Single or combined effects of fructo‐ and mannan oligosaccharide supplements and Bacillus clausii on the growth,feed utilization,body composition,digestive enzyme activity,innate immune response and lipid metabolism of the Japanese flounder Paralichthys olivaceus

In this study, we examined the effects of the following eight experimental diets, which varied in fructo oligosaccharides (FOS), mannan oligosaccharides (MOS) and Bacillus clausii concentrations, on the Japanese flounder: control diet (no FOS, MOS and B. clausii), diet F (5 g kg⁻¹ FOS), diet M (5 g kg⁻¹ MOS), diet FM (2.5 g kg⁻¹ FOS + 2.5 g kg⁻¹ MOS), diet B (10⁷ cells g⁻¹B. clausii), diet FB (5 g kg⁻¹ FOS + 10⁷ cells g⁻¹B. clausii), diet MB (5 g kg⁻¹ MOS + 10⁷ cells g⁻¹B. clausii) and diet FMB (2.5 g kg⁻¹ FOS + 2.5 g kg⁻¹ MOS + 10⁷ cells g⁻¹B. clausii). Japanese flounder, initially weighing an average of 21 g, were distributed into 24 net cages at a stocking density of 20 fish per cage. Each diet was hand‐fed to three groups of fish twice daily for 56 days. The weight gain rate (WGR) in fish fed diets B, MB and FMB were significantly higher than in fish fed the control diet, where the fish fed diet FMB had the highest WGR. Fish fed any of the diets, except diets F and B, exhibited better feed conversion ratio than those fed the control diet. Diets MB and FMB significantly elevated intestinal protease activity compared with the control diet, but only the diet FMB promoted amylase activity. Feeding diets FB and FMB increased body protein deposition; additionally, feeding diets B, MB and FMB significantly reduced body lipid deposition. Lysozyme (LSZ) activity was significantly higher in fish fed diets B, FB, MB and FMB than in fish fed the control diet. All diets, except diet M, decreased triglyceride (TG) levels compared to the control diet. Low‐density lipoprotein cholesterol levels in fish fed diets F, FB and FMB were significantly lower than in fish fed the control diet. Without exception, no diets affected feeding rate, condition factor, body moisture, ash contents, phagocytic activity of leucocytes or cholesterol or high‐density lipoprotein cholesterol levels. Our results suggest that diets supplemented with FOS, MOS and B. clausii improved growth performance and health benefits of the Japanese flounder more than other diets or the control diet.     

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.     

Natural dietary additive yellow loess as potential antibiotic replacer in Japanese eel,Anguilla japonica: Effects on growth,immune responses,serological characteristics and disease resistance against Edwardsiella tarda

The present experiment was conducted to evaluate the efficacy of an additive derived from the nature as an alternative of dietary antibiotic in Japanese eel, Anguilla japonica. Six experimental diets were formulated to contain no antibiotics or additive (yellow loess/YL) (control/CON), three graded levels of yellow loess at 5 (YL₅), 10 (YL₁₀) and 20 g/kg (YL₂₀), oxytetracycline at 5 (OTC) and amoxicillin at 10 g/kg amoxicillin (AMX) of diet. Weight gain (WG) and specific growth rate (SGR) from fish fed CON or YL₅ diets were significantly lower than those of fish fed YL₂₀ or OTC diets. Among non‐specific enzyme, lysozyme activity of fish fed YL₂₀, OTC or AMX was detected to be significantly higher than that from fish fed CON or YL₅ diets, whereas superoxide dismutase (SOD) activity of the fish fed CON was significantly lower than that for fish fed other experimental diets. Challenge test with bacteria, Edwardsiella tarda, showed improved disease resistance among the fish fed different levels of natural additive without any statistical difference from those fed antibiotics (OTC and/or AMX) supplemented diets. Therefore, these results demonstrated the potential of natural feed additive, yellow loess to replace oxytetracycline and/or amoxicillin in Japanese eel, A. japonica.     

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.     

Fructooligosaccharide supplementation in diets for tropical gar (Atractosteus tropicus) juvenile: Effects on morphophysiology and intestinal barrier function

Supplementary fructooligosaccharides (FOS) were evaluated on growth, survival, gut morphology, digestive enzyme activity and expression of intestinal barrier genes in tropical gar (Atractosteus tropicus). Four treatments were designed to include FOS (5, 10, 15 and 20 g/Kg) and were compared with a control (0 g/Kg) and the current commercial trout diet. Ten fish were stocked (0.25 ± 0.01 g and 4.2 ± 0.4 cm total length) per experimental unit by triplicate in a 45‐day experiment. Fish fed with 5 and 10 g/Kg of FOS had the highest average weight and total average length. Fish fed 5 g/Kg FOS showed the best growth indexes (absolute weight gain: 2.16; specific growth rate: 4.96; and feed conversion rate: 1.23) and survival (96.66%) and also had the highest acid protease, chymotrypsin and leucine aminopeptidase activities. Fish fed 5 g/Kg FOS had a high absorption area and accumulation of lipids in the liver. Finally, relative overexpression of occluding (occ), nucleotide‐binding oligomerization domain‐2 (nod2) and mucin 2 (muc2) was detected in fish fed 10 and 15 g/Kg FOS. The supplementation between 5 and 10 g/Kg FOS in diets for A. tropicus juveniles could be beneficial for growth, digestive enzyme activities, gut morphology and intestinal barrier function.     

Combined effects of dietary mannan‐ and fructo‐oligosaccharide on growth indices,body composition,intestinal bacterial flora and digestive enzymes activity of regal peacock (Aulonocara stuartgranti)

A 56‐d feeding trial was conducted to investigate the effect of dietary mannan‐oligosaccharides (MOS) and fructo‐oligosaccharide (FOS) on growth indices, body composition, intestinal bacterial community and digestive enzymes activity of regal peacock. A total of 240 fish were randomly distributed to 15 experimental units (40‐L aquariums) of 16 fish each. These replicates were randomly assigned to one of five treatments in a 2 × 2 + 1 factorial arrangement. The treatments were control diet (no MOS and FOS), diet A (2 gkg^?1 MOS + 1.5 g kg^?1 FOS), diet B (2 g kg^?1 MOS + 3 g kg^?1 FOS), diet C (4 g kg^?1 MOS + 1.5 g kg^?1 FOS) or diet D (4 g kg^?1 MOS + 3 g kg^?1 FOS). The results showed that feeding diet C increased specific growth rate and protein efficiency ratio and decreased feed conversion ratio compared with control diet. Higher intestinal trypsin activity and increased Lactobacillus counts were observed in fish fed diets B and C. All diets significantly elevated body protein deposition and intestinal amylase activity compared to the control diet. In conclusion, the diet supplemented with 4 g kg^?1 MOS + 1.5 g kg^?1 FOS was advantageous over other MOS + FOS‐supplemented diets, with respect to growth performance and health benefits of regal peacock.     

Use of probiotics to enhance growth,stimulate immunity and confer disease resistance to Aeromonas salmonicida in rainbow trout (Oncorhynchus mykiss)

An 8‐week feeding trial was conducted to evaluate the effects of dietary probiotics on growth, non‐specific immune responses and disease resistance in juvenile rainbow trout, Oncorhynchus mykiss. Fish averaging 5.8 ± 0.8 g (mean ± SD) were fed one of the five experimental diets; one control (Cont), and four other diets were prepared by supplementing single probiotics 1 (Bacillus subtilis; SP₁, 0.5%), single probiotics 2 (Bacillus licheniformis; SP₂, 0.5%), multi‐probiotics (B. subtilis + B. licheniformis; MP, 0.5%) and oxytetracycline (OTC) at 5 g OTC kg^?1 diet. After 8 weeks of the feeding trial, weight gain and specific growth rate of fish fed SP₁, SP₂ and OTC diets were significantly higher than those of fish fed Cont diet (P < 0.05). Superoxide dismutase (SOD) and lysozyme activities of fish fed SP₁, SP₂ and MP diets were significantly higher than those of fish fed Cont diet (P < 0.05). There were no significant differences in SOD and lysozyme activities among fish fed SP₁, SP₂, MP and OTC diets. In challenge test with Aeromonas salmonicida for 15 days, fish fed SP₁, SP₂ and MP diets showed significantly higher cumulative survival rate than those of fish fed Cont diet (P < 0.05). However, there were no significant differences in cumulative survival rate among fish fed SP₁, SP₂, MP and OTC diets. Although there was a little advantage in fish fed MP diet in terms of non‐specific immune responses, single or multi‐probiotics are equally effective statistically. These results indicate that single or multi‐probiotics had equal beneficial effects as an antibiotic replacer on growth performance, non‐specific immune responses and disease resistance in juvenile rainbow trout.     

Dietary supplement of fructooligosaccharides and Bacillus subtilis enhances the growth rate and disease resistance of the sea cucumber Apostichopus japonicus (Selenka)

The effects of two dietary supplements, entrapped fructooligosaccharide (FOS) and microencapsulated Bacillus subtilis, on the growth and disease resistance of the sea cucumber Apostichopus japonicus were investigated. Sea cucumbers (a total of 810 animals, with initial weight of 3.72 ± 0.16 g each) were fed with basal diet only or basal diet supplemented with three different doses of B. subtilis (0.2, 0.4 and 0.8%), three different doses of FOS (0.4, 0.8 and 1.6%), 0.2% B. subtilis plus 0.4% or 0.8% FOS. Growth and lysozyme activity were measured after 50 days feeding. The results showed that dietary 0.2% and 0.4% B. subtilis alone or 0.2% B. subtilis plus 0.8% FOS significantly increased the specific growth rate (SGR) of sea cucumbers compared with control (P < 0.05). The addition of B. subtilis with or without FOS had no significant effect on lysozyme activity. The animals were also challenged with Vibrio splendidus to assess the level of disease resistance provided by the two dietary supplements. Sea cucumbers fed with 0.8% B. subtilis or 0.2% B. subtilis plus 0.8% FOS exhibited the highest survival (P > 0.05). Under these experimental conditions, dietary B. subtilis and FOS had no synergistic effect on enhancing SGR and disease resistance of sea cucumber.     

Probiotic applications for rainbow trout (Oncorhynchus mykiss Walbaum) II. Effects on growth performance,feed utilization,intestinal microbiota and related health criteria postantibiotic treatment

The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) was assessed on rainbow trout (Oncorhynchus mykiss Walbaum) previously treated with oxolinic acid. After feeding on supplemented diets for 10 weeks growth performance, feed utilization, gastrointestinal colonization and health status were assessed. B. subtilis + B. licheniformis fed fish displayed a significant improvement of feed conversation ration (FCR), specific growth rate (SGR) and protein efficiency ratio (PER). High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta associated populations and potentially resident mucosal populations. Levels of Bacillus spp. reached log 3.74 CFU g^?1 on the mucosal epithelium and log 7.41 CFU g^?1 in the digesta of fish fed diets supplemented with B. subtilis and B. licheniformis. Enterococci levels reached log 2.84 CFU g^?1 on the mucosa and log 7.78 CFU g^?1 in the digesta of fish fed E. faecium supplemented diets. Feeding trout the Bacillus probionts alone or synergistically with E. faecium resulted in elevated leucocyte levels. The results of the current study demonstrate a potential role of probiotics for stabilizing/reinforcing the gastrointestinal microbiota after antibiotic treatment. This could reinvigorate the intestinal defensive barrier mechanism and provide protection against secondary potential pathogens.     

Evaluation of solid‐state fermented protein concentrates as a fish meal replacer in the diets of juvenile rainbow trout,Oncorhynchus mykiss

We evaluated four fermented protein concentrates (FPCs) as a fish meal replacer in juvenile rainbow trout, Oncorhynchus mykiss. Ten diets were formulated to contain low‐temperature fish meal (LT‐FM), Vietnam fish meal (VT‐FM) and four types of FPCs as fish meal replacers (FPC‐A, B, C & D) at 30% and 50% FM replacement levels. FPC‐A was a mixture of solid‐state fermented soybean meal (SBM) and corn gluten meal (CGM) with Bacillus subtilis; FPC‐B was pretreated acid‐hydrolysed FPC‐A; FPC‐C and FPC‐D were FPC‐A + 2% shrimp soluble extract (SSE) and FPC‐B + 2% SSE, respectively. Triplicate groups of fish (average 15.4 g) were fed one of the experimental diets for 8 weeks. At the end of the feeding trial, fish fed the LT‐FM, FPC‐B, FPC‐C and FPC‐D diets showed significantly higher growth performance at 30% FM replacement than those of fish fed the FPC diets at 50% FM replacement. Fish fed 30FPC‐B, 30FPC‐C and 30FPC‐D diets showed higher weight gain (WG) than fish fed 30FPC‐A diet. Haematological parameters showed no clear trends among the experimental groups. Superoxide dismutase, lysozyme and myeloperoxidase activities were found to be higher in fish fed the LT‐FM, FPC‐A, FPC‐B, FPC‐C and FPC‐D diets at 30% FM replacement than in fish fed the FPC diets at 50% FM replacement. Antinutritional factors such as α‐ and β‐conglycinin, glycinin, trypsin inhibitors or zein were absent in FPC compared with SBM and CGM. Intestinal villi length and muscular thickness were significantly reduced in fish fed the VT‐FM and FPC diets at 50% FM replacement compared to fish fed the LT‐FM and FPC diets at 30% FM replacement. The results show that FPC‐B, FPC‐C, FPC‐D could replace up to 30% of LT‐FM in juvenile rainbow trout.     

Organic acids blend as dietary antibiotic replacer in marine fish olive flounder,Paralichthys olivaceus

The present study was conducted to evaluate the efficacy of organic acid blends as dietary antibiotic replacer in marine fish olive flounder, Paralichthys olivaceus. Fish averaging 3.5 ± 0.05 g (mean ± SD) were fed one of the four experimental diets: (1) without antibiotic or organic acid (Control/CON); (2) with antibiotic—50 mg oxytetracycline per kg body weight per day (OTC); (3) with organic acid blend A—4 g/kg diet (OA_A); and (4) with organic acid blend B—4 g/kg diet (OA_B), for 10 weeks. At the end of the experiment, total intestinal bacterial counts in fish‐fed OA_A, OA_B and OTC were significantly lower than that of fish‐fed CON diet (p < 0.05). Further, the group of fish‐fed organic acid blends (OA_A, OA_B) or antibiotic (OTC)‐supplemented diets exhibited lower intestinal Vibrio sp. counts compared with fish‐fed CON diet. Disease challenge test with bacteria Edwardsiella tarda showed significantly lower cumulative mortality rates for the group of fish‐fed OA_A, OA_B or OTC than that of fish‐fed CON diet (p < 0.05). There were no negative effects on the growth, serological characteristics and proximate composition among the group of fish‐fed different experimental diets. Therefore, the present experiment demonstrates that blends of organic acid could be a promising alternative to dietary antibiotics for the preventive and/or curative health management in marine fish olive flounder aquaculture.     

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.     

Probiotic applications for rainbow trout (Oncorhynchus mykiss Walbaum) I. Effects on growth performance,feed utilization,intestinal microbiota and related health criteria

The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) used singularly and synergistically on the growth performance, intestinal microbiota and health status of rainbow trout (Oncorhynchus mykiss Walbaum) were assessed after 10 weeks feeding on supplemented diets. No significant improvements of weight gain or specific growth rate were observed in the probiotic fed groups. However, a significant improvement of feed conversion ratio was observed in the group fed E. faecium. High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta‐associated populations and potentially resident mucosal populations. Bacillus subtilis and B. licheniformis levels accounted for 36% of the total culturable microbial population adhered to the mucosa and 62% in the digesta. E. faecium levels accounted for 45% of the mucosal population and 89% of the population in the digesta. An increase of serum lysozyme activity was observed in the fish fed diets containing the Bacillus probionts and elevated leukocyte levels were observed in fish fed diets containing Bacillus + E. faecium synergistically. The results of the current study demonstrate potential for B. subtilis, B. licheniformis and E. faecium to improve feed utilization, modulate intestinal microbiota and the health status of rainbow trout.     

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.     

Evaluation of dietary natural mineral materials as an antibiotic replacer on growth performance,non‐specific immune responses and disease resistance in rainbow trout,Oncorhynchus mykiss

We evaluated the effects of some dietary natural mineral materials as an antibiotic replacer based on growth performance, non‐specific immune responses and disease resistance in juvenile and subadult rainbow trout, Oncorhynchus mykiss. First experiment, juvenile rainbow trout averaging 2.7 ± 0.02 g (mean ± SD) were fed one of the six experimental diets; a basal commercial diet as a control (CON), CON with oxytetracycline (OTC), with yellow loess (YL), with Macsumsuk^® (MS), with Song‐Gang^® stone (SG) and with barley stone (BS) at 0.4% of each diet. At the end of 8‐week feeding trial, weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) of fish fed YL diet were significantly higher than those of fish fed CON diet. Non‐specific immune responses such as superoxide dismutase (SOD), myeloperoxidase (MPO), lysozyme (LYS) activity and oxidative radical production of fish fed YL diet were higher than those of fish fed CON diet. At the end of 15 days of challenge test with Aeromonas salmonicida, average cumulative survival rate of fish fed YL diet was significantly higher than that of fish fed BS and CON diets. However, there were no significant differences among fish fed YL, SG and OTC diets. Second experiment, subadult rainbow trout averaging 261.5 ± 3.5 g (mean ± SD) were fed one of the four experimental diets for 22 weeks: CON, and CON with OTC, YL or SG at 0.4% of each diet. At the end of feeding, growth performance of fish fed SG and YL diets was significantly higher than that of fish fed CON diet. Non‐specific immune responses in terms of SOD, MPO, LYS and NBT of fish fed SG and YL diets were significantly higher than those of fish fed CON diet. However, there were no significant differences among the fish fed YL, SG and OTC diets. The results indicate that dietary yellow loess or Song‐gang^® stone at 0.4% of diet could replace oxytetracycline in juvenile and subadult rainbow trout.     

Effects of dietary supplementation of fructooligosaccharide on growth performance,body composition,intestinal enzymes activities and histology of blunt snout bream (Megalobrama amblycephala) fingerlings

A feeding trial was conducted to investigate the effects of dietary fructooligosaccharide (FOS) on growth performance, body composition, intestinal enzymes activities and histology of fingerling Megalobrama amblycephala. A total of 1200 fish (1.42 ± 0.01 g) were fed diets containing graded levels of FOS (0, 0.5, 1, 2, 4 and 8 g kg⁻¹ diet) for 8 weeks in a recirculating system indoor. The weight gain, specific growth rate (SGR) and survival rate were all improved in dietary supplementation of FOS fed fish. Increasing FOS levels resulted in both higher whole‐body lipid and lower moisture contents, whereas ash and protein contents showed no significant differences among all the treatments. Intestinal amylase, protease, Na⁺, K⁺‐ATPase, alkaline phosphatase, γ‐glutamyl transpeptidase and creatine kinase activities all increased with dietary FOS levels up to 4 g kg⁻¹ (P < 0.05). Transmission electron microscopy analysis indicated that microvilli length in the mid‐intestine was significantly increased with increased dietary FOS levels (P < 0.05). In conclusion, dietary supplementation of FOS could confer benefits on growth performance, intestinal digestive and absorptive ability, histology of fingerling Megalobrama amblycephala.     

Evaluation of growth performance and intestinal barrier function in Arctic Charr (Salvelinus alpinus) fed yeast (Saccharomyces cerevisiae), fungi (Rhizopus oryzae) and blue mussel (Mytilus edulis)

Arctic charr (Salvelinus alpinus) were fed for 99 days on experimental diets with 40% of fish meal replaced, on a crude protein basis, with intact yeast (Saccharomyces cerevisiae) (ISC), extracted yeast (ESC), Rhizopus oryzae fungus (RHO) or de‐shelled blue mussels (Mytilus edulis) (MYE). The fish were evaluated for growth performance, nutrient digestibility and fish intestinal function. Growth performance, retention of crude protein and sum of amino acids were not affected in fish fed diets ISC or MYE compared with those fed the reference (REF) diet. However, fish fed diet ISC displayed decreased digestibility of crude protein and indispensable amino acids and decreased intestinal barrier function compared with fish fed the REF diet. Fish fed diet ESC exhibited decreased growth performance and protein retention, but had comparable digestibility to fish fed the REF diet. Fish fed diets MYE and RHO showed similar performance in terms of growth, nutrient digestibility and intestinal barrier function. Overall, the results indicated that blue mussel and intact S. cerevisiae yeast are promising protein sources for Arctic charr.     

In vitro selection of a synbiotic and in vivo evaluation on intestinal microbiota,performance and physiological response of rainbow trout (Oncorhynchus mykiss) fingerlings

The aim of this study was to determine the best synbiotic combination (based on growth and short chain fatty acids production) between Pediococcus acidilactici and five prebiotics in vitro, inulin, fructooligosaccharide (FOS), xylooligosaccharide (XOS), galactooligosaccharide (GOS), isomaltooligosaccharide (IMO). The best in vitro growth under aerobic and anaerobic culture condition was observed in the treatment, P. acidilactici + GOS. Furthermore, the study of short chain fatty acids (SCFA) production at the end of exponential growth phase revealed that the major SCFA produced was propionic acid in all synbiotic treatments except for the P. acidilactici + GOS treatment where butyric acid production was significantly higher compared with the other treatments. Based on the results of in vitro studies, P. acidilactici + GOS that were selected as synbiotic and rainbow trout fingerlings (15.04 ± 0.52 g) were fed on diet supplemented with the selected synbiotic. After 8 weeks of feeding, growth performance, intestinal microbiota and physiological responses were evaluated. Growth performance was significantly improved by synbiotic feeding. No significant differences of haematological parameters were revealed between the different treatments. Level of presumptive autochthonous lactic acid bacteria was elevated, while total autochthonous bacterial level remained unaffected. These results showed that P. acidilactici + GOS can be considered as an efficient synbiotic for rainbow trout.     

Sensory Analysis of Rainbow Trout,Oncorhynchus mykiss,Fed Enriched Black Soldier Fly Prepupae,Hermetia illucens

A growth trial and fillet sensory analysis were conducted to examine the effects of replacing dietary fish meal with black soldier fly (BSF) prepupae, Hermetia illucens, in rainbow trout, Oncorhynchus mykiss. A practical‐type trout diet was formulated to contain 45% protein; four test diets were developed by substituting 25 and 50% of the fish meal with normal (BSF) or fish offal‐enriched black soldier fly (EBSF) prepupae. Dietary fat was adjusted to approximately 20% lipid using fish oil and poultry fat. Diets were fed to three replicate tanks of fish per treatment (10 fish/tank) for 8 wk. After the trial, three fish per tank were sampled for determination of hepatosomatic index, intraperitoneal fat ratio and muscle ratio, and muscle proximate and fatty acid composition. Fish remaining after sampling were used for sensory evaluation. Growth of fish fed the EBSF diets was not significantly different from those fish fed the fish meal‐based control diet, while the growth of fish fed the BSF diets was significantly reduced as compared to the control diet. A group of 30 untrained panelists did not detect a significant difference in a blind comparison of fish fed the fish meal containing control diet as compared to fish fed the EBSF or BSF diets.     

Soya bean‐based diets plus probiotics improve the profile of fatty acids,digestibility, intestinal microflora,growth performance and the innate immunity of beluga (Huso huso)

This study was conducted to investigate the effect of different methods of using probiotics Bacillus subtilis and Bacillus licheniformis in soya bean‐based diets on the physiology of beluga (Huso huso) (351 ± 4 g). Five experimental diets were formulated to feed beluga for 10 weeks. The results showed that there was no significant difference in weight gain between control (446 g) and 70%SBM‐SPRAY2 (409 g) treatments. Long‐chain polyunsaturated fatty acids in the muscle of beluga fed control (203.2 g/kg) and 70%SBM‐SPRAY2 (166.4 g/kg) diet did not change statistically. Blood performance as a newly introduced factor in individuals fed dietary control (64.06) and 70%SBM‐SPRAY2 (64.33) had higher value as compared with those fed dietary 70%SBM‐DIET2 (61.90) (p < 0.05). Also, total protein (1.68 g/dl) and RBC (0.74 × 10⁶/mm³) in fish fed 70%SBM were statistically lower than other treatments (p < 0.05). Lysozyme, alternative complement activity and total viable counts in beluga fed dietary probiotics were significantly higher than others. In conclusion, feeding fish with the 70%SBM‐SPRAY2 diet improved fish growth and health.