potential alternative approach in aquaculture. The peculiarity of the archaeal cell wall provides them with heat stability and rigidity under industrial processing conditions. Besides, archaea being one of the gut microbial communities participates in various health-oriented biological functions in animals. Thus, the current review devoted that administration of archaea in aquafeed could be a promising strategy in aquaculture. Archaea may be used as a potential probiotic with the possible modes of functions and advantages over conventional probiotics in aquafeed preparation. The present review also provides the challenges associated with the use of archaea for aquaculture and a brief outline of the patents on archaea to highlight the various use of archaea in different sectors.

Effects of Potential Probiotic Enterococcus casseliflavus (EC-001) on Growth Performance, Immunity, and Resistance to Aeromonas hydrophila Infection in Common Carp (Cyprinus carpio)

The effects of different levels of dietary Enterococcus casseliflavus (EC-001), as a potential probiotic, were investigated on the growth performance, hemato-biochemical parameters, immune responses, and resistance to Aeromonas hydrophila infection in common carp (Cyprinus carpio) fingerlings. Accordingly, fish (N = 720; 12.0 ± 0.5 g) were distributed into four treatments receiving different dietary levels of E. casseliflavus, EC-001 (0 [control], 1 × 10⁷, 10⁸, and 10⁹ CFU g^-1 feed), for 8 weeks. The fish fed with a diet containing 10⁹ CFU g^-1 showed the highest weight gain and specific growth rate, along with the lowest feed conversion ratio, compared with the control group (P < 0.05). Red and white blood cells, hemoglobin, hematocrit, neutrophils, and monocytes significantly increased in the fish fed with 1 × 10⁸ and 10⁹ CFU g^-1 (P < 0.05). Dietary inclusion of 1 × 10⁸ and 10⁹ CFU g^-1 significantly increased serum total protein, albumin, and immunoglobulin content (P < 0.05). Feeding the fish with 1 × 10⁹ CFU g^-1 resulted in a significant increase in serum and skin mucus lysozyme activity compared with the other groups (P < 0.05). Complement component 3 and skin mucus protease activity were also significantly higher in all the fish treated with dietary E. casseliflavus (EC-001) compared with the control group (P < 0.05). The cumulative mortality in the treated fish was lower (ranging from 10 to 22%) than the control group (31%) after challenging the fish with A. hydrophila infection, while the fish fed with E. casseliflavus (EC-001) at 1 × 10⁹ CFU g^-1 exhibited the lowest mortality rate (P < 0.05). In conclusion, our results revealed the potential probiotic effects of E. casseliflavus (EC-001) for enhancing growth performance, immunity, and disease resistance of common carp.

The effect of Pediococcus acidilactici on mucosal immune responses, growth, and reproductive performance in zebrafish (Danio rerio)

A completely randomized experimental design carried out to investigate the effects of different levels of Pediococcus acidilactici (PA) including 0 (basal diet as a control diet), 1 × 10⁶, 2 × 10⁶, 4 × 10⁶, and 8 × 10⁶ colony-forming unit (CFU) per gram of the diet for 60 days on the mucosal immunity responses, growth, and reproductive performance, in zebrafish, Danio rerio (with mean weigh ± SE: 120 ± 10 mg). The obtained results revealed that the best growth and reproduction indices were related to the concentration of 4 × 10⁶ CFU PA g^-1 diet (P < 0.05). The maximum activities of mucosal immune responses including total protein, alternative complement system, IgM, and lysozyme were observed in the fish fed with 4 × 10⁶ CFU PA g^-1 diet (P < 0.05). Furthermore, the maximum alkaline phosphatase activity of skin mucus was recorded in the fish fed with 8 × 10⁶ CFU PA g^-1 diet (P < 0.05). Fish fed with 4 × 10⁶ CFU PA g^-1 diet had the highest villus length and width of the intestine (P < 0.05). Supplementing the diet with 4 × 10⁶ CFU PA g^-1 diet more significantly enhanced Cyp19a gene expression in comparison with this in other groups. Hence, PA with a concentration of 4 × 10⁶ CFU g^-1 diet can be considered as a proper level of probiotic for improving the health, growth, and reproductive performance of the D. rerio.

Extract of grape seed enhances the growth performance, humoral and mucosal immunity, and resistance of common carp (Cyprinus carpio) against Aeromonas hydrophila

This study evaluated the effects of grape seed extract (GSE) on the growth performance, immune response, and disease resistance of common carp (Cyprinus carpio). Fish were distributed in four groups and fed diets with varying levels of GSE at 0, 10, 20, and 30 g/kg for 56 days. The final length in fish fed with 20 and 30 g GSE/kg diet significantly increased in comparison with the control group (P<0.05). The final weight and weight gain of fish fed with GSE were statistically higher than for the control diet, while the feed conversion ratio was lower in GSE groups than the control. Hematological parameters did not statistically improve with GSE supplemented diets (P>0.05). However, fish fed with 30 g GSE/kg diet displayed a significantly higher WBC count than the other group (P<0.05). The serum total protein and globulin in fish fed with 20 g GSE/kg diet significantly increased compared to the control (P<0.05). A similar pattern was noticed in results for serum and mucus lysozyme activity with a significant increase in fish fed with 20 and 30 g GSE/kg diet compared to the control (P<0.05). Total antibody levels in serum and mucus samples were also increased in fish by dietary GSE with maximum levels by 20 and 30 g GSE/kg diet. Besides, mucus protease activity was higher in fish that received 20 and 30 g GSE/kg diet with maximum level shown in fish fed with 30 g GSE/kg diet compared to the control group (P<0.05). Meanwhile, all groups showed higher mucus antibacterial activity against Aeromonas hydrophila with the highest activity in 30 g GSE/kg diet in comparison with the control group. The cumulative mortality was 36.67% when fish were fed with 30 g GSE/kg diet and challenged with A. hydrophila. However, the mortality rate was 40% and 53.33% in fish fed 20 and 30 g GSE/kg diet, respectively. This study suggests that supplementation of GSE could significantly enhance the growth performance, immune responses, and disease resistance against A. hydrophila in common carp.

Probiotics, lactic acid bacteria and bacilli: interesting supplementation for aquaculture

Probiotics administration in aquafeed is known to increase feed consumption and absorption due to their capacity to release a wide range of digestive enzymes and nutrients which can participate in digestion process and feed utilization, along with the absorption of diet components led to an increase in host's health and well-being. Furthermore, probiotics improve gut maturation, prevention of intestinal disorders, predigestion of antinutrient factors found in the feed ingredients, gut microbiota, disease resistance against pathogens and metabolism. The beneficial immune effects of probiotics are well established in finfish. However, in comparison, similar studies are less abundant in the shellfish. In this review, the discussions will mainly focus on studies reported the last 2 years. In recent studies, native probiotic bacteria were isolated and fed back to their hosts. Although beneficial effects were demonstrated, some studies showed adverse effects when treated with a high concentration. This adverse effect may be due to the imbalance of the gut microbiota caused by the replenished commensal probiotics. Probiotics revealed greatest effect on the shrimp digestive system particularly in the larval and early post-larval stages, and stimulate the production of endogenous enzymes in shrimp and contribute with improved the enzyme activities in the gut, as well as disease resistance.

A New Isolate of Pediococcus pentosaceus (SL001) With Antibacterial Activity Against Fish Pathogens and Potency in Facilitating the Immunity and Growth Performance of Grass Carps

Probiotic-feeding continues to be a promising strategy to control the bacterial pathogens in aquaculture. A new Pediococcus pentosaceus strain (SL001) was isolated from 1000s of soil samples, which exhibited wide antimicrobial spectrum of against fish pathogens, involving Aeromonas hydrophila, Aeromonas veronii, Aeromonas sobria, Edwardsiella tarda, Lactococcus garvieae, and Plesiomonas shigelloide. The challenge test against A. hydrophila showed that the survival rate of SL001-supplemented group was significantly higher than that of control group (P < 0.05). Moreover, SL001 could stably colonize in gut of grass carp and increased mucus-secreting goblet cells and extended intestinal villi could be observed in SL001-supplemented group (P < 0.05). Feeding with SL001 supplemented diet could significantly enhance the growth rate (P < 0.05) and markedly affect gut microbiota structure of grass carps, resulting in reduced potential pathogens and increased potential probiotics. Furthermore, feeding grass carps with SL001 caused the up-regulated expression of insulin-like growth factor (IGF-1 and IGF-2) and down-regulated expression of myostatin (MSTN-1 and MSTN-2) (P < 0.05), which probably also account for the increased growth rate of SL001-fed group. Meanwhile, relative mRNA expression levels of immune-related genes in liver, spleen, and head kidney were analyzed in grass carps after feeding for 30 days with SL001 supplemented diets. In all three immune organs, the expression levels of immunoglobulin M (IgM) and complement 3 (C3) were significantly increased (P < 0.05), whereas the interleukin-8 (IL-8) was down-regulated (P < 0.05). Besides, whole genome sequencing revealed several probiotics properties of SL001, including organic acid synthesis, bacteriocin synthesis (coagulin), superoxide dismutase, and digestive enzymes. In conclusion, P. pentosaceus SL001 which could enhance immunity and promoter growth rate of grass carps, is prospective to be used as a dietary probiotic in freshwater fish aquaculture.