Using stable isotope analysis to assess the relationship among dietary protein sources,growth, nutrient turnover and incorporation in Nile tilapia (Oreochromis niloticus)

Nile tilapia (1.20 g) were fed for 56 days in five treatments (FM100 containing only fish meal [FM] as a protein source; soybean meal (SBM) replace 25%, 50%, 75% and 100% of FM protein in the diets of FM75, FM50, FM25 and FM0, respectively) to assess the effects of dietary protein sources on growth, turnover half‐life of nitrogen and carbon stable isotopes (δ¹³C and δ¹⁵N) in muscle, isotope discrimination factors (Δ¹⁵N and Δ¹³C), and the relative contribution of protein sources to muscle growth. Results showed that the final body weight, weight gain and specific growth rate of fish fed diet FM25 were significantly higher than other treatments (p < .05). By day 35, fish under all treatments reached isotopic equilibrium, and the equilibrium values consistently increase as a function of stable isotope values in diets. Growth accounted for most isotopic changes in muscle and resulted in significantly shorter half‐lives of nitrogen and carbon in FM25 (p < .05). The Δ¹⁵N of FM25 and Δ¹³C of FM0 were significantly lower than other treatments (p < .05). The proportional contributions of SBM protein were significantly higher than their respective levels in FM75 and FM25 (p < .05), indicating a preferential incorporation of nitrogen from the SBM in muscle tissue.     

A combination of rapeseed,cottonseed and peanut meal as a substitute of soybean meal in diets of Yellow River carp Cyprinus carpio var

A feeding trial was conducted to evaluate the results of replacing soybean meal (SBM) with other blend plant protein (BP) (rapeseed meal, cottonseed meal and peanut meal) sources on growth, fish body composition, biochemical parameters, non‐specific immune index and gene expression of growth hormone/insulin‐like growth factor‐1 in Yellow River carp Cyprinus carpio. The results showed that the 600 g/kg replacement with BP in diet did not affect the growth performance of Yellow River carp, but the 800 g/kg SBM replacement diet could depress the growth of fish (p < .05). The 800 g/kg SBM replacement diet significantly impacted the superoxide dismutase, malondialdehyde contents, lysozyme, alanine aminotransferase and aspartate aminotransferase activities (p < .05). Fish fed 800 g/kg SBM replacement diet showed lowest insulin‐like growth factor 1 and highest growth hormone level than that of other diets (p < .05). Both gene expression levels of GH and IGF‐I in hepatic showed significant difference among dietary treatments (p < .05), and the lowest GH and IGF‐I mRNA level in liver were found in fish fed 800 g/kg SBM replacement diet (p < .05). In conclusion, no more than 600 g/kg SBM could be replaced by BP in diet of Yellow River carp without adverse effects on the growth performance. However, 800 g/kg SBM replacement with BP in diet inhibited the growth performance, affected some blood parameters and immune response index, and down‐regulated GH and IGF‐1 gene expression of liver in Yellow River carp. Further, GH level in serum was negatively correlated with GH mRNA level in liver; meanwhile, serum concentrations of IGF‐I were positively correlated with hepatic IGF‐I mRNA expressions.     

Effects of three carbohydrate sources on water quality,water consumption,bacterial count,growth and muscle quality of Nile tilapia (Oreochromis niloticus) in a biofloc system

This study compared the effect of three sources of carbohydrates: sugar, wheat and malt flours, on water quality, water consumption, bacterial load, growth and flesh quality of Nile tilapia. Adults (120.6 ± 0.64 g) were stocked in 1.2‐m³ fibreglass tanks at a rate of 25 fish/m³. Carbohydrates were added to the biofloc tanks at a C:N ratio of 20:1. Water flow in the non‐biofloc control tanks was adjusted to 0.6 L/day. The 105‐day experiment was conducted in triplicates. Results showed that biofloc treatments (BFT) with zero water exchange had significantly higher mean total ammonia, nitrites, nitrates, alkalinity, total suspended solids and lower pH than the control treatment. The sugar BFT had the highest floc volume. Growth parameters and feed conversion ratio did not differ significantly among treatments. However, tilapia in the malt flour and control treatments had close values. Gross fish yield was higher (p < .05) in the control than the BFT treatments. Water consumption/kg tilapia produced in the control was 42 times higher than the BFT groups. Protozoa dominated the biofloc biota, and wheat flour was the best in harbouring higher bacterial populations in the gut. Protein content and ∑n‐3 fatty acids were highest in the wheat flour biofloc, while malt flour biofloc had the highest lipids. The sugar biofloc had the highest n‐3/n‐6 ratio. Tilapia muscles in the malt flour and control treatments had the highest protein and lipid contents respectively. Tilapia muscles in the wheat flour BFT had the highest ∑n‐3 fatty acids and n‐3/n‐6 ratio. It can be concluded that farming tilapia in BFT using malt or wheat flours as carbon sources is more economical in saving great amount of water with minimal discharge of pollutants without affecting tilapia growth or flesh quality.     

Evaluation of dietary protein requirement for the growth performance of minor carp,Cirrhinus reba (Hamilton, 1822) fingerlings

An experiment was designed to evaluate the requirement of dietary protein for Reba carp, Cirrhinus reba fingerlings using semi‐purified diet. Five isocaloric diets were prepared containing 20%, 25%, 30%, 35% and 40% level of protein using casein, gelatin as a major protein source. The experiment was conducted for 105 days in triplicates to evaluate the growth, survival, feed utilization, carcass composition of C. reba. Mean weight gain was highest (p < .05) in T3. Specific growth rate was highest in T3 and lowest in T1. Similarly, significantly (p < .05) highest net fish yield were recorded in T3. No significant difference was recorded in survivability. Feed conversion ratio, protein efficiency ratio, feed conversion efficiency and protein conversion efficiency were significantly (p < .05) higher for T3 compared with other treatments. Highest carcass protein and lipid values were recorded in T3. So, conclusion can be drawn that 30% crude protein is optimum for overall performance. Furthermore, broken‐line analysis for specific growth rate, final biomass and net fish yield indicated that dietary protein level of 28.148 to 28.253% is optimum for the best growth performance of fingerling C. reba.     

Dietary lipid influences gonadal maturation,digestive enzymes and serum biochemical indices of Cyprinus carpio reared in biofloc system

An experiment was conducted for 120 days to evaluate optimum dietary lipid requirements for gonadal maturation of Cyprinus carpio fed with varying dietary lipid levels under biofloc‐based systems (BFT). About 180 fingerlings (22 g ± 0.05) were randomly distributed in 15 tanks (300 L) at the rate of 48 no./m² and fed with varying lipid levels (T1—4% lipid with BFT, T2—6% lipid with BFT, T3—8% lipid with BFT, T4—10% lipid with BFT, control—10% lipid without BFT). The C/N ratio of 20:1 was maintained using tapioca flour as carbon source. Biofloc units supplemented with 8% dietary lipid (T3) showed advanced maturation in terms of absolute fecundity (9,913 ± 7.62), relative fecundity (229.0/g ± 11.92), gonadosomatic index (24.47% ± 1.27), hepatosomatic index (1.97% ± 0.07), condition factor (0.02 g/cm³ ± 0.00) compared with control (clear water with 10% lipid) (p < .05). Histological observations of gonads also revealed that the biofloc groups with supplementation of 8% dietary lipid promoted gonadal maturation for female oocyte and 6% dietary lipid promoted maturation for males, compared with control (clear water with 10% lipid). The results obtained in this experiment elucidate that the biofloc improves gonadal maturation of common carp broodstock at a dietary supplementation with 8% lipid compared with conventional system of broodstock management.     

Effect of fungal fermentation on apparent digestibility coefficient for dry matter,crude protein and amino acids of various plant protein sources in Penaeus vannamei

Four commercial solvent‐extracted oilseed meals/cakes, viz. soybean meal (SBM), groundnut oil cake (GNC), rapeseed meal (RSM) and sunflower oil cake (SFC), were fermented with fungus Aspergillus niger, and its effect on apparent digestibility coefficient (ADC) was studied in Penaeus vannamei. Reference diet and eight experimental diets containing 700 g/kg reference diet and 300 g/kg test ingredient with 5 g/kg chromic oxide were formulated. Each diet was randomly allotted to three tanks containing ten shrimps. Shrimps were adapted to the experimental diets for a week, and faeces were collected using Falcon tube from second week onwards. The ADC of all the ingredients significantly (p < .05) increased with fermentation and the increase being higher in SBM (78.46%–91.71%) for dry matter and in SFC (71.51%–87.02%) for protein. Analysis of variance showed that the ADC of both dry matter and protein significantly (p < .05) differed in treatments (p = <.001) and ingredients (p = <.001). The average ADC of ingredients was ranked as SBM > GNC > RSM > SFC. The most digestible essential amino acid (EAA) in fermented ingredients was methionine in SBM, arginine in GNC, valine in RSM and histidine in SFC. A better improvement in amino acid digestibility was observed in fermented SFC. Results indicated that P. vannamei efficiently digests fermented ingredients compared to unfermented ones.     

Feeding fermented soybean meal diet supplemented with taurine to yellowtail Seriola quinqueradiata affects growth performance and lipid digestion

Feeding experiment was conducted to determine whether fermentation and taurine supplementation of soybean meal (SBM) fed to yellowtail improve growth performance and lipid digestion. Six diets were formulated and designated as SBM, SBM supplemented with taurine (SBM + T), SBM fermented by Bacillus spp. (FSBM1), SBM fermented by Lactobacillus spp. (FSBM2), FSBM2 supplemented with taurine (FSBM2 + T), and fish meal (FM). Yellowtail fingerlings with an initial body weight of 42 g were stocked in 200‐L tanks. The fish were fed, each diet was fed twice daily in two separate tanks for 8 weeks. Results showed that lipid digestibility of the SBM diet was significantly lower than that of the FM diet, but SBM diet lipid digestibility was improved by taurine supplementation and fermentation. Lipase activity in anterior intestinal digesta, lipid contents in liver and muscle, and bile acid concentrations in gallbladder and anterior intestinal digesta were significantly lower in fish fed SBM diet than in fish fed FM diet; these parameters were not significantly different between fish fed SBM + T, FSBM2, FSBM2 + T diets and FM diet. Although taurine supplementation or fermentation improved lipid digestibility compared with FM diet, growth parameters were only improved in the fish fed FSBM2 + T diet, indicating that apart from a lack of taurine, SBM contains other factors responsible for inferior growth of yellowtail. These factors can be partially eliminated by Lactobacillus spp. fermentation.     

Effect of tributyrin supplementation in high‐soya bean meal diet on growth performance,body composition,intestine morphology and microbiota of juvenile yellow drum (Nibea albiflora)

Six equal‐protein and equal‐lipid diets were formulated: the fish meal (FM) diet, the soya bean meal (SBM) diet with 40% of FM protein replaced by SBM protein and tributyrin (TB) diets with 0.05% (TB0.05), 0.10% (TB0.1), 0.20% (TB0.2) and 0.40% (TB0.4) tributyrin supplemented in the SBM‐based diet. Each kind of diet was randomly fed to triplicate tanks with 20 fish per tank. Fish were fed apparent satiation twice daily for 56 days. No significant difference in weight gain rate (WGR) and feed efficiency rate (FER) was observed between fish fed the FM, TB0.1 and TB0.2 diets (p > .05). Muscle histidine and arginine proportion of fish fed TB0.1 diet was significantly higher than that of fish fed the SBM diet (p < .05). Intestine morphology results indicated that the supplementation of 0.1% tributyrin significantly improved the mucosal fold height, microvilli length and microvilli density when compared with those of fish fed the SBM diet (p < .05). The supplementation of dietary tributyrin suppressed the pro‐inflammatory gene expression, which may be due to the improvement of physical barrier and modification of microbial communities, such as Acinetobacter, Rhodocyclaceae, Brevundimonas, Sphingopyxis, Hydrogenophaga, Methyloversatilis and Devosia. In conclusion, dietary 0.1% tributyrin supplementation in high‐soya bean meal diet improved growth performance, flesh quality and intestinal morphology structure integrity of yellow drum.     

Dietary bee pollen affects hepatic–intestinal histomorphometry of Nile tilapia fingerlings

The bee pollen is considered an excellent source of flavonoids, carotenoids, phenolic compounds, sterols and minerals; and possesses the ability to boost the immune system, antioxidant action and other interesting therapeutic effects. This study was carried out aiming to evaluate the inclusion of bee pollen in extruded commercial diets of Nile tilapia fingerlings and its effects on the hepatic‐intestinal histomorphometry and zootechnical performance. A total of 225 tilapia fingerlings (1.25 ± 0.05 g) were distributed in a completely randomized design in 15 tanks (30 L) maintained in a recirculation water system with three treatments (0% or control, 1.5% and 2.5% of bee pollen inclusion) and five replicates. Feeding rates were defined from the weekly biometrics and periodic monitoring of the physical–chemical water quality parameters. The water quality variables remained within the appropriate range for the species throughout the experiment. There was no significant difference for the somatic indexes and zootechnical parameters in this experiment. However, the inclusion of bee pollen in Nile tilapia fingerlings diets showed a linear increase in hepatocyte morphology (p = .0098). For the intestinal variables of villus height a significant linear increase was observed (p < .05) as the pollen inclusion increased. In fish that received 2.5%, the number of goblet cells was significantly higher (p < .001) than control group and 1.5%. In this sense, the inclusion up to 2.5% bee pollen in extruded commercial diets of Nile tilapia fingerlings had a positive impact on hepato‐intestinal histomorphometry without causing negative effects on the zootechnical performance.     

Dietary Moringa oleferia leaf meal induce growth,innate immunity and cytokine expression in grass carp,Ctenopharyngodon idella

The present research was designed to investigate the growth promoting and immunostimulating properties of Moringa oleferia leaf meal (MLM) in grass carp. Juvenile grass carp (22.03 g ± 1.164) were fed with diets supplemented with 0, 50, 100 and 150 g/kg MLM for 48 days. At the end of feeding trial, skin mucus was used for analysis of lysozyme, protease, antiprotease and peroxidase activity. Head kidney was used for expression analysis of tumour necrosis factor‐alpha, interleukin‐8 and interferon‐γ. The obtained results showed that fish fed with 100 and 150 g/kg MLM had significant increase in weight gain and specific growth rate (p < .05). However, condition factor was not altered. The MLM (50 and 100 g/kg) inclusion resulted in higher mucus lysozyme and protease activity (p < .05), while peroxidase activity increased only in fish fed with 100 g/kg MLM and antiprotease activity was not altered. Expression of tnf‐α increased in a dose‐dependent manner, and significant (p < .05) increase was recorded in fish fed with 150 g/kg MLM. The expression of il‐8 and ifn‐γ increased in fish fed with 50 and 150 g/kg MLM; however, the increase was not significant (p > .05). In conclusion, supplementing juvenile grass carp feed with MLM up to 150 g/kg has growth promoting and immunostimulating effects.     

Effects of fish origin probiotics on growth performance,immune response and intestinal health of shrimp (Litopenaeus vannamei) fed diets with fish meal partially replaced by soybean meal

This study was conducted to evaluate the application of four fish origin probiotics to relieve the side effects induced by SBM in shrimp. Shrimps were fed with high fish meal diet (C0, positive control containing 500 g/kg FM and 0 g/kg SBM), low fish meal diet (C, control containing 250 g/kg FM and 340 g/kg SBM) or the control diet (C) supplemented, respectively, with 1.0 × 10⁸ CFU/g Bacillus pumilus SE5 (T1), Psychrobacter sp. SE6 (T2), Enterococcus faecium MM4 (T3) or Bacillus claussi DE5 (T4). After 6 weeks of feeding, the growth performance, hepatopancreatic digestive enzymes, intestinal histological structure and immune parameters were determined. The results showed that compared with high FM group (C0), significantly lower WGR and SGR as well as higher FCR were observed in the low FM group (C) (p < .05). Compared with the control, significantly lower FCR was observed in treatment T1 (p < .05), but not in treatments T2–T4. Protease, amylase and lipase activities in all the treatments (T1‐T4) were significantly higher than the control (p < .05). GOT and GPT activities in the control were significantly lower than the C0 (p < .05), while higher MDA level was recorded in the control (p < .05). Meanwhile, higher GPT activities were observed in treatments T1‐T4 compared with the control (p < .05). Compared with the C0, lower SOD, ACP and AKP activities were observed in the control. Significantly improved SOD and AKP activities were observed in all probiotic feeding groups compared with the control (p < .05). The control diet led to significant reduction of intestinal wall thickness and villus height compared with the C0 (p < .05), while significantly higher intestinal wall thickness and villus height were exhibited in all the probiotic groups compared with the control (p < .05), except intestinal wall thickness in treatment T3. Thus, these results demonstrated that the four fish origin probiotic strains could relieve the side effects induced by high level of SBM in shrimp, while probiotic B. pumilus SE5 showed the best performance.     

Growth performance and robustness of African Catfish Clarias gariepinus (Burchell) in biofloc‐based nursery production with different stocking densities

The aim of this research is to evaluate the effects of biofloc system application at different fish density on the nursery production performance and the robustness of African catfish Clarias gariepinus (Burchell) against Aeromonas hydrophila and salinity stress. An economic analysis was also performed to determine the most optimum fish density in biofloc‐based African catfish nursery production. African catfish with an average body weight of 0.96 ± 0.04 g and average body length of 4.20 ± 0.46 cm, respectively, were distributed in 12 units of circular plastic‐lined tanks (1,020 L). The experiment consisted of four treatments in triplicates, that is, a control without carbon source addition at a density of 4 fish/L, and three biofloc treatments at different densities, that is, BFT4 (4 fish/L), BFT6 (6 fish/L) and BFT8 (8 fish/L). Tapioca flour was used as the organic carbon source in biofloc systems and was added at an estimated C/N ratio of 10. Housing the fish in biofloc systems resulted in higher fish growth, more efficient feed utilization, higher fish robustness against A. hydrophila infection and salinity stress, as well as higher profitability of nursery production. Increasing the fish density resulted in higher mortality. However, higher number of fish produced and lower feed conversion ratio were observed in the treatments with higher density (6 and 8 fish/L). In conclusion, the application of biofloc technology at a density of 8 fish/L could be recommended to increase the production and profitability of African catfish nursery culture.     

Response of juvenile tench (Tinca tinca L.) fed practical diets with different protein contents and substitution levels of fish meal by soybean meal

A basal practical diet for juvenile tench (Tinca tinca) was formulated and elaborated to test several protein contents and substitution possibilities of fish meal (FM) by soybean meal (SBM) in a 90‐day trial with 5‐month‐old juveniles (30.54 mm TL, 0.30 g W). A factorial design included nine feeding treatments: three protein contents (50%, 40% or 30%) and three levels of replacement (0%, 25% or 45%) of FM protein by SBM protein. In addition, a commercial carp feed was used as reference. Final survival ranged from 98.2% to 99.4%. The 50% dietary protein with 0% or 25% replacement and 40% dietary protein with 25% replacement diets enabled higher growth (P < 0.05) and lower FCR (P < 0.05) than the rest of practical diets. Fish fed 50% dietary protein had similar growth than those fed carp feed (63.8% protein). Deformed fish averaged 1% for the practical diets and 87.6% for the carp feed. The basal practical diet has showed to be feasible and levels of 40–50% dietary protein with 25% replacement of FM protein by SBM protein can be recommended for juvenile tench aged 5–8 months.     

An evaluation of replacing fish meal with fermented soybean meal in the diets of largemouth bass (Micropterus salmoides): Growth,nutrition utilization and intestinal histology

A 56‐day feeding trial was conducted to investigate the effects of replacing fish meal (FM) with soybean meal (SBM) and fermented soybean meal (FSBM) on growth performance, nutrition utilization and intestinal histology of largemouth bass. The basal diet contained 350 g/kg FM (control), and then, FM was replaced with SBM or FSBM of 15%, 30%, 45% and 60% respectively. The results showed that the specific growth rate of fish fed FSBM‐60, SBM‐45 and SBM‐60 diets significantly decreased, and the feed conversion ratio of SBM‐30, SBM‐45, SBM‐60, FSBM‐45 and FSBM‐60 groups increased when compared to the control group (p < .05). The apparent digestibility coefficients of dry matter and crude protein of SBM‐45, SBM‐60 and FSBM‐60 groups were significantly lower than those of the control group (p < .05), and the substitution of FM with SBM and FSBM (45% and 60%) significantly reduced the protein retention (p < .05). Serum total protein contents of SBM‐60 and FSBM‐60 groups and serum cholesterol contents of SBM‐45, SBM‐60 and FSBM‐60 groups were significantly lower than those of the control group (p < .05). The SBM‐30 and SBM‐60 groups showed significantly higher alanine aminotransferase activity than the control group (p < .05). The intestinal histology analysis resulted that the villus length of the SBM‐60 group and the villus width of the SBM‐45, SBM‐60 and FSBM‐60 groups decreased when compared to the control (p < .05). In conclusion, FSBM could replace 30% FM in diet of largemouth bass containing 350 g/kg FM, while the substitution level of FM with SBM was only 15%.     

Effects of dietary sodium butyrate on growth,diet conversion,body chemical compositions and distal intestinal health in yellow drum (Nibea albiflora,Richardson)

The present study was conducted to investigate the effects of sodium butyrate (SB) on the physical barrier function, pro‐inflammatory response and possible underlying mechanisms in the distal intestine (DI) of yellow drum when fed a high‐SBM diet. Three iso‐proteic and iso‐lipidic diets were formulated with fish meal (FM, the control), 45% fish meal protein replaced by SBM (SBM) and 45% fish meal protein replaced by SBM but supplemented with 0.15% SB (SBM + SB). Fish were fed twice daily for 10 weeks. Results indicated that SB supplementation significantly increased the specific growth rate (SGR) and feed efficiency ratio (FER) and methionine content of muscle when compared with those of fish fed the SBM diet (p < .05). The morphologic histology results showed that SB dramatically improved the physical barrier structure, characterized as increases of fold height (FH) and muscular thickness (MT) (p < .05). RT‐qPCR data were accordant with morphologic histology results, in which claudin 3, claudin 4 and occludin were increased while claudin 7 and myosin light chain kinase (MLCK) mRNA expression levels were decreased (p < .05). Sodium butyrate also exerted anti‐inflammatory function, which may be attributed to the suppression of nucleus p65 protein expression. Results suggest SB can be incorporated in high‐SBM diets to ameliorate the negative consequences of alternative dietary ingredients on yellow drum physiology.     

Partial substitution of soybean meal with fermented soybean residue in diets for juvenile largemouth bass,Micropterus salmoides

A feeding trial was conducted to investigate the effects of partial replacement of soybean meal (SBM) with fermented soybean residue (FSR) on growth performance, body composition and plasma biochemical parameters of largemouth bass, Micropterus salmoides. Soybean residue was fermented with a mixture of microorganisms (Bacillus subtilis, Lactobacillus spp. and Molasses yeast) using the solid‐state fermentation. Four isonitrogenous (crude protein 430 g/kg) and isoenergetic (gross energy 18 MJ/kg) diets were formulated by replacing 0 (the control), 20, 40 and 60g/kg of protein from SBM with FSR (FSR0, FSR20, FSR40 and FSR60, respectively). Each diet was fed to four replicate groups of fish (initial body weight: 17.1 ± 0.19 g) for 12 weeks. Results showed that dietary FSR substitution significantly improved growth of juvenile largemouth bass. The weight gain, specific growth rate and protein efficiency ratio were all significantly improved by dietary FSR level up to 40g/kg substitution level (p < .05) and then levelled off beyond this level. Fish fed the diet with 40g/kg and 60g/kg protein from FSR had lower feed conversion ratio than the control group (p < .05). The hepatosomatic index, viscera ratio and liver lipid content significantly decreased with increasing dietary FSR level. Total protein content, superoxide dismutase and alkaline phosphates activities in plasma were lower in fish fed the control diet (p < .05) than the other groups. However, both alanine aminotransferase and aspartate transaminase were higher in fish fed the control diet (p < .05) compared to the other treatments. The plasma catalase activity significantly increased with increasing dietary FSR level, while plasma triglyceride, total cholesterol, glucose and malondialdehyde contents significantly reduced. No significant difference was observed in the glutathione peroxidase activity among dietary treatments. These findings demonstrated that replacing dietary SBM with FSR has beneficial effects on growth of M. salmoides, and the best growth performance was obtained at 40g/kg replacement for SBM protein. In addition, there is a great potential to apply FSR to improve lipid metabolism and antioxidant capacity of M. salmoides.     

Effect of supplementation of dietary fibre concentrates on biochemical parameters,stress response,immune response and skin mucus of jundiá (Rhamdia quelen)

The aim of this study was to assess the effects of different dietary fibre concentrates (DFC: Mucilage = MG; pectin = PN or β‐glucan+mannan = βg+M), on biochemical parameters, stress and immune response and skin mucus of jundiá (Rhamdia quelen). The fish (7.16 ± 0.06 g) were fed with Control diet (0 g/kg of DFC); diet supplemented with 5 g/kg of commercial prebiotic (CP 5) or diets supplemented with 5 or 10 g/kg of MG; PN or βg+M. After 8 weeks of the feeding trials, biochemical parameters (cholesterol, glucose, albumin and total protein), cortisol, immunoglobulin IgM and mucoproteins of skin mucus were assessed. Results demonstrated that supplementation with PN increased cholesterol levels (p<.05). After application of the stressor, most fish, except those in the PN and 10 g/kg MG groups, showed significant increases (p<.05) in cholesterol, glucose and albumin levels. The jundiás showed no difference in cortisol levels after application of the stressor (p>.05). IgM levels were significantly high in fish supplemented with DFC (p<.05). However, the concentration of mucoproteins in skin mucus was not influenced in the different treatments (p>.05). The results showed that supplementation with DFC promoted beneficial effects on the metabolism of jundiá.     

Effects of soybean meal and high‐protein sunflower meal on growth performance,feed utilization,gut health and gene expression in Arctic charr (Salvelinus alpinus) at the grow‐out stage

The effects of two plant ingredients (solvent‐extracted soybean meal [SBM] and high‐protein sunflower meal [HPSFM]) and three inclusion levels (0 percent, practical diet containing 25 percent fish meal; 12.5 percent; and 25 percent) of these ingredients were investigated on the growth, feed utilization, gut histology and gene expression in the distal intestine of Arctic charr Salvelinus alpinus (average initial weight, 330.1 ± 8.9 g per fish). Feeding experimental diets for 12 weeks resulted in no difference between HPSFM diets in body weight gain (BWG), thermal‐unit growth coefficient (TGC), feed efficiency (FE), feed intake (FI) or pro‐inflammatory mRNA expression (PIE) with increasing dietary inclusion and between SBM FE, FI and PIE. Differences in quadratic contrasts were observed for nitrogen deposition rate (NDR) and nitrogen retention efficiency (NRE) (p < .05), whereby HPSFM diets elicited the strongest positive response. SBM resulted in linear reduction in BWG, TGC and distal intestine simple fold length and width measurements (p < .05) with stepwise increases in dietary inclusion, whereas dietary HPSFM had no effect. Histological observations of individual villi indicated several symptoms of non‐infectious subacute gastrointestinal enteritis in tanks fed SBM, many of which were not present in tanks fed HPSFM. The dietary HPSFM seems to be more adequate to replace fishmeal in Arctic charr diet than SBM, when fed at a level of up to 25 percent at the grow‐out stage.     

The effects of two fish species mullet,Mugil cephalus,and tilapia,Oreochromis niloticus,in polyculture with white shrimp,Litopenaeus vannamei,on system performances: A comparative study

A comparative study was carried out to compare the effect of caging mullet and tilapia in a shrimp polyculture system. In six shrimp tanks (three tanks for each fish species), either mullet, Mugil cephalus (CCT‐SM), or tilapia, Oreochromis niloticus (CCT‐ST), was stocked in cages. In three other tanks, mullets were allowed to roam freely in shrimp tanks (D‐SM). White shrimp, Litopenaeus vannamei (0.50 g), was cultured as the predominant species were distributed randomly into nine fibreglass tanks (5 m³) at a density of 300 shrimp/tank, while fish (1.50 g) were stocked at the same density of 10% of the initial total shrimp biomass. The results showed that water quality parameters were not significantly different among treatments (p > .05), except for total suspended solids (TSSs). System performances based on parameters such as total weight gain (2,808.15 g/tank) and nutrient recovery were higher in D‐SM treatment (39.80% for nitrogen and 27.40% for phosphorus) than in CCT‐SM and CCT‐ST treatments (p < .05). These system performance parameters were significantly affected by the mullet‐holding strategy; however, they were not affected by fish species. The addition of mullet or tilapia in shrimp tanks did not affect shrimp growth differentially. Fish growth performances based on parameters such as final weight (98.43 g/fish) and DGR (1.29 g/day) were significantly higher in D‐SM treatment and were significantly different among D‐SM, CCT‐SM and CCT‐ST treatments (p < .05). It is concluded that in shrimp–fish polyculture with a stocking density of fish at 10% of the initial total shrimp biomass, tilapia is more effective than mullet, when caged. However, under free‐roaming conditions, the use of mullet is more effective in terms of system performances relative to a system holding caged tilapia.