Dietary supplement of Enterococcus faecalis on digestive enzyme activities,short‐chain fatty acid production,immune system response and disease resistance of Javanese carp (Puntius gonionotus,Bleeker 1850)

This study investigated the effects of Enterococcus faecalis on digestive enzyme activities and short‐chain fatty acid production in fish intestine, resistance against Aeromonas hydrophila and humoral immunity response by 3 experiments on Javanes carp (Puntius gonionotus). The experiment 1 revealed that diet supplemented with E. faecalis significantly (P < 0.05) increased protease and lipase activities compared to control fed fish. Moreover, E. faecalis supplementation significantly enhanced the production of propionic and butyric acid in the intestine, while no significant difference (P > 0.05) in acetic acid production was observed. In the challenge study (experiment 2), fish were injected (intraperitoneal) with 10⁷ A. hydrophila per ml and survival was significantly improved when fish were fed diet supplemented with E. faecalis compared to control fish. In experiment 3, dietary E. faecalis affected immune system response as fish fed the probiont and exposed to 10⁶ A. hydrophila per ml displayed significantly elevated antibody levels compared to control fed fish. Fish fed diet supplemented with E. faecalis but not exposed to the pathogen revealed significantly higher antibody level than control fish (P < 0.05). Therefore, E. faecalis can be used as a probiotic in Javanese carp farming.     

Effect of β‐glucooligosaccharides as a new prebiotic for dietary supplementation in olive flounder (Paralichthys olivaceus) aquaculture

β‐Glucooligosaccharides (BGO), produced from barley β‐glucan, were used as a feed supplement (0.1%) for juvenile olive flounder (Paralichthys olivaceus) to identify and quantify its oral administration effects on innate immunomodulation and infectious disease protection. Juvenile flounders (14 ± 0.5 g) were divided into two groups fed either 0.1% BGO (treatment) or a standard diet (control) for 8 weeks. At the end of the experiment, investigation of the effects was carried out through systemic studies on growth performance, serum and mucus biochemical parameters, innate immunity, microvillus length, and relative pro‐inflammatory cytokine gene expression. The results demonstrated that the BGO diet produced slightly higher levels of growth performance, serum protein, microvillus length and pro‐inflammatory cytokine gene (tumour necrosis factor‐α, interleukin [IL]‐1β, and IL‐6) expression without any significant differences (p > .05). All innate immunity parameters were up‐regulated by BGO administration and, among these, respiratory burst, lysozyme and superoxide dismutase (SOD) were significantly different (p < .05). Fish in the both groups were challenged with Streptococcus iniae (1.35 × 10⁸ CFU/ml), and BGO group was focused to confirm the promotion of innate immunity parameters. The results showed a significantly (p < .05) lower death rate compared with that of the control. Therefore, BGO could be used as a new prebiotic in future olive flounder aquaculture as well as to control streptococcosis.     

Comparison of effects of dietary‐specific fatty acids on growth and lipid metabolism in Nile tilapia

The dominant fatty acids (FAs) in oils are often used to explain different nutritional effects of dietary oils in fish. However, the amounts of dominant FAs among oils are different, and the nutritional roles of these important FAs in fish have not been precisely compared at similar levels in feeding trials. In the present study, different amounts of palmitic acid were added to safflower oil (SO), olive oil (OO) and fish oil (FO) to obtain comparable amounts (about 550 g/kg of total FAs) of 18:2n‐6, 18:1n‐9 and 20:5n‐3 + 22:6n‐3 and subsequently fed to Nile tilapia (11.1 ± 0.01 g) for 8 weeks. The results showed similar growth among groups but FO group obtained lower fat deposition, serum ALT and AST activities, compared to OO. Lipogenesis‐related gene expressions were higher in OO group than FO group in liver, muscle and adipose tissue, but there were only few differences in these genes between SO and FO groups. Lipid catabolism genes in FO group were higher than OO and SO groups in adipose tissue, but not in muscle, and the significantly higher expressions of CPT1b and PPARα were only observed in liver. Overall, dietary 18:2n‐6, 20:5n‐3 and 22:6n‐3 were beneficial to normal growth and lipid metabolism, whereas high amount of 18:1n‐9 induced lipid deposition and liver damage in Nile tilapia.     

Effect of nucleotides supplementation to low‐fish meal feed on long‐chain polyunsaturated fatty acid composition of juvenile rainbow trout Oncorhynchus mykiss

A feeding trial was conducted to evaluate the effect of nucleotides supplementation to low‐fish meal feed on growth and fatty acid composition of rainbow trout. Six isonitrogenous (42% crude protein) and isolipidic (18% crude lipid) diets were formulated containing fish meal and plant ingredients as main protein sources. The control diet was a basal diet without supplementation of nucleotides, and five experimental diets were prepared by supplementing one of the five different nucleotides in the form of 5′‐monophosphate (0.15%), that is inosine (IMP), adenosine (AMP), guanosine (GMP), uridine (UMP) and cytidine (CMP) onto basal diet. Two hundred forty juvenile rainbow trout with an initial average body weight 9.8 g were randomly distributed into twelve aquaria. After 15 weeks of feeding period, growth performance and feed utilization of rainbow trout were not significantly different among dietary treatments. Dietary GMP, UMP and CMP tended to accumulate crude lipid in the muscle and whole fish body. Moreover, dietary GMP, UMP and CMP significantly increased hepatic 18:3n‐3 and long‐chain homologue 18:4n‐3 and 20:4n‐3 contents. Hepatic 18:2n‐6 content showed also increase in fish fed GMP, UMP and CMP diets, but decreased in long‐chain homologue 20:3n‐6 and 20:4n‐6 contents. Decrease in 20:4n‐6, 20:5n‐3 and 22:6n‐3 contents was also found in the muscle of fish fed IMP, GMP and CMP diets. The present study clearly showed that there was no positive effect of dietary nucleotides on growth of fish, but dietary nucleotides particularly GMP, UMP and CMP altered polyunsaturated fatty acid composition of rainbow trout.     

The effects of dietary long‐chain essential fatty acids on growth and stress tolerance in pikeperch larvae (Sander lucioperca L.)

The nutritional requirements of pikeperch larvae have been sparsely examined. Dietary polyunsaturated fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may affect growth and physiological stress response in marine fish larvae, but these mechanisms have not received as much attention in freshwater fish. Pikeperch larvae were reared on Artemia from day 3 until 21 days posthatch. Artemia were enriched with six formulated emulsions, with inclusion of either fish oil, pure olive oil (POO) or olive oil supplemented with various combinations of ARA, EPA and DHA. Larval tissue FA was significantly related to the content in the diets, but larval growth was similar for all treatments. When exposed to stress by confinement in small tanks with culture tank water or saline water (15 g L^?1.), mortality in larvae treated with POO was significantly higher than in the remaining treatments while tissue cortisol contents in these fish seemed lower. The findings of a lower stress response in larvae fed POO may be related to the lower tissue content in these larvae of essential fatty acids especially DHA but also EPA and ARA.     

Fish oil–based finishing diets strongly increase long‐chain polyunsaturated fatty acid concentrations in farm‐raised common carp (Cyprinus carpio L.)

This study investigated effects of linseed or fish oil–enriched finishing diets on the polyunsaturated fatty acids (PUFA) composition in dorsal muscle tissues of pond‐cultured common carp (Cyprinus carpio). After 180 days of dietary exposure to cereal diet containing vegetable oil (1%), carp were exposed to 7% linseed (LO) or 7% fish oil–enriched (FO) finishing diets for 30 days. FO supplied 17 and 20 mg fish^?1 day^?1, respectively, of the long‐chain n‐3 fatty acids eicosapentaenoic and docosahexaenoic acid for 30 days and doubled long‐chain PUFA concentrations in carp of the FO pond. The increased supply of short‐chain PUFA in LO resulted in higher short chain, but not long‐chain PUFA, showing that there was very little PUFA conversion. Thus, dietary short‐chain PUFA could not compensate for the low levels of dietary long‐chain PUFA in LO. However, moderate supply of dietary long‐chain PUFA in finishing diets for 30 days is very efficient in increasing nutritionally important long‐chain PUFA concentrations in carp.     

Temperature modulates liver lipid accumulation in Atlantic salmon (Salmo salar L.) fed low dietary levels of long‐chain n‐3 fatty acids

Atlantic salmon (Salmo salar) were fed five graded levels of eicosapentaenoic acid (EPA, 20:5n‐3) and docosahexaenoic acid (DHA, 22:6n‐3), from 1.4 to 5.2% of total fatty acids (FA, 5–17 mg kg^?1 feed), and grew from ~160 g to ~3000 g, with the period from 1450 g onwards conducted both at 6 °C and at 12 °C. All fish appeared healthy, and there were no diet‐related differences in haematological or plasma parameters, as well as intestinal histological or gut microbiota analysis. Fish reared at 6 °C had higher accumulation of storage lipids in the liver compared to fish reared at 12 °C. Liver lipids also increased with decreasing dietary EPA + DHA at 6 °C, while there was no such relationship at 12 °C. Gene expression of SREBP1 and 2, LXR, FAS and CPT1 could not explain the differences in liver lipid accumulation. In liver polar lipids, DHA was found to be reduced when dietary EPA + DHA was <2.7% of FAs, while the level of EPA in the membranes was not affected. In conclusion, reducing dietary EPA + DHA from 5.2 to 1.4% of total FAs had a minor impact on fish health. Temperature was the factor that most affected the liver lipid accumulation, but there was also an interaction with dietary components.     

1,3‐1‐6 ß‐glucans enhance tissue regeneration in zebrafish (Danio rerio): Potential advantages for aquaculture applications

High aquacultural rearing density and handling of fish may frequently result in skin or gills wounds, thereby facilitating the onset of secondary infections. The capacity of the zebrafish to regenerate tissues, as well as fins and other organs, makes it an ideal animal model for studying the mechanisms of tissue regeneration. Since macrophages are involved in tissue regeneration, a diet including ß‐glucans might positively affect the process through activation of macrophages and other immune pathways. Consequently, the aim of this study was to investigate the effects of the oral administration of 1,3‐1,6 β‐glucans on the regeneration process of the caudal fin after its amputation in zebrafish. One hundred and twenty zebrafish were randomly distributed into four groups with three replicates each: an untreated non‐amputated group (CNA) and an untreated amputated group (CA) fed a control diet; two treated and amputated groups (MI and MII) fed for 14 days the same diet with the addition of two differently extracted 1,3‐1,6 ß‐glucans (MacroGard^® and Experimental MacroGard^®, Biorigin^©). ß‐glucans were added to allowed the administration of 12.5 mg/kg of fish body weight (0.35 g/kg of feed). Results showed that 1,3‐1,6 ß‐glucans decreased fish mortality rate and enhanced both daily and cumulative regenerated fin area, independent of the specific ß‐glucan extraction method used. Based on the mechanisms similarities of the innate immune system and tissue regeneration among different teleost species, these results may likely be extended to species of interest for the aquaculture sector.     

Testing the yield of a pilot‐scale bubble column photobioreactor for cultivation of the microalga Rhodomonas salina as feed for intensive calanoid copepod cultures

A dual column photobioreactor (PBR) (2 × 47 L) with mixed CO₂/air bubbling was tested for cultivation of the microalga Rhodomonas salina as food for live feed copepods. In the continuous growth phase, the cell density was relatively stable at 2.40 ± 0.13 × 10⁶ cells/ml at an average dilution rate of 0.46 ± 0.02 per day throughout the 30‐day experiment. The produced algae had a high content of both total fatty acids (TFA) and free amino acids (FAA). Especially, the harvested algae contained a high proportion of poly‐unsaturated fatty acids that made up 80% of the TFA and of essential amino acids (35% of all FAA), implicating desirable components as feed for copepods. The current PBR was sufficient to feed a culture of the calanoid copepod Acartia tonsa at a density of 2,500 adult/L in ca. 500 L culture with a daily yield of approximately 17 × 10⁶ eggs. To be able to sustain the integrated copepods production, the suggested volume of the algae cultures should be ca. 20% of the copepod culture volume.     

Effects of the prebiotic mannan‐oligosaccharide on feed deprived zebrafish: Growth and reproduction

This study was designed to investigate whether the prebiotic mannan‐oligosaccharides (MOS) can reduce the deleterious impacts of feed deprivation on growth and reproduction in zebrafish. In the growth performance experiment, juvenile fish were distributed in the following four treatments: normal‐control (NC), starved‐control (SC), normal‐prebiotic (NP) and starved‐prebiotic (SP). After 8 weeks, NP and SC fish showed the highest and lowest growth patterns, respectively among treatments. Standard length, specific growth rate and feed conversion ratio did not differ significantly between NC and SP treatments. Autochthonous lactic acid bacteria (LAB) were significantly higher in NP and SP than the NC and SP treatments. Feed restriction resulted in significantly lower concentrations of thyroxine. In the reproductive performance experiment, additional juveniles were fed as in the growth experiment. Crossing in the final week of the experiment resulted in successful spawning in only NP fish, which showed mature sperm and oocytes in histological examinations. The number of spermatozoa was significantly lower in the fish that experienced feed restriction; however, the oocytes of SP females were at the same maturation level to that observed in NC females. Sex‐steroids changed after both starvation and MOS supplementation where NC and SP showed no differences in the levels of testosterone and female's 17β‐estradiol. These results indicate that MOS supplemented diet reduced some side effects of feed deprivation (final weight and length, SGR, FCR and levels of LAB and T3), and suggest that supplementation of the diet with MOS may ameliorate some of the negative effects of feed deprivation in zebrafish.     

Effects of Panax ginseng extract in practical diets for rainbow trout (Oncorhynchus mykiss) on growth performance,immune response and resistance to Yersinia ruckeri

In a preliminary in vitro study, a Panax ginseng extract exhibited an evident antibacterial activity against Yersinia ruckeri and Lactococcus garvieae and affected the respiratory burst and proliferation of rainbow trout Oncorhynchus mykiss leukocytes. Subsequently, the effects of a dietary ginseng extract supplementation on growth, blood biochemical profile, innate immune response and resistance against Y. ruckeri infection were investigated in vivo in rainbow trout juveniles. Four experimental diets were obtained by adding 0.0%, 0.01%, 0.02%, 0.03% of ginseng ethanolic extract to a commercial feed. Each diet was fed to triplicate groups of fish (mean body weight 30.5 ± 0.15 g) at 1% of body weight day^?1 for 10 weeks. The dietary supplementation with ginseng extract did not affect growth performance, feed utilization, biometric traits and fish whole body composition (P > 0.05). No major changes due to graded levels of ginseng extract in the diet were observed in blood biochemical parameters except for increasing plasma triglycerides and non‐esterified fatty acids in fish fed diets including 0.01% and 0.02% of extract (P < 0.05). The innate immune response was barely modulated by the dietary addition of ginseng extract. Serum lysozyme and leukocytes respiratory burst activities were just slightly increased in fish fed all the ginseng extract‐supplemented diets compared with controls, whereas serum antiproteases and leukocyte MPO were not affected (P > 0.05). The dietary administration of ginseng extract induced a reduction in mortality of rainbow trout infected with Y. ruckeri, although no significant differences between treated and control groups were observed (P > 0.05).     

Enhancing highly unsaturated ω‐3 fatty acids in phase‐fed rainbow trout (Oncorhynchus mykiss) using Alaskan fish oils

Rainbow trout, average weight 185–187 g, were fed feeds containing menhaden oil, canola oil or fish oils (pollock, pink salmon or rockfish) produced from Alaskan seafood processing waste as the added oil for 8 weeks, at which time the fish weighed 391–411 g (average 404 g, pooled SE = 5.7). The fish were previously fed from 75 g average weight fed commercial feed containing poultry oil as the added oil. No significant differences were measured in final weight or feed conversion ratio among dietary treatment groups. Significant differences were found in fillet ω‐3 fatty acid (FA) levels from fish receiving fish oil‐supplemented feeds compared to those from fish receiving feeds containing canola oil. Fillet contents of eicosapentaenoic acid (EPA; 20:5ω3) and decosahexaenoic acid (DHA; 22:6ω3) were highest in the pollock oil treatment group, although all fish oils increased highly unsaturated ω‐3 FA contents (mg 100 g^?1) of fillets. Fish oil used through the production cycle was reduced by 25% by supplementing feeds with poultry oil during the middle phase of production (75–175 g) compared to using feeds containing fish oil throughout the production cycle. Fish oils recovered from Alaskan seafood processing waste were suitable alternatives to conventional fish oil as ingredients in rainbow trout production feeds.     

Study on an integrated eco‐aquaculture system for rearing the yellow seahorse,Hippocampus kuda Bleeker

Seahorse aquaculture is challenged by insufficient feeding supply and lack of biological and nutritional knowledge, resulting in low survival rate and poor economical profitability. We report here an integrated eco‐aquaculture system in which the yellow seahorse and its natural prey were co‐cultured with fertilized water and seaweed in cement ponds. In the first stage, urea (10 g m^?3) and chicken manure (50 g m^?3) were used to fertilize the cultured water, 5–7 days later, rotifer and micro‐crustaceans were flourishing. Then, seahorse juveniles were stocked at 200 ind m^?3. After 2 weeks, seaweed Gracilaria lichevoides was transplanted into the ponds to regulate water quality, light and to provide holdfast attachment for seahorses. The optimal density of G. lichevoides was controlled between 0.5 and 2 kg m^?3. The introduction of seaweed provides the habitat for natural food of seahorse. Within the cluster of the seaweed, small crustacean density was over 450 individuals per 100 g of fresh weight. Initial size of seahorse juvenile was 1.03 ± 0.091 cm, After the 146‐day rearing period, seahorse survival rates were 70.8%, 57.7% and 42.5%, and body standard lengths were 11.33 cm, 10.84 cm and 10.04 cm in the integrated eco‐aquaculture system (GFA) and in monoculture systems of FA (fertilized + feeding) and BA (only feeding) respectively. This system incorporated traditional Chinese aquaculture technique in which feedings nature food organisms were cultivated by fertilization and ecological regulation. Results from these preliminary experiments suggest that the integrated system could be technically feasible, suitable and exemplary.     

Effect of size‐fractionated fish protein hydrolysate on growth and feed utilization of turbot (Scophthalmus maximus L.)

Four experimental diets were fed to turbot to examine the effect of fish hydrolysate and ultra‐filtered fish hydrolysate on growth performance, feed utilization and non‐specific immune response. Fish hydrolysate was produced by enzymatic treatment and size fractionated using ultra‐filtration (UF). The permeate (molecular weight <1000 Da) after UF and the non‐ultra‐filtered fish hydrolysate (NUF) were tested as feed ingredients. Diets UF1, UF2 contained 3.7%, 1.2% ultra‐filtered fish hydrolysate to replace fish meal protein respectively. The diets UF1, NUF were identical in composition except that the molecular weight of fish hydrolysate in the diet. Fish meal was used in the control diet. All diets were made equal in protein, lipid and energy. Each experimental diet was fed to juvenile turbot (27.87 ± 0.04 g) in triplicate for 8 weeks. Results of this study indicate that the best overall growth and feed utilization of turbot juveniles were obtained with a diet containing higher dose of the small molecular weight compounds in fish hydrolysate. Acid phosphatase, alkaline phosphatase, lysozyme and superoxide dismutase activity in serum were not affected by diet. Total antioxidant capacity was improved with increasing level of low molecule weight fish hydrolysate (UF1).     

The effect of soybean oil containing stearidonic acid on growth performance,n‐3 fatty acid deposition and sensory characteristics of pacific white shrimp (Litopenaeus vannamei)

The ability of shrimp Litopenaeus vannamei to utilize soy oil (SO) modified to contain stearidonic acid (SDA) in replacement of fish oil (FO) by converting SDA to highly unsaturated fatty acids (HUFA) was examined. Six diets with either supplemental modified SO or FO and three levels of fishmeal (FM) replacement (0%, 50% and 100%) by soybean meal (SBM) were fed to shrimp (1.7 g) for 12 weeks. The effect of oil source at the three SBM levels on growth and fatty acid profiles was examined by contrast analysis and sensory attributes by t‐tests (5% error rate). At 0% SBM inclusion, there was no effect of dietary oil source, while at the highest SBM inclusion level, shrimp fed the FO diet outperformed those fed the corresponding SO diet. Oil source had no effect on sensory attributes. The fatty acid profiles of the shrimp reflected that of the diets. SDA SO can replace supplemental FO in diets for shrimp with no reduction in growth when there is sufficient oil present from FM. At low FM, however, replacing FO with SDA SO reduces shrimp performance and tissue n‐3 HUFA levels. It is concluded that SDA is unable to meet the essential fatty acid needs of shrimp.     

Effects of dietary n‐3HUFA on juvenile white shrimp,Litopenaeus vannamei: Growth,feed utilization,antioxidant enzymes activities and fatty acid compositions

Present study investigates the effects of n‐3 high‐unsaturated fatty acid (n‐3HUFA) levels on growth performance, antioxidant enzymes activities and fatty acid compositions of juvenile Litopenaeus vannamei. These represented seven iso‐nitrogenous and iso‐lipidic diets. Analysed n‐3HUFA concentrations were 0.16% (control), 0.48%, 0.74%, 1.39%, 2.39%, 2.92% and 3.44% respectively. A total of 840 juvenile L. vannamei were randomly stocked into 21 0.5 m³ tanks for 56 days. A significant increase (p < 0.05) was observed from 0.16% to 0.74% n‐3HUFA and a decrease when n‐3HUFA was above these levels in weight gain rate (WGR) and specific growth rate. Total cholesterol, triglyceride and low‐density lipoprotein in serum showed a significant decrease, high‐density lipoprotein showed a significant increase (p < 0.05). Phenoloxidase activity in serum and sodium‐potassium adenosine triphosphatase activity in gill were significantly affected by dietary n‐3HUFA (p < 0.05), both of them showing a downward trend after upward. Malic dehydrogenase and superoxide dismutase activities in serum were also significantly affected by dietary n‐3HUFA (p < 0.05), which rose first and then decreased in general, both of them have a maximum in 2.39% group. No significant differences of the activities of aspartate transaminase and alanine transaminase were observed among all groups (p > 0.05). With dietary n‐3HUFA increase, both ∑HUFA and n‐3HUFA contents gradually increased in hepatopancreas and tail muscles (p < 0.05). Based on broken‐line regression analysis of WGR, the optimal n‐3HUFA requirement is 0.89% for juvenile L. vannamei with initial weight of 0.50 ± 0.01 g.     

Dietary effects of poly‐β‐hydroxybutyrate on the growth performance,digestive enzyme activity,body composition,mineral uptake and bacterial challenge of rainbow trout fry (Oncorhynchus mykiss)

This study investigated the effects of diet supplementation with poly‐β‐hydroxybutyrate (PHB) on growth performance, digestive enzyme activity, lipid metabolism, mineral uptake and bacterial challenge of the rainbow trout fry (initial weight: 111.3 ± 13.7 mg) during a 6‐week experimental period. In the experimental set‐up, the commercial diet of rainbow trout fry was replaced with 0.5%, 1% and 2% PHB. The results of our work showed that the replacing of diets with PHB in experimental treatments decreases the weight of rainbow trout fry during the first 2 weeks before significantly increasing final weight at the end of the 6‐week period. PHB also improved digestive enzyme activity in experimental treatments. The highest total protease, pepsin activity and pancreatic enzyme secretion were observed with the 0.5% PHB treatment. A higher concentration of Na and K was observed in the whole body of the fry fed on 1% and 2% PHB‐supplemented diets. Enhanced survival rates occurred in all groups of fry after bath exposure to Yersinia ruckeri compared to rates in those fed the control diet. Our results suggest that the diet supplemented with PHB may improve growth performance, digestive enzyme activity and the functioning of the immune system. These positive effects could be considered for new applications in aquaculture.     

Effects of dietary n‐3 long‐chain unsaturated fatty acid on growth performance,lipid deposition,hepatic fatty acid composition and health‐related serum enzyme activity of juvenile Japanese seabass Lateolabrax japonicus

Studies were conducted to investigate the effects of dietary n‐3 long‐chain polyunsaturated fatty acid (n‐3 LC‐PUFA) on growth performance, lipid deposition, hepatic fatty acid composition and serum enzyme activities of juvenile Japanese seabass Lateolabrax japonicus (initial mean weight 29.2 ± 1.34 g). Triplicate groups of 30 Japanese seabass were fed with six diets containing grade levels of n‐3 LC‐PUFA (1.30, 2.98, 5.64, 10.31, 14.51, 24.13 g kg^–1 of dry weight) to apparent satiation twice daily for 9 weeks. The specific growth rate (SGR) was the highest in 10.31 g kg^–1 dietary n‐3 LC‐PUFA group. Crude lipid content of the fish decreased significantly with increasing dietary n‐3 LC‐PUFA. Meanwhile, the hepatic lipid content increased significantly in the 24.13 g kg^–1 group. Hepatic n‐3 LC‐PUFA content of total fatty acids was closely correlated with that in diet. No significant difference was observed in serum alanine transaminase (ALT) and aspartate aminotransferase (AST) activities. Moderate n‐3 LC‐PUFA level (10.31 g kg^–1 of dry weight) in the diet was beneficial to enhance the activity of lysozyme in serum. Based on SGR, the optimum dietary n‐3 LC‐PUFA content was estimated to be around 10.94 g kg^–1 of dry weight by second‐order polynomial regression method.     

Inclusion of macroalgae meal (Macrocystis pyrifera) as feed ingredient for rainbow trout (Oncorhynchus mykiss): effect on flesh fatty acid composition

The use of macroalgae as an additional component in animal feeding has been studied. However, information on how it could influence muscle composition of fish body is scarce. This study evaluates four diets with different macroalgae inclusion levels (0%, 1.5%, 3% and 6%) to test the effect on body fatty acid composition of rainbow trout. Tanks with a volume of 600 L were stocked with 60.6 ± 7.9 g fish at a density of 45 individuals tank^?1 and fed for 124 days. At the end of the experiment there were not significant differences (P<0.05) in muscle proximate composition among fish fed the different treatments. However, it was determined that inclusion of 3% and 6% of macroalgae meal resulted in a significant increase (P<0.05) of polyunsaturated fatty acids (PUFAs) in muscle. In summary, macroalgae meal in rainbow trout diets do not enhance the quantity of protein and lipid contents at muscle level but an addition of 3–6% might contribute to increase the level of PUFAs, specially EPA, DHA and LIN. Thus, use of macroalgae meal might help to increase lipid quality content in the final product due the beneficial effects of PUFAs for human health.     

Fatty acid,fat‐soluble vitamin and sterol contents in testis and semen,testis‐somatic index and spermatologic values of broodstock rainbow trout (Oncorhynchus mykiss) fed with different levels of omega‐3 fatty acids under regular stripping conditions

In this study, the testis and semen fatty acid, fat‐soluble vitamin and sterol levels, testis‐somatic index and spermatological values were investigated in the broodstock rainbow trout fed with the different levels of omega‐3 polyunsaturated fatty acid (PUFA) under the regular stripping conditions. For this purpose, a control and three test diets were prepared. The control, D1, D2 and D3 diets were contained the omega‐3 PUFA at 3.14%, 7.84%, 13.63% and 20.54% as a percentage of the total fatty acids respectively. The fish in the experimental groups were fed with these diets for 60 days. The testis‐somatic index (3.81–4.50), semen volume (9.30–18.5 ml) and pH (8.05–8.99), initial sperm motility (68.1%–93.7%), duration of 50% sperm motility (141.3–258.9 s), total duration of sperm motility (268.7–489.6 s) and sperm density (9.95–17.5 cells × 10⁹ ml^?1) values of the fish fed the control diet were significantly decrease (p < 0.05) depending on decline of the omega‐3 PUFA, fat‐soluble vitamin and sterol contents in the testis and semen. The omega‐3 PUFA (3.40%–14.76% and 3.96%–16.31%), vitamin A (33.9–61.2 ml/mg and 9.12–26.7 ml/mg), D₂ (0.10–0.19 ml/mg and 0.04–0.10 ml/mg), D₃ (0.75–1.30 ml/mg and 0.06–0.24 ml/mg), alpha‐tocopherol (30.1–60.4 ml/mg and 8.93–25.3 ml/mg), K₁ (0.30–0.94 ml/mg and 0.03–0.08 ml/mg) and K₂ (2.0–3.19 ml/mg and 0.25–0.34 ml/mg) vitamins, cholesterol (1,201–1,588 ml/mg and 330–596 ml/mg), ergosterol (3.12–6.40 ml/mg and 2.10–4.08 ml/mg), stigmasterol (5.57–10.4 ml/mg and 10.2–12.6 ml/mg) and beta‐sitosterol (0.20–0.60 ml/mg and 0.14–0.41 ml/mg) contents in the testis and semen of the fish were significantly affected (p < 0.05) by the dietary omega‐3 PUFA supplementation. The highest values for these parameters were provided from the fish fed the D2 and D3 diets (p > 0.05), followed by the fish fed the D1 diet (p < 0.05). These results showed that the dietary omega‐3 PUFA at 13.63% of the total fatty acids could increase the omega‐3 PUFA, fat‐soluble vitamin and sterol contents in the testis and semen, the testis‐somatic index and spermatologic values of the broodstock rainbow trout under the regular stripping conditions.