Effects of dietary supplementation with β‐glucan and synbiotics on growth,haemolymph chemistry,and intestinal microbiota and morphology in the Pacific white shrimp

The goal of this study was to investigate the effects of dietary supplementation with β‐glucan and microencapsulated probiotics (Bacillus subtilis or Pediococcus acidilactici) on growth performance, body composition, haemolymph constituents, and intestinal morphology and microbiota of the Pacific white shrimp Litopenaeus vannamei. Four treatment diets [basal diet (C), β‐glucan‐containing diet (β‐glu), β‐glucan plus B. subtilis‐containing diet (β‐glu+Bs), and β‐glucan plus P. acidilactici‐containing diet (β‐glu+Pa)] were fed to L. vannamei for 90 days. Shrimp fed the β‐glu and β‐glu+Pa diets exhibited similar growth performance and body protein content, which were significantly higher than those of shrimp fed the control diet (P < 0.05). No significant differences in haemolymph triglyceride, cholesterol, protein, haemolymph urea nitrogen or chloride were detected among the experimental diets. However, dietary β‐glucan alone increased the haemolymph glucose level and osmolarity (P < 0.05). Synbiotic supplementation had greater effects on intestinal microbiota and morphology than dietary β‐glucan alone. For example, β‐glu+Bs increased the number of intestinal lactic acid bacteria and decreased the number of Vibrio spp. (P < 0.05), and β‐glu+Pa increased the height of intestinal villi.     

Modulation of growth performances,survival, digestive enzyme activities and intestinal microbiota in common carp (Cyprinus carpio) larvae using short chain fructooligosaccharide

This study investigates the effects of inclusion of low levels of dietary short chain fructooligosacchairde (sc‐FOS) on physiological response and intestinal microbiota of carp (Cyprinus carpio) larvae. After acclimation, fish (550 ± 20 mg) were allocated into nine tanks (40 fish per tank) and triplicate groups were fed a control diet (0%) or diets containing 0.5% and 1% sc‐FOS for 7 weeks. At the end of the experiment, the growth performance parameters (final weight, weight gain, specific growth rate (SGR), food conversion ratio (FCR) and condition factor (CF), survival rate as well as digestive enzyme activities (amylase, lipase and protease), total viable counts of heterotrophic aerobic bacteria (TVC) and lactic acid bacteria (LAB) level in intestinal microbiota were measured. Our results revealed no significant (P > 0.05) effects of sc‐FOS on growth performance and TVC when compared with the control group. However, administration of low levels of dietary sc‐FOS significantly increased digestive enzyme activities (lipase and amylase) and LAB levels (P < 0.05). Also, survival rate was significantly elevated in sc‐FOS fed carp. These results revealed that administration of low levels of sc‐FOS can be considered as a beneficial dietary supplement for larval stage of common carp.     

Impacts of diet on hindgut microbiota and short‐chain fatty acids in grass carp (Ctenopharyngodon idellus)

Diet is known to influence intestinal microbiota in fish, but the specifics of these impacts are still poorly understood. Different protein/fibre ratio diets may result in differing structures and activities of gut microbiota. We examined the hindgut microbiome of grass carp (Ctenopharyngodon idellus) fed three different diets: fish meal (FM, high protein – low fibre), Sudan grass (SG, high fibre – low protein) and compound feed (CF, intermediate). Microbial profiles of fish fed on FM were significantly different from profiles of fish fed CF and SG (F = 18.85, p < .01). Cetobacterium, known to be positively associated with protein digestion, was the dominant microbial group in FM samples (approximately 75.7%), while Lachnospiraceae and Erysipelotrichaceae, thought to be involved in fermentation of plant polysaccharides, were dominant in CF and SG samples (46.8% and 42.9% respectively). Network analyses indicated that the abundance of Lachnospiraceae and Erysipelotrichaceae was in a significantly positive correlation (r = .895, p = .001). Short‐chain fatty acid (SCFA) levels may indicate that the digestibility of diet by microbiota in the grass carp gut decreased from FM to SG (FM>CF>SG). Overall low SCFA levels indicate that hindgut fermentation probably provides a low proportion of energy requirements in grass carp.     

Effects of Pediococcus pentosaceus supplementation on growth performance,intestinal microflora and disease resistance of white shrimp,Litopenaeus vannamei

Litopenaeus vannamei is economically important shrimp species in worldwide aquaculture. This study was conducted to assess the effect of different levels of probiotic Pediococcus pentosaceus (PP) on growth performance, feed utilization, digestive enzyme activity, intestinal microflora count and body composition of L. vannamei. Four diets containing different concentrations [0 (PP0), 10⁶ (PPI), 10⁷ (PPII) and 10⁸ (PPIII) CFU/g] of PP were formulated. After 8 weeks feeding trial, the experimental shrimps were challenged with Vibrio anguillarum and noted the surveillance. At the end of the feeding trial, the obtained results revealed a significant increase (p < .05) in final body weight, final length, weight gain (WG), survival rate, protease and amylase activities, lactobacillus sp. and Bacillus sp. intestinal count, total haemocyte counts (THC) and lysozyme activity in PPIII group when compared with the other groups. Similarly, WG, amylase activity, Bacillus sp. count, THC and lysozyme activity were significantly enhanced in case of PPII compared to the control group (p < .05). Interestingly, FCR and Vibrio sp. counts were significantly decreased in case of PPIII group when compared to the other groups (p < .05). Also, significant level of surveillance was noted in the challenging test with V. anguillarum. These results suggested that the P. pentosaceus improved the growth performance, digestive enzyme activity, immunity and tolerance against V. anguillarum of L. vannamei.     

饲用枯草芽孢杆菌HGcc-1对鲤肠肝健康、血清补体及肠道菌群的影响

为了研究枯草芽孢杆菌HGcc-1对鲤肠肝健康、血清补体和肠道菌群的影响,实验选择体质量为(13.10±0.39) g健康鲤,随机分为HGcc-1添加组和对照组,养殖20周后测定生长指标,用试剂盒检测了鲤血清内毒素(LPS)、谷丙转氨酶(ALT)、谷草转氨酶(AST)、总补体和溶菌酶,并对肠道菌群进行了16S rRNA测序,同时将添加组和对照组的肠道菌群转接至无菌斑马鱼,然后检测无菌斑马鱼体内毒素结合蛋白(LBP)、ALT、AST的水平和C3、C4基因表达量;最后还检测了HGcc-1直接作用于无菌斑马鱼时,无菌斑马鱼的ALT、AST的水平和C3、C4基因表达量。结果显示,HGcc-1对鲤的增重率无显著影响;与对照组相比,饲料中添加HGcc-1显著降低鲤血清内毒素、ALT和AST水平;同时HGcc-1添加组血清总补体水平显著升高。在门水平上,HGcc-1添加组中梭杆菌门丰度比对照组增加了47.1%;变形菌门丰度比对照组减少了70.7%;在属水平上,HGcc-1添加组中鲸杆菌属(的丰度比对照组增加了47.1%;柠檬酸杆菌属和气单胞菌属(的丰度比对照组分别减少了56.6%和70.9%。利用无菌斑马鱼模型进一步发现,HGcc-1添加组鲤肠道菌群显著降低了无菌斑马鱼LBP含量和AST水平,显著上调了无菌斑马鱼补体C3和C4基因表达;与此同时,HGcc-1与无菌斑马鱼直接互作也降低了鱼体ALT和AST水平。研究表明,饲料中添加枯草芽孢杆菌HGcc-1能够改善鲤肠肝健康、血清补体以及肠道菌群稳态。本研究为枯草芽孢杆菌HGcc-1的下一步应用奠定了理论基础。     

Gut histology,immunology and the intestinal microbiota of rainbow trout,Oncorhynchus mykiss (Walbaum), fed process variants of soybean meal

Processed soybean meal ingredients have become an emerging plant‐based protein used in aquafeed formulations and have been shown to influence gastrointestinal health and microbiota in cultured species. Two 60‐day feeding trials with juvenile rainbow trout (Oncorhynchus mykiss, Walbaum) were conducted to compare the effects of fishmeal (FMC), defatted soybean meal (SBM), bioprocessed soybean meal (BSBM) and commercial soy protein concentrate (CSPC) ingredients on intestinal histology, innate immunity and microbiota profiles. Results indicated no significant differences in intestinal immunoglobulin concentrations (p = .41) or gut leukocyte phagocytosis at day 15 samplings (p = .41). Intestinal lysozyme content was found to be highest at day 60 in the BSBM treatment group (p < .01). No significant differences across treatments were observed in histological profiles at day 0 (p = .75), day 15 (p = .08) and day 60 (p = .22). ANOSIM analysis for microbiota beta diversity showed differences among all treatment groups, with the exception of the high and low levels of BSBM (p = .40). There were also differences observed in the alpha diversity ratios, with significant differences in gut communities among dietary groups as demonstrated by Chao‐1 (p < .01) and Shannon indices (p = .02). The incorporation of processed soy‐based proteins alters the microbial community composition within the distal intestine, and modulates lysozyme concentrations within the distal intestinal tissues.     

Effects of kelp residues fermented with probiotics on the culture of sea cucumber,Apostichopus japonicus

The kelp aquaculture production in China is the largest in the world, and a large amount of kelp residue is produced by kelp processing. Kelp residues contain substantial quantities of crude fibre, protein, and residual alginic acid, and may be used as feedstuff for aquaculture animals. In this study, we used probiotics to ferment kelp residues to improve kelp nutrient content and then fed the fermented kelp to the sea cucumber, Apostichopus japonicus. To study the effect of fermented feed on sea cucumber, its growth performance, digestive enzyme activity, diversity of intestinal microbiota and water quality of the sea cucumber culture water were determined. Growth performance of sea cucumber fed with fermented feed significantly (p < .01) increased when compared with sea cucumber fed with formulated feed. Amylase, cellulose and alginase activities were significantly (p < .01) higher in the fermented feed group when compared with the formulated feed group. The total number and diversity of intestinal microbiota showed a significant increase in sea cucumbers fed with the fermented feed. The water quality of the fermented feed group showed much lower ammonia and nitrite (<0.050 mg/L) levels when compared with the formulated feed group. These results suggest that kelp residues fermented with probiotics enhance the growth, digestive enzyme activities and intestinal microbiota of sea cucumbers and improve the culture water quality. Fermented kelp residues are a new supplementary nutrient source for sea cucumbers and may be applicable to other animal aquacultures.     

Bacterial population in intestines of white shrimp,Litopenaeus vannamei fed a synbiotic containing Lactobacillus plantarum and galactooligosaccharide

The aims of this study were to unravel the intestinal microbiota of Litopenaeus vannamei after being fed a diet without (control) or with the synbiotic (SYN) for 60 days using next‐generation sequencing technology to see if changes in the intestinal microbiota were involved in the improved growth performance and health status of the shrimp. Next‐generation sequencing data showed that six phyla, 11 classes, 19 orders, 30 families, 58 genera and 73 species with taxonomic names assigned were detected. The majority of the operational taxonomic units (OTUs) was shared between the SYN and control shrimp and comprised 37 OTUs. However, intestinal biodiversity analyses revealed that SYN‐fed shrimp had a higher species richness, evenness and Shannon–Weaver index than did shrimp fed the control diet, but without reaching statistical significance. Interestingly, shrimp fed the SYN diet exhibited improved colonization of Lactobacillus plantarum and reduced prevalences of Vibrio harveyi and Photobacterium damselae in the intestines. These findings indicate that the SYN was able to modulate the intestinal bacterial community of shrimp and could be used to control vibriosis in shrimp.     

The effects of oligofructose on growth performance,survival and autochthonous intestinal microbiota of beluga (Huso huso) juveniles

Preliminary experiments were undertaken to investigate the effects of oligofructose on beluga sturgeon (Huso huso) growth performance, survival and culturable autochthonous intestinal microbiota. Juveniles (20 g) were fed diets containing varying levels of oligofructose (10, 20 and 30 g kg^?1) at 2–3% body weight per day for 7 weeks. Compared to the control group, no significant (P > 0.05) effect on growth performance was observed in fish fed diets supplemented with oligofructose at 10 and 20 g kg^?1. However, compared to the 20 g kg^?1 group, feeding oligofructose at 30 g kg^?1 resulted in adverse effects on growth performance. Dietary supplementation of oligofructose at 20 g kg^?1 significantly increased survival rate. Microbiological assessment indicated that the viable culturable autochthonous levels were not affected by dietary oligofructose. Although lactic acid bacteria (LAB) were not a dominant component of the endogenous autochthonous microbiota, LAB levels were significantly elevated in fish fed 20 g kg^?1 dietary oligofructose. This elevated LAB population was able to persist for at least 1 week after reverting the prebiotic group back to a control diet. This study encourages further research on different aspects of oligofructose in sturgeon culture with clear emphasis on optimizing dosage levels.     

Assessment of the effects of vegetative and lyophilized Pediococcus acidilactici on growth,feed utilization,intestinal colonization and health parameters of rainbow trout (Oncorhynchus mykiss Walbaum)

A study was conducted to assess the probiotic effect of different dietary forms of Pediococcus acidilactici on rainbow trout (Oncorhynchus mykiss Walbaum). Growth performance, feed utilization, intestinal colonization and basic health status were investigated after a 10 week feeding trial. Fish were fed either vegetative (Veg) or lyophilized (Lyo) cells incorporated into a basal diet at either 10⁷ (Lo) or 10⁸ (Hi) CFU g^?1. P. acidilactici temporarily colonized the digestive tract (as both epithelium associated and transient populations) in all probiotic groups during supplemented feeding. Scanning electron microscopy confirmed the presence of localized colonization of P. acidilactici‐like cells between intestinal folds of the probiotic fed fish. Compared to the control group, no significant improvements in growth performance, feed utilization or carcass composition were observed in the probiotic fed fish (P > 0.05). However, a significant reduction of condition factor (K) was evident in fish fed the lyophilized diets. Increased leucocyte levels were observed in fish fed the low level vegetative P. acidilactici supplemented diet yet leucocyte types were not affected. The study demonstrates some potential for the application of P. acidilactici with rainbow trout but further research is required to optimize applications.     

Peruvian fish meal has comparative potential to enzyme-treated Chilean fish meal as protein source of diet for larvae and juvenile Pacific bluefin tuna Thunnus orientalis

The present study aimed to evaluate suitable protein sources of formulated diet to replace prey fish. Regarding the test diet, the two dietary treatments (FM: Peruvian anchovy fish meal, and ETFM: enzyme-treated Chilean fish meal) were employed. Prey fish (PF; spangled emperor fish Lethrinus nebulosus) was used as a control. FM and ETFM diets are fed together with a limited amount of PF to Pacific bluefin tuna (PBT) larvae having an initial mean total length of 17.9 mm and body weight of 52.8 mg at 20 days post-hatching during the weaning period. Survival and growth were compared after 10 days of the feeding trial. Survival was significantly higher in the PF group than the FM and ETFM group. The PF group had significantly greater growth performance than the other groups. Between FM and ETFM groups, fish in the FM group showed significantly better growth than the ETFM group. Regarding the essential amino acids of the carcass, similar amino acid content was recorded in all treatments. However, carcass docosahexaenoic acid in the PF group was significantly higher than in the other groups. These results suggest that Peruvian anchovy meal without enzyme digestion can be used as the protein source in the formulated diet for juvenile PBT.

     

配合饲料和冰鲜鲢对大口黑鲈生长、血浆生化指标、抗氧化能力和组织学的影响

为探讨不同来源饲料对大口黑鲈生长、血浆生化指标、抗氧化能力以及肝脏和肠道组织学的影响,实验选取初始体质量为(12.45±0.07)g的大口黑鲈180尾,随机分成2个处理,每个处理3个重复,每个重复30尾,分别投喂配合饲料和冰鲜鲢,养殖84 d。结果显示,配合饲料组大口黑鲈的增重率(WGR)、特定生长率(SGR)和饲料系数(FCR)显著低于冰鲜鲢组,而蛋白质效率(PER)、肝体比(HSI)和脏体比(VSI)显著高于冰鲜鲢组。大口黑鲈摄食配合饲料后,肝糖原含量显著高于冰鲜鲢组,肝脏蛋白酶活性显著低于冰鲜鲢组,而肌糖原和肠淀粉酶活性无显著差异。饲喂配合饲料组大口黑鲈血浆谷草转氨酶(AST)活性、血糖和丙二醛(MDA)含量以及Ca/P比值显著高于冰鲜鲢组,而血浆碱性磷酸酶(ALP)、超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)活性以及总蛋白(TP)、甘油三酯(TG)、尿素、钙和磷含量显著低于冰鲜鲢组。各实验组血浆谷丙转氨酶(ALT)活性以及胆固醇(TC)和胰岛素含量均无显著差异。配合饲料明显影响大口黑鲈肝脏和肠道的组织结构,饲喂配合饲料组实验鱼的肝脏空泡化现象严重,小肠绒毛受到严重机械性损伤。研究表明,在本实验条件下,冰鲜鲢更适合饲喂大口黑鲈,配合饲料不仅影响大口黑鲈的生长,而且损伤肝脏和肠道的健康。因此,可以借鉴冰鲜鲢的营养组成和大口黑鲈的代谢特性,深入研发大口黑鲈的饲料配制技术。     

Effects of dietary inulin and Jerusalem artichoke (Helianthus tuberosus) on intestinal microbiota community and morphology of Nile tilapia (Oreochromis niloticus) fingerlings

This study investigated the effects of dietary inulin and Jerusalem artichoke (JA) on intestinal microbiota and morphometry of Nile tilapia fingerlings. Five treatment diets were designed to supplement inulin at 0 (basal diet), 2.5 and 5.0 g/kg, and JA at 5.0 and 10.0 g/kg. Nile tilapia larvae were fed experimental diets from the first feeding through the fingerling stage (84 days). The cultivation‐dependent technique showed that dietary inulin at 5.0 g/kg and JA (at both levels) increased lactic acid bacteria and Bifidobacterium spp., but decreased Vibrio spp. (p < .05). PCR‐DGGE targeting 16S ribosomal RNA gene revealed that dietary inulin and JA generated different profiles of microbial community compared with fish fed a basal diet. Compared with fish fed the basal diet, a greater intestinal villi height was observed in fish fed 5.0 g/kg inulin and JA at both levels (p < .05). A larger relative goblet cell number were observed in the anterior intestine of fish fed 5.0 g/kg inulin or JA (p < .05). Overall, dietary inulin (5.0 g/kg) and JA (5 and 10.0 g/kg) since the first feeding had effects on modulating the intestinal microbiota and morphology of Nile tilapia fingerlings.     

Phylogenetic analysis of intestinal bacteria of freshwater salmon Salmo salar and sea trout Salmo trutta trutta and diet

The microbial diversity of culturable intestinal microflora of wild freshwater salmonid fishes salmon Salmo salar and sea trout Salmo trutta trutta juveniles (0+ years old) from the same environmental conditions were investigated by means of molecular identification techniques and analysis of diet. Significant differences in the intestinal microbial diversity were observed in different fish species. The predominant group in the intestinal tract of the salmon comprised representatives of the Enterobacteriaceae family (23%), Plesiomonas (19.2%) and Carnobacterium (15.3%). Predominant microbiota in sea trout intestinal tract were Enterobacteriaceae (52%), Aeromonas (22%) and Pseudomonas (14%). The results show that Enterobacteriaceae were predominant in the intestinal tract of the salmon and the sea trout juveniles raised on diets of different compositions. However, molecular identification of the intestinal microbiota at the species or genus level revealed differences in these fish species. Bacteria in the hindgut of salmon included Pragia and Serratia. However, bacteria in the gut contents of sea trout from the Enterobacteriaceae family were Buttiauxella, Enterobacter, Moellerella, Pantoea, Rahnella and Tiedjeia arctica. A novel phylotype of T. arctica is harbored in the intestinal tract of wild salmon, and may correspond to a previously undescribed species.     

Effect of dietary glutathione supplementation on the biological value of rapeseed meal to juvenile grass carp,Ctenopharyngodon idellus

An 8‐week feeding trial was conducted to investigate the effects of dietary rapeseed meal (RM) and glutathione supplementation (400 mg kg^?1) on growth and intestinal microbiota of grass carp (Ctenopharyngodon idellus). Dietary 450 g kg^?1 RM decreased growth and feed intake, while increased the activities of serum alkaline phosphatase (ALP), aspartate aminotransferase (AST) and alanine transaminase (ALT). The hepatic damages were also observed the significant lower condition factor (CF), hepatosomatic index (HSI) and the symbol of parenchymal damage. Glutathione supplementation increased weight gain and feed intake while significantly decreased the three serum biochemistry parameters compared with the RM group. In addition, HSI, CF and pathology reports revealed that glutathione supplementation alleviated the damage caused by RM on the fish liver. In addition, glutathione had a positive effect on the intestinal digestive capacity. PCR‐denaturing gradient gel electrophoresis (DGGE) analysis indicated a higher similarity between dietary glutathione supplementation and control group. In conclusion, we demonstrated dietary 450 g kg^?1 rapeseed meal lead to negative health outcomes, while glutathione supplementation neutralize the adverse effect of rapeseed meal presented in aqua feed through alleviating the damage factors on the fish liver.     

A comparison of the effect of organic acids and dicalcium phosphate supplementation on phosphorus bioavailability,growth performance and digestive enzyme activities of Labeo rohita fingerlings

The effect of organic acids (OA) and dicalcium phosphate (P_i) supplementation in the feed of Labeo rohita fingerlings was studied by formulating seven practical diets, designed as D1 with no feed additives {dicalcium phosphorus (P_i) and organic acid (OA) blend} while, D2, D3, D4 and D5 were supplemented with P_i at the graded levels of 5, 10, 15 and 20 g/kg, respectively, whereas D6 and D7 contained blend of OA at 15 and 30 g/kg, respectively. The diet supplemented with OA blend exhibited increase (p < .05) in growth of L. rohita fingerlings compared with the diet supplemented with P_i. The OA supplementation at both levels showed significant improvement in nutrients digestibility and minerals absorption in fingerlings. Moreover, in case of muscle proximate composition, crude fat (CF) and crude protein (CP) were increased (p < .05) with the inclusion of OA blend in the diet while crude ash (CA) was improved by P_i supplementation. Additionally, digestive enzyme activities were not affected (p ? .05) by OA blend supplementation while increased activities were observed in the fingerlings fed with P_i diet. Consequently, supplementation of OA blend in the diet improved the growth performance and nutrient status while P_i enhanced digestive enzyme activities of L. rohita fingerlings.     

The use of Pseudoalteromonas sp. F15 in larviculture of the Yesso scallop,Patinopecten yessoensis

A 49‐day rearing trial was conducted to investigate the effects of Pseudoalteromonas sp. F15 on growth, survival, digestive and immune‐related enzyme activities in larval and juvenile Yesso scallop, Patinopecten yessoensis. Larvae (Day 2 post‐fertilization) (d2 PF)) were provided with a diet only of microalgae (control) and supplemented with F15 at final concentrations of 1×10⁴ and 1×10⁶ cells/mL, respectively. Results indicated that the specific growth rates and survival rates of umbo larvae (d13 PF), crawling pediveliger larvae (d28 PF) and juveniles (d51 PF) fed the F15 supplementation diets at 10⁴ and/or 10⁶ cells/mL were significantly higher than those fed the diet of microalgae. Larvae and juveniles fed 10⁴ and/or 10⁶ cells/mL F15 supplementation diets showed a significant increase in pepsin, amylase and cellulase activities compared with the control group. The lysozyme, superoxide dismutase and catalase activities of larvae and juveniles fed the F15 supplementation diets at 10⁴ and/or 10⁶ cells/mL significantly increased compared to those fed the diet of microalgae. In addition, F15 protected juveniles against challenge with Vibrio splendidus. These data suggest that F15 can be useful in scallop larviculture.     

Comparative effects of dietary Na+-lactate on Arctic char, Salvelinus alpinus L., and Atlantic salmon, Salmo salar L.

Arctic char, Salvelinus alpinus L., and Atlantic salmon, Salmo salar L., were fed a commercial diet with or without supplementation of 1.5% Na⁺-lactate. Dietary Na⁺-lactate enhanced growth of Arctic char, while that of salmon was unaffected. Dietary ¹⁴C-lactate was retained for significantly longer in the stomach of Arctic char than that of Atlantic salmon. Changes in intestinal cholytaurin hydrolase activity, a bacterially produced enzyme, may indicate that dietary lactate affects the intestinal microbiota of Arctic char but not that of Atlantic salmon. Analysis of bile acids of char showed that dietary Na⁺-Iactate influenced neither intestinal nor gallbladder bile acid composition. Although Arctic char possesses the classical entero-hepatic circulation pathway, no extra loss of bile acids from the fish was observed. It is concluded that the retention time of diet in the stomach of char is significantly longer than that of salmon. This may increase the antibacterial action of lactate in the former, favouring the colonization of lactic-acid-tolerant bacteria in the intestinal tract, some of which produce the enzyme cholytaurin hydrolase.     

Effect of dietary sodium butyrate on growth performance,enzyme activities and intestinal proliferation‐related gene expression of juvenile golden pompano Trachinotus ovatus

The present study was conducted to investigate the effects of dietary sodium butyrate on growth performance, intestine enzyme activities and intestinal proliferation‐related gene expression of juvenile golden pompano Trachinotus ovatus. A basal diet was supplemented with sodium butyrate at 0.0 (control), 0.25, 0.5, 1, 2 and 4 g/kg feed for 8 weeks. The final body weight, weight gain (WG), specific growth rate (SGR) and condition factor (CF) increased with increasing dietary sodium butyrate up to 2.0 g/kg, and thereafter declined, while feed conversion ratio exhibited an opposite trend. Compared with the control, the 2.0 g/kg sodium butyrate group had higher condition factor (CF) significantly (p < 0.05). Whole body ash decreased with increasing dietary sodium butyrate level, with the lowest whole body ash content in 4.0 g/kg sodium butyrate (p < 0.05). Compared with the control, the 2.0 g/kg sodium butyrate group had significantly increased plasma glucose, cholesterol, albumin level, A/G ratio, ALT and AST contents (p < 0.05), while significantly decreased plasma ALT/AST ratio (p < 0.05). As for the intestinal digestive and brush border enzymes activities, compared with the control, the 2.0 and 4.0 g/kg sodium butyrate groups had significantly increased intestinal protease, amylase, AKP and Na⁺‐K⁺‐ATPase activities (p < 0.05), respectively. The relative level of intestinal CDX2 mRNA of fish significantly increased with dietary sodium butyrate level. Compared with the control, the 2.0 g/kg sodium butyrate groups had significantly increased the expression of intestinal CDX2 and CREB mRNA (p < 0.05), respectively. In conclusion, these results suggested that the optimum sodium butyrate level for juvenile golden pompano could be 2.0 g/kg of the diet.