Effects of dietary organic selenium on immune responses,total selenium accumulation and digestive system health of marron,Cherax cainii (Austin, 2002)

A 90‐day feeding trial was conducted to determine the effects of dietary organic selenium (OS) supplementation on immune responses, total selenium accumulation in various tissues and the digestive system health of marron Cherax cainii. A group of marron (initial weight 3.65 ± 0.05 g) were fed 0.2 g kg^?1 of Sel‐Plex^® as a source of OS and were compared to a control group of marron that were not fed OS. After 90 days of feeding OS, total haemocyte counts (THC) and the percentages of granular and semigranular cells in marron were significantly higher than in marron fed a control diet. However, dietary OS did not affect the proportion of hyaline cells. The marron fed OS had significantly lower bacteraemia and longer neutral red retention times than the control group. Total selenium levels in the haemolymph, hepatopancreas and muscle tissues of the OS‐fed marron group were significantly higher (P < 0.05) than in control diet group. The highest total soluble selenium levels were found in the muscle tissues of OS‐fed marron on the final day of the feeding trial. Amylase and protease activity, soluble protein, and numbers of microvilli were significantly higher (P < 0.05) in marron fed OS. These findings demonstrate the benefits of including 0.2 g kg^?1 OS in marron diet to enhance immune parameters, increase total selenium accumulation in muscle and improve marron digestive system health.     

Isolation and screening of probiotic candidates from marron,Cherax cainii (Austin, 2002) gastrointestinal tract (GIT) and commercial probiotic products for the use in marron culture

Six strains of bacteria including Bacillus mycoides (A10) and Shewanella species (A12) isolated from healthy marron intestine, Bacillus species (PM1), Bacillus subtilis (PM3), Bacillus sp. (PM4) and Bacillus sp. (AQ) from commercial probiotic products were investigated for probiotic potential in marron culture. Antibiotic susceptibility tests indicated PM3 and PM4 were susceptible to all nine antibiotics evaluated. A10, A12 and AQ were resistant to class penicillins, whereas PM1 was resistant to class penicillin and macrolides. All strains were non‐pathogenic for marron. Strong inhibition against Vibrio mimicus and Vibrio cholerae non‐01 was exhibited by PM4 and PM3. A10 inhibited V. mimicus at 72 h of growth, but not V. cholerae non‐01, whereas A12 inhibited V. cholerae non‐01 but not V. mimicus, and AQ showed no inhibition activity. A wide range of enzymes were produced by A10 and AQ using the API ZYM test. Protease enzymes were produced by PM3, PM4, AQ and PM1. In order of effectiveness, the following bacteria have probiotic potential: B. subtilis (PM3), Bacillus sp. (PM4) and B. mycoides (A10). Further study is required to determine the bacterium or any combination that gives a multibeneficial effect on marron.     

Effects of dietary Bacillus pumilus on growth performance,innate immunity and digestive enzymes of giant freshwater prawns (Macrobrachium rosenbergii)

The present study was conducted to investigate the effects of Bacillus pumilus on the growth performance, innate immunity and digestive enzymes of the giant freshwater prawn, Macrobrachium rosenbergii. Prawns (mean weight: 1.81 ± 0.01 g) were fed different levels of B. pumilus at doses of 0, 1 × 10⁷, 1 × 10⁸ and 1 × 10⁹ CFU/g to produce one control group and three experimental groups (G1, G2 and G3), respectively. After a 60‐day experimental feeding period, the results showed that the final weight, weight gain rate (WGR) and specific growth rate (SGR) were significantly higher in experimental groups than in the control (p < 0.05), whereas these improvements did not differ significantly (p > 0.05) among experimental groups. The improvements in phagocytic activity, respiratory burst (RBs) activity and the activity of catalase (CAT), nitric oxide synthase (NOS) and acid phosphatase (ACP) were significantly higher in G2 and G3 than in the control and G1 (p < 0.05). Further, the activity of CAT, NOS and ACP significantly increased with an increase in the dietary level of B. pumilus (p < 0.05). The activity of phenoloxidase (PO) in G3 was significantly higher than that in the control (p < 0.05). The activity of amylase was significantly higher in the groups G2 and G3 than that in the control group. G3 improved the activity of protease compared with the control (p < 0.05). In conclusion, the results of this study indicated that the potential use of B. pumilusat a dose of 1 × 10⁸ CFU/g feed could improve the growth, immunity and digestive enzymes of M. rosenbergii.     

Recovery of Bacillus mycoides,B. pseudomycoides and Aeromonas hydrophila from common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) with gill disease

During a 3‐month period from June to the end of August 2016, ~5% mortalities were observed in a farm with rainbow trout (Oncorhynchus mykiss Walbaum) and one farm of common carp (Cyprinus carpio L.) in Bulgaria. The disease was manifested by gill ulcers/rot, asphyxiation and bloody ascites. Aeromonas hydrophila was isolated from the internal organs of all the diseased fish. Bacillus mycoides or B. pseudomycoides were recovered from the gill lesions on diseased carp and rainbow trout, respectively, with identification achieved by conventional phenotyping and by sequencing of the 16S rRNA gene. In vivo experiments confirmed that all three organisms were pathogenic to rainbow trout.     

Comparing the effects of dietary selenium and mannan oligosaccharide supplementation on the growth,immune function,and antioxidant enzyme activity in the cultured marron Cherax cainii (Austin, 2002)

This study was conducted to compare the effects of dietary supplementation of selenium (Se, both inorganic and organic) and mannan oligosaccharide (MOS) on the growth, immune function, and antioxidant enzyme activities in the haemolymph of the marron Cherax cainii (Austin, 2002); 0.4 mg kg^?1 of sodium selenate, 0.2 g kg^?1 Sel-Plex^®, or 0.4 % Bio-MOS^® was added to the basal diet as sources of inorganic selenium (IS), organic selenium (OS), and MOS, respectively. After 90 days, marron fed all 3 supplemented test diets had significantly higher final weight, specific growth rate (SGR), survival, total haemocyte count (THC), percentage of hyaline cells, glutathione-S-transferase (GST), and glutathione peroxidase (GPx) activities than marron fed without any supplements. The marron fed OS showed significantly higher THC and percentage of hyaline cells than those fed IS and MOS. Marron fed MOS showed the highest final weight, SGR, and percentage of granular cells; however, there was no significant difference in the neutral red time retention between marron fed IS and OS, whereas marron fed OS resulted in the highest GPx activity and total Se levels in the haemolymph but the lowest lipid peroxidase activity; therefore, it is suggested that dietary supplementation with any source of Se and MOS is beneficial to improving growth, survival, and antioxidant activity.     

Effects of soluble dietary cellulose on specific growth rate,survival and digestive enzyme activities in three freshwater crayfish (Cherax) species

The current study evaluated the effect of soluble dietary cellulose on growth, survival and digestive enzyme activity in three endemic, Australian freshwater crayfish species (redclaw: Cherax quadricarinatus, marron: C. tenuimanus, yabby: C. destructor). Separate individual feeding trials were conducted for late‐stage juveniles from each species in an automated recirculating freshwater, culture system. Animals were fed either a test diet (TD) that contained 20% soluble cellulose or a reference diet (RD) substituted with the same amount of corn starch, over a 12‐week period. Redclaw fed with RD showed significantly higher (P < 0.05) specific growth rates (SGR) compared with animals fed the TD, while SGR of marron and yabby fed the two diets were not significantly different. Expressed cellulase activity levels in redclaw were not significantly different between diets. Marron and yabby showed significantly higher cellulase activity when fed the RD (P < 0.05). Amylase and protease activity in all three species were significantly higher in the animals fed with RD (P < 0.05). These results indicate that test animals of all three species appear to utilize starch more efficiently than soluble dietary cellulose in their diet. The inclusion of 20% soluble cellulose in diets did not appear, however, to have a significant negative effect on growth rates.     

Improvement of growth performance,digestive enzymes and body composition of Persian sturgeon (Acipenser persicus) following feeding on probiotics: Bacillus licheniformis,Bacillus subtilis and Saccharomyces cerevisiae

The individual and combinational effects of probiotics on Persian sturgeon (Acipenser persicus) were evaluated through assessing the growth performance, proximate body composition, digestive enzymes and intestinal morphology. On the basis of feeding with experimental diets, the fish were assigned into four groups denoted as follows: control (basal diet), D‐Pro (basal diet + Bacillus subtilis and Bacillus licheniformis), D‐Pro/Yeast (basal diet + B. subtilis and B. licheniformis + Saccharomyces cerevisiae), Yeast (basal diet + S. cerevisiae). Maximum mean weight and length were measured for the fish fed with D‐pro regime. weight gain (WG), body weight gain (BWI%),  feed efficiency (FE%), protein efficiency rate (PER), lipid efficiency rate (LER), and condition factor (CF) demonstrated the highest values for the fish fed with the diets containing D‐Pro and/or D‐Pro/yeast. LER and food conversion ratio (FCR) showed the highest performance for the fish received the D‐Pro diet. The diets containing D‐Pro exhibited higher performance in enhancing the activity of protease and lipase than the one supplemented only with the yeast, whereas the regimes treated with the yeast exhibited higher amylase activity. The fish received D‐Pro exhibited the highest protein and fat contents, yet did the lowest contents of moisture and total ash. Taken together, the findings revealed that the dietary administration of the D‐Pro and D‐Pro/Yeast could improve the growth performance of A. persicus.     

Growth,enzymatic glutathione peroxidase activity and biochemical status of juvenile barramundi (Lates calcarifer) fed dietary fermented lupin meal supplemented with organic selenium

To investigate the effects of high level of lupin meal (LM) supplemented with organic selenium (OS) on the growth and blood biochemistry of barramundi (Lates calcarifer), four isocaloric and isonitrogenous diets were prepared, containing either non‐fermented or fermented LM, and either supplemented with 2 mg OS/kg (LM, LM_OS, FLM and FLM_OS), or not. A fishmeal (FM)‐based diet formulated for juvenile barramundi was used as a control diet. Fish (initial mean weight of 5.88 g) were triplicated and fed the test diets for 75 days. The findings demonstrated that growth performance of fish fed with the FLM and FLM_OS diets were similar to fish fed with the FM diet (p > .05). The antioxidant glutathione peroxidase (GPx) activity, and haemoglobin (Hb) of fish fed with the FLM_OS diet were significantly higher than that of FM‐fed fish (p < .05). Plasma alanine aminotransferase (ALT) activity was significantly increased in fish fed with non‐fermented diets (LM and LM_OS) than in those fed with fermented LM diets (FLM and FLM_OS) (p < .05). However, there were no significant differences in ALT activity among LM_OS, FLM, FLM_OS and FM diets. There was an interaction between the LM and OS on plasma CK activity; the CK of fish fed with diets supplemented with OS was higher in non‐fermented LM diets but lower in fermented LM diets (p < .05). This study suggests that fermented LM have an obvious potential to substantially replace 75% FM protein in the diets of barramundi.     

Effects of dietary phosphorus on growth,body composition and immunity of young taimen Hucho taimen (Pallas, 1773)

The effects of dietary phosphorus (P) on growth, body composition and immunity of young taimen (Hucho taimen) were studied. Six purified diets contained graded levels (2.3‐control, 4.0, 5.6, 7.5, 9.1 and 10.8 g kg^?1 diet) of available P. Each diet was fed to triplicate groups of 30 fish with an initial average weight (55.31 ± 0.38) g for 84 days. The weight gain, specific growth rate and feed conversion ratio were improved by dietary available P up to 4.35 g kg^?1 (P < 0.05) and then levelled off. Hepatosomatic index and body crude lipid content decreased significantly with increasing P levels, while ash contents and P concentrations in the whole body and vertebrae increased by dietary available P up to 4.36 and 4.44 g kg^?1 and then levelled off respectively (P < 0.05). Liver superoxide dismutase and glutathione peroxidase and plasma alkaline phosphatase activities in the treatment groups were significantly higher compared with the control group (P < 0.05). Plasma IgM contents increased linearly with increasing dietary P from 4.0 to 9.1 g kg^?1 group and then decreased. Dietary P supplementation reduced plasma triglyceride, malondialdehyde and liver malondialdehyde contents. There were no significant effects on plasma total protein, albumin, globulin, glucose, aspartate aminotransferase and alanine aminotransferase, catalase, lysozyme and liver catalase compared with the control group (P > 0.05). Broken line regression analysis indicated that dietary available P requirement was 4.34 and 4.35 g kg^?1, based on weight gain and P concentration in the whole body respectively.     

Effects of dietary selenium on the growth,selenium status,antioxidant activities,muscle composition and meat quality of blunt snout bream,Megalobrama amblycephala

An 8‐week feeding trial was performed to investigate effects of dietary selenium (sodium selenite, Na₂SeO₃; selenium nanoparticle, Nano‐Se; selenium yeast, Se‐yeast) on the growth, selenium status, antioxidant activities, muscle composition and meat quality of blunt snout bream. Na₂SeO₃ and Nano‐Se were supplemented at 0.2 mg Se kg^?1, and Se‐yeast was supplemented at 0.1, 0.2, 0.4 and 0.8 mg Se kg^?1 in basal diet; no Se was added as a control. The results indicated that groups of 0.2 and 0.4 mg kg^?1 Se‐yeast had significantly higher weight gain and Nano‐Se, 0.2, 0.4 mg kg^?1 Se‐yeast had significantly lower feed conversation ratio compared with the control group. The Se concentrations of whole body, muscle and liver linearly increased with increasing dietary Se‐yeast levels. Group of 0.4 mg kg^?1 Se‐yeast significantly increased activities of catalase and glutathione peroxidase. Muscle colour of Nano‐Se, 0.2, 0.4 mg kg^?1 Se‐yeast groups, the water‐holding capacity of 0.4, 0.8 mg kg^?1 Se‐yeast groups showed significant differences compared with the control group. The results suggest that Se‐yeast and Nano‐Se had a better growth performance than Na₂SeO₃ at 0.2 mg Se kg^?1, and supplementing appropriate Se‐yeast in diet can increase antioxidant activities and enhance meat quality of blunt snout bream.     

Dietary supplementation with Bacillus subtilis LT3‐1 enhance the growth,immunity and disease resistance against Streptococcus agalactiae infection in genetically improved farmed tilapia,Oreochromis niloticus

A feeding trial was conducted to investigate the effect of different levels of Bacillus subtilis LT3‐1 in diets on growth, immune parameters, intestinal morphology and disease resistance in genetically improved farmed tilapia, Oreochromis niloticus. Fish (46.91 ± 0.17 g) were fed with a basal diet supplemented with B. subtilis LT3‐1 at 0 (B0), 3.8 × 10¹⁰ (B1), 7.6 × 10¹⁰ (B2), 1.14 × 10¹¹ (B3) and 1.52 × 10¹¹ (B4) CFU kg^?1 for 6 weeks. The results showed that the weight gain of fish in B1 group was significantly enhanced compared to that in B0 group (p < 0.05). The addition of B. subtilis significantly affected serum biochemical indices (total protein, albumin, aspartate aminotransferase, alkaline phosphatase). Besides, the haematocrit, total counts of red and white blood cells, as well as the serum catalase and lysozyme activities, were increased, whereas the serum malondialdehyde, the serum immunoglobulin M and complement three contents were reduced. Parameters for intestinal morphology suggested a healthier intestine for the fish fed B. subtilis‐supplemented diets than fish fed the control diet. The survival rate after Streptococcus agalactiae challenge increased in tilapia fed with B. subtilis. The present study demonstrated B. subtilis can effectively improve growth, immunological status and resistance against S. agalactiae infection in tilapia farming.     

Combined effects of dietary malic acid and Bacillus subtilis on growth,gut microbiota and blood parameters of Nile tilapia (Oreochromis niloticus)

The study investigated effect of dietary supplementation with malic acid, Bacillus subtilis and a mixture of the two (3 × 2 factorial trial) on Nile tilapia (Oreochromis niloticus) health. Treatment groups (T1–T6) were fed diets containing three levels of malic acid (0.0, 5.0 and 10.0 g/kg), each of which was supplemented with 0 and 1.1 × 10⁵ cfu/g B. subtilis, respectively. Each treatment group was assigned randomly to triplicate groups of 35 fish (5.26 ± 0.06 g) in 18 tanks for 84 days. The results indicated that survival was higher in all dietary treatments as compared to the control fed fish. The highest values of FBW, WG and SGR (%), PER, PPV and ER were recorded in groups T4 and T6, which were fed diets supplemented with 5 g malic acid/kg and 1.1 × 10⁵ cfu/g B. subtilis and 10 g malic acid/kg and 1.1 × 10⁵ cfu/g B. subtilis, respectively. The best value of FCR was obtained in groups T4 and T6. The lowest total bacterial count in the gut and faeces was detected in fish from group T6. The values of haematocrit, haemoglobin, red blood cells, white blood cells, total protein, albumin and globulin were significantly higher (p < .05) in fish from groups T4 and T6 (diets supplemented with malic acid and B. subtilis). As compared to the control fed fish, te mixture of these substances are promising as immune enhancher in aquacultured fish.     

Effect of temperature on growth,digestion and immunity of green,white and purple sea cucumbers,Apostichopus japonicus (Selenka)

Three color morphs (white, green and purple strains) of Apostichopus japonicus (Selenka) were cultured in artificial seawater, for approximately 90 days, in three temperature ranges: 27–22°C (high), 22–17°C (mid) and 17–12°C (low). All strains grew in all temperature ranges. Temperature significantly affected growth rate, digestibility, digestive enzymes and immune‐related enzymes. Highest specific growth rates were exhibited in 4‐month‐old sea cucumbers at mid and high temperatures, and in 16‐month‐old sea cucumbers at mid and low temperatures. Specific growth rates of green and purple strains were not significantly different, but were significantly higher than that of the white strain at mid temperatures. The digestibility of each strain was significantly higher at 27°C, 22°C and 17°C than at 12°C. Green‐strain digestibility was higher than that of purple and white strains at specific temperatures. Protease and amylase activities of all strains followed bell‐shaped temperature curves with maximum digestive enzyme activity at 17°C. The activities of alkaline and acid phosphatases were higher in the guts of the green strain than in the white or purple strains at the same temperature. Superoxide dismutase activity was higher in the purple strain than in white and green strains.     

Effects of dietary immunostimulant combination on the growth performance,non‐specific immunity and disease resistance of cobia,Rachycentron canadum (Linnaeus)

The aim of this study was to examine the effects of the immunostimulant combination (IC) containing β‐glucan, A3α‐peptidoglycan, vitamin C and vitamin E on the growth performance, non‐specific immunity and protection against Vibrio harveyi infection in cobia (Rachycentron canadum). Fish were fed diets containing six graded levels of IC (0, 1, 2, 3, 4 and 5 g kg^?1 diet) for 8 weeks. The results showed that the survival rate ranged from 81.1 to 84.4% with no significant difference among all the groups (P > 0.05) after the feeding experiment. Dietary IC significantly increased the specific growth rate (SGR), serum lysozyme, alternative complement pathway (ACH50) activity, phagocytosis percentage (PP) and respiratory burst activity of head kidney macrophages of cobia. Moreover, feeding of supplemented diets containing 3.0 g kg^?1 IC resulted in significantly lower mortality against the pathogens, V. harveyi compared with the control group. To elevate the growth and immune resistance ability of cobia, the optimal dose of dietary IC administration, determined by second‐order polynomial regression analysis was 3.43 and 2.71 g kg^?1 diet, respectively, on the basis of the SGR and mortality after challenge with V. harveyi.     

Supplementation of heat‐inactivated Bacillus clausii DE5 in diets for grouper,Epinephelus coioides,improves feed utilization,intestinal and systemic immune responses and not growth performance

In recent years, more and more attentions have been paid to the development and application of probiotics in aquaculture, and viable probiotics have been extensively studied, while rare information was available about inactivated probiotics in aquaculture. Therefore, in this study, a feeding trial was designed to investigate the effect of dietary supplementation of heat‐inactivated probiotic Bacillus clausii DE5 on growth performance, immune response and key immune genes expression in head kidney and intestine in grouper Epinephelus coioides. Fish were fed for 60 days with control diet (C) and two experimental diets containing 1.0 × 10⁸ CFU/g live (T1) and heat‐inactivated (T2) B. clausii DE5, respectively. The probiotic treatments did not affect the final weight, weight gain (WG) and specific growth rate (SGR) of E. coioides at days 30 and 60 (p > .05), while both heat‐inactivated and live B. clausii DE5 significantly decreased the feed intake and feed conversion ratio (FCR) at day 60 (p < .05). Serum lysozyme activity and complement C3 level in the two probiotic treatments were significantly higher than those in the control (p < .05). The lysozyme activity and complement C3 level at day 60 were significantly higher than those at day 30 (p < .05), while no significant interaction effect between diet and administration date was observed. Moreover, the heat‐inactivated B. clausii DE5 significantly improved the expression of TLR5, pro‐inflammatory cytokines (IL‐8 and IL‐1β) and TGF‐β1 in head kidney and intestine (p < .05), while the live probiotic did not show any significant effect on the expression of these key immune‐related genes in head kidney and intestine. These results indicate that dietary supplementation of heat‐inactivated B. clausii DE5 effectively improved feed utilization and both the local and systemic immune responses of E. coioides.     

Effect of replacing dietary fish meal with silkworm (Bombyx mori L) caterpillar meal on growth and non‐specific immunity of sea cucumber Apostichopus japonicus (Selenka)

The effect of dietary substitution of silkworm (Bombyx mori L) meal (SM) for fishmeal (FM) on the growth performance and non‐specific immunity of sea cucumber (Apostichopus japonicus) (initial weight: 12.8 ± 0.16 g) was determined. Four isonitrogenous and isocaloric diets were formulated: Diet 1, which served as the control diet, contained 5% FM; Diet 2 contained 3.75% FM and 1.25% SM; Diet 3 contained 2.5% FM and 2.5% SM; and Diet 4 contained 5% SM. Other ingredients in each of the four diets were kept in the same proportion. After 8 weeks of feeding, the results showed that sea cucumbers fed Diet 2 had 18.7% increases in weight over those fed the control diet, but no significant difference was observed. No obvious difference in body wall composition was detected among the sea cucumbers fed the four different diets. Immunity analysis indicated that phagocytosis and serum alkaline phosphatase activity were not significantly (P > 0.05) affected when FM was partially or completely replaced with SM. Serum lysozyme activity of sea cucumbers fed Diet 4 showed a significant (P < 0.05) growth increase compared with those fed control diet. The results revealed that SM could be an effective substitute for FM in sea cucumber diet.     

Combined or individual effects of dietary magnesium and selenium nanoparticles on growth performance,immunity, blood biochemistry and antioxidant status of Asian seabass (Lates calcarifer) reared in freshwater

This study was conducted to investigate effects of and interactions between nanoselenium (NanoSe) and nanomagnesium (NanoMg) on growth, humoral immunity, serum biochemistry and antioxidant capacity of juvenile Asian seabass Lates calcarifer reared in freshwater. Four groups of fish with an average weight of 32.78 ± 2.23 g were fed one of the experimental diets for 6 weeks: (a) control (basal diet); (b) NanoSe (basal diet + 4 mg NanoSe/kg diet); (c) NanoMg (basal diet + 500 mg NanoMg/kg diet); and (d) combination (basal diet + 4 mg NanoSe/kg diet + 500 mg NanoMg/kg diet). Fish fed with NanoSe‐supplemented diets (NanoSe and combination) showed higher weight gain, specific growth rate and feed intake. The combination of NanoSe and NanoMg enhanced the immune response. Also, fish fed on combination diet showed higher serum alanine aminotransferase and aspartate transaminase levels but lower glucose concentration. The activities of liver superoxide dismutase, glutathione peroxidase and catalase were not different among all groups, but liver malondialdehyde level was lower in fish fed diets supplemented with NanoSe and/or NanoMg. It could be concluded that NanoSe improved growth performance; the combination of both NanoSe and NanoMg enhanced humoral immunity; and NanoSe and/or NanoMg improved antioxidant capacity in Asian seabass.     

Combined effects of dietary fructooligosaccharide and Bacillus licheniformis on growth performance,body composition,intestinal enzymes activities and gut histology of triangular bream (Megalobrama terminalis)

This study was conducted to investigate the effects of fructooligosaccharide (FOS) and Bacillus licheniformis (B. licheniformis) on growth performance, body composition, intestinal enzymes activities and gut histology of Megalobrama terminalis. Nine experimental diets were formulated to contain three FOS levels (0, 3 and 6 g kg^?1) and three B. licheniformis levels (0, 1 and 5 × 10⁷ CFU g^?1) following a 3 × 3 factorial design. Accordingly, diets were named as 0/0, 0/3, 0/6, 1/0, 1/3, 1/6, 5/0, 5/3 and 5/6 (B. licheniformis/FOS). At the end of the 8‐week feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed 6 g kg^?1 FOS were both significantly (P < 0.01 and P < 0.05) higher than that of the other groups in terms of dietary FOS levels. Besides, WG and SGR of fish fed 1 × 10⁷ CFU g^?1 B. licheniformis were significantly (P < 0.05) higher than that of the control group in terms of dietary B. licheniformis levels. In addition, a significant interaction (P < 0.05) between dietary FOS and B. licheniformis was observed in finial weight, WG, SGR as well as the survival rate with the highest values all observed in fish fed diet 1/3. Hepatosomatic index, carcass lipid content, lipase activities as well as microvilli length increased significantly (P < 0.05) from 0 to 1 × 10⁷ CFU g^?1, but no significant difference (P > 0.05) was observed in terms of dietary FOS levels. In addition, a significant (P < 0.05) interaction of FOS and B. licheniformis was observed in both protease and Na⁺, K⁺‐ATPase activities with the highest value obtained in fish fed diet 1/3. The results indicated that the dietary applications of dietary FOS and B. licheniformis alone or in combination can significantly improve the growth performance, survival rate, intestinal enzymes activities as well as microvilli length of triangular bream. In addition, there is a significant interaction between dietary FOS and B. licheniformis. The best combination for this species is 3 g kg^?1 FOS with 1 × 10⁷ CFU g^?1 B. licheniformis.     

Dietary supplementation effects of Pediococcus acidilactici as probiotic on growth performance,digestive enzyme activities and immunity response in zebrafish (Danio rerio)

This study was carried out to assess the effects of Pediococcus acidilactici on zebrafish (Danio rerio). Different levels of P. acidilactici including 0, 1 × 10⁶, 2 × 10⁶, 4 × 10⁶ and 8 × 10⁶ colony‐forming unit per g of the diet (cfug^?1) were examined in fish with 120 ± 10 mg weight for 60 days in a completely randomized design. The results showed that the best growth indices were recorded in group 4 × 10⁶ cfug^?1 (p < 0.05). The highest number of total viable count and lactic acid bacteria of intestine were found in group 4 × 10⁶ cfug^?1 (p < 0.05). The maximum activity of digestive enzymes including amylase, lipase, protease and alkaline phosphatase was observed in group 4 × 10⁶ cfug^?1. The highest activity for superoxide dismutase was recorded in group 4 × 10⁶ cfug^?1 while catalase, glutathione peroxidase and glutathione reductase showed the highest activity in group 8 × 10⁶ cfug^?1. The most growth inhibition zone of Aeromonas hydrophylla, Flavobacterium columnare, Vibrio anguillarum and Edwardsiella tarda was found in group 4 × 10⁶ cfug^‐1 (p < 0.05). Therefore, P. acidilactici as a probiotic improved growth and immunity of the zebrafish and could be used by zebrafish farmers.     

Effect of farming patterns on growth,antioxidant activity and nonspecific immunity of loach,Paramisgurnus dabryanus

This study was carried out to compare growth, intestinal enzymes activity, antioxidation and nonspecific immunity of loach between farmed and imitative ecological farming loach, Misgurnus anguillicaudatus. Loach from farmed (average body weight 15.03 ± 0.36 g) and imitative ecological farming (average body weight 12.44 ± 0.62 g) population were used to analyse growth, whole-body composition, intestinal enzymes, antioxidant enzymes activity and resistance to bacteria. The results showed specific growth rate, average daily gain and protease, lipase, amylase and γ-GT activities in intestine and hepatopancreas of farmed loach were significantly higher (p < 0.05) than of imitative ecological farming loach. However, total protein, lysozyme and albumin contents and superoxide dismutase, catalase and glutathione peroxidase activities of imitative ecological farming loach were significantly higher (p < 0.05) than of farmed loach. Moreover, resistance to Aeromonas hydrophila of imitative ecological farming loach was higher than of farmed loach (p < 0.05). Taken together, ecological farming loach possesses higher antioxidant capacity and resistance to bacteria than farmed loach.