Alternative vegetable lipid sources in diets for grouper, Epinephelus coioides (Hamilton): effects on growth, and muscle and liver fatty acid composition

The aim of this study was to investigate the effects of different oils on growth performance and lipid metabolism of the grouper, Epinephelus coioides. Five experimental fish meal‐based isonitrogenous and isolipidic diets were formulated containing either 5.5%‐added fish oil (FO), soybean oil (SBO), corn oil (CO), sunflower oil (SFO) or peanut oil (PO). Each diet was fed to triplicate groups of 20 fish (initial body weight 13.2±0.02 g) grown in seawater at 28.0–30.5 °C for 8 weeks. Fish were fed twice a day to visual satiety. No significant differences in the survival, weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio or hepatosomatic index were found between fish fed the FO or vegetable oils (VO) diets. Dietary lipid sources did not affect whole‐body composition among grouper fed the various diets. Muscle of fish fed the FO diet had significantly higher levels of 14:0, 16:0, 16:1n‐7, 20:5n‐3[eicosapentaenoic acid (EPA)] and docosahexaenoic acid (DHA)+EPA (except for PO fed fish) compared with those of fish fed VO diets. However, the levels of 18:1n‐9, 18:2n‐6 and DHA/EPA ratios in the muscle of fish fed FO diet were significantly lower than those of fish fed the VO diets. The liver of fish fed the FO diet had significantly higher levels of 18:0, 20:5n‐3, 22:6n‐3, n‐3 highly unsaturated fatty acids and DHA+EPA than those of fish fed the VO diets, whereas increases in 18:1n‐9, 18:2n‐6 and mono‐unsaturated fatty acid levels were observed in the liver of fish fed the VO diets.     

Fish proteins not lipids are the major nutrients limiting the use of vegetable ingredients in catfish nutrition

The objective of this study was to determine the major nutrient limiting growth and lipid metabolism in African catfish fed diets composed of vegetable ingredients. Four diets were formulated from contrasted meal (fish meal: FM; vegetable meal: VM) and oil (fish oil: FO; vegetable oil: VO) sources. Replacement of FO by VO did not affect specific growth rate (SGR) and feed efficiency, whereas lower values were recorded in the case of FM replacement. LC‐PUFAs muscle contents were higher in fish fed control FMFO diet than in fish fed vegetable ingredients. However, the decrease in docosahexaenoic acid (DHA) concentration in FMVO group was limited compared to VM groups despite the same low DHA level in those three diets. These results may suggest an activation of LC‐PUFA biosynthesis from PUFA precursors brought with vegetable oils in FMVO group. This hypothesize is reinforced by the significant stimulation of elovl5 gene expression in liver and intestine from fish fed FMVO. Therefore, this study demonstrated that African catfish is able to bioconvert LC‐PUFAs at a significant biological level when FO is replaced by VO whereas the use of plant proteins has strong detrimental effects on growth performances.     

Short‐term food deprivation before a fish oil finishing strategy improves the deposition of n‐3 LC‐PUFA,but not the washing‐out of C18 PUFA in rainbow trout

This study aimed to test the hypothesis that the efficiency of a finishing period can be improved by reducing the initial fat content of fish fillets, by means of a period of food deprivation. Two groups of rainbow trout (Oncorhynchus mykiss) were fed for an 18‐week grow‐out period on a vegetable oil‐based diet (VO) or a fish oil‐based diet (FO). VO fed fish were then split into two sub groups: one (VO/FO) was shifted to the FO diet for 8 weeks, whilst the other (UF/FO) was deprived of food (unfed) for 2 weeks and then fed the FO diet for the remaining 6 weeks. The control treatment (FO/FO) was represented by fish continuously fed FO. The subsequent reduction of total fat in the UF/FO treatment was then responsible for a much faster recovery towards a FO‐like fatty acid profile, validating the proposed hypothesis. However, the modification of the fatty acid composition of fish fillets during the feed withholding period, coupled with the postponement of the finishing diet, resulted in only minor beneficial effects of this strategy, and the loss of potential weight gain. However, the n‐3 LC‐PUFA content in UF/VO fish fillets was significantly higher than fish subjected to the VO/FO treatment.     

Growth Performance,Fatty Acid Composition,Peroxisome Proliferator‐activated Receptors Gene Expressions,and Antioxidant Abilities of Blunt Snout Bream,Megalobrama amblycephala,Fingerlings Fed Different Dietary Oil Sources

A 60‐d feeding trial was conducted to evaluate the effects of different dietary oil sources on growth, fatty acid composition, peroxisome proliferator‐activated receptor (PPAR) gene expression levels, and antioxidant responses of blunt snout bream, Megalobrama amblycephala, fingerlings. Fish (average initial weight, 0.35 ± 0.01 g) were fed five experimental diets respectively containing fish oil (FO), soybean oil, canola oil, peanut oil, and palm oil (PaO). Results showed that body weight gain, specific growth rate, and feed conversion ratio did not significantly differ among treatments. Fish fed PaO diet showed significantly higher hepatosomatic index value and liver lipid content than those fed FO diet. The FO group showed significantly higher liver eicosapentaenoic acid (20:5n‐3) + docosahexaenoic acid (22:6n‐3) concentrations than other groups in both neutral lipid and polar lipid fractions. The mRNA expression levels of PPAR‐α and PPAR‐γ in the liver were significantly increased by feeding vegetable oil diets compared to FO. The activities of catalase, superoxide dismutase, and glutathione peroxidase in livers of fish fed PaO diet were lower than those fed FO diet. Meanwhile, PaO group had significantly lower malondialdehyde value than other groups. In conclusion, we suggested that a combination of FO and vegetable oil diet should be used in feed formulations for blunt snout bream fingerlings.     

Effects of alternative dietary oils on immune response,expression of immune‐related genes and disease resistance in juvenile Nile tilapia,Oreochromis niloticus

The expression of immune‐related genes and immune responses to Aeromonas hydrophila were investigated on Oreochromis niloticus (6.07 ± 0.07 g), by feeding them six different diets for 8 weeks to apparent satiation. Diets contained fish oil (60g/kg FO), virgin coconut oil (60g/kg VCO) and corn oil (60g/kg CO) as sole lipids or blends of 30g/kg FO + 30g/kg VCO (3FVCO), 30g/kg FO + 30g/kg CO (3FCO) and 30g/kg VCO + 30g/kg CO (VO). Fish fed 3FCO recorded higher final weight, percentage weight gain (%WG) and specific growth rate (%SGR) but not significantly higher than all other groups. Triglyceride was higher in fish fed 3FCO than 3FVCO and CO (p ? 0.05), whereas total immunoglobulin (TIg) was not significant (p ? 0.05) between groups. Lysozyme activity was significantly higher in fish fed diet CO while groups FO, 3FCO and VCO recorded the least activities (p ? 0.05). Although alternative complement activity (ACH₅₀), complement proteins (C3 and C4), was not influenced, antibody titre production was significantly higher in fish fed diet 3FCO and lower in group CO. mRNA expression of IL‐1β was significantly upregulated in fish fed VO while the expression of C‐type lysozyme and TGF‐β was not significantly influenced across treatments, although group fed FO recorded higher expression levels, respectively. Lower mortalities of fish were recorded in groups fed 3FCO and VO after 14 days postchallenge with A. hydrophila disease indicating the enhancing effects of vegetable oils to boost immune response and resistance to disease. The study concludes that alternative lipid sources with high polyunsaturated fatty acids (PUFAs‐ALA and LA) (CO) and blend of saturated fatty acids (SFA)(VCO) can partially and or exclusively replace FO with an improved effect on tilapia and resistance to A. hydrophila in tilapia.     

Effect of dietary fish meal and fish oil replacement on lipogenic and lipoprotein lipase activities and plasma insulin in gilthead sea bream (Sparus aurata)

The effects of a double replacement of fish oil (FO) and fish meal (FM) by dietary vegetable ingredients in juvenile gilthead sea bream (Sparus aurata L. 1758) on some indices of lipid metabolism and plasma insulin levels were analysed. Four experimental diets with a replacement of 75% of FM by plant proteins (PP) were administered. Added oil was either FO (75PP/FO diet), or a vegetable oil mix (VO), replacing 33%, 66% or 100% of FO (75PP/33VO, 75PP/66VO, 75PP/100VO diets). Another diet with 50% of substitution of FM by PP and with 100% of VO was also tested (50PP/100VO diet). Final body weight was similar in all diet groups, except for the 75PP/100VO group, which presented lower values. Circulating insulin levels increased with feed administration in all groups and no differences between diets were observed, with the exception of the 75PP/FO group, which presented higher plasma insulin values. In adipose tissue, glucose‐6‐phosphate dehydrogenase and malic enzyme activities decreased with the inclusion of vegetable oil, especially 5 h after feeding. Diet had no significant effect on the hepatic activity of either enzyme. Lipoprotein lipase activity decreased in white muscle and adipose tissue with the replacement of fish oil in 75PP diets, 5 h after feeding. In conclusion, the use of a combined replacement of fish oil and fish meal by vegetable ingredients in gilthead sea bream permits satisfactory growth, with moderate changes in tissue lipogenesis and lipid uptake.     

The influence of dietary fish oil replacement with mixture of vegetable oils on reproductive performance,immune responses and dynamic of fatty acids during embryogenesis in Oncorhynchus mykiss

A 90‐day feeding trial was carried out to examine the influence of fish oil (FO) substitution with blends of vegetable oils (VOs) on reproductive efficiency of female brooders and fluctuation in fatty acid (FA) profile of embryos in Oncorhynchus mykiss. A basal diet was formulated in which 20% (80FO/20VO), 50% (50FO/50VO), 75% (25FO/75VO) and 100% (100VO) of FO were replaced by mixture of VO. Reproductive performance of brooders was not affected by drastic alternations in FA profile of diets. The level of saturated and monounsaturated FAs (MUFAs) significantly increased, whereas the levels of long‐chain polyunsaturated FAs (LC‐PUFAs), mainly docosahexaenoic acid, profoundly decreased during embryogenesis. The concentrations of MUFA and n?6 PUFA increased in the eggs with increasing the incorporation of VO mixture in diets; however, the concentration of LC‐PUFA and n?3/n?6 PUFA ratio decreased. Haematological parameters and humoral immune responses including total immunoglobulin content, lysozyme and alternative complement pathway activities in brooders fed with the experimental diets did not statically different. In summary, incorporating mixture of various VO sources especially linseed and sunflower oils as good sources of α‐linolenic and linoleic acids, respectively, along with low levels of residual fat from fish meal in diet suggested a good strategy for providing the appropriate essential FA requirements of O. mykiss brooders for their successful reproduction.     

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.     

饲料脂肪源和碘酸钾对中华鳖稚鳖生长、存活率、肝肠组织形态和脂类代谢的影响

为了比较饲料中添加鱼油、茶籽油、亚麻籽油以及碘酸钾对中华鳖（）稚鳖生长和脂类代谢的影响,本研究配制了4种油脂含量为10%的饲料,分别为鱼油料（FO,对照组）、鱼油+碘酸钾料（FO+PI,碘酸钾添加量为75 mg/kg）、茶籽油料（TO）和亚麻籽油料（LO）,饲喂初重为（5.06±0.05）g的中华鳖66 d。FO+PI组和LO组中华鳖稚鳖的存活率显著低于FO组（<0.05）。各组中华鳖稚鳖血浆中葡萄糖、总胆固醇和甘油三酯水平无显著差异（ACACA）的表达水平,上调了中华鳖-499的表达水平（-23b的表达水平（<0.05）。FO+PI组和TO组的稚鳖肝脏细胞内脂滴空泡较少,同时TO显著影响了肠道组织的黏膜褶。结论认为,相比于鱼油组,在饲料中添加10%茶籽油、亚麻籽油和添加75 mg/kg碘酸钾不会引起稚鳖生长差异,但是亚麻籽油和碘酸钾降低了稚鳖的存活率,茶籽油和碘酸钾影响肝脏的脂类代谢。     

Reducing the levels of dioxins and dioxin-like PCBs in farmed Atlantic salmon by substitution of fish oil with vegetable oil in the feed

Atlantic salmon were fed extruded diets based on either 100% fish oil (FO) or 100% vegetable oil blend (VO) substitution for 22 months. A total of seven distinct feeding periods were studied that incorporated higher levels of dietary oil inclusion, and larger pellet size as fish size increased. Whole fish levels of polychlorinated dibenzo‐p‐dioxins and dibenzofurans (PCDD/F) and dioxin‐like PCBs (DLPCB) were analysed at the beginning and end of each of the seven feeding periods. The PCDD/F and DLPCB concentrations in the FO diets increased from 2.43 to 4.74 ng WHO‐TEQ kg^?1 (TEQ, toxic equivalents), while VO diets decreased from 1.07 to 0.33 WHO‐TEQ kg^?1 as oil inclusion increased. Partial least square regression analyses identified feed concentration, growth rate and feed utilization, but not variations in lipid content, as factors significantly affecting fish PCDD/F and DLPCB levels. Accumulation efficiencies for DLPCB (740 ± 90 g kg^?1) were significantly (P < 0.01) higher than for PCDD/F (430 ± 60 g kg^?1), explaining the increasing dominance of DLPCB levels over PCDD/F levels in whole fish (DLPCB : PCDD/F ratio of 2.4 ± 0.1 for both VO and FO fed fish) compared with feed (DLPCB : PCDD/F ratio of 1.5 and 0.34 for FO and VO feed respectively). Vegetable oil substitution significantly reduced the level of PCDD/F and DLPCB (eightfold and twelve‐fold, respectively) in the fillet of a 2 kg salmon, but, also negatively affected beneficial health components such as fillet n‐3/n‐6 fatty acid ratio.     

Dietary lipid level and source affect metabolic responses in hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus)

This study was undertaken to evaluate the effect of dietary lipid source [linseed oil (LO, rich in 18:3 n?3); corn oil (CO, rich in 18:2 n?6); olive oil (OO, rich in 18:1n?9); and fish oil (FO, rich in LC‐PUFA)] and level (9% L and 18% L) on growth, body composition and selected plasma biochemistry parameters in hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus) juveniles. Moreover, liver histology (lipids, glycogen, cell vacuolization) and key metabolic enzyme activities were also evaluated. After 8 weeks of feeding, there were no differences in growth performance and whole‐body composition between groups. Plasma lipoprotein, muscle and liver composition, and G6PD and ME activity were affected by lipid level and source. No differences were observed between groups in hepatic ALT activity; however, AST activity was lower in fish fed the 9% L diets. Overall, liver and muscle fatty acid composition reflected that of diet FA composition, with increased n3/n6 ratio, high HUFA and low MUFA in fish fed FO compared with the VO diets. Higher liver glycogen content was observed in fish fed the 18% L than the 9% L diets, except for fish fed FO diet. Considering the experimental diets used, these results indicate that hybrid catfish can efficiently utilize VO supplementation as an energy source, without affecting growth performance and fillet composition.     

Effects of different dietary lipids on growth,body composition and lipid metabolism‐related enzymes and genes in juvenile largemouth bass,Micropterus salmoides

This study investigates the effects of different lipids on growth, body composition and lipid metabolism of largemouth sea bass fish Micropterus salmoides. A total of 360 juvenile M. salmoides (mean ± SD mass = 33.83 ± 0.15 g) were randomly stocked into 12 tanks of 0.5 m³ volume for 8 weeks. Four replicates were made in each group, which were fed one of three diets containing fish oil (FO), soybean oil (SO) or lard oil (LO). The weight gain rate and specific growth rate did not differ among the groups (p > 0.05). Fish oil fish had the lowest condition factor (p < 0.05) and highest serum glucose content (p < 0.05). Crude lipid contents in the whole body and in the liver and muscle of FO fish were significantly lower than in the SO and LO groups (p < 0.05). The fatty acid composition of whole‐body lipids was closely correlated with that of the diet. The carnitine palmitoyltransferase 1 (cpt1) activity in the FO group was significantly higher than those in the SO and LO groups (p < 0.05). No significant differences in fatty acid synthase (fasn) activity were observed among the groups (p > 0.05). The Cpt1 and fasn gene expression levels in the FO group were significantly higher than those of the SO and LO groups (p < 0.05). The apolipoprotein B100 gene expression level was significantly higher in the SO group than in the FO group (p < 0.05). Fatty acid‐binding protein 1 gene expression levels in the FO and SO groups were not different (p > 0.05) but were both higher than that of the LO group (p < 0.05). The delta‐6 fatty acyl desaturase gene expression level in the LO group was significantly higher than that in the FO group (p < 0.05), but lower than that in the SO group (p < 0.05). It can be concluded that FO can be completely replaced by SO or LO in the M. salmoides diet, at least within the 8‐week culture period. Different types of dietary lipids significantly affect body condition and hepatic lipid metabolism in M. salmoides.     

Complete replacement of dietary fish oil with a vegetable oil blend affect liver lipid and plasma lipoprotein levels in Atlantic salmon (Salmo salar L.)

To study how hepatic lipid turnover and lipid transport may be affected by complete replacement of dietary fish oil (FO) with a vegetable oil blend (VO) from start feeding until the adult stages, Atlantic salmon (Salmo salar L.) were fed either 100% FO‐ or 100% VO‐based diets (55% rapeseed oil, 30% palm oil and 15% linseed oil) from start feeding until 22 months. Liver and plasma lipoprotein lipid class levels and lipoprotein fatty acid composition were analysed through the seawater phase, whereas liver fatty acid composition, plasma cholesterol, triacylglycerol (TAG) and protein levels were analysed through both freshwater and seawater stages. Further, enzyme activity of liver fatty acid synthetase (FAS), NADH‐isocitrate dehydrogenase, malic enzyme, glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase and expression of the gene Peroxisome proliferator‐activated receptor γ (PPARγ) was analysed during both fresh water and seawater stages through the experiment. Dietary VO significantly increased salmon liver TAG and hence total liver lipid stores after 14 and 22 months of feeding. Further, after 22 months of feeding, plasma lipid levels and plasma low‐density lipoprotein (LDL) levels were significantly decreased in VO‐fed salmon compared with FO‐fed fish. The same trend, although not statistically significant, was seen for plasma very low‐density lipoprotein (VLDL). The activity of FAS was generally low throughout the experiment with the VO group having significantly lower activity after 16 months of feeding. The expression of PPARγ in livers increased prior to seawater transfer followed by a decrease, and then another increase towards the final sampling (22 months). Dietary vegetable oil replacement had no impact on PPARγ expression in salmon liver. In summary, liver TAG stores, plasma lipid and LDL levels were affected by dietary vegetable oil replacement in Atlantic salmon during a long–term feeding experiment. Current results indicate that high dietary vegetable oil inclusion increase hepatic TAG stores and decrease plasma lipid levels possible through decreased VLDL synthesis.     

Effects of dietary fish oil replacement by microalgae raw materials on growth performance,body composition and fatty acid profile of juvenile olive flounder,Paralichthys olivaceus

Replacing dietary fish oil with DHA‐rich microalgae Schizochytrium sp. and EPA‐rich microalgae Nannochloropsis sp. for olive flounder (Paralichthys olivaceus) was examined. Three experimental isonitrogenous and isolipidic diets with lipid source provided by 50% fish oil (F50S50), 50% (M50F25S25) and 100% microalgae raw material (M100) respectively were compared with a soybean oil (S100) diet as control. Triplicate groups of olive flounder juveniles (16.5 ± 0.91 g) were fed the experimental diets, and a group was fed the control diets for 8 weeks in a recirculation system. Results showed feed efficiency and growth performance were not significantly changed when fish oil (FO) was totally substituted by soybean oil (SO) or microalgae raw material (MRM). The whole‐body composition, lipid content of liver and muscle, and lipid composition of plasma were not significantly influenced by the total substitution of FO by MRM. The polyunsaturated fatty acids (PUFA) content of muscle and liver declined in fish fed S100 diet, whereas it was not significantly reduced in fish fed M50F25S25 and M100 diets. The total substitution of FO by MRM not only maintained the levels of arachidonic acid, EPA or DHA but also increased n‐3/n‐6 ratio. In conclusion, MRM as the sole lipid source is sufficient to obtain good feed efficiency, growth performance and human health value in olive flounder juveniles.     

Effects of total fish oil replacement to vegetable oils at two dietary lipid levels on the growth,body composition,haemato‐immunological and serum biochemical parameters in caspian brown trout (Salmo trutta caspius Kessler, 1877)

This research aimed to evaluate the effects of two dietary fat levels [low fat (LF) (10%), high fat (HF) (20%)] and sources [fish oil (FO), vegetable oil (VO)] on the growth and some physiological parameters of Caspian brown trout fingerlings for 60 days. Tuna oil or blends of canola and soybean oils (85:15) were added to diets to design four feeds namely LFFO, HFFO, LFVO and HFVO according to the fat levels and sources. The fish fed the LFFO diet had lower weight gain than the other fish (P<0.05). The total n‐6 fatty acids increased in fish fed diets with the blends of VO, while the total n‐3 fatty acids decreased in these fish (P<0.05). Serum lysozyme activity was higher in fish fed the HFVO diet than the other fish (P<0.05). Serum glucose, total cholesterol, triglyceride and very low‐density lipoprotein were lower in fish fed LFFO than the other fish (P<0.05). The present study demonstrates that in terms of fish growth, VOs can be used as an alternate source of dietary fat, whereas fish health and nutritional value are improved with the LFFO diet. According to these results, a partial substitution of FO by VO in high‐level fat diets is suggested for long‐term feeding of Caspian brown trout.     

Effects of feeding frequency and dietary energy level on growth and body composition of juvenile flounder, Paralichthys olivaceus (Temminck & Schlegel)

A two (dietary energy levels; low energy, LE and high energy, HE) × 4 (feeding frequency; one feeding in 2 days, one feeding daily, two times daily and three times daily) factorial experiment was performed to determine the effects of dietary energy level and/or feeding frequency on the growth and body composition of juvenile flounder Paralichthys olivaceus. The survival rate was not significantly different among treatments. Weight gain of fish fed the LE and HE diets significantly increased as feeding frequency increased. The weight gain of fish fed the LE diet was higher at each level of increasing feeding frequency. The weight gain of fish fed the HE diet was higher than that of fish fed the LE diet once in 2 days and once daily, but weight gain of fish fed the HE diet was lower than the LE diet three times daily. Daily feed intake was significantly influenced by feeding frequency, but not by dietary energy level. Feed efficiency of fish fed the HE diet once daily was significantly higher than that of fish fed the LE diet once in 2 days, but no significant difference in feed efficiency was observed among other groups of fish. The protein efficiency ratio of fish fed the LE diet once in 2 days was the lowest. Feeding frequency and dietary energy level had a significant effect on the body lipid content. A feeding frequency of two times or three times daily would be effective, depending on dietary energy level for maximum growth of juvenile flounder grown from 3.5 to 15 g.     

The effect of fish and rapeseed oils on growth performance,egg fatty acid composition and offspring quality of sterlet sturgeon (Acipenser ruthenus)

The aim of this study was to evaluate the long‐term effects (7‐month experiment) of diets consisting of fish oil (Kilka fish) and vegetable oil (rapeseed) on the reproductive performance of sterlet sturgeon (Acipenser ruthenus) broodstock. Forty‐five broodstock (990.3 ± 20.05 g) were randomly allocated to three different diet treatments. Three experimental diets were formulated with graded levels of fish oil (100% FO), vegetable oil (100% VO), and a combination of fish and vegetable oil (50% FO + 50% VO). At the end of the 7‐month feeding trial period, the weight gain and final weight were changed significantly different between the treatments (p < 0.05). Broodstock fed the FO + VO diet had higher growth than those fed the only FO or VO diets (p < 0.05). The highest germinal vesicle migration percentage was observed in FO + VO treatment (p < 0.05). The DHA/EPA, DHA/ARA and EPA/ARA ratios in oocyte exhibited a significant difference in the different treatments (p < 0.05). This study indicates that nutrition of broodstock with diet including FO + VO (p < 0.05) can positively affect the growth performance of larvae compared with only FO or VO diets. Furthermore, the high levels of 18:1n‐9, AL and ALA contents in oocytes from broodstock fed VO and the lowest ALA content in oocytes from broodstock fed FO underlined the important role of broodstock diets in the reproductive process and embryonic and/or larval developments of sterlet.     

Effects of dietary sunflower oil on growth parameters,fatty acid profiles and expression of genes regulating growth and metabolism in the pejerrey (Odontesthes bonariensis) fry

Aquaculture fish diets usually contain an addition of fish oil to improve their nutritional value. The effect of the replacement of dietary fish oil (FO) by sunflower oil (SfO) on growth, fatty acid composition and expression of genes implicated in somatic growth, feed intake and fatty acid metabolism was studied in pejerrey fry. Fry were fed per 45 days with diets containing FO/SfO ratios of 100% FO; 50% FO:50% SfO; 20% FO:80% SfO; and 100% SfO. No differences were detected in growth and in the total per cent of saturated and monounsaturated fatty acids. Gh, ghr‐I and ghr‐II showed a higher mRNA expression in head and trunk of fry fed with 100% SfO diet. Expression of igf‐II was higher in trunk of fry fed with 100% SfO diet compared with 100% FO diet. The Δ6‐desaturase gene expression was upregulated in head and trunk of fry fed with 100% SfO diet. The nucb2/nesfatin‐1 gene expression decreased in the trunk of fry with increasing dietary SfO. We conclude that the replacement of fish oil by sunflower oil in pejerrey fry feed does not affect growth and is a viable strategy to reduce production costs of this fish.