Effects of varying dietary fatty acid profile on growth performance, fatty acid, body and tissue composition of juvenile pike perch (Sander lucioperca)

Pike perch (Sander lucioperca) has been identified as specie destined to diverse European inland aquaculture, but knowledge on the nutritional requirements is weak. Therefore, we investigated the effect of varying dietary fatty acid (FA) profile by partial replacement of fish oil (FO) with vegetable oils on growth, FA and body composition of juvenile pike perch. An extruded basal diet containing 59 g kg^?1 crude lipids (FO) was added with 60 g kg^?1 FO, 60 g kg^?1 linseed oil (LO) or 60 g kg^?1 soybean oil (SO). The resulting dietary FA composition differed mainly in the triglyceride fraction and was characterized by highest amounts of linolenic acid (18:3 n‐3) in the LO diet and linoleic acid in the SO diet. Diet enriched with FO contained highest contents of highly unsaturated FA 20:5 n‐3 (eicosapentaenic acid) and 22:6 n‐3 (docosahexaenic acid). Pike perch were held in a recirculation system and each feeding group (in triplicate) was fed with experimental diets at a daily rate of 35 g kg^?1 of biomass for 57 days by automatic feeders. Weight gain and specific growth rate of experimental feeding groups ranged between 18.47 and 19.58 g and 1.37–1.45% day^?1 and was not affected by the dietary composition indicating that FO can be replaced by vegetable oils without negative impact on growth performance. In contrast to the whole body and muscle composition, liver tissue was affected by the varying diets. Liver tissues of fish fed diets enriched with vegetable oils showed significantly increased lipid contents of 162 (LO) and 147 (SO) g kg^?1 and indicate decreased lipid utilization compared with fish fed FO diet (liver lipid content 112 g kg^?1). Nevertheless, hepatosomatic index of pike perch was not influenced by dietary lipid composition. The FA profile of pike perch was generally determined by the dietary FAs.     

The Variations in Proximate Chemical Composition and Fatty Acid Profile in Different Parts of the Thornback Ray (Raja clavata) Caught from Black Sea,Turkey

Proximate chemical composition and fatty acid (FA) profile of different parts and sexes of ray (Raja clavata) were compared. The proximate values of liver samples significantly differed from other body parts (p < 0.05). Pectoral fin had the highest moisture, protein, and ash contents (78.6, 20.5, and 1.2%, respectively). The highest fat content (39.7%) was observed for liver samples. A significant variation was also observed between sexes in terms of proximate and FA values (p < 0.05). The levels of saturated (SFA), monounsaturated (MUFA), and polyunsaturated fatty acids (PUFA) varied between 27.1–32.1, 14.9–19.0, and 34.3–39.5%, respectively, in total fatty acid methyl esters (FAME). The highest total PUFA and docosahexaenoic acid (DHA) values were observed in the edible portion of liver for both sexes due to high contents of fat, despite the low values of % total FAME in comparison with other body parts. Significant variations among FA levels were observed for different body parts (p < 0.05). The highest DHA and eicosapentaenoic acid (EPA) values were found in the edible portion of the liver and calculated as 6.8 and 2.3 g/100 g, respectively, indicating the importance of utilizing the liver of this species.     

Utilization and metabolism of palmityl and oleoyl fatty acids and alcohols in caecal enterocytes of Atlantic salmon (Salmo salar L.)

The substitution of fish oil with wax ester‐rich calanoid copepod‐derived oil in diets for carnivorous fish, such as Atlantic salmon, has previously indicated lower lipid digestibility. This suggests that the fatty alcohols (FAlc) present in wax esters may be a poorer substrate for intestinal enzymes than the fatty acids (FA) in triacylglycerol (TAG), the major lipid in fish oil. The hypothesis tested was that the possible lower utilization of dietary FAlc by salmon enterocytes is at the level of uptake and that subsequent intracellular metabolism was identical to that of FA. A dual‐labelled FAlc–FA metabolism assay was employed to determine simultaneous FAlc and FA uptake and relative utilization in enterocytes isolated from pyloric caeca of Atlantic salmon fed either a diet supplemented with fish oil or wax ester‐rich Calanus oil. The diets were fed for 10 weeks before caecal enterocytes from each dietary group were isolated and incubated with equimolar mixtures of either [1‐¹⁴C]16:0 FA and [9,10(n)‐³H]16:0 FAlc, or [1‐¹⁴C]18:1n‐9 FA and [9,10(n)‐³H] 18:1n‐9 FAlc. Uptake was measured after 2 h with relative utilization of labelled FAlc and FA calculated as a percentage of uptakes. Differences in uptake were observed, with FA showing higher uptake than FAlc, and 18:1 chains a higher uptake than 16:0. A proportion of unesterified FAlc was possibly recovered in the cells, but the majority of FAlc was recovered in lipid classes such as TAG and phospholipids indicating substantial conversion of FAlc to FA followed by esterification. However, incorporation of FA and FAlc into esterified lipids was higher when derived from FA than from FAlc. Twenty‐five to fifty percentage of the absorbed 16:0 FA was recovered in TAG fraction of the enterocytes compared with 15–75% of 18:1 FA. Twenty to thirty percentage of the absorbed 16:0 FA was recovered in the phosphatidylcholine fraction of the enterocytes compared with only 5–15% of the 18:1 FA. Less than 15% of the fatty chains taken up by the cells were used for energy production, with significantly higher oxidation of 18:1 in enterocytes from fish fed the fish oil diet compared with the Calanus oil diet. However, overall, dietary copepod oil had little effect on FAlc and FA metabolism. Metabolic modification by elongation and/or desaturation was generally low at 1–5% of the uptake. We conclude that our hypothesis was generally proved in that the uptake of FAlc by salmon enterocytes was lower than the uptake of FA and that subsequent intracellular metabolism of FAlc was similar to that of FA. However, unesterified FAlc was possibly recovered in the cells suggesting that the conversion to FA may not be concomitant with uptake.     

Dietary fulvic acid effects on survival and expression of immune‐related genes in Litopenaeus vannamei challenged with Vibrio parahaemolyticus

The effects of fulvic acid (FA) on survival and immune‐related gene expression were investigated in Litopenaeus vannamei challenged with Vibrio parahaemolyticus by immersion. Shrimp were fed with different dietary FA concentrations (1, 2, 4 and 6 g/kg feed) for 20 days (first bioassay) or 8 days (second bioassay, 2 g/kg feed of FA added every 2 days) and then challenged with V. parahaemolyticus. In a third bioassay, the expression of three immune‐related genes (translationally controlled tumour protein [TCTP], superoxide dismutase [SOD] and heat‐shock protein 70 [HSP70]) in haemocytes or hepatopancreas of experimental shrimp was measured by real‐time quantitative PCR at 0, 6, 12, 24, 48, 72 and 96 hr after FA (2 g/kg feed) administration. Fulvic acid increased survival at a concentration of 2 g/kg feed supplied every two days. Interestingly, TCTP gene expression was upregulated, whereas gene expression of SOD and HSP70 was downregulated. In conclusion, dietary fulvic acid improves survival in white shrimp challenged with V. parahaemolyticus and modulates the immune response. Therefore, FA merits further evaluation as prophylactic treatment in commercial shrimp farms.     

You are what you eat? Differences in lipid composition of cod larvae reared on natural zooplankton and enriched rotifers

A laboratory experiment with larval cod fed natural zooplankton and enriched rotifers was carried out to investigate the effects of feed type on fatty acid (FA) and lipid composition. A divergence in FA composition was observed within a week of feeding on respective diets, and subsequent transfers of larvae from one feeding regime to the other also confirmed a rapid change in FA composition towards that of the newly provided feed source. The rapid change in FA composition after switching diet is in part expected to be due to the high growth and tissue turnover of cod larvae during the early life stages and provides an opportunity to assess recent feeding history by means of FA analysis. The FA contents also varied between the main analysed lipid classes, with relatively higher eicosapentaenoic acid levels in neutral lipids than in polar lipid classes. Although zooplankton contained notably more polar lipids and less neutral lipids than enriched rotifers, the relative amounts of polar and neutral lipids in larvae from respective prey groups were similar, signifying that the larval composition only partly reflects what they have been eating. Still, the FA composition of the previous diet was still discernible in larvae after 1–2 weeks of transfer to a new diet or after weaning to a formulated feed. The potential long‐term effects of these nutritional differences are discussed.     

Egg and larval quality,and egg fatty acid composition of Eurasian perch breeders (Perca fluviatilis) fed different dietary DHA/EPA/AA ratios

In Eurasian perch (Perca fluviatilis), the variability in spawning quality is a major limiting factor for successful production, especially when breeders are fed with an artificial diet. The influence of the dietary DHA/EPA/AA ratio on the egg and larval quality and on the fatty acid and lipid class composition of eggs has been investigated in perch broodstock. Two experimental diets (16% lipids) with two different DHA/EPA/AA ratios, D1 (3/2/2) and D2 (23/9/1), were compared with a natural diet consisting of cultured carp juveniles, CC (10/10/1) and with a commercial diet for salmonids, CDS (14/16/1). Percentages of fertilization and hatching were comparable between fish fed D1, D2 and CC, with the highest hatching rate observed for D1 (63.5 ± 3.8%). These diets supported better values than the CDS. Larval survival and TL50 observed after osmotic stress were higher for the D1 group, followed by larvae produced by fish fed D2 and CC. Larvae from fish fed D1, D2 and CC were significantly more robust than larvae from the CDS group. Differences were observed regarding the fatty acid (FA) profile in the eggs, which was related to the dietary FA composition. The results indicate that a ratio of 3/2/2 seemed to be effective for obtaining eggs and larvae of good quality.     

Effect of replacing dietary fish oil with soybean oil on production performance and fillet lipid and fatty acid composition of juvenile cobia Rachycentron canadum

As a marine carnivore exhibiting exceptionally high growth rates, cobia are considered a species for which fish oil (FO) replacement may be difficult. However, partial, if not complete, FO replacement is necessary to ensure sustainability. We evaluated the effects of graded substitution of dietary FO with soybean oil (SO) in cobia culture. Feeds contained FO (100% FO), SO (0% FO) or blends of the two (67% FO, 33% FO) as the supplemental lipid source. Production performance was largely unaffected by partial replacement of FO with SO: feed intake and final weight were reduced only in the 0% FO dietary treatment. Fillet total lipid fatty acid (FA) composition differed among the dietary treatments, closely approximating dietary FA profile. As increasing amounts of FO were replaced, SO‐associated FA became enriched within the fillet lipid at the expense of FO‐associated FA. Fillet lipid classes were associated with a particular FA signature, regardless of dietary FA profile. SO can replace a substantial amount of dietary FO; however, juvenile cobia appear to exhibit a nominal requirement for intact long‐chain polyunsaturated FA. Therefore, aggressive FO replacement may result in essential fatty acid deficiencies unless the feeds can be amended with alternative sources of these essential nutrients.     

Efficacy of various lipid supplements in formulated pellet diets for juvenile Scylla serrata

Efficacy of sunflower oil (diet SF) and soybean oil (diet SB) alone and in combination with cod liver oil (diets M1‐2.80:1.40:1.40, M2‐2.80:2.24:0.56 and M3‐2.80:0.56:2.24; cod liver oil:sunflower oil:soybean oil) as lipid supplements (5.6%) in formulated diets (crude fat ～9.79%) for juvenile Scylla serrata (weight=0.28±0.07 g, carapace width=9.7±0.1 mm) were compared with diet CL, containing cod liver oil alone as the lipid supplement (6 diets × 24 crabs stocked individually, randomized block design). Growth performance, nutrient (protein and lipid) intake and gain of crabs fed M1, M2 and M3 were higher (P≤0.05) than the crabs fed SF and SB, but were not significantly different (P≥0.05) from crabs fed CL. Dietary fatty acids (FAs) are found to influence the FA profile of test crabs. Higher tissue levels of 16:1n‐7, 18:1n‐9 and 18:1n‐7 reflected the essential FA deficiency in crabs fed diets supplemented only with vegetable oils. Results confirmed that S. serrata could utilize vegetable oil supplements in the formulated diets as a partial replacement (50%) of cod liver oil without compromising growth and survival. Partial substitution of marine fish oil with suitable vegetable oils can reduce the feed cost considerably, in the context of rising fish oil prices.     

Semisynthetic ferulic acid derivative: an efficient feed additive for Genetically Improved Farmed Tilapia (Oreochromis niloticus)

Ferulic acid (FA) derivative was synthesized by modifying the functional groups of FA as dietary additive in the feeding of Genetically Improved Farmed Tilapia (GIFT) juveniles. Structural confirmation of this compound was based on IR, ¹H and ¹³C NMR techniques. This study was conducted to evaluate the effects of dietary FA derivative supplementation on growth performance, antioxidant status and serum biochemical parameters of GIFT juveniles compared with that of FA. A total of 675 fish with an average initial weight of 10.73 ± 0.40 g were fed nine diets supplemented with 0, 0.26, 0.52, 1.04 and 2.08 mmol kg^?1 FA, or 0.26, 0.52, 1.04 and 2.08 mmol kg^?1 FA derivative. Each diet was assigned to three replicate groups of 25 experimental tilapia for 56 days. Weight gain (WG) in groups of fish fed FA derivative was much higher than that of fish fed FA diet (P < 0.05). The antioxidant enzyme activities (SOD, CAT and GPx) in serum and liver of tilapia fed the FA derivative diets were significantly higher, while the malondialdehyde values were significantly lower than those of the fish fed the FA diets (P < 0.05). The serum biochemical parameters of GIFT were significantly improved by the FA derivative supplement. Moreover, feed conversion ratio, hepatosomatic index and viscerosomatic index were significantly decreased in fish fed FA or FA derivative diet at 0.52 mmol kg^?1 feed (P < 0.05). The investigation on the semisynthetic FA derivative provides a new way for developing safe and efficient feed additives.     

Characterization of phenotype variations of luminescent and non‐luminescent variants of Vibrio harveyi wild type and quorum sensing mutants

Vibrio harveyi, a luminescent Gram‐negative motile marine bacterium, is an important pathogen responsible for causing severe diseases in shrimp, finfish and molluscs leading to severe economic losses. Non‐luminescent V. harveyi obtained by culturing luminescent strains under static and dark condition were reported to alter the levels of virulence factors and metalloprotease gene and luxR expression when compared to their luminescent variants. Presently, we conducted an in vitro study aiming at the characterization of virulence‐related phenotypic traits of the wild‐type V. harveyi BB120 strain and its isogenic quorum sensing mutants before and after switching to the non‐luminescent status. We measured the production of caseinase, haemolysin and elastase and examined swimming motility and biofilm formation. Our results showed that switching from the bioluminescent to the non‐luminescent state changed the phenotypic physiology or behaviour of V. harveyi resulting in alterations in caseinase and haemolytic activities, swimming motility and biofilm formation. The switching capacity was to a large extent independent from the quorum sensing status, in that quorum sensing mutants were equally capable of making the phenotypic switch.     

Dummy regression analysis for modelling the nutritionally tailored fillet fatty acid composition of turbot and sole using gilthead sea bream as a reference subgroup category

Farmed turbot and sole were sampled at different stages of the production cycle for analysis of fillet lipid content and fatty acid (FA) composition. The entire data set along with our own published data on gilthead sea bream were fitted to dummy regression equations with turbot and sole as dummy variables, gilthead sea bream as a reference subgroup category, and diet FA composition and fillet lipid content as independent variables. The relative contribution of each independent variable to the total variance was found to vary within and among FAs and fish species, but strong correlation coefficients (0.76 <  r² > 0.99) were found for almost all of the FA equations, including saturated FAs, monoenes and long‐chain polyunsaturated fatty acids (PUFA) of n‐3 and n‐6 series. Given the differences in lipogenic activities of the fish species, major interaction effects between fillet lipid content and dummy variables were found for monoenes and saturated FAs. The proposed equations (hosted at www.nutrigroup-iats.org/aquafat ) were able to fit different proportions of EPA, DPA and DHA underlying the fish species differences in FA desaturation/elongation pathways. The robustness of the model was proven with extra data from the three fish species, allowing a close linear association near to equality for the scatter plot of observed and predicted values.     

Incorporation dynamics of dietary vegetable oil fatty acids into the triacylglycerols and phospholipids of tilapia (Oreochromis niloticus) tissues (fillet,liver, visceral fat and gonads)

Tilapia (Oreochromis niloticus) previously reared on a commercial feed were fed three experimental diets with added 60 g kg⁻¹ of soybean (SO), linseed (LO) or fish oils (FO), for 6 weeks. The final bodyweight (week 6) of fish was significantly lower when feeding the vegetable oils. At 0, 2, 4 and 6 weeks, fillet, liver, visceral fat, testis and ovary triacylglycerols (TAG) and phospholipids (PL) were analysed for their fatty acid (FA) composition. The simple FA dilution model has been successfully applied to describe the incorporation of numerous dietary FAs into both tissue TAGs and PLs. Fillet PL FAs reacted more sensitively on the FAs of the SO and LO diets, when compared to the TAGs. Alterations of the hepatic TAG and PL fractions were minor and less predictable. Testicular PLs have been found to preferentially accumulate n3 FAs, in particular docosahexaenoic acid (DHA) (C22:6 n3). In contrast, ovarian TAGs showed a predominant accretion of oleic acid by the FO diet. The increased dietary unsaturation index (SO, FO) was found to augment hepatic in vivo lipid peroxidation, as assessed by the tissue malondialdehyde concentrations.     

Effects of six alternative lipid sources on growth and tissue fatty acid composition in Japanese sea bass (Lateolabrax japonicus)

Ten-week experiment was carried out on Japanese sea bass (5.87 ± 0.02 g) to study the effects of replacement of fish oil with six alternative lipid sources: pork lard, PL; beef tallow, BT; poultry fat, PF; soybean oil, SO; corn oil, CO; and a mixed-fat (MF: tallow, 60%; soy oil, 20%; fish oil, 20%) on growth performance and fatty acid (FA) composition in fillet and liver. Seven isoenergetic and isonitrogenous experimental diets were formulated, containing 10% of added lipid. Fish oil was used in control diet, which was substituted by 50% with the alternative lipid sources in the other six diets.

Weight gain (WG), specific growth rate (SGR), Feed conversion ratio (FCR) feed intake and hepatosomatic index (HSI) of fish fed the experimental diets were not significantly different (P > 0.05). Protein efficiency ratio (PER) in fish fed the PF diet were significantly lower than those of fish fed SO and CO diets. Significant differences in carcass moisture and lipid contents of carcass and liver were observed among fish fed the dietary treatments. Generally, the fatty acid composition of fish fillets and livers reflected the dietary FA composition.     

Total Replacement of Dietary Fish Oil with a Blend of Vegetable Oils in the Marine Herbivorous Teleost,Siganus canaliculatus

To investigate the feasibility of total replacement of dietary fish oil (FO) with vegetable oils (VOs) and the optimal dietary polyunsaturated fatty acid (PUFA) level in the marine herbivorous teleost Siganus canaliculatus, six isonitrogenous (32%) and isolipidic (8%) diets were formulated. Control diet used FO as lipid source, whereas diets VO1–VO5 contained various blends of palm, soybean, rapeseed, and linseed oils, in which the dietary PUFA levels were 42.0, 38.2, 33.8, 29.9, and 27.1%, respectively. After S. canaliculatus juveniles were fed with the diets for 9 wk, their growth performance exhibited no significant difference among the dietary groups. The tissue fatty acid (FA) profiles in liver and fillet generally reflected the dietary FA compositions and showed no significant difference among the VO dietary groups. The results suggest that dietary FO can be replaced completely by VO, without affecting their growth performance. Concerning the effects of the dietary FA profile on the survival rate, hepatosomatic index and viscerosomatic index, and PUFA composition in fillets, diets VO1 and VO2 were more favorable compared with diets VO3–VO5. Considering the availability and cost of the VOs, diet VO2 was recommended for practical use in S. canaliculatus.     

Interacting effects of dietary lipid level and temperature on growth, body composition and fatty acid profile of rohu, Labeo rohita (Hamilton)

Three isonitrogenous (320 g kg^?1 crude protein, casein and gelatine) semi‐purified diets with 80 (L8), 130 (L13) and 180 (L18) g kg^?1 lipid (sunflower oil at increasing levels and cod liver oil fixed at 50 g kg^?1) at three digestible energy levels (12 096, 13 986 and 15 876 kJ kg^?1 dry weight) and were tested, in triplicate, on rohu fingerlings (3.2 ± 0.08 g) at two different temperatures (21 and 32 °C). Fish were fed to apparent satiation, twice daily, at 09.00 and 15.00 h, 7 days a week for 56 days. Maximum growth was obtained at a lipid level of 80 g kg^?1 (L8) at 21 °C (439.37%) and 130 g kg^?1 (L13) at 32 °C (481.8%). In general growth rate was higher at 32 °C than at 21 °C at all lipid levels. Tissue monounsaturated fatty acid (MUFA) contents decreased with increasing lipid level at 32 °C, but the reverse occurred at 21 °C. At 21 °C, Polyunsaturated fatty acid (PUFA) level increased significantly (P > 0.05) over initial values, but was affected insignificantly by dietary lipid level. At 32 °C, fish fed diet L13 had more n‐3 fatty acid (FA) in liver and muscle than the other two dietary groups while at 21 °C, both liver and muscle FA profiles exhibited significant change (P > 0.05) in n‐3 and n‐6 FA content which corresponded to variation in percent addition of dietary lipid. However, n‐3/n‐6 ratio was higher for fish fed diet L13 at 32 °C and diet L8 at 21 °C and may be correlated with fish growth.     

A comparison of fatty acid composition and quality aspects of eggs and larvae from cultured and wild broodstock of common sole (Solea solea L.)

Eggs from a F₁ cultured broodstock of sole were compared with eggs from wild‐caught breeders throughout one spawning season, to evaluate if egg quality may be affected by culture‐related conditions. Fourteen batches of eggs from cultured broodstock and 17 batches from wild‐caught sole were compared with respect to fatty acid (FA) composition, egg size, fertilization rate and hatching rate. Based on a multivariate analysis of the FA profiles, it was possible to discriminate between culture and wild inheritance. Eggs from cultured broodstock had high levels of C20:1(n‐9), C18:2(n‐6) and C18:3(n‐3), whereas eggs from wild fish had high levels of C16:1(n‐7), C20:4(n‐6) and C20:5(n‐3). Differences in FA profiles were most likely related to dietary differences. Fertilization and hatching rates were generally low and lowest in eggs from cultured broodstock, but not related to FA composition. Larval growth of one batch from each group was compared. Larval growth was not correlated to broodstock origin, FA composition or egg or larval size. However, larval survival was significantly lower for larvae from cultured broodstock.     

Influence of dietary linoleic acid (18:2n‐6) and α‐linolenic acid (18:3n‐3) ratio on fatty acid composition of different tissues in freshwater fish Songpu mirror carp,Cyprinus Carpio

Six isonitrogenous and isoenergetic purified diets were formulated to feed Songpu mirror carp for 60 days. The control diet (CD) was only supplemented with soybean oil. The other five experimental diets contained soybean oil, linseed oil and lard oil blended at various inclusion levels to attain different linoleic acid (LA)/α‐linolenic acid (LNA) ratios (0.53, 1.04, 2.09, 3.95, 6.82) with a constant total C₁₈ polyunsaturated fatty acids (PUFA; LA+LNA, 2% dry weight) content. The fatty acid (FA) profiles of hepatopancreas, dorsal muscle, intestine, intraperitoneal fat (IPF), spleen and kidney reflected those of the diets, but with some differences. The spleen showed the lowest correlation with diet compared with other tissues, followed by the hepatopancreas (P < 0.05). The intestine and IPF showed relatively higher correlation. On the other hand, the control group had the lowest tissue‐diet correlation, followed by the LA/LNA0.53 group (P < 0.05), whereas the LA/LNA2.09 showed the highest. The LA/LNA ratios in the tissues were up‐regulated in the LA/LNA0.53, 1.04 groups and down‐regulated in the LA/LNA3.95, 6.82 groups. This was due to when LA (or LNA) was highly added in diet, the decrease in this FA was huge in tissue. The contents of saturated fatty acids and monounsaturated fatty acids increased in the control group, but seemed not influenced by dietary LA/LNA ratios. These results demonstrated that the FA deposition was tissue‐specific, and also influenced by the dietary FA composition in the experimental fish. Finally, we suggest that 2.09 is the optimal LA/LNA ratio (2% C₁₈ PUFA) of Songpu mirror carp for fillet FA composition.