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1.
Bacillus subtilis E20, an isolate from natto – a Japanese fermented soy product – is used in a wide variety of marine and freshwater aquatic species to enhance growth and immunity. This paper describes the cloning, expression and characterization of xylanase isolated from B. subtilis E20 in B. subtilis RIK1285. The BsXynE20 gene was identified to encode a 213‐amino‐acid protein for a glycoside hydrolase family 11 xylanase containing a 28‐residue signal peptide whose cleavage yields a 185‐residue mature protein with a predicted molecular weight of 20.25 kDa. The full length of the BsXynE20 gene was subcloned into the pBE‐S expression vector for secretory production of recombinant BsXynE20 in B. subtilis RIK1285. Western blot and zymogram analysis, respectively, revealed that recombinant BsXynE20 can be secreted into culture medium and is a functional xylanase. The xylanase exhibited optimal activity at pH 5.0–6.0 and 60°C. Using recombinant BsXynE20‐pretreated duckweed meal for feed preparation improved the growth performance of tilapia. Finally, we achieved secretive expression of functional BsXynE20, which can improve the nutrient utilization of a plant‐derived diet. Thus, the use of BsXynE20 may be beneficial for tilapia aquaculture.  相似文献   

2.
Phagocytosis is an important function of both invertebrate and vertebrate blood cells. In this study, the phagocytic activity of haemocyte subpopulations of penaeid shrimp, Litopenaeus vannamei, (Boone), against pathogenic and non‐pathogenic particles was investigated in vitro. The haemocytes of penaeid shrimp were firstly separated by centrifugation on a continuous density gradient of iodixanol into four fractions with five subpopulations (sub), of which sub 1 (hyalinocytes) and sub 4 (semi‐granulocytes) have the main function in phagocytosis of both pathogenic and non‐pathogenic bacteria as well as fluorescent polystyrene beads. It was found that these haemocyte subpopulations engulfed virulent Vibrio campbellii and Vibrio harveyi at a higher rate than non‐virulent Escherichia coli and polystyrene beads. When these bacteria were mixed with shrimp haemocyte subpopulations and incubated for 180 min, the percentage of viable intracellular V. campbellii (25.5 ± 6.0%) recovered was significantly higher than the percentage recovered from V. harveyi (13.5 ± 1.1%). No viable intracellular E. coli was observed in this study. In contrast to V. harveyi and E. coli, V. campbellii containing endosomes did not acidify in time. Incubation of haemocyte subpopulations with the most virulent V. campbellii strain resulted in a significant drop in haemocyte viability (41.4 ± 6.3% in sub 1 and 30.2 ± 15.1% in sub 4) after 180 min post‐inoculation in comparison with the less virulent V. harveyi (84.1 ± 5.6% in sub 1 and 83.4 ± 4.1% in sub 4) and non‐virulent E. coli (92.7 ± 2.8% in sub 1 and 92.3 ± 5.6% in sub 4) and polystyrene beads (91.9 ± 1.6% in sub 1 and 84.4 ± 3.4% in sub 4). These findings may be a valuable tool for monitoring shrimp health and immunological studies.  相似文献   

3.
An 8‐week study was conducted to explore the results of Macsumsuk® as a feed additive on the stress tolerance and growth of Litopenaeus vannamei in 15 culture tanks of 36 L each. Three hundred shrimp averaging 0.1 ± 0.01 g were fed with five isonitrogenous (48.38 ± 0.38% CP) diets (in triplicate groups) containing kaolinite (Macsumsuk®) at 0%, 0.3%, 0.6%, 1.2% and 2.4%, namely Mk0, Mk0.3, Mk0.6, Mk1.2 and Mk2.4. Specific growth rate (SGR) and weight gain (WG) of shrimp fed diets Mk1.2 and Mk2.4 were significantly better than those of shrimp fed diet Mk0 (p < .05). However, SGR and WG of shrimp fed diets Mk0.6, Mk1.2 and Mk2.4 were not significantly different. Protein efficiency ratio (PER) and feed efficiency (FE) of shrimp fed diets Mk1.2 and Mk2.4 were significantly better than those of shrimp fed diets Mk0, Mk0.3 and Mk0.6. Furthermore, the survival of shrimp fed diet Mk2.4 was significantly lower than that of shrimp fed diet Mk0.6 (p < .05). Cumulative mortality of shrimp fed diet Mk1.2 was significantly lower than that of shrimp fed diet Mk0 at 1–1.5 hr post‐stress to low dissolved oxygen (from 6.1 mg/L to 2.9 mg/L) and 4–5 hr post‐stress to low salinity (from 32‰ to 1‰) (p < .05). The optimum dietary Macsumsuk® level for juvenile L. vannamei was determined as 1.97% by the polynomial regression analysis of weight gain.  相似文献   

4.
This study aimed to improve the nutritional value and utilization of soybean meal (SBM) used as feed ingredient for shrimp by an approach of solid‐state fermentation with Bacillus subtilis E20. The protein content and B. subtilis E20 proliferation significantly increased, as the initial moisture increased from 30% to 50% during fermentation. Compared with SBM, the protein content of FSBM increased by 19% after fermentation, accompanied by an increase of 18.75% in the total hydrolyzed amino acids. The free amino acid profile and content in FSBM also obviously increased by 374.9% compared with SBM. The FSBM is a good substitute for fish meal (FM) in a diet with 37% protein and 7% lipid content. The maximal replacement levels of FM in shrimp diet with SBM and FSBM were 37.42% and 61.67%, respectively, based on the feed efficiency estimated by a broken‐line analysis. The B. subtilis E20‐FSBM can be a potential protein source used as a replacement for FM in shrimp diet.  相似文献   

5.
A 10‐week feeding trial was conducted to evaluate the effects of supplementing different levels of dl ‐methionyl‐dl ‐methionine (AQUAVI® Met‐Met) in plant protein–based diets on Litopenaeus vannamei. The positive control (PC) and negative control (NC) diets were designed with 20% and 8% fishmeal respectively, and other six diets were formulated with graded levels of Met‐Met from 0.05% to 0.30% with a 0.05% increment on the basis of NC diet (MM 0.05–MM 0.3). Six replicates were randomly assigned to each diet with 50 shrimp each having initial weight of 0.98 ± 0.02 g. The variation of FM concentration from 20% to 8% and supplemented with graded levels of Met‐Met did not affect the survival rate, feed conversion ratio, protein efficiency ratio, whole body and muscle proximate compositions (p > 0.05). However, diets with ≤0.20% Met‐Met supplementation resulted in significantly increased weight gain and specific growth rate, after which both parameters reached plateau. Shrimp fed the NC diet showed significantly lower total essential amino acid (EAA) content in muscle (p < 0.05). Supplementation of Met‐Met significantly improved apparent digestibility coefficients of dry matter, crude protein, lipid, phosphorus and EAAs (p < 0.05). Based on broken‐line analysis, the methionine requirement for white shrimp was estimated to be 0.87% when using Met‐Met as methionine source.  相似文献   

6.
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.  相似文献   

7.
This study aimed to evaluate the effect of increasing the carbohydrate to lipid ratio in diets supplemented with Bacillus subtilis in white seabass (Atractoscion nobilis) juveniles on digestibility, growth performance, feed utilization efficiency and tissue composition. Four experimental isoenergetic and isoproteic diets supplemented with B. subtilis were formulated with increasing starch to lipid ratios (g/g) of 10:19; 14:17; 18:15 and 22:13 (diets PD10, PD14, PD18 and PD22 respectively). A negative control diet for B. subtilis supplementation was also formulated to be similar to diet PD10 (diet CD10). Each experimental diet was fed to triplicate groups of 20 fish per tank (IBW: 9.5 g), three times a day, to apparent satiation, for 60 days. Supplementation with B. subtilis, of the low starch‐high lipid diet (10:19), significantly enhanced the overall growth performance, digestibility and feed efficiency. Moreover, the increase in starch to lipid ratio, in supplemented probiotic diets, significantly increased growth performance, feed intake, feed utilization efficiency and protein and energy digestibility, being maximum for the highest dietary starch to lipid level. Lipid content of whole body, muscle and liver and hepatosomatic index significantly increased with the increase in starch to lipid ratio. The results of this study indicate that B. subtilis supplementation significantly enhanced growth performance, digestibility and feed utilization of low starch‐high lipid diet. However, further improvement of growth performance and feed utilization efficiency may be achieved combining B. subtilis supplementation with increased dietary starch to lipid ratio to 22:13.  相似文献   

8.
The purpose of the present study is to profile the microfloral structure in the intestines of the white shrimp, Litopenaeus vannamei, after being fed a control diet, in comparison with the diets containing Bacillus subtilis E20‐fermented soybean meal (FSBM) or an antimicrobial peptide (AMP) isolated from B. subtilis E20‐FSBM (diets designated FSBMD and AMPD, respectively) for 60 days. Metagenomic data showed detection of eight phyla, 20 classes, 40 orders, 68 families and 96 genera. Despite no statistically significant difference, an evaluation of microbial diversity recorded higher species richness, Shannon–Weaver diversity index and evenness in the AMPD and FSBMD groups, compared to the control diet group. Venn diagrams showed that 58 of the operational taxonomic units (OTUs) were shared among the control, FSBMD and AMPD groups, but additional beneficial microbes were only found in the FSBMD and AMPD groups. In addition to the augmentation of beneficial bacteria in the FSBMD and AMPD groups, the abundance of potential pathogens, Vibrio and Flavobacterium, was lower in the gut of shrimp fed the FSBMD and AMPD. The results clearly suggest that the FSBMD and AMPD have the capability to change the microfloral structure of shrimp intestines and could be used for disease prevention in shrimp aquaculture.  相似文献   

9.
An experiment was conducted to evaluate the potential of a Bacillus subtilis E20‐fermented mixture (FSFEM) containing soybean meal (SBM) and Eisenia fetida earthworm meal (EM) at a ratio of 4:1 to increase the methionine level in order to satisfy the methionine requirement of white shrimp, Penaeus vannamei in a diet with fish meal (FM) completely replaced by mixtures. B. subtilis E20 fermentation improved the mixture's palatability and utilization based on better growth performance in comparison to shrimp fed FSEM (contains fermented SBM and EM at a ratio of 4:1) diets. FSFEM is a good substitute for FM. Maximal replacement levels of FM with FSFEM were 80% in a shrimp diet with 37% of crude protein and 7% of crude lipid based on weight gain and 100% based on feeding efficiency. In addition, shrimp fed experimental diets had no significant differences in survival after being challenged by Vibrio alginolyticus. It is suggested that B. subtilis E20‐FSFEM has the potential to replace FM in cultured shrimp diets.  相似文献   

10.
The main objective of this study was to evaluate the effect of methionine supplementation when reducing fishmeal levels in diets for white shrimp (Litopenaeus vannamei). Tested diets consisted of a positive control with 260 g/kg fishmeal (D1), two negative controls with 100 g/kg fishmeal and no amino acid (AA) supplementation (D2) or supplemented with lysine but not methionine (D3), and four additional diets with 100g/kg fishmeal supplemented with increasing levels of DL‐Met (1.0, 2.0 or 3.0 g/kg) (D4, D5, D6) or Met‐Met (1.0 g/kg) (D7). Each diet was fed to four groups of 30 shrimp for 8 weeks at a daily rate of 70 g/kg body weight. Reduction in fishmeal from 260 g/kg down to 100 g/kg did not significantly affect survival rate, feed conversion ratio (FCR), protein efficiency ratio (PER) or protein retention efficiency (PR%) of white shrimp. However, growth performance (final body weight, FBW; weight gain, WG; specific growth rate, SGR) was reduced when dietary fishmeal level was reduced from 260 g/kg (D1) to 100 g/kg without methionine supplementation (D2). The growth performance (FBW, WG and SGR) of shrimp was significantly increased by supplementation of the 100 g/kg fishmeal diet with increasing levels of DL‐Met (p < .05). Same performance as positive control (D1) was achieved with diets containing 100 g/kg fishmeal and supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. The highest values of growth performance (FBW, WG and SGR) were found in shrimp fed D6 and D7 diets, which were significantly higher than those of shrimp fed D2 and D3 diets (p < .05) but without statistical differences with shrimp fed D1, D4 and D5 diets (p > .05). The highest values of whole‐body and muscle protein contents were found in shrimp fed D1 diet, which were significantly higher than those of shrimp fed all other diets (p < .05). The highest value of intestinal tract proteolytic enzyme activity was found in shrimp fed Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) and 3 g/kg DL‐Met‐supplemented diet (D6) (p < .05). The highest values of apparent digestibility coefficients (ADCs) of dry matter and crude protein were found in Met‐Met‐supplemented diet (D7) and followed by the positive control diet (D1) (p < .05). Shrimp fed the D1 diet showed the highest value of total essential amino acid (EAA) and was significantly higher than shrimp fed D2–D3 (p < .05) but without significant difference with shrimp fed D4–D7 (p > .05). In conclusion, results showed that same performance can be achieved with diets containing 260 or 100 g/kg fishmeal supplemented with 3.0 g/kg DL‐Met or 1.0 g/kg Met‐Met. Moreover, supplementation of limiting methionine in low‐fishmeal diets seems to improve the digestive proteolytic activity, improving digestibility of dry matter and protein, and eventually to promote growth of juvenile white shrimp in fishmeal reduction diets.  相似文献   

11.
Cryptocaryonosis is a major problem for mariculture, and the absence of suitable sero‐surveillance tools for the detection of cryptocaryonosis makes it difficult to screen Cryptocaryon irritans‐infected fish, particularly asymptomatic fish. In this study, we proposed a serum‐based assay using selected C. irritans proteins to screen infected and asymptomatic fish. Eight highly expressed genes were chosen from an earlier study on C. irritans expressed sequence tags and ciliate glutamine codons were converted to universal glutamine codons. The chemically synthesized C. irritans genes were then expressed in an Escherichia coli expression host under optimized conditions. Five C. irritans proteins were successfully expressed in E. coli and purified by affinity chromatography. These proteins were used as antigens in an enzyme‐linked immunosorbent assay (ELISA) to screen sera from experimentally immunized fish and naturally infected fish. Sera from both categories of fish reacted equally well with the expressed C. irritans recombinant proteins as well as with sonicated theronts. This study demonstrated the utility of producing ciliate recombinant proteins in a heterologous expression host. An ELISA was successfully developed to diagnose infected and asymptomatic fish using the recombinant proteins as antigens.  相似文献   

12.
The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non‐enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso®, until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA‐enriched or PUFAs‐enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA‐enriched nematodes (5.1 ± 0.5 mm; 33.1%–44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6.  相似文献   

13.
Problems of limited number of dry feeds as supplement or replacement of live feeds have led to poor larval nutrition in many species of fish. Therefore, the suitability of co‐feeding 8‐day‐old African catfish (Clarias gariepinus) posthatch larvae using live feed (Artemia salina) and formulated dry diet containing freshwater atyid shrimp (Caridina nilotica) during weaning was investigated. The experiment ended after 21 days of culture and respective groups compared on the basis of growth performance, survival, feed utilization and nutrient utilization. Larvae co‐fed using 50%Artemia and 50% formulated dry diet resulted in significantly (P < 0.05) better growth performance, food gain ratio (FGR), protein efficiency ratio (PER) and productive protein values (PPV) than other treatments. The lowest growth performance occurred in larvae weaned using 100% formulated and commercial dry diets. Better survival of over 90% was obtained in larvae weaned using 50%Artemia and 50% dry diet, while abrupt weaning using 100% dry diets resulted in lower survival (<75%). These results support a recommendation of co‐feeding C. gariepinus larvae using a formulated dry diet containing C. nilotica and 50% live feed when weaning is performed after 8 days posthatching period.  相似文献   

14.
This study evaluated the effect and phosphorus equivalency value of dietary microbial phytase based on growth performance and nutrient utilization of Channel catfish (Ictalurus punctatus). An all plant‐protein basal diet containing 7.9 g/kg total Phosphorus (P) (Phytate P of 4.5 g/kg) was supplemented with graded levels 0, 300, 500, 1,000, 1,500 and 2,000 U phytase/kg of diet or with 3, 5, 8, 12 g/kg of Ca(H2PO4)2, namely with 0.7, 1.2, 2.0, 3.09 g/kg P as Ca(H2PO4)2. Triplicate groups of Channel catfish (Ictalurus punctatus) juveniles (initial weight, 1.70 ± 0.04 g) were fed the experiment diets for 90 days. The results indicated that dietary phytase supplementation significantly improved growth performance, apparent digestibility coefficient of P and P retention, and decreased feed conversion ratio (FCR), faecal P content and P excretion per gain. Line relation was found between the effects of P and phytase supplementation levels, and the linear response equations of the effects of P and phytase levels were generated and used to calculate the P equivalency values. The average function of P equivalency values (Y, g/kg) of microbial phytase (X, U/kg of diet) was developed: Y = 0.1695 + 0.0021X; R2 = 0.996. The results showed that about 0.38 g of P/kg diet was released by per 100 U of phytase over the range of 300–2,000 U of phytase/kg diet for Channel catfish (Ictalurus punctatus) fed all plant‐protein diet.  相似文献   

15.
Two consecutive studies were conducted to evaluate the dietary supplementation of citrus by‐products (CB) fermented with probiotic bacteria on growth performance, feed utilization, innate immune responses and disease resistance of juvenile olive flounder. In Experiment I, five diets were formulated to contain 0% (control) or 3% four different CB fermented with Bacillus subtilis (BS), Enterococcus faecium (EF), Lactobacillus rhamnosus (LR) and L. plantarum (LP) (designated as CON, CBF‐BS, CBF‐EF, CBF‐LR and CBF‐LP, respectively). During 10 weeks of a feeding trial, growth performance and feed efficiency were not significantly different among all the fish groups. However, fish fed CBF containing diets had significantly higher survivals than the CON group. Disease resistance of fish against Edwardsiella tarda was increased by the fermentation of CB. In Experiment II, we chose the BS as a promising probiotic and formulated five diets to contain 0%, 2%, 4%, 6% and 8% CBF‐BS. Growth performance was not significantly affected by the CBF‐BS supplementation during 6 weeks of a feeding trial. Innate immunity of fish was significantly enhanced by CBF‐BS supplementation. Myeloperoxidase and lysozyme activities were increased in a dose‐dependent manner by dietary CBF‐BS inclusions. In a consecutive challenge test against E. tarda, an increased disease resistance was found by CBF‐BS supplementation. These studies indicate that the fermentation process of CB with probiotic has beneficial effects on innate immunity and thereby increases disease resistance of olive flounder against E. tarda. Bacillus subtilis can be used as a promising probiotic microbe for by‐product fermentation in fish feeds.  相似文献   

16.
To improve feed management strategies for the semi‐intensive culture of Litopenaeus vannamei, outdoor tank and pond trials were conducted. In the tank trial, shrimp (35 shrimp/m2, n = 4) were offered feed for 6 weeks based on a standard feeding protocol (SFP, designed as T100) with five variations (T80:90:100, T90, T90:100, T100:110, T110) of this protocol produced by varying the feed inputs and expressing the treatments as a percentage. Results demonstrated no significant differences in survival rate and feed conversion ratio (FCR) among treatments. The mean final weight and final biomass in the treatments T100:110 and T110 were significantly higher than those in treatment T90 but were not different from the other treatments. In the pond trial, juvenile shrimp (28 shrimp/m2, n = 4) were stocked into twelve 0.1‐ha ponds over a 16‐week period. Three feeding protocols were evaluated including a SFP, a 10% reduction in the SFP (SFP:90), and a variable feed input (SFP:80:90:100), which included 80% SFP at week 4th–8th, 90% SFP from week 9th–12th and 100% SFP for week 12th–16th. There were no significant differences in growth performance and economic return among treatments. Based on previous studies, in which higher feed inputs were evaluated, and results of this study, it does not appear to be economically beneficial to use high feed inputs. Instead, feed input could be either applied at a standard ration to optimize growth and economic return or at restricted rations to reduce FCR (feed cost) albeit at the expense of some growth.  相似文献   

17.
An 8‐week feeding trial was conducted to evaluate the effects of dietary nucleotide (NT)‐rich yeast supplementation on growth, innate immunity and intestinal morphology in Pacific white shrimp (Litopenaeus vannamei). Four isonitrogenous and isolipidic practical diets were formulated to contain 0 (control), 10, 30 and 50 g/kg of NT‐rich yeast, respectively. A total of 480 shrimp with an average initial body weight of 1.86 ± 0.02 g were randomly allocated into four groups, with four replicates per group and 30 shrimp each replicate. The results indicated that shrimp fed the diet containing 50 g/kg NT‐rich yeast had significantly higher weight gain (WG), specific growth rate (SGR) and protein efficiency ratio (PER) than those fed the control diet, and the lowest feed conversion ratio (FCR) was observed in the shrimp fed the 50 g/kg NT‐rich yeast supplemental diet. However, there was no significant difference in survival among all treatments. The crude protein of whole shrimp in the 50 g/kg NT‐rich yeast group was higher than that in the control group. Total protein, triglyceride concentrations, the activities of aspartate aminotransferase and alanine aminotransferase in serum were significantly influenced by the dietary NT‐rich yeast supplementation. The activities of serum phenoloxidase (PO) and lysozyme (LZM) of shrimp fed the diet containing 50 g/kg NT‐rich yeast were higher than those in shrimp fed the other diets. Relative expressions of alp and lzm significantly upregulated in the 30 g/kg NT‐rich yeast group compared to the control group. The intestinal fold height and fold width in the 30 g/kg NT‐rich yeast group were significantly higher than those fed the control diet; and the highest microvillus height occurred in the shrimp fed the 50 g/kg NT‐rich yeast diet. In summary, dietary 30–50 g/kg NT‐rich yeast supplementation promotes growth performance, enhances innate immunity and improves intestinal morphology of Litopenaeus vannamei.  相似文献   

18.
Effects of artificial substrates in zero‐water‐exchange culture system on the rearing performance of Litopenaeus vannamei under winter indoor condition were investigated in this study. Growth, survival, feed conversion rate (FCR), production rate of L. vannamei and water quality were compared between artificial substrate‐treated group (AST) and control group (without artificial substrates presented in the rearing environment). Artificial substrates can significantly improve the water quality, the ammonia and nitrite‐N concentrations in the AST group were significantly lower than in the control group (P < 0.05), and the total heterotrophic bacteria and Vibrio spp. were also significantly lower in the AST group (P < 0.05). The survival, growth and production rate of L. vannamei in the AST group were significantly higher than in the control group (P < 0.05). Significantly lower FCR was observed in the AST group (P < 0.05). Results from this study indicate that the utilization of artificial substrates in the indoor shrimp culture system could effectively control the water quality, improve the survival and growth of shrimp and significantly reduce the FCR. This study provides a guideline for employing artificial substrates in rearing of shrimp in the zero‐water‐exchange culture system under lower temperature, which could be applicable to other similar species.  相似文献   

19.
The efficacy and tolerance of a novel microbial 6‐phytase were investigated in rainbow trout, Oncorhynchus mykiss, and Nile tilapia, Oreochromis niloticus. Reference diets were sufficient in available phosphorus (P). The test diet limiting in available P was supplemented with phytase at 500, 1000, or 2000 phytase units/kg feed. The enzyme was effective in increasing total P apparent digestibility coefficient in relation to increasing the dose of phytase in rainbow trout and Nile tilapia. Zinc apparent digestibility improved in relation to phytase supplementation in rainbow trout. P release due to phytase supplementation ranged from 0.06 to 0.18% P/kg feed in rainbow trout and from 0.13 to 0.26% P/kg feed in Nile tilapia. A 58‐d performance trial was conducted to evaluate tolerance of fish to phytase supplementation. Dietary treatments consisted of a basal diet without phytase or supplemented with 2000 and 200,000 phytase units/kg feed. Results indicate that this novel microbial 6‐phytase is well tolerated by fish. Significant improvements for growth as well as feed conversion ratio were observed when the phytase was fed at 2000 phytase units/kg feed. This phytase is proven efficient in releasing P from phytate and could be added when plants are used for fish meal replacement in diets for salmonid and omnivorous fish.  相似文献   

20.
The feeding trial was conducted to evaluate the potentials of Clostridium butyricum in the diet of tilapia. Fish (~14 g) were fed with basal diet supplemented with 0 (Control), 0.5 (C‐1), 1 (C‐2), 2 (C‐3), 4 (C‐4) and 8 (C‐5) g/kg commercial probiotic‐containing C. butyricum (1.5 × 108 CFU/g) for 8 weeks. The results showed that weight gain significantly increased, and feed conversion ratio decreased in the C‐2, C‐3 and C‐4 groups (p < .05). The protein retention (except C‐1 group), lipid retention and apparent digestibility coefficient (ADC) of dry matter in probiotic supplementation groups were significantly enhanced, and ADC of protein in the C‐4 group was also improved (p < .05). The supplementation of probiotic significantly increased villus height in anterior intestines and reduced the numbers of intestinal Escherichia coli (p < .05). High‐throughput sequencing showed that top three phyla namely Planctomycetes in all probiotic‐containing groups, Proteobacteria in the C‐1 and C‐2 groups and Chloroflexi in the C‐3 group had higher level than the NC group. The cumulative mortality was reduced by dietary probiotic after challenging with Aeromonas hydrophila (p < .05). In conclusion, C. butyricum can be supplemented at 1–2 g/kg feed for promoting the growth, feed utilization, gut health and microbiota of tilapia.  相似文献   

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