Growth performance,nutrient digestibility and digestive enzyme activity in Asian seabass,Lates calcarifer juveniles fed diets supplemented with cellulolytic and amylolytic gut bacteria isolated from brackishwater fish

Asian seabass, Lates calcarifer juveniles were fed for 30 days to evaluate the efficacy of cellulolytic (Bacillus sp. DDKRC1.) and amylolytic (Bacillus subtilis DDKRC5.) bacteria supplemented diets. Four experimental groups were maintained in triplicate of which group I was the control group and received no bacterial supplementation. Groups II, III and IV were fed diet supplemented with B. subtilis DDKRC5. (14.25 × 10⁷ CFU/mL), Bacillus sp. DDKRC1. (2.94 × 10⁷ CFU/mL) and mixture of both the microbes (1:1 ratio), respectively, @ 1% (v/w). After 30 days of feeding, fish reared as group IV showed significantly higher (P < 0.01) weight gain (141.42%), survival (91.50%), protein efficiency ratio (1.18) and significantly lower (P < 0.01) FCR (2.15) than that of other groups. Nutrient digestibility parameters were significantly (P < 0.01) higher in group IV followed by groups III, II and I. Digestive cellulase, amylase and protease activities in the gastrointestinal tract were also significantly (P < 0.01) higher in group IV. Amylolytic and cellulolytic microbial count in the gastrointestinal (GI) tract were significantly (P < 0.01) higher in groups II, III and IV as compared with that of control. It can be concluded that feed supplemented with mixture of B. subtilis DDKRC5. and Bacillus sp. DDKRC1. showed better performance in Asian seabass juveniles.     

Fishmeal levels can be successfully reduced in white shrimp (Litopenaeus vannamei) if supplemented with DL‐Methionine (DL‐Met) or DL‐Methionyl‐DL‐Methionine (Met‐Met)

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.     

Replacement of squid and krill meal by snail meal (Buccinum striatissimum) in practical diets for juvenile of kuruma shrimp (Marsupenaeus japonicus)

A 60‐day feeding trial was conducted to investigate the effects of substituting squid and krill meal with marine snails (Buccinum striatissimum) into the diets of juvenile kuruma shrimps (Marsupenaeus japonicus). Five experimental diets were formulated to contain varying levels of snail meal at 0%, 25%, 50%, 75% and 100% (D1, D2, D3, D4 and D5, respectively) and fed to juvenile kuruma shrimps (initial mean weight 0.27 ± 0.02 g). The results showed that weight gain, feed intake and specific growth rate were improved significantly in D4 and D5 groups when compared with D1 group (p < 0.05). Significant differences were not detected in survival rate among all shrimps fed diets containing several levels of snail meal (p > 0.05). Crude protein content of shrimps fed the control diet was significantly lower than other treatments (p < 0.05). Lipid content in shrimps fed 50% snail meal were significantly higher than the control while cholesterol content in shrimps fed 100% snail meal were significantly decreased and polyunsaturated fatty acid contents were significantly increased in shrimps fed 75%–100% snail meal (p < 0.05). These results suggest that supplementing snail meal for complete replacement of squid and krill meal can be done to improve juvenile kuruma shrimps’ growth and reducing their cholesterol levels.     

Dietary pantothenic acid requirement of fingerling Channa punctatus (Bloch) based on growth,feed conversion,liver pantothenic acid concentration and carcass composition

A 16‐week feeding trial was conducted to determine the dietary pantothenic acid requirement of fingerling Channa punctatus. Six casein–gelatin‐based diets (450 g/kg CP; 18.39 kJ/g GE) with graded levels of pantothenic acid (0, 10, 20, 30, 40 and 50 mg/kg diet) were fed to triplicate groups of fish (6.2 ± 0.71 cm; 4.26 ± 0.37 g) near to apparent satiation. The growth evaluation in terms of absolute weight gain (AWG), feed conversion ratio (FCR) and protein retention efficiency (PRE) indicated the best performance (p < .05) in fish fed diet containing 30 mg/kg pantothenic acid. Highest haemoglobin, haematocrit and RBCs counts were also obtained in fish fed diet with 30 mg/kg pantothenic acid. Mean cell haemoglobin and mean cell volume were found to be lowest in fish fed pantothenic acid‐free diet indicating the anaemia in this group of fish. Superoxidase dismutase and catalase activities of liver tissue were found to improve (p < .05) with the increasing levels of dietary pantothenic acid from 0 to 30 mg/kg. However, liver pantothenic acid concentration responded positively with the increasing levels of pantothenic acid up to 40 mg/kg diet and then stagnation in liver pantothenic acid concentration with the further inclusion of pantothenic acid was recorded. Second‐degree polynomial regression analysis of AWG, FCR and PRE exhibited the pantothenic acid requirement at 36.4, 32.8 and 34.7 mg/kg diet, respectively. Data generated during this study would be useful in formulating pantothenic acid‐balanced commercial feeds for the intensive culture of this fish.     

Effect of dietary lysine and genetics on growth and indices of lysine catabolism in rainbow trout (Oncorhynchus mykiss)

The level of the essential amino acid lysine is of concern in trout feed. The objective of this study was to investigate the response of different families of fish to lysine‐deficient (LD) versus lysine‐adequate (LA) soy protein‐containing diets. For each treatment combination, there were five replicates. As expected, feed efficiency (p < .0001) and thermal growth coefficient (TGC, p < .0001) were improved in fish fed the LA compared to the LD diet. Hepatosomatic index (HSI, p < .01) and whole‐body lipid content (p < .01) were higher for fish consuming the LD compared to the LA diet. There was no effect (p > .05) of diet on hepatic lysine α‐ketoglutarate reductase (LKR) activity, LKR mRNA abundance or lysine oxidation. There was a family effect on feed efficiency (p < .0001), TGC (p < .0001) and condition factor (p < .05) and there was a trend for differences in oxygen consumption (p < .07) across families while consuming the LD diet; however, there was no effect on ammonia excretion, HSI, lipid content, efficiency of nitrogen or lysine retention or indices of lysine catabolism. One family, in particular, had more favourable feed efficiency and thermal growth coefficient when fed the LD diet, indicating that it may possess an enhanced genetic potential for performance when consuming LD, soybean meal‐containing diets.     

Effects of multienzyme complex and probiotic supplementation on the growth performance,digestive enzyme activity and gut microorganisms composition of snakehead (Channa argus)

The major objective of this study conducted for 7 weeks was to investigate the influence of supplementation with multienzyme complex and probiotic and their interaction effects on the growth performance, body composition, serum biochemical parameters and gut microorganism composition of snakehead (Channa argus). There were four treatments in this experiment coded as control, probiotic (Bacillus amyloliquefaciens), multienzyme (amylase, acid protease and papain) and pro‐multi (B. amyloliquefaciens and amylase, acid protease and papain), respectively. The results demonstrated that snakeheads on the multienzyme resulted in better growth performance in terms of final body weight (FBW), weight gain ratio (WGR) and feed conversion ratio (FCR) significantly (p < 0.05) than those on the control diet, while they did not (p > 0.05) on probiotic and pro‐multi. Snakeheads receiving multienzyme increased significantly (p < 0.05) the serum parameters, including albumin, total protein and AKP and probiotic increased AKP and lysozyme meanwhile decreased the LDL‐C significantly (p < 0.05) compared with control. Analysis of the composition of gut microorganisms showed that four dominant microorganisms were Spirochaetes, Proteobacteria, Firmicutes and Bacteroidetes. Probiotic could enhance the richness and diversity of gut microorganisms in snakeheads, furthermore revealing a means of evaluating the relationship between feed supplementation and microorganisms.     

Effect of Arthrospira supplementation on Oreochromis niloticus gut microbiota and flesh quality

Supplementing fish feed with Arthrospira platensis has several beneficial effects, such as improved growth, survival and feed conversion, but little is known about how it affects gut microbiota or flesh quality. In this trial, feed with 3% A. platensis was given to Oreochromis niloticus (SPR, spirulina supplemented) over a period of 50 days and their gut microbiota and flesh quality were compared with controls (CTRs, no supplementation). Average daily growth was higher in SPR fish (p < 0.05). Regarding microbiota, a total of 5,470,272 readings (individuals) were obtained from 16 gut samples (n = 8 CTR, n = 8 SPR), with a gamma diversity of 1,563 species but no significant differences were found between treatments. Among the high inter‐individual variability found, some individual microbiota were dominated by Proteobacteria (36.6%) and Fusobacteria (32.9%) and others more by Actinobacteria (37%). Regarding flesh quality, significant differences were observed in flesh colour post‐mortem (a*, b* and chroma) (p < 0.05), with higher reflectance in the range of 470–500 and 620–670 nm in SPR tilapia, which corresponds with the reflectance range of β‐carotene and phycocyanin. However, rigor mortis was resolved earlier in SPR fish (p < 0.05), which suggests a shorter shelf life. Adding 3% of A. platensis in O. niloticus diet can improve growth and flesh colour and does not appear to modify intestinal microbiota.     

Effects of Chinese herbal medicines mixture on growth performance digestive enzyme activity immune response of juvenile Japanese seabass,Lateolabrax japonicus

A single factorial experiment was conducted to investigate the effects of Chinese herbal medicines mixture (CHMM) on growth performance, digestive enzyme activity and immune response of Japanese seabass, Lateolabrax japonicus (initial weight 5.01 ± 0.32 g). The fish were fed diets containing six levels of CHMM (0, 4, 8, 12, 16 and 20 g/kg) for 4 weeks. The results showed that the weight gain rate and specific growth rate (SGR) enhanced significantly in fish fed diet containing 8 g/kg CHMM (p < .05), while the feed conversion ratio (FCR) in the 4 and 8 g/kg CHMM groups reduced significantly compared with the control (p < .05). The body crude protein levels in 8 and 16 g/kg groups were significantly higher than the control (p < .05). The pepsin, amylase and lipase activities elevated significantly in the stomach of fish fed 8 g/kg CHMM, while the erepsin and lipase in the intestine of fish in 12 and 16 g/kg groups were higher significantly than the control (p < .05). The lysozyme, alkaline phosphatase, acid phosphatase (ACP), total antioxidative capacity activities in serum of fish fed 12 g/kg CHMM were higher significantly than those in the control (p < .05), while the total superoxide dismutase (SOD), total antioxidative capacity, catalase, alkaline phosphatase (AKP) and ACP activities in hepatopancreas of fish in 12 g/kg group were all significantly higher than those in the control (p < .05). Regression analysis showed that the relationships between dietary CHMM levels and either FCR, SGR, erepsin, pepsin or lysozyme activities were best expressed by quadratic or cubic regression equations, and the optimal inclusion levels are 11.4, 10.7, 10.7, 8.4 and 10.5 g/kg for maximum FCR, SGR, erepsin, pepsin and lysozyme activities, respectively. Under the present experimental condition, the optimal supplementary level of CHMM in the diet of Japanese seabass is 8–12 g/kg.     

Dietary calcium requirement of red swamp crayfish (Procambarus clarkia)

To investigate dietary calcium requirement of red swamp crayfish (Procambarus clarkia), six semi‐purified diets were formulated to contain different concentrations of calcium (2.7(control group), 6.1, 11.9, 17.6, 23.5 and 29.1 g/kg calcium). Each diet was hand‐fed to triplicate of 15 crayfish with average initial body weight (6.22 ± 0.87) g for 8 weeks. The results showed that weight gain rate (WGR) significantly increased and feed conversion ratio (FCR) significantly decreased from 11.9 to 23.5 g/kg groups (p < .05). Protease activities in intestine and hepatopancreas and parathyroid hormone concentrations in serum significantly decreased with increasing dietary calcium levels (p < .05), while calcium and phosphorus contents in exoskeleton, calcium content in muscle and calcitonin concentrations in serum significantly increased (p < .05). The activities of lipase and amylase in intestine and hepatopancreas, serum alkaline phosphatase and total vitamin D concentrations in serum had significant increase as dietary calcium content increased up to 11.9–17.6 g/kg (p < .05). The inorganic phosphorus content in 29.1 g/kg group was significantly lower than those in other groups (p < .05). Broken‐line model analysis based on WGR and quadratic curve model analysis based on FCR showed that optimal dietary calcium requirement of red swamp crayfish ranged from 12.7 to 17.1 g/kg.     

Clostridium butyricum as probiotic for promoting growth performance,feed utilization,gut health and microbiota community of tilapia (Oreochromis niloticus × O. aureus)

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.     

Effects of dietary coated protease on growth performance,feed utilization,nutrient apparent digestibility,intestinal and hepatopancreas structure in juvenile Gibel carp (Carassius auratus gibelio)

This study was conducted to investigate the effects of dietary protease on growth performance, feed utilization, whole‐body proximate composition, nutrient digestibility, intestinal and hepatopancreas structure of juvenile Gibel carp, Carassius auratus gibelio (mean weight 8.08 ± 0.18 g). Six diets were prepared, including a positive control diet (dietary protein 350 g/kg, PC), one negative control diet (dietary protein 33 g/kg, NC) and four protease supplementations diets, which were 75, 150, 300 and 600 mg/kg protease NC diet. After 12 weeks of diet feeding in indoor recycle aquarium tanks, no significant difference (p > .05) was found on growth performance between fish fed diet with 75–600 mg/kg protease and the PC group. Compared with the fish fed the NC diet, the specific growth rate of fish fed 300 mg/kg protease increased significantly (p < .05), as well as protein efficiency ratios (p < .05), while feed conversion was the opposite (p < .05). The nutrient digestibility of crude protein and lipid was higher (p < .05) in fish fed 150 mg/kg protease diet than the PC diet. Whole‐body proximate composition of fish was not affected (p > .05) by the dietary treatment. Serum alkaline phosphatase and albumin were significantly affected by dietary protease (p < .05), while the content of total protein, glucose, triglyceride, total cholesterol, aspartate aminotransferase and alanine aminotransferase activities in serum was not affected (p > .05). Foregut muscular thickness was thinner (p < .05), when the fish fed diets supplementation of protease in 150 or 600 mg/kg diet than the NC diet. Protease activities in hepatopancreas and foregut were higher (p < .05), in the fish fed 150 or 300 mg/kg protease diet than the fish fed the PC diet, but those in the mid‐ and hindgut were not significantly affected (p > .05) by the dietary treatments. Based on the regression analysis of weight gain rate, the optimal dietary inclusion level of protease was 400 mg/kg in the diet for juvenile Carassius auratus gibelio.     

Effects of garlic powder on feeding attraction activity,growth and digestive enzyme activities of Japanese seabass,Lateolabrax japonicus

The study was to investigate the effects of garlic (Allium sativum) powder on feeding attraction activity, growth performance and digestive enzymes of juvenile Japanese seabass, Lateolabrax japonicus (initial weight: 29.82 ± 0.24 g). Six concentration gradients (0, 5, 10, 15, 20 and 25 g/kg diets) were formulated for luring and feeding experiment. The results showed a clear attractive trend of garlic powder for L. japonicus. A 28‐day feeding experiment indicated garlic could reduce the feed conversion ratio (FCR) (p < .05). The content of the body crude lipid was significantly increased at 10–15 g/kg diet (p < .05). Digestive enzyme activities including trypsin, amylase (AMS) and lipase (LPS) in the intestine were the highest at 10 g/kg diet (p < .05). Overall, garlic powder provides a promising and effective method for Japanese seabass healthy culture by improving fish growth and digestive ability. The results of this research suggested the additive suitable dosage of garlic powder was about 10 g/kg diet.     

Immune responses by dietary supplement with Astragalus polysaccharides in the Pacific white shrimp,Litopenaeus vannamei

Two experiments were conducted to investigate the immune‐enhancing effect of dietary supplement with Astragalus polysaccharides (APS) on the Pacific white shrimp, Litopenaeus vannamei. In experiment 1, the optimal APS dose was determined based on the immune responses of shrimps fed APS diet for 30 days. In experiment 2, the effect of APS supplementation on immune response of shrimp suffering white spot syndrome virus (WSSV) challenge was determined. Results showed that the total haemocyte count and phagocytic activity in shrimps fed APS diets significantly (p < .05) increased in comparison with those fed the basal diet. Dietary supplement with APS markedly (p < .05) increased the activity of phenoloxidase (PO), total superoxide dismutase (SOD), lysozyme (LZM), acid phosphatase and alkaline phosphatase in shrimp hemolymph, but decreased the maleic dialdehyde (MDA) content. Significantly higher (p < .05) activity on PO, SOD and LZM and lower (p < .05) MDA content have also been found in shrimps suffering WSSV challenge. Therefore, APS could be used as a safe and effective feed additive in shrimp aquaculture, and the optimal dose of APS for the Pacific white shrimp was suggested to be 0.2 g/kg based on our results.     

Dietary supplementation of red alga Pyropia spheroplasts on growth,feed utilization and body composition of sea cucumber,Apostichopus japonicus (Selenka)

A feeding experiment was conducted in a closed recirculating system to evaluate the effects of freeze‐dried spheroplasts prepared from Pyropia yezoensis (Ueda) on feed intake, growth and biochemical composition of sea cucumber, Apostichopus japonicus (Selenka). Pyropea spheroplasts (PS) were prepared through enzymatic treatment to break down the complex mixture of polysaccharides cell walls that might be easier for growth energy partitioning. Sea cucumbers were fed‐formulated diets with 10 (Diet 1), 30 (Diet 2) and 50 g/kg (Diet 3) inclusion level of PS. A diet without PS was used as a control (Diet 4). The experiment was conducted for 6 weeks maintaining water temperature 15 ± 1°C, photoperiod 18:06 hours (D:L). Feed was supplied ad‐libitum at 16.00 h once in a day, and the remaining feed and faeces were removed in the next day. Results showed that the highest growth was observed in the 50 g/kg PS diet compared to other treatments. Total weight gain, mean weight gain, net yield, protein efficiency ratio (PER) and protein gain (%) were significantly higher in the 50 g/kg PS diet (p < .05). A significantly higher percentage of energy was allocated for growth in the 50 g/kg PS diet. The highest specific growth rate and feed conversion efficiency (p < .05) were observed in the higher percentage of PS diet. Both the growth performance and biochemical analysis showed that superior growth was observed with increasing levels of PS in the diet. We infer that PS can be used as a new, cheaper feed ingredient in the formulated diet of A. japonicus.     

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.     

Effect of vitamin E on spermatophore regeneration and quality of pond‐reared,black tiger shrimp (Penaeus monodon)

The objective of the present work was to evaluate the effects of different levels of vitamin E in feed on the spermatophore regeneration and quality of male Penaeus monodon. The experiment was carried out with the four following treatments: the basal diet no added vitamin E, the diet added 200, 600 and 1,000 mg/kg respectively. Spermatophore regeneration and quality were evaluated by spermatophore weight, sperm count and spermatophore absence rates, which male P. monodon were extruded spermatophore for feeding 20 and 40 days. In the experiment, the weight of the twice regenerated spermatophore of the males added to the vitamin E group was higher than that of the untreated control group. The weight of the first regenerated spermatophore with the addition of 1,000 mg/kg group was the highest and significantly higher than the control group (p < .05), but there was no significant difference among the three groups with different levels of vitamin E. The weight of the second regenerated spermatophore with the addition of 600 mg/kg group was the highest, followed by 1,000 mg/kg group, both of which were higher than the control group and the addition of 200 mg/kg group. Within the same group, the regeneration spermatophore weight showed overall upward trend as the feeding time, twice regenerate experiment spermatophore weight with added to the vitamin E groups were significantly higher than the initial value (p < .05), but three spermatophore weight of male shrimp at the control group had no significant difference. The sperm quantity and the percentage of normal sperm of the twice regenerated spermatophore of the males with added to the vitamin E group was higher than that of the untreated control group, and those of the addition of 200 mg/kg group was significantly higher than that of control group (p < .05). The total number of sperm and the percentage of living sperm of male shrimp in the experimental group decreased with the increase of vitamin E in the feed. Within the same group, the total number of sperm and the percentage of living sperm of male shrimp with added to the vitamin E groups showed overall upward trend as the feeding time and were significantly higher than the initial value (p < .05), but the control group was slightly down and had no significant difference. Comprehensive sperm weight, sperm quantity and living sperm percentage of three indicators, that adding 200 mg/kg of vitamin E in feed could effectively promote the spermatophore regeneration in the male P. monodon and improve the sperm quantity. The experimental results provide a scientific basis for the breeding of P. monodon.     

Effects of dietary supplementation of probiotics on the growth,activities of digestive and non‐specific immune enzymes in hybrid grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀)

Effects of Bacillus cereus BC‐01, Lactobacillus acidophilus LAG01, Clostridium butyricum CBG01 and their combinations as supplementation on the growth performance, digestive enzyme activities and serum non‐specific immunity of hybrid grouper (Epinephelus lanceolatus ♂×E. fuscoguttatus ♀) were assessed. Seven different diets, that is one control diet (basal feed without any probiotics, CT) and six treatment diets containing single B. cereus (Bs), L. acidophilus (Ls) and C. butyricum (Cs) at 1.0 × 10⁹ cfu/kg feed, and also their combinations in equal proportion at 1.0, 2.0 and 3.0 × 10⁹ cfu/kg feed (BLC1, BLC2 and BLC3) were prepared respectively. After 60‐day feeding trial, the final weight, specific growth rate,food consumption, food conversion efficiency and apparent digestibility coefficient of fish in Ls and BLC3 were significantly higher compared with the control (p < .05). The activities of pepsin and trypsin in the intestine of fish for Ls and BLC3 were significantly higher relative to the control (p < .05). Relative to controls, significantly enhanced amylase and lipase activities in proximal intestine except for Cs and BLC1 and lipase activities in distal intestine except for Cs were observed (p < .05). Meanwhile, activities of superoxide dismutase in the serum of fish for all treatments, lysozyme and catalase in Ls and BLC3, and glutathione peroxidase except for Cs were significantly enhanced (p < .05). Based on the above, dietary supplementation of single L. acidophilus at 1.0 × 10⁹ cfu/kg or combination of three strains at 3.0 × 10⁹ cfu/kg for hybrid grouper is recommended.     

A Comparison between dietary effects of Cuminum cyminum essential oil and Cuminum cyminum essential oil,loaded with iron nanoparticles,on growth performance,immunity and antioxidant indicators of white leg shrimp (Litopenaeus vannamei)

This study evaluates the effect of dietary cumin essential oil's (CEO) and cumin essential oil's loaded iron nanoparticles (CEO‐loaded NPs) on growth performance, haematological parameters and antioxidant status of white leg shrimp. Shrimps with the initial weight of 3.38 ± 0.014 g were allocated into 15 fibreglass tanks (300 L, 60 shrimps per tank) and were fed with five experimental diets containing 0 g/kg CEO (the control diet), 5 g/kg CEO, 10 g/kg CEO, 5 g/kg CEO‐NPs and 10 g/kg CEO‐NPs for 56 days. After 56 days of culture, the shrimps fed with CEO and CEO‐loaded NPs supplemented diets showed a more significant increase in growth performance (p < .05) than in the control diet. Total haemocyte count (THC) value, large‐granule cells (LGC), hyaline cells (HC)%, superoxide dismutase (SOD) and Alkaline phosphatase (AKP) activity were significantly higher (p < .05) in the shrimps fed with CEO and CEO‐loaded NPs supplemented diets than the shrimps fed with the control diet. Glutathione peroxidase (GPX) enzyme activities along with the glucose and cholesterol concentrations significantly decreased in the shrimps fed with the CEO and CEO‐loaded NPs supplemented diets more than those fed with the control diet. The results suggest that the dietary CEO‐loaded NPs can improve the growth performance, the health status and the antioxidant capacity of L. vannamei.     

Effects of dietary fishmeal replacement with Spirulina platensis on the growth,feed utilization,digestion and physiological parameters in juvenile gibel carp (Carassis auratus gibelio var. CAS III)

A 60‐day growth experiment was conducted to investigate the effect of dietary replacement of fishmeal by Spirulina platensis on growth performance, digestion and physiological parameters in juvenile gibel carp (5.0 ± 1.0 g). Four diets were formulated to replace 0 (SP0), 50% (SP50), 75% (SP75) and 100% (SP100) of dietary fishmeal protein by S. platensis respectively. Other two diets based on SP100 were supplemented with 2% dicalcium phosphate (SP100 + P) or 0.28% coated lysine (SP100 + Lys). The results showed that no significant differences of specific growth rate (SGR), feed efficiency (FE), feeding rate (FR) and protein efficiency ratio (PER) were observed between SP0 group and the replacement groups (SP50, SP75 and SP100). FE and PER of fish‐fed SP100 + Lys diet were significantly higher than the fish‐fed SP100 diet (p < .05). Apparent digestibility coefficients (ADCs) of dry matter, protein, energy and phosphorus increased significantly with the increasing S. platensis inclusion. Meanwhile, fish from SP100 + P or SP100 + Lys group had higher ADCs of nutrients compared to the SP100 group (p < .05). Compared with SP0 diet, fish‐fed S. platensis diets had higher activities of plasma superoxide dismutase, hepatopancreas total antioxidant capacity, plasma alkaline phosphatase and plasma lysozyme, as well as the lower content of plasma malondialdehyde. The present results indicated that dietary fishmeal could be fully replaced by S. platensis without any negative effects on growth performance of gibel carp. Supplementation of lysine in the S. platensis replacement diet could further improve the feed utilization of gibel carp.     

Formulated diet alters gut microbiota compositions in marine fish Nibea coibor and Nibea diacanthus

Nibea, an economical marine fish, is generally fed on trash fish (the low‐value fish), which can cause high feed costs and waste pollutions in high‐density aquaculture. To assess the effect of formulated diet on the gut microbiota in Nibea coibor and Nibea diacanthus, denaturing gradient gel electrophoresis, clone libraries analysis and Illumina sequencing of the 16S ribosomal RNA gene were used in this study. Two Nibea fishes were both dominated by Gammaproteobacteria (especially Photobacterium) and shared a set of gut microbiota, including Bacilli, Mollicutes, Alphaproteobacteria and Fusobacteriia. Statistical analyses revealed that formulated diet led to lower feed conversion ratio (p < 0.001), lower abundance of Vibrio (p = 0.040) and infectious diseases pathways (p = 0.001), higher abundance of polysaccharide‐degrading bacterium Cellvibrio (p = 0.006) in two Nibea species, with higher weight gain rate (p = 0.023) and microbial diversity (Shannon, p = 0.049 and Simpson, p = 0.044) and more carbohydrate metabolism (p = 0.020) observed in N. coibor. The distribution and correlation network of 17 potential short‐chain fatty acid producing bacteria were obtained and visualized in all treatment groups. The results reveal that formulated diet has beneficial effects on the gut microbial ecology in two Nibea fishes, which suggests the possibility of replacing trash fish diet with formulated diet in Nibea aquaculture.