Combined and Singular Effects of Ethanolic Extract of Persian Shallot (Allium hirtifolium Boiss) and Synbiotic Biomin®IMBO on Growth Performance, Serum- and Mucus-Immune Parameters and Antioxidant Defense in Zebrafish (Danio rerio)

Synbiotic Agents and Their Active Components for Sustainable Aquaculture: Concepts, Action Mechanisms, and Applications

Aquaculture is a fast-emerging food-producing sector in which fishery production plays an imperative socio-economic role, providing ample resources and tremendous potential worldwide. However, aquatic animals are exposed to the deterioration of the ecological environment and infection outbreaks, which represent significant issues nowadays. One of the reasons for these threats is the excessive use of antibiotics and synthetic drugs that have harmful impacts on the aquatic atmosphere. It is not surprising that functional and nature-based feed ingredients such as probiotics, prebiotics, postbiotics, and synbiotics have been developed as natural alternatives to sustain a healthy microbial environment in aquaculture. These functional feed additives possess several beneficial characteristics, including gut microbiota modulation, immune response reinforcement, resistance to pathogenic organisms, improved growth performance, and enhanced feed utilization in aquatic animals. Nevertheless, their mechanisms in modulating the immune system and gut microbiota in aquatic animals are largely unclear. This review discusses basic and current research advancements to fill research gaps and promote effective and healthy aquaculture production.

Effects of Dietary Medlar (Mespilus germanica L.) Extract on Growth Performance, Innate Immune Characteristics, Antioxidant Status, and Responses to Crowding Stress in Rainbow Trout (Oncorhynchus mykiss)

High stocking density is a stress factor that potentially affects physiological and immune responses. In this study, the effects of medlar (Mespilus germanica) extract (ME) supplementation on growth performance, antioxidant, immune status, and stress responses in rainbow trout (Oncorhynchus mykiss) were studied. Six hundred fish (40.19 ± 1.09 g; average fish weight ± standard error) were distributed randomly into five experimental groups (assayed in triplicates). The experimental diets were formulated as follows: 0 (T1, control), 0.5% (T2), 1% (T3), 1.5% (T4), and 2% (T4). After 60 days feeding trial, the fish were confined, and the density increased (60 kg/m3) for further 14 days. Results showed significant increases in final weight (FW), weight gain (WG), specific growth rate, and feed intake in the T4 compared to the control (P < 0.05). The feed conversion ratio (FCR) in T4 significantly decreased compared to the control (P < 0.05). Also, the treated groups showed significant improvements in catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), lysozyme (LYZ), total immunoglobulin (total Ig), respiratory burst activity (RBA), total protein, and phagocytosis (PHA) (P < 0.05). Moreover, compared with the control group, supplementation could significantly decrease glucose (GLU) and cortisol (CORT), alanine transaminase (ALT), lactate dehydrogenase (LDH), aspartate transaminase (AST), and alkaline phosphatase (ALP) (P < 0.05). After the challenge, FW and WG in all treated challenge groups were significantly improved compared to the control group (P < 0.05). FCR showed a significant decrease in all treated challenged groups compared to the control group (P < 0.05). However, malondialdehyde, CAT, GPx, SOD, LYZ, complement activity (C3 and C4), total Ig, RBA, peroxidase, and PHA in challenged treated groups were significantly increased compared to the control group (P < 0.05). All treated challenged groups showed lower ALT, LDH, AST, ALP, GLU, and CORT levels than the control group (P < 0.05). The experiment herein successfully demonstrated that dietary ME stimulated fish growth, antioxidant status, and immune responses in crowding conditions and can be recommended as beneficial feed additives for rainbow trout.

Role of Clostridium butyricum, Bacillus subtilis, and algae-sourced β-1,3 glucan on health in grass turtle

This study investigated the effects of two probiotics namely Clostridium butyricum and Bacillus subtilis, and one prebiotic known as algae-sourced β-1,3 glucan, on the overall performances of grass turtles (Chinemys reevesii) juveniles. Growth performance, immune responses, enzymatic antioxidant activities, intestinal histomorphology, and disease resistance against the challenge with Aeromonas veronii were assessed. Two hundred and sixteen (216) juvenile turtles with an average initial weight of 106.35 ± 0.03 g were divided into four groups, each containing three replicates with 18 turtles per each replicate, which were fed a basic diet (control group, GD) and a basal diet supplemented with C. butyricum 1.0 × 10⁸ CFU per kg (GA group), or with B. subtilis 1.0 × 10⁸ CFU per kg (GB group) and with algal-sourced β-1,3-glucan 50 mg per kg (GC group), respectively. After the turtles had been fed for 60 d, 90 d, and 120 d of the experimental period, the growth performance and survival rate (SR), intestinal digestive enzyme, hepatic and intestinal antioxidant capacity, serum biochemical indexes, and immune performance were measured. The results showed that the weight gain rate and SR were significantly enhanced (P < 0.05) after fed probiotics and algae-sourced β-1,3-glucan in all test times;The pepsin, amylase, acid phosphatase, total antioxidant capacity, triglyceride, alkaline phosphatase, urea nitrogen, cholesterol, total protein, IgA, IgG, IgM at 120 d were significantly enhanced (P<0.05) after fed C. butyricum. The intestinal villi heights, widths, and the thickness of the muscle layer were significantly higher in groups GA, GB, and GC than those reared within the GD control group (P < 0.05). After injecting the challenge by A. veronii the survival rate of grass turtles in the GA group (75%) was significantly higher than the other three groups (P<0.05), while there was no significant difference between the GB and GC groups compared with the control GD group, respectively (P>0.05). Overall, these results indicated that dietary supplementation with probiotics or algae-sourced β-1,3 glucan, exhibited positive effects on C. reevesii. In particular, C. butyricum, showed the greatest improvements relating to growth, immune response, antioxidant activity, intestinal health, and disease resistance.

A mini-review on co-supplementation of probiotics and medicinal herbs: Application in aquaculture

The aquaculture industry is geared toward intensification and successfully meets half of the world's demand for fish protein. The intensive farming system exposes the animal to the risk of disease outbreaks, which has economic consequences. Antibiotics are commonly used for the health management of aquaculture species. However, this has several drawbacks, including the increase in antibiotic resistance in pathogenic bacteria and the entry of antibiotic residues into the human food chain, which is a public health and environmental concern. The potential of probiotics, prebiotics, synbiotics, and medicinal herbs as alternatives to antibiotics for the health management of aquaculture species has been investigated in numerous studies. This review discusses the potential use of combinations of probiotics and medicinal herbs as prophylactic agents in aquaculture, along with the definitions, sources, and modes of action. The positive aspects of combining probiotics and medicinal herbs on growth performance, the immune system, and disease resistance of aquaculture species are also highlighted. Overall, this review addresses the potential of combinations of probiotics and medicinal herbs as feed additives for aquaculture species and the key role of these feed additives in improving the welfare of aquaculture species.

Lactobacillus casei (IBRC-M 10,711) ameliorates the growth retardation, oxidative stress, and immunosuppression induced by malathion toxicity in goldfish (Carassius auratus)

Probiotics can functionality improve fish wellbeing and are suggested as antioxidative agents to protect fish from xenobiotics toxicity. Herein, dietary Lactobacillus casei (IBRC-M 10,711) was included in the diets of goldfish (Carassius auratus) to protect against malathion toxicity. Fish (12.47 ± 0.06 g) were randomly allocated to six groups (triplicates), as follows: T1) control; T2) fish exposed to 50% of malathion 96 h LC50; T3) L. casei at 106 CFU/g diet; T4) L. casei at 107 CFU/g diet; T5) fish exposed to 50% of malathion 96 h LC50 + L. casei at 106 CFU/g diet; T6) fish exposed to 50% of malathion 96 h LC50 + L. casei at 107 CFU/g diet. After 60 days, goldfish fed T4 had the highest final body weight (FBW), weight gain (WG), and specific growth rate (SGR), and the lowest feed conversion ratio (FCR) among the groups (P < 0.05). However, the T2 group showed lower FBW, WG, and SGR and higher FCR than fish in T1 (P < 0.05). Fish in the T4 group had the highest blood total proteins, albumin, and globulin, while fish in T2 had the lowest levels (P < 0.05). Fish in the group T2 had the highest triglycerides, cholesterol, cortisol, lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) levels in the blood, while fish fed T4 had the lowest values (P < 0.05). The superoxide dismutase (SOD) and catalase (CAT) showed the highest activities in T3 and T4 groups, and the lowest SOD was seen in the T2 group, whereas the lowest CAT was seen in the T2, T5, and T6 groups (P < 0.05). Fish in the T5 and T6 groups had higher glutathione peroxidase (GSH-Px) activities than fish in T1 and T2 groups but T3 and T4 groups showed the highest values (P < 0.05). T2 group had the highest malondialdehyde (MDA) level, while T3 and T4 groups had the lowest MDA level (P < 0.05). Blood immunoglobulin (Ig) and lysozyme activity were significantly higher in T3 and T4 groups and lower in the T2 group than in the control (P < 0.05). The alternative complement pathway (ACH50) was significantly higher in T2, T3, T4, T5, and T6 groups than in the T1 group (P < 0.05). Skin mucus Ig was significantly higher in T3 and T4 groups and lower in the T2 group than in the control (P < 0.05). The highest lysozyme activity, protease, and ACH50 in the skin mucus samples were in the T4 group, while the lowest values were in the T2 group (P < 0.05). In conclusion, dietary L. casei protects goldfish from malathion-induced growth retardation, oxidative stress, and immunosuppression.