Influences of Bacillus subtilis and fructooligosaccharide on growth performances, immune responses, and disease resistance of Nile tilapia, Oreochromis niloticus

The present study investigated the effects of Bacillus subtilis and fructooligosaccharide (FOS) on growth performances, immunity improvement, and disease resistance of Nile tilapia (Oreochromis niloticus). The fish (24.5 ± 1.6 g) were fed a basal diet (G1), diets supplemented with 1 g/kg (G2), 3 g/kg (G3) and 5 g/kg (G4) of FOS as well as diets supplemented with 1 × 10⁹ CFU/g (G5), 3 × 10⁹ CFU/g (G6) and 5 × 10⁹ CFU/g (G7) of B. subtilis for 56 days. After the feeding trial, the complement C3, IL-1β, TNF-α, IFN-γ, hsp70 gene expression in the liver was then analyzed by a quantitative Real-time PCR. Then, fish were infected with Streptococcus agalactiae, and the survival rate was recorded. The results showed that FOS and B. subtilis had no significant effect (P > 0.05) on growth performances and survival rate. Lysozyme activity was significantly greater in the G4, G5, G6, and G7 groups. Also, all fish fed FOS and B. subtilis showed significantly (P < 0.05) higher respiratory burst activity than other groups. The expressions of complement C3, IL-1β, TNF-α, IFN-γ, and hsp-70 in the liver were significantly higher for fish fed 5 g/kg of FOS as well as for fish that received any concentration level of B. subtilis (P < 0.05) used in the study. After the S. agalactiae challenge test, the survival rate of fish-fed diets supplemented with FOS and B. subtilis was slightly higher than for the control group. The results indicated that FOS and B. subtilis could stimulate immune responses and immune-related genes in tilapia. However, further investigation of other prebiotics or herbs in combination with B. subtilis is encouraged at molecular levels and screening for beneficial metabolites that may increasingly improve digestive enzymes, growth performances, and health benefits in tilapia. In addition, on-farm experiments are needed.

Modulation of growth, immune response, and immune-antioxidant related gene expression of Nile tilapia (Oreochromis niloticus) reared under biofloc system using mango peel powder

This study aimed to investigate the effects of mango peel powder (MGPP) on growth, innate immunity, and immune-antioxidant related gene expression of Nile tilapia reared under biofloc system. Three hundred Nile tilapia (average weight 14.78 ± 0.05 g) were distributed into 15 fiber tanks (300 L per tank) assigned to five treatments in triplication. Fish were fed basal diet containing different levels MGPP as follows: 0 (MGPP0: control), 6.25 (MGPP 6.25), 12.5 (MGPP 12.25), 25 (MGPP 25), and 50 (MGPP 50) g kg^-1 diet for 8 weeks. Specific growth rate (SGR), weight gain (WG), final weight (FW), feed conversion ratio (FCR), skin mucus of lysozyme (SMLA), and peroxidase activities (SMPA), serum of lysozyme (SL) and peroxidase (SP) were measured every for weeks; while immune-antioxidant-related gene expressions were determined after 8 weeks post-feeding. The results indicated that MGPP 25 diet resulted in higher SGR, WG, FW, and FCR but no significant differences among treatments were noticed. In terms of immune responses, lysozyme and peroxidase activities in mucus and serum were significantly higher in MGPP 12.5 and MGPP 25 diets against the control. Similarly, significant up-regulation of IL-1 and IL-8 gene expressions was observed in fish fed MGPP 25 against the control. However, no significant differences in LBP, GSTa, GPX, and GSR among treatments were observed. Overall, dietary inclusion of MGPP 25 significantly enhanced immune response and immune related gene expressions but not growth performance and antioxidant gene expressions. The results implied that MGPP can be potentially used as an immunostimulants in Nile tilapia culture.

Effects of dietary rambutan (Nephelium lappaceum L.) peel powder on growth performance, immune response and immune-related gene expressions of striped catfish (Pangasianodon hypophthalmus) raised in biofloc system

This study aimed to evaluate the effects of rambutan peel powder (RP) on growth, skin mucosal and serum immunities, and immune-related gene expression of striped catfish (Pangasianodon hypophthalmus) reared in a biofloc system. Three hundred fingerlings (17.14 ± 0.12 g fish^-1) were randomly selected and assigned to five treatments corresponding to five diets: 0 g kg^-1 (control - RP0); 10 g kg^-1 (RP10); 20 g kg^-1 (RP20); 40 g kg^-1 (RP40), and 80 g kg^-1 (RP80) for 8 weeks. At weeks 4 and 8 post-feeding, growth, skin mucus, and serum immunity parameters were determined, whereas immune-related gene expressions were performed at the end of the feeding trial. Based on the results, skin mucus lysozyme (SML) and skin mucus peroxidase (SMP) were significantly higher in fish fed the RP diets compared to the control diet (P < 0.05). The highest SML and SMP levels were observed in fish fed RP40 diet, followed by RP20, RP80, RP10, and RP0. Fish-fed RP diets had higher serum lysozyme and serum peroxidase activities, with the highest value found in the RP40 diet (P < 0.05), followed by RP20, RP80, and RP10. Similarly, immune-related gene expressions (IFN2a, IFN2b, and MHCII) in the liver were significantly up-regulated in fish fed RP40. Up-regulation (P < 0.05) of IL-1, IFN2a, IFN2b, and MHCII genes was also observed in fish intestines, with the highest values observed in fish fed RP40 diet, followed by RP10, RP20, RP80, and RP0. Fish-fed diet RP diets also showed enhanced growth and FCR compared to the control, with the highest values observed in fish fed diet RP40. However, no significant differences in survival rates were found among diets. In conclusion, dietary inclusion of RP at 40 g kg^-1 resulted in better growth performance, immune response, and immune related gene expressions of striped catfish (Pangasianodon hypophthalmus).

Modulatory effects of longan seed powder on growth performance, immune response, and immune-antioxidant related gene expression in Nile tilapia (Oreochromis niloticus) raised under biofloc system

This study evaluates the effects of longan seed powder (LS) on the growth performance, immunological response, and immune-antioxidant related gene expression of Nile tilapia (Oreochromis niloticus). Three hundred fish (13.82 ± 0.06 g) were divided into five experiments and fed 5 diets, including the basal diet (control without LS) and basal diet containing 10 (LS10), 20 (LS20), 40 (LS40), and 80 (LS80) g kg^-1 LS for eight weeks. A completely randomized design (CRD) with three replications was utilised. The growth performance and immune response were measured at weeks 4 and 8 post feeding, while the gene expressions were determined at the end of the feeding trial. The results revealed that administration of LS could significantly (P < 0.05) improve specific growth rate (SGR), weight gain (WG), and feed conversion ratio (FCR) in Nile tilapia as compared to the control group. However, no significant differences (P > 0.05) were observed in survival rates among treatments. LS-supplemented diets showed enhanced serum peroxidase activity (SPA), serum lysozyme activity (SLA), skin mucus lysozyme activity (MLA), and skin mucus peroxidase activity (MPA) at weeks 4 and 8 post-feeding, with the highest values observed in the LS20 diet (P < 0.05). Additionally, LS-supplemented diets significantly up-regulated (P < 0.05) immune and antioxidant related gene expressions (IL1, IL8, LBP, GSTa, GPX, and GSR) in the liver and intestine, with highest values observed in the LS20 treatment. The present results confirmed the beneficial effects of LS as a functional feed additive and immunostimulant for Nile Tilapia culture in a biofloc system.

Dietary inclusion of rambutan (Nephelium lappaceum L.) seed to Nile tilapia (Oreochromis niloticus) reared in biofloc system: Impacts on growth, immunity, and immune-antioxidant gene expression

An eight-week feeding trial was carried out to determine the effects of rambutan seed (RS) as a feed additive on the growth, skin mucus, serum immune parameters, and gene expression of Nile tilapia (Oreochromis niloticus) raised under a biofloc system. Nile tilapia fingerlings (14.77 ± 0.80 g fish^-1) were fed five experimental diets containing 0, 5, 10, 20, and 40 g kg^-1 of RS, corresponding to five treatments (RS0, RS5, RS10, RS20, and RS40) with three replications per treatment. The results showed that fish consuming the RS10 and RS20 diets presented a substantial (P < 0.05) improvement in specific growth rate (SGR), weight gain (WG), and feed conversion ratio (FCR) after eight weeks. The highest values were recorded in the RS10 diet; however, there were no significant (P > 0.05) differences exhibited in the fish survival rates between treatments. The RS supplementation diets demonstrated greater immunological parameters, particularly skin mucus and serum immune responses (P < 0.05), than that of the control after eight the eight-week feeding trial. The highest level was seen in fish fed the RS10; followed by the RS20, RS40 (P > 0.05), and RS5 diets. Regarding gene expressions, IL1, IL8, LBP, GSTa, and GSR genes were significantly up-regulated in fish provided the RS10 diet in comparison to the control and other supplemented diets (P < 0.05). However, no significant up-regulation was found in these genes among the RS0, RS5, RS20, and RS40 diets, with the exception of the GPX gene. Similarly, up-regulation of IL-8, LBP, GSTa, GPX, and GSR were noted in fish fed the RS10 diet (P < 0.05). Notably, no significant differences were evident in these genes among the RS5, RS20, and RS40 diets. In conclusion, fish fed RS10 (10 g kg^-1) significantly enhanced growth, skin mucus, serum immunities, and immune-antioxidants related gene expressions of Nile tilapia raised under biofloc system.

Modulation of growth, innate immunity, and disease resistance of Nile tilapia (Oreochromis niloticus) culture under biofloc system by supplementing pineapple peel powder and Lactobacillus plantarum

Eight weeks feeding experiment was managed to evaluate the impacts of dietary addition of pineapple peel powder (PAPP) and Lactobacillus plantarum CR1T5 (LP) individual or mixed on growth performance, skin mucus and serum immunities, as well as disease resistance of Nile tilapia. Fish (average weight 20.91 ± 0.11 g) were fed four diets: Diet 1 (0 g kg^-1 PAPP and 0 CFU g^-1 L. plantarum, Diet 2 (10 g kg^-1 PAPP), Diet 3 (10⁸ CFU g^-1L. plantarum), and Diet 4 (10 g kg^-1 PAPP + 10⁸ CFU g^-1L. plantarum). Serum and mucus immune responses, as well as growth rate, were assessed every 4 weeks. Ten fish were chosen for the challenge test with Streptococcus agalactiae after 8 weeks post-feeding. The findings showed that PAPP and/or LP diets increased (P ≤ 0.05) growth performance, skin mucus, and serum immune responses. The best data were obtained in fish fed a mixture of PAPP and LP. Nevertheless, no variation (P > 0.05) was recorded between groups fed PAPP or LP. The relative survival percentage (RSP, %) in Diet 2, Diet 3, and Diet 4 was 46.15%, 50.0%, and 73.08%. Fish fed mixture of PAPP + LP recorded the best (P < 0.05) survival rate versus other treatments. The current findings recommended using a mixture of PAPP and LP as promising functional additives for aquaculture practice.

Effects of orange peels derived pectin on innate immune response, disease resistance and growth performance of Nile tilapia (Oreochromis niloticus) cultured under indoor biofloc system

The present study investigates the effects of orange peels derived pectin (OPDP) on skin mucus and serum immune parameters, disease resistance and growth performance of O. niloticus cultured under indoor biofloc system. Six hundred Nile tilapia (average weight 9.09 ± 0.05 g) were distributed into 15 fiber tanks (300 L per tank) assigned to five treatments repeated in triplicate. Fish were fed experimental diets contain different levels OPDP as follows: 0 (control in clear water), 0 (control in biofloc system), 5, 10, and 20 g kg^-1 OPDP for 8 weeks. At weeks 4 and 8 post feeding, skin mucus lysozyme (SMLA), peroxidase activities (SMPA), serum lysozyme (SL), serum peroxidase (SP), alternative complement (ACH50), phagocytosis (PI), and respiratory burst activities (RB) as well specific growth rate (SGR), weight gain (WG), final weight (FW), and feed conversion ratio (FCR) were measured. Also, resistance against Streptococcus agalactiae was assessed after 8 weeks post-feeding. Nile tilapia fed OPDP supplemented diets had significantly higher SMLA and SMPA compared to the controls (P < 0.05). The maximum values were observed in tilapia fed 10 g kg^-1 OPDP followed by 5 and 20 g kg^-1 OPDP. Nevertheless, no significant differences were observed between these two supplemented diets and between the control groups (P > 0.05). Regarding the serum immunological parameters, dietary inclusion of 10 g kg^-1 OPDP showed significant higher SL and PI than other supplemented groups and control groups (P < 0.05). However, no significant differences were observed in SL and PI of fish fed 5 and 20 g kg^-1 OPDP (P > 0.05). Dietary administration of OPDP significantly increased SP and ACH50 compared to the controls (P < 0.05), regardless of inclusion level. Additionally, non-significant change was found in RB of OPDP fed fish when compared with the controls (P > 0.05). The challenge test revealed that relative percent of survival (RPS) in OPDP treatments were 45.45%, 81.82%, 50%, respectively. The highest RPS was noticed in fish fed 10 g kg^-1 OPDP. Furthermore, dietary administration of OPDP significantly improved SGR, WG, FW, and FCR (P < 0.05). Overall, the present findings suggested that OPDP can be taken into account as functional feed additives for O. niloticus.

Effects of Cordyceps militaris spent mushroom substrate and Lactobacillus plantarum on mucosal, serum immunology and growth performance of Nile tilapia (Oreochromis niloticus)

An 8-weeks feeding trial was performed to investigate the possible effects of supplementation of Nile tilapia diet with Cordyceps militaris spent mushroom substrate (SMS) single or combined with Lactobacillus plantarum on immune parameters and growth performance. For this aim, Nile tilapia fingerlings were fed with four experimental diets namely: Diet 1 (0 - control), Diet 2 (10 g kg^-1 SMS), Diet 3 (10⁸ CFU g^-1L. plantarum), and Diet 4 (10 g kg^-1 SMS + 10⁸ CFU g^-1L. plantarum). At the end of feeding trial, skin mucus parameters, serum immune parameters, and growth performance were measured. The results indicated that supplementations SMS + L. plantarum or/and resulted in a significant increase in skin mucus lysozyme and peroxidase activities compared with the control group after 8 weeks of feeding trial (P < 0.05). The highest values of these parameters were recorded for fish fed both SMS + L. plantarum supplementations. Nonetheless, no significant difference was recorded between other supplemented groups (P < 0.05). For serum immunology, the results showed that serum lysozyme activity, alternative complement, phagocytosis, serum peroxidase, and respiratory burst activities were significantly higher in supplemented groups compared to the control (P < 0.05). The highest values were recorded in fish fed both SMS and L. plantarum with respect to the individual application. No significant differences were observed between fish fed SMS and L. plantarum (P < 0.05). Results on growth performance indicated that fish fed supplemented diets showed a statistically significant increase in the specific growth rate (SGR), weight gain (WG), final weight (FW) compared to the control group (P < 0.05). The highest SGR and WG values were observed in fish fed both dietary SMS and L. plantarum. However, no significant differences in these parameters were observed in fish fed SMS or L. plantarum alone (P > 0.05). The FCR was significantly lower in fish fed 10 g kg^-1 SMS + 10⁸ CFU g^-1L. plantarum than in other groups, while control group presented the highest values (P < 0.05). The present results suggested that the combination of these natural substances could be considered as potential feed-additives for aquaculture farmed fish.

Effects of Cordyceps militaris spent mushroom substrate on mucosal and serum immune parameters, disease resistance and growth performance of Nile tilapia, (Oreochromis niloticus)

The aim of present study was determination effects of dietary administration of C. militaris spent mushroom substrate (SMS) on mucosal and serum immune parameters, disease resistance, and growth performance of Nile tilapia (Oreochromis niloticus). Two hundred twenty five fish of similar weight (37.28 ± 0.10 g) were assigned to the following diets [0 (T1- Control), 5 (T2), 10 (T3), 20 (T4) and 40 g kg^-1 (T5) SMS]. After 60 days of feeding trial, growth performance, skin mucus lysozyme and peroxidase activities as well as serum innate immune were measured. In addition, survival rate and innate immune responses were calculated after challenge test (15 days) against Streptococcus agalactiae. The results revealed that regardless of inclusion levels, feeding Nile tilapia with SMS supplemented diets significantly increased skin mucus lysozyme and peroxidase activities as well as serum immune parameters (SL, ACH50, PI, RB, and RB) compared control group (P < 0.05). The highest increment of immune parameters was observed in fish fed 10 g kg^-1 SMS which was significantly higher than other treatments (P < 0.05). Also, the relative percent survival (RSP) in T2, T3, T4, and T5 was 61.11%, 88.89%, 66.67, and 55.56%, respectively. Among the supplemented groups, fish fed 10 g kg^-1 SMS showed significant higher RPS and resistance to S. agalactiae than other groups (P < 0.05). Regarding the growth performance, SGR, WG, FW, and FCR were remarkably improved (P < 0.05) in SMS groups; the highest improvement observed in 10 g kg^-1 SMS treatment. According to these finding, administration of 10 g kg^-1 SMS is suggested in tilapia to improve growth performance and health status.

Predator Avoidance of Transgenic Channel Catfish Containing Salmonid Growth Hormone Genes

Transgenic channel catfish (Ictalurus punctatus) containing salmonid growth hormone genes can grow 33% faster than normal channel catfish under aquaculture conditions. However, before transgenic catfish are released and utilized by the private sector, their genetic impact on the natural environment must be examined. Predator avoidance is one of the major fitness traits determining potential environmental risk. To determine the predator avoidance ability and growth performance of transgenic catfish in a natural habitat, various densities of transgenic and nontransgenic channel catfish were communally stocked in 0.04-ha earthen ponds without supplemental feeding. Largemouth bass (Micropterus salmoides) and green sunfish (Lepomis cyanellus) were stocked as predators. Nontransgenic fry had better predator avoidance than transgenic channel catfish when data were pooled (p <.01). When data were not pooled, nontransgenic catfish had better predator avoidance in six trials and transgenic individuals had better predator avoidance in four trials. There was no difference in predator avoidance in three trials. Overall predator avoidance was also better for nontransgenic individuals (p <.01) when the fish were evaluated as 3.5-g fingerlings, more clearly than as fry, as transgenic individuals were more vulnerable in 3 of 4 trials at this life stage. There was no significant difference in growth performance between transgenic and nontransgenic channel catfish in ponds without supplemental feeding. These findings indicate that transgenic channel catfish could be used for commercial aquaculture without affecting the natural environment. Although transgenic channel catfish may be released to nature by accident, any ecological effect would be unlikely because the increased susceptibility of transgenic channel catfish to predators would most likely decrease or eliminate the transgenic genotype.