In Vitro and In Vivo Evaluation of the Prebiotics GroBiotic®-A, Inulin, Mannanoligosaccharide, and Galactooligosaccharide on the Digestive Microbiota and Performance of Hybrid Striped Bass (Morone chrysops × Morone saxatilis)

Two separate experiments were conducted with hybrid striped bass to evaluate four potential prebiotics: GroBiotic®-A (partially autolyzed brewer’s yeast, dairy ingredient components, and fermentation products), mannanoligosaccharide (MOS), galactooligosaccharide (GOS), and inulin. In the in vitro experiment, intestinal contents were incubated with the individual prebiotics (0.5% by weight) at 25°C for 24 and 48 h. Analysis of volatile fatty acids in the supernatant showed that GroBiotic®-A, MOS, and GOS tended to produce lower acetate levels but higher butyrate levels at 48 h compared to diet alone. However, denaturing gradient gel electrophoresis (DGGE) analysis failed to detect any differences in the composition of the microbial community among treatments. DNA sequencing of a common band for all inoculated samples revealed close similarity to the anaerobic Fusobacteria bacterium. An 8-week feeding trial also was conducted to evaluate the four prebiotics looking at growth performance; weight gain, feed efficiency ratio, protein efficiency ratio, whole-body ash, moisture, and lipid did not vary among fish fed the various diets. However, DGGE analysis revealed that all prebiotics produced a different type of microbial community in the intestinal tract of hybrid striped bass compared to fish fed the basal diet. Thus, GroBiotic®-A, FOS, GOS, and MOS exhibited prebiotic effects in hybrid striped bass.     

Nutrient digestibility and intestinal enzyme activity of Clarias batrachus (Linn.) juveniles fed on dried fish and chicken viscera incorporated diets

A feeding trial was conducted for 56 days to study the effect of replacement of fish meal by dried fish and chicken viscera, and a combination of oil cakes, in the diet of Clarias batrachus juveniles. The nutritional values of these by-products were studied through a digestibility experiment. No significant difference in nutrient digestibility was observed in different diets. Even 19.59% lipid in the diet of catfish did not affect the nutrient digestibility. Both amylolytic and proteolytic enzymes in the intestine of juveniles were studied. A decreased protease activity due to replacement of animal protein by plant protein and a decreased (P < 0.01) aspartate aminotransferase (ASAT) activity could be observed after inclusion of 22% of dried fish viscera in the diet of the catfish. Though body lipid content increased in fish fed a high level of lipid, fat-free body composition did not vary among the fish fed on different diets.     

A combination of corn gluten and soybean meal as a substitute for fishmeal in diets of turbot (Scophthalmus maximus Linnaeus, 1758) in brackish water

This study was conducted to test the replacement of fishmeal (FM) with a combination of corn gluten meal (CGM)‐soybean meal (SBM) (at a ratio of 58 : 42, respectively) fortified with lysine, taurine and monocalcium phosphate (MCP) in turbot (Scophthalmus maximus) diets. FM as the main protein source in the control diet (FM100) was replaced in 15% decrements while increasing the combination of replacement material: 85% FM (FM85), 70% FM (FM70), 55% FM (FM55) and 40% FM (FM40). The diets were fed to triplicate groups (n = 25 per group) for 9 weeks (water temperature, dissolved oxygen, pH and salinity of 18.59 ± 0.06°C, 7.32 ± 0.02 mg L^?1, 7.73 ± 0.01 and 8.46 ± 0.04 g L^?1, respectively). Initial weight of fish was 286.1 ± 0.1 g. At the end of the experiment, growth, feed and nutrient utilization performance of fish fed FM85 and FM70 were similar to FM100, but a further increase in plant protein led to a significant reduction of these parameters. Whole body, fillet, viscera and liver nutrient compositions were not affected significantly; however, whole body lipid levels were significantly lower in fish on FM55 and FM40 than those on FM100. The fish in–fish out ratio in the diets decreased from 2.12 in FM100 to 1.00 in FM40. The results suggest that the FM level could be reduced by 30% with a combined use of CGM‐SBM supplemented with lysine, taurine and MCP.     

Effect of extrusion on trypsin inhibitor activity and nutrient digestibility of diets based on fish meal,soybean meal and white flakes

Abstract

The effects of moist extrusion processing of diets containing fish meal (FM) and conventional defatted soybean meal (SBM) or untoasted defatted soybean meal (white flakes [WF]) on amino acid composition, trypsin inhibitor activity (TIA), and apparent total tract digestibility of nutrients were studied. Three diets with the nutritional characteristics of feeds for salmonid fish were formulated: one control based on FM as protein source and two others where 40% of total amino acids from FM were substituted by either SBM or WF. Each diet was fed to mink either as an unextruded mixture of the ingredients or as extruded pellets in order to determine the effect of extrusion processing. Extrusion did not change the amino acid composition of the diets significantly, but reduced the TIA of both diets containing soy products by approximately 76%. Intake of the unextruded WF diet was only one-third compared with the other diets. The dry matter concentration in faeces from mink fed diets containing soy products was significantly lower than in mink fed the FM diet. Digestibility of crude protein, all amino acids and fat was lower, but starch higher, in the unextruded WF diet than in the FM and SBM diets, whereas no significant differences were found among the extruded diets. Extrusion of the WF diet increased digestibility of protein and all amino acids. The greatest increase in digestibility after extrusion of the WF diet was observed for cysteine followed by tryptophan. Extrusion of the FM and SBM diets had no significant effect on amino acid digestibility. Digestibility of starch was, in general, increased by extrusion. It is concluded that the heat treatment involved in typical moist extrusion processing used for fish feed may be sufficient to inactivate most of the TIA in unheated soybean meal, and to increase digestibility of the protein in WF to approximately the same level as found for SBM and FM. Still, extrusion is a lenient process with minor effects on nutrient digestibility of diets containing fish meal or toasted soybean meal as major protein sources.     

Partial and total fish meal replacement by agricultural products in the diets improve sperm quality in African catfish (Clarias gariepinus)

This study investigated the long-term effects of total and partial replacement of dietary fish meal (FM) by a mixture of agricultural products on sperm quality of African catfish Clarias gariepinus. Four isonitrogenous and isoenergetic diets were formulated containing graded levels of either 50% FM and maize meal (diet 1); 25% FM mixed with crude sunflower oil cake (SFOC) and bean meal (BM) (diet 2); 12.5% FM mixed with sunflower oil cake, BM and ground nut oil cake (GOC) (diet 3) and 0% FM mixed with de-hulled sunflower oil cake (SFOCD), BM and ground nut oil cake (diet 4). Gonadosomatic index (GSI), sperm quality, plasma sex steroids (11-keto testosterone [11-KT]; testosterone [T]; estradiol-17beta [E2]) were evaluated on 10 to 24 fish fed on each diet. Sperm quality was assessed using computer-assisted sperm analysis (CASA). Total replacement of fish meal by plant products markedly increased sperm volume, spermatocrit, spermatozoa integrity, and sperm motility. Fish fed diet 3 (12.5% fish meal) provided intermediate results on sperm quality whereas the lowest values were obtained in fish fed diets 1 and 2. In fish fed 0% fish meal (diet 4), androgen levels were higher and estrogen levels were lower than in fish fed fish meal diets. Based on dietary lipid and fatty acid analyses, these results suggest a positive impact of short chain n-6 fatty acids on androgen synthesis and sperm quality. In conclusion, a combination of ground nut oil cake, bean meal and sunflower oil cake (preferably when the sunflower is dehulled) in African catfish diet improves the sperm quality.     

Larval rearing of fringe-lipped carp,Labeo fimbriatus (Bloch) with low cost diets including green bottle fly Lucilia sericata (Meigen) larvae meal incorporated diet

A study was conducted with non-conventional ingredients to test their efficacy as fishmeal (FM) replacers in the diet of fringe- lipped carp. Labeo fimbriatus first feeding larvae and fry were reared for 30 and 60 days in indoor, 50 L, aerated, circular plastic tanks at 100 and 30 numbers tank⁻¹, respectively. In the first feeding larvae to fry rearing experiment (Exp. 1), the fish were fed with either of the following isonitrogenous and isocaloric diets – live plankton, FM diet, green bottle fly (Lucilia sericata) larvae meal (GBFLM) diet and silkworm pupa (SWP) diet. The fry to fingerling rearing (Exp. 2), was also conducted using the same diets described above except live plankton. All compounded diets were formulated to contain 40% crude protein for the experiment 1 and 35% for experiment 2 and were fed ad libitum. Triplicate tanks were maintained for each treatment in both the experiments. In Exp. 1, the mean final weight of fry was higher with plankton and FM diets, while no difference (p > .05) was observed between FM and GBFLM diets. Weight of fish fed SWP diets was not statistically different from those fed GBFLM diet. No difference (p > .05) in final length, survival and condition factor was recorded. Analysis of digestive enzyme activity of whole fish revealed lower (p < .05) activity of amylase in fish fed plankton. In Exp. 2, no difference (p > .05) was observed between the different diet groups in terms of mean final weight, length, survival and condition factor. Analysis of digestive enzyme activity of whole fish revealed no difference (p > .05) in the activity of digestive enzymes between the treatments except a lower (p < .05) activity of trypsin in FM diet and lipase in FM and GBFLM diets. Since the survival and condition factors of animals is the most important aspect during nursery rearing, similar (p > .05) values recorded in different treatments indicate the possibility of incorporation of these non-conventional protein sources in the diet of L. fimbriatus during first feeding larvae to fry and fry to fingerling rearing.     

Amino acid availability of protein meals of different quality for adult and growing mink (Neovison vison)

ABSTRACT

Protein and amino acid (AA) availability of three protein meals of expected different quality were evaluated in young growing and adult mink. Lamb meal (LM), poultry meal (PM) or fishmeal (FM) were used as main protein sources in three extruded diets investigated by determining apparent total tract digestibility (ATTD) and nitrogen balance in 12 growing mink males aged 8–11 weeks in a Latin square design. In adult mink, ATTD of the diets was determined. The diets had lower protein content than recommended for growing mink, protein contributing 23% of total metabolisable energy (ME), to ensure differences in growth response. The LM diet with expected low protein quality revealed lower content of essential AA than the PM and FM diets. The ATTD of major nutrients and essential AA was significantly affected by diet, with the poorest values for LM, intermediate for PM and the highest values for FM. Mink kits revealed lower ATTD values than adults for protein, AA and especially fat, resulting in lower dietary ME content for kits than for adults. The mean difference was greatest for the LM diet with lowest ATTD and smallest for the FM diet with the highest ATTD. Nitrogen retention and growth rate differed significantly among diets and was lowest for diet LM and highest for diet FM, respectively. Different dietary essential AA contents and ATTD, especially of methionine, were the main factors to explain the difference in growth response. Generally, plasma essential AA concentrations did not clearly reflect the different dietary supply and the different growth response. The study shows that a recommended level of 0.31 g apparent total tract digestible methionine per MJ ME covers the minimum requirement with a safety margin. To obtain optimal growth, the lower digestive capacity in young mink kits should be considered when choosing feed ingredients.     

Protein Retention Assessment of Four Levels of Poultry By-Product Substitution of Fishmeal in Rainbow Trout (Oncorhynchus mykiss) Diets Using Stable Isotopes of Nitrogen (δ15N) as Natural Tracers

This is second part from an experiment where the nitrogen retention of poultry by-product meal (PBM) compared to fishmeal (FM) was evaluated using traditional indices. Here a quantitative method using stable isotope ratios of nitrogen (δ¹⁵N values) as natural tracers of nitrogen incorporation into fish biomass is assessed. Juvenile rainbow trout (Oncorhynchus mykiss) were fed for 80 days on isotopically distinct diets in which 0, 33, 66 and 100% of FM as main protein source was replaced by PBM. The diets were isonitrogenous, isolipidic and similar in gross energy content. Fish in all treatments reached isotopic equilibrium by the end of the experiment. Two-source isotope mixing models that incorporated the isotopic composition of FM and PBM as well as that of formulated feeds, empirically derived trophic discrimination factors and the isotopic composition of fish that had reached isotopic equilibrium to the diets were used to obtain a quantitative estimate of the retention of each source of nitrogen. Fish fed the diets with 33 and 66% replacement of FM by PBM retained poultry by-product meal roughly in proportion to its level of inclusion in the diets, whereas no differences were detected in the protein efficiency ratio. Coupled with the similar biomass gain of fishes fed the different diets, our results support the inclusion of PBM as replacement for fishmeal in aquaculture feeds. A re-feeding experiment in which all fish were fed a diet of 100% FM for 28 days indicated isotopic turnover occurred very fast, providing further support for the potential of isotopic ratios as tracers of the retention of specific protein sources into fish tissues. Stable isotope analysis is a useful tool for studies that seek to obtain quantitative estimates of the retention of different protein sources.     

The first insight into black soldier fly meal in brown trout nutrition as an environmentally sustainable fish meal replacement

Insect meals are considered among the most promising feed materials in fish nutrition due to their sustainability and possibility of fish meal replacement. The present study is the first application of full-fat black soldier fly larvae (BSFL) meal in brown trout (Salmo trutta m. fario) diets. Two experiments were performed on 240 brown trout fingerlings (average body mass 4.85 g) distributed into four groups (12 tanks for the growth performance experiment, 10 fish/tank; and 12 metabolic tanks for the digestibility test, 10 fish/tank). The experimental group design was conducted as follows: control diet, with no BSFL and 35% fish meal, and experimental diets: BSFL5 – with 5% BSFL full-fat meal and 32.5% fish meal; BSFL10 – with 10% BSFL full-fat meal and 30% fish meal; and BSFL20 – with 20% BSFL full-fat meal and 25% fish meal. No effects were recorded in the case of growth performance and feed utilization parameters. The environmental sustainability of the usage of insect meals in fish diets was proven – due to the lower fish meal inclusion, the fish-in-fish-out ratio decreased by 31% in BSFL20. In the case of the viscerosomatic index, increases in BSFL5 and BSFL20 were reported. In all experimental groups, decreases in hepatosomatic index values were observed. Crude protein digestibility decreased in BSFL5 and BSFL20, while crude fat digestibility decreased only in the BSFL20 group. The effect of including BSFL full-fat meal in a brown trout diet on serum biochemical parameters was reported. The aspartate transaminase concentration increased in BSFL10 and BSFL20, while the gamma-glutamyl transpeptidase values decreased in BSFL20. In the case of total cholesterol, higher values were observed in BSFL10 and BSFL20. The albumin content decreased in the BSFL20 group, while globulin showed the highest values in the control group. The microbiota composition was not affected by insect meal inclusion. In conclusion, the results of the present study showed the high potential of BSFL full-fat meal application of up to 20% in a brown trout diet.     

Effects of amino acid supplementation on the nutritive quality of fermented linseed meal protein in the diets for rohu, Labeo rohita, fingerlings

A feeding trial was conducted for 8 weeks to examine the effects of partial substitution of fish meal (FM) protein (crude protein content: 58.5%) with linseed meal protein with and without supplemental amino acids in diets for rohu Labeo rohita (Hamilton), fingerlings (mean weight: 1.50 ± 0.3 g). Prior to incorporation into the diets, linseed meal was fermented with lactic acid bacteria ( Lactobacillus acidophilus ) to reduce/eliminate the antinutritional tannin and phytic acid factors. Twelve experimental diets (diets D1–D12) were formulated to replace the FM protein from a reference diet (RD) with linseed meal protein at different levels (four sets of diets, of which each set of three diets contained 25%, 50% and 75% replacement of FM protein by linseed meal protein, respectively). Diets D1–D3 were not supplemented with any amino acid. Lysine was supplemented in diets D4–D6. Diets D7–D9 were supplemented with methionine + cystine (together), and diets D10–D12 contained lysine and methionine + cystine (together). Lysine and methionine + cystine (together) were added to the diets at 5.7% and 3.1% of dietary protein, respectively. The groups of fish fed diets without amino acid supplementation had significantly lower percentages of weight gain, specific growth rate and high feed : gain ratio than the fish groups fed other experimental diets. The addition of lysine and methionine + cystine to the diet in which 50% of the FM protein was replaced by linseed meal protein (diet D11) significantly improved fish performance. The results of the present study suggest that rohu fingerlings can effectively utilize the supplemented amino acids and that linseed meal protein can replace up to 50% of the FM protein in rohu diets if the linseed meal is properly processed (fermented) and supplemented with the lacking amino acids.     

Inclusion of alternative marine by-products in aquafeeds with different levels of plant-based sources for on-growing gilthead sea bream (Sparus aurata,L.): effects on digestibility,amino acid retention,ammonia excretion and enzyme activity

The search for new sustainable aquafeeds for the species with greater economic importance, such as the gilthead sea bream in Europe, is one of the main challenges in the aquaculture sector. The present work tested fishmeal replacement by a mixture of plant meals at different levels, as well as the use of marine by-products with attractant properties and high-quality protein in high plant protein diets. In order to do that, effects on growth and biometric parameters, digestibility, amino acid retention, excreted ammonia and proteases and amylase activity were assessed, using six different diets: FM100 (100% of protein provided by fishmeal), FM50 (50% of replacement), FM25 (75% of replacement) and FM0 (100% of replacement), but also FM25+ (75% of replacement and 15% of squid and krill meal inclusion), and FM0+ (100% of replacement and 15% of squid and krill meal inclusion). In group FM0, a clear impact of dietary changes was observed on growth, survival and ammonia excretion. Amino acid retention in group FM0+ was also significantly affected, which can be explained by the limited content of certain amino acids in this diet. On the other hand, no significant differences were observed in most biometric parameters or in enzyme activity. In conclusion, complete fishmeal replacement can be achieved by using a mixture of plant-based sources, but supplementation with complementary marine ingredients can prevent detrimental effects on growth, survival, nutritional parameters and protein metabolism.     

Potential use of high levels of vegetal proteins in diets for market-sized gilthead sea bream (Sparus aurata)

The effect of partial or total dietary substitution of fishmeal (FM) by vegetal protein sources on growth and feed efficiency was carried out in on-growing gilthead sea bream (mean initial weight 131 g). The Control diet (FM 100) contained FM as the primary protein source, while in Diets FM 25 and FM 0 the FM protein was replaced at 75% and 100%, respectively, by a vegetable protein mixture consisting of wheat gluten, soybean meal, rapeseed meal and crystalline amino acids. Diets FM 25 and FM 0 also contained krill meal at 47 g/kg in order to improve palatability. At the end of the trial (after 158 d), fish survival was above 90%. Final weight and the specific growth rate were statistically lower in fish fed the Control diet (361 g and 0.64%/d), compared with 390–396 g and 0.69–0.70%/d after feeding vegetal diets. No significant differences were found regarding feed intake and feed conversion ratio. The digestibility of protein and amino acids (determined with chromium oxide as indicator) was similar in all diets. The blood parameters were not significantly affected by treatments. The activity of trypsin and pepsin was significantly reduced after feeding Diet FM 0. In the distal intestine, the villi length in fish fed Diet FM 25 was significantly longer and the intestine of the fish fed the FM 100 diet showed a smaller number of goblet cells. In conclusion, a total FM substitution by a vegetal mix supplemented with synthetic amino acids in on-growing sea bream is feasible.     

Partial Evaluation of Autochthonous Probiotic Potential of the Gut Microbiota of Seriola lalandi

Seriola lalandi is an economically important species that is globally distributed in temperate and subtropical marine waters. Aquaculture production of this species has had problems associated with intensive fish farming, such as disease outbreaks or nutritional deficiencies causing high mortality. Intestinal microbiota are involved in many processes that benefit a host, such as disease control, stimulation of the immune response, and the promotion of nutrient metabolism. The aim of this study is to evaluate the in vitro probiotic properties of bacteria isolated from the intestinal content of wild Seriola lalandi. The probiotic potential was evaluated in terms of (i) the antimicrobial activity against vibrios causing outbreaks in farmed fish; (ii) the ability to stimulate genes related to an innate immune response in fish; and (iii) antibiotic resistance. Nineteen isolates identified as Pseudomonas, Shewanella, Psychrobacter, and Acinetobacter showed antimicrobial activity and significant relative expression of cytokines, serum amyloid A protein (SAA), hepcidin, and lysozyme. A positive correlation was observed between the levels of expression and the bacterial load after 24 h of exposure. Pseudomonas isolates showed a level of antibiotic resistance. In conclusion, isolates of the genera Shewanella, Psychrobacter, and Acinetobacter could serve as potential probiotics in S. lalandi culture.

     

Growth and product quality of European eel (Anguilla anguilla) as affected by dietary protein and lipid sources

A 12‐week feeding trial was undertaken to evaluate the effects of partial replacement of marine raw materials in the diet with soybean meal and beef tallow on growth and product quality of European eel (Anguilla anguilla). Based on growth, feed efficiency and chemical composition, soybean meal was found to be an unsuitable ingredient for eel diets as a substitute for fishmeal (25% on a protein basis), probably because of the low digestibility of its carbohydrate content. However, beef tallow can be used to replace 50% of fish oil without reduction in growth, provided that digestible carbohydrates are present in the diet. No major effects of protein and lipid sources in the diet were found on fillet chemical composition. Sensory analysis revealed no significant differences between fish fed the control and the experimental diets, with the exception of salty taste which was significantly higher in fish fed combined soybean meal and beef tallow compared with fish fed the control diet.     

Effects of dietary replacement of fish meal by soybean meal on growth,feed utilization,and health condition of stinging catfish,Heteropneustes fossilis

Soybean meal (SBM) is a cost-effective alternative protein source to replace costly fish meal in aquaculture. This present study determined to measure the effects of replacing fish meal (FM) protein with SBM on growth, feed utilization, and health condition of stinging catfish, Heteropneustes fossilis. Four isonitrogenous (35 %) diets were applied in four treatment groups designed as SBM₀, SBM₂₅, SBM₅₀, and SBM₇₅, where 0 %, 25 %, 50 %, and 75 % of FM protein were substituted by SBM, respectively. Significantly higher mean final weight (g), weight gain (g), percent weight gain (%), specific growth rate (% day^?1), and protein efficiency ratio (PER) were recorded in SBM₀, SBM₂₅, and SBM₅₀ groups than SBM₇₅ group. Consequently, significantly lower feed conversion ratio (FCR) was found in SBM₀, SBM₂₅, and SBM₅₀ groups than SBM₇₅ group. Moreover, protein content of whole-body carcass was significantly higher in SBM₂₅ and lower in SBM₀ group however, lipid content was significantly higher in SBM₀ and SBM₇₅ than in other groups. Hemoglobin, red blood cells, and white blood cells were significantly higher in SBM₀, SBM₂₅, and SBM₅₀ groups compared to SBM₇₅. However, the higher the substitution of FM protein by SBM in diets higher the values of glucose. Morphological analysis of the intestine including villi length (μm), width (μm), and area (mm²); crypt depth (μm); wall thickness (μm); abundance of goblet cell (GB); and muscle thickness (μm) showed an increasing trend in fish fed diet containing upto 50 % replacement of FM protein by SBM. Therefore, the results suggest that SBM could replace upto 50 % FM protein in diets of H. fossilis without compromising growth, feed efficiency, and health status.     

Sustainability assessment of salmonid feed using energy,classical exergy and eco-exergy analysis

Reduction of the environmental impact of feed products is of paramount importance for salmon farming. This article explores the potential to compare three thermodynamically based ecological indicators. The environmental impact of partial replacement of fish meal (FM) and fish oil with alternative ingredients was investigated using energy, classical exergy and eco-exergy analysis. Seven hypothetical feeds were formulated: one with high levels of FM and fish oil, four feeds based on plant ingredients, one containing krill meal, and one based on algae-derived products. Analysis included cultivation of crops and algae, fishing for fish and krill, industrial processing of these ingredients and production of complete fish feed. Because most harvested products are refined in multiple product outputs that have good value to society, two scenarios were compared. In the base case scenario, no allocation of co-products was used and all the environmental costs were ascribed to one specific co-product. Co-product allocation by mass was used in the second scenario; this is considered to be the preferred scenario because it accurately reflects the individual contributions of the co-products to the environmental impact of the feed products. For this scenario, the total energy consumption for a fish-based diet was 14,500 MJ, which was similar to a krill diet (15,600 MJ), about 15–31% higher than plant-based diets, and 9% higher than an algae diet. Substituting FM and fish oil with alternative ingredients resulted in minor changes in total classical exergy degradation (2–16% difference). The calculations based on energy only consider the energy conservation based on the First Law of Thermodynamics, whereas those based on classical exergy also takes the Second Law of Thermodynamics into account; energy that can do work is distinguished from energy that is lost as heat to the environment. The calculations based on eco-exergy consider the total loss of work energy in the environment including the work energy associated with the information embodied in the genomes of organisms. The diet based on fishery-derived ingredients was the highest total work energy consumer compared with plant-based diets (24–30% greater), the diet containing krill meal (25% greater), and the algae diet (four times higher). Thus, reducing FM and fish oil levels in fish feed can contribute significantly to more sustainable aquaculture. In particular, algae-derived products in aquafeeds could drastically decrease environmental costs in the future.     

Environmental remediation potential of Perinereis aibuhitensis (Polychaeta) based on the effects of temperature and feed types on its carbon and nitrogen budgets

The effects of three temperatures (15°C, 20°C and 25°C) and four feed types (artificial feed, AF; sediment, SM; fish faeces, FF; and fish meat, FM) on the growth, carbon budget and nitrogen budget of the polychaete Perinereis aibuhitensis were evaluated over a 35 day period. The final body weight and specific growth rate (SGR) of P. aibuhitensis were significantly affected by temperature and feed types (T, F?=?15.831, P?=?0.000; Feed, F?=?81.827, P?=?0.000), but the interaction between these factors was not significant (F?=?0.435, P?=?0.848). The worms achieved the highest SGR in the AF group at 20°C. However, the SGR in the SM group was only half that of the other groups. The food conversion efficiency (FCE) was significantly lower at 25°C than at 15°C and 20°C (P?P?=?0.000), with a mean of 39.83%. The apparent digestibility rate (ADR) at 25°C was significantly higher than at 15°C and 20°C (P?相似文献   

Diet,intestinal morphology,and nitrogen assimilation efficiency in the damselfish,Stegastes lividus,in Guam

Synopsis Analysis of stomach contents of Stegastes lividus revealed a shift from omnivory in juveniles to herbivory in adults. Red algae, primarily Polysiphonia spp., Gelidiopsis intricata and Ceramium spp., formed the bulk of the diet in all size classes. Foraminifera and small crustaceans were of particular importance in the diet of juveniles. Net nitrogen assimilation efficiency of field-fed S. lividus was approximately 61%, and did not vary with fish size. The net assimilation efficiencies of fish fed on Enteromorpha in the laboratory ranged from size-class means of 36–79% for nitrogen and from 29–72% for total organic material, and increased from juveniles to adults. Apparently, juveniles compensate for a lower efficiency in assimilating plant food by including a higher percentage of animal material in their natural diets. The ratios of intestine length to standard length (IL/SL) and to intestine diameter (IL/ID) increased rapidly in juveniles and leveled off in adults. The retention time for ingested food items may only be about one-half as long in juveniles as in adults. The combination of observed IL/ID ratios and estimated retention times proved most valuable in the interpretation of ontogenetic changes in feeding habits and assimilation efficiency.     

Effects of dietary thymol‐carvacrol on growth performance,hematological parameters and tissue composition of juvenile rainbow trout,Oncorhynchus mykiss

Growth performance, carcass quality, survival and hematological responses of Oncorhynchus mykiss juveniles (initial weight 8.4 ± 0.1 g) fed diets containing thymol‐carvacrol powder at the levels of 0, 1.0, 2.0, 3.0 g kg^?1 were tested. Thymol‐carvacrol powder originated from Origanum vulgare, a Mediterranean plant, added to diets. Each diet was fed to triplicate groups of fish for 45 days. Fish fed diets containing thymol‐carvacrol had significantly higher final weight and growth than the control group. Food conversion ratio in fish fed diets containing 2.0 and 3.0 g kg^?1 thymol‐carvacrol was statistically better than in other treatments. Survival was not different among all treatments. The number of lymphocytes increased when thymol‐carvacrol was used at higher levels. Furthermore, whole body lipid content was higher in fish fed 1.0 and 2.0 g kg^?1 thymol‐carvacrol than the other groups, but body protein in the group fed 3.0 g kg^?1 was higher than in other groups. Also, body ash in control and 1.0 g kg^?1 was higher than in other groups. Whole body dry matter was not affected by dietary treatments. These results indicated that dietary administration of thymol‐carvacrol can influence some growth, hematological parameters and tissue composition in rainbow trout juveniles.