Increase In Dietary Lipid Research Articles

Inland saline culture of GIFT (Oreochromis niloticus) juveniles: effect of graded levels of lipid on growth and haemato-biochemical responses.

60-days trial was performed to study the effect of inland saline water (ISW) at 10ppt salinity on lipid requirement of Genetically Improved Farmed Tilapia (GIFT) juveniles. Six purified iso-nitrogenous (37% crude protein) and hetero-caloric (380-430 Kcal DE/100g) diets having graded levels of dietary lipid viz., 4, 6, 8, 10, 12 and 14% were prepared. Two hundred and seventy acclimated GIFT juveniles (1.90 ± 0.1g) were randomly distributed (15 fish per 300L tank) into six different treatments viz., T4, T6, T8, T10, T12 and T14 in triplicates. The increase in dietary lipid resulted in an increase in body lipid and a diminution in moisture levels in fish. There was a significant (p < 0.05) increase in weight gain (g), percent weight gain (WG%), protein efficiency ratio (PER) and feed efficiency ratio (FER) with increasing dietary lipid level up to 8% and decreased thereafter, but an opposite trend was noted in the feed conversion ratio (FCR). The serum glucose level linearly elevated with the rise in dietary lipid level, but higher lipid (beyond 8%) fed groups showed significantly (p < 0.05) more total protein in serum. Though there was a significant (p < 0.05) difference in cholesterol levels, no clear trend was observed; while other parameters viz., body indices (VSI and HSI), serum albumin, globulin and A-G ratio was not showed any significant (p > 0.05) variation with varying dietary lipid level. Based on regression models, it was observed that the optimum lipid level required for GIFT in ISW (10ppt) is in the range of 8.35-9.05%.

Growth, reproduction, fatty acid profiles and offspring performance of broodstock yellow catfish Pelteobagrus fulvidraco fed diets with different lipid levels

Parental nutrition plays important roles in reproductive performance and offspring health of broodstock yellow catfish. However, there is a lack of relevant knowledge concerning the broodstocks of many fish species. This study investigated the influence of dietary lipid levels on growth, spawning performance, tissue fatty acid profiles, sex hormone secretion, and offspring health status of yellow catfish (Pelteobagrus fulvidraco). Five experimental diets were designed containing a 7:3 ratio of fish oil and corn oil blends with graded lipid levels (6.3%, 8.2%, 10.8%, 12.2%, and 14.4% by dry weight) and were fed to female broodstock yellow catfish for 8 weeks. The results showed that weight gain, egg diameter, fertilization ratio, and hatching ratio increased initially and then decreased with increasing dietary lipid levels, reaching optimal peaks in the L10.8 group. Broodstock fed a diet with 10.8% lipid obtained the highest 17-β estradiol concentration. The deposition of highly unsaturated fatty acids in tissues increased initially and then decreased with the increase in dietary lipids, reaching a peak in the 10.8% group. Plasma superoxide dismutase activity and total glutathione content were lowest in fish fed a diet with a 6.3% lipid level, while the contents of malondialdehyde and cortisol in larvae 3 days post-hatching showed an opposite trend, indicating that a low-fat diet reduced the antioxidant capacity of broodstock and induced a stress response that had negative effects on offspring health. Broodstock fed a diet with an appropriate lipid level could increase the expression of antioxidant enzymes by activating the nrf2 signaling pathway. Based on the regression of dietary lipid level and weight gain, reproductive performance, and egg quality of fish, the optimal dietary lipid level was 10.1–11.7% for broodstock yellow catfish.

Macronutrient signals for adaptive modulation of intestinal digestive enzymes in two omnivorous Galliformes

According to the adaptive modulation hypothesis, digestive enzyme activities are matched to their respective dietary substrate level so that ingested nutrients are not wasted in excreta due to insufficient digestive capacity, and so membrane space or expenditures building/maintaining the intestinal hydrolytic machinery are not wasted when substrate levels are low. We tested predictions in juvenile northern bobwhites (Colinus virginianus) and juvenile and adult domestic chickens (Gallus gallus domesticus) by feeding them on diets varying in starch, protein, and lipid composition for 7–9 d (bobwhites) or 15 d (chickens). Birds were euthanized, intestinal tissue harvested, and enzyme activities measured in tissue homogenates from proximal, medial and distal small intestine. We found that (1) α-glucosidase (AG; maltase and sucrase) activities were induced by dietary starch in both juvenile and adult chickens but not in northern bobwhites; (2) aminopeptidase-N (APN) activities were induced by dietary protein in both bobwhites and juvenile but not adult chickens; (3) AG activities were suppressed by an increase in dietary lipid in both bobwhites and juvenile but not adult chickens; and (4) APN activities were not suppressed by high dietary lipid in any birds. We review findings from 35 analogous trials in 16 avian species. 100% of avian omnivores modulate at least one enzyme in response to change in dietary substrate level. AG induction by dietary carbohydrate occurs in more members of Galloanserae than in Neoaves, and all omnivorous members of Neoaves tested so far increase APN activity on high dietary protein, whereas fewer of the Galloanserae do.

Effects of dietary lipid levels on growth, feed utilization, RNA/DNA ratio, digestive tract enzyme activity, non-specific immune response and optimum inclusion in feeds for fingerlings of rohu, Labeo rohita (Hamilton)

The current investigation was conducted to assess the effects of different levels of dietary lipid on growth performance, feed utilization, digestive tract enzyme activity, lipid deposition, and non-specific immune response of fingerling Labeo rohita (2.23 ± 0.06 g). Six isonitrogenous (400 g kg−1) purified diets with increasing levels of lipid (20, 40, 60, 80, 100, 120 g kg−1 diet) were fed to triplicate groups of 30 fish per tank at 08:00, 12:00, and 16:00 h to apparent satiety for 8 weeks. Absolute weight gain (AWG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE) and RNA:DNA ratio improved significantly (P < 0.05) up to 100 g kg−1 lipid in diet. Somatic indices and whole body lipid positively correlated with the increase in dietary lipid. Dietary lipid levels significantly affected hepatic antioxidant activities. Liver superoxide dismutase (SOD) and catalase (CAT) activities improved significantly up to 100 g kg−1 lipid in diet. However, liver thiobarbituric acid reactive substances activity (TBARS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities showed a negative correlation with the increase in levels of lipid in the diets. Highest intestinal protease and lipase activity was also noted in fish received 100 g kg−1 lipid in diet. Second-order polynomial analysis of AWG, FCR, RNA/DNA ratio, SOD and serum lysozyme activity against varying levels of dietary lipid reflected the requirement in the range of 94.77–98.35 g kg−1 dietary lipid for optimum growth of L. rohita.

Effects of dietary lipid level on growth performance, feed utilization, fatty composition and antioxidant parameters of juvenile walleye pollock, Gadus chalcogrammus

We evaluated effects of dietary lipid level on growth performance, feed utilization, fatty acid composition, plasma chemistry, and antioxidant responses in juvenile walleye pollock (Gadus chalcogrammus). Two-hundred forty juvenile pollock averaging 4.4 g in weight were randomly distributed between 12 400-L flow-through circular tanks (20 fish per tank). Fish were fed four isonitrogenous experimental diets with crude lipid levels of 8.1%, 12.6%, 16.7%, or 20.8% for 8 weeks. Each diet was assigned to three tanks, and the fish were hand-fed to satiation twice daily. At the end of the trial, weight gain, specific growth rate, feed efficiency, and protein efficiency ratio were increased with increasing dietary lipid up to 16.7%, and then decreased with a further increase in dietary lipid. The hepatosomatic index showed an increasing trend with increasing dietary lipid. The crude lipid content in liver increased with increasing dietary lipid. Saturated fatty acid levels in the muscle and liver decreased, whereas essential fatty acids and polyunsaturated fatty acids in the muscle and monounsaturated fatty acids in the liver increased with increasing dietary lipid. The hematological and antioxidant parameters were not affected by the dietary lipid content. In conclusion, on the basis of a second-order polynomial regression analysis of weight gain, the optimum dietary lipid level for juvenile walleye pollock was estimated to be 15.8%.

An increase in dietary lipid content from different forms of double-low rapeseed reduces enteric methane emission in Datong yaks on the Qinghai-Tibetan Plateau.

Enteric methane (CH4 ) emission in cattle generally decreases by approximately 1g/g dry matter intake (DMI) with an increase in dietary lipids of 10g/kg dry matter (DM). The effect of dietary lipids on CH4 emission in yaks has not been reported and is the subject of this study. Four Datong yaks were used in a 4×4 Latin-square design in which the four treatments included restricted intakes of double-low rapeseed differing in form and lipid (ether extract-EE) content: (a) rapeseed meal (EE 32.6g/kg DM); (b) rapeseed meal and rapeseed cake (EE 45.8g/kg DM); (c) rapeseed meal and whole cracked rapeseed (EE 54.5g/kg DM) and (d) rapeseed meal and rapeseed oil (EE 62.7g/kg DM). The digestibility of feed components did not differ among treatments. The ruminal total volatile fatty acids (p=.082) and acetic acid (p=.062) concentrations tended to be lowest in yaks consuming the diet with highest lipid content. In addition, CH4 production was lowest in this group (p=.004), and declined by 1.75g/g DMI per 10g/kg DM reduction in dietary lipid content, a rate substantially faster than in cattle.

Effect of Different Dietary Lipid Levels on Spawning Performance and Egg Quality of Pangasianodon hypophthalmus (Sauvage, 1878)

Dietary lipid manipulation of broodstock diet offers a strategy for improving spawning performance and egg quality of broodstock fish. Although many studies were conducted on basic nutrient requirements for fingerlings and juveniles of Pangasianodon hypophthalmus (Sauvage, 1878); the artificial feed for P. hypophthalmus broodstock is still lacking. This study analysed the effect of different levels of lipid in the diet on spawning performance and egg quality of female P. hypophthalmus broodstock. Three test diets were formulated containing 1:1 ratio of palm oil and fish oil blends at the level of 60, 90 and 120 g.kg-1 with a constant 300 g.kg-1 protein and fed to triplicate groups of female broodstock for 150 days at the rate of 20 g.kg-1 body weight twice daily. The ovary weight, gonadosomatic index, fecundity, egg weight and diameter and egg fertilisation rate were significantly (P < 0.05) increased for fish fed with 90 and 120 g.kg-1 lipid diet compared to 60 g.kg-1 lipid diet. However, there was no significant difference between fish fed with 90 and 120 g.kg-1 lipid diet; thus an increase in dietary lipid above 90 g.kg-1 would not make any significant contribution. The increased performance of female broodstock fed with higher dietary lipid and fish oil at the ratio of 1:1 for crude palm oil and fish oil up to 90 g.kg-1 contributed in the enhancement of the reproductive performance and egg quality of P. hypophthalmus.

Effects of dietary lipid level and n-3/n-6 fatty acid ratio on growth, fatty acid composition and lipid peroxidation in Russian sturgeonAcipenser gueldenstaedtii

The growth performance, fatty acid composition, hepatic lipid content, hepatic somatic index and lipid peroxidation in Russian sturgeon were investigated using diets containing three lipid levels 50 g kg−1 (L5), 150 g kg−1 (L15) and 250 g kg−1 (L25) and three n-3/n-6 fatty acid ratios (1 : 3, 1 : 1 and 3 : 1) for 8 weeks. Weight gain significantly increased with the increase in dietary lipid levels at n-3/n-6 fatty acid ratios of 1 : 3 and 1 : 1, but not at the 3 : 1 ratio. Correspondingly, fish survival gradually decreased with the increase in dietary lipid at the 3 : 1 n-3/n-6 fatty acid ratio. The dietary lipid level significantly affected the composition of whole-body fatty acid. The retention of highly unsaturated fatty acid dramatically decreased at the level of 250 g kg−1 dietary lipid. The liver malondialdehyde increased with the increase in dietary lipid levels and the n-3/n-6 fatty acid ratios. The contents of lipid and triglyceride in the liver and the hepatic somatic index also increased with the increase in dietary lipid. The diet combination of L25 + 3 : 1 showed the highest aspartate transaminase and alanine transaminase, indicatives of hepatic injury. This study indicates that the L25 + 1 : 3 diet can improve fish growth performance, whereas the L25 + 3 : 1 diet may lead to poor growth performance due to high lipid peroxidation.

Influence of dietary protein and lipid levels on growth performance and the incidence of cannibalism inPseudoplatystoma punctifer (Castelnau, 1855) larvae and early juveniles

The aim of the study was to evaluate the influence of different dietary protein and lipid levels and their ratios on larval growth, survival and the incidence of cannibalism in Pseudoplatystoma punctifer. Larvae were raised in a recirculation system from 3 to 26 days post-fertilization (dpf) (2–25 days post hatching, dph) at an initial density of 40 larvae L−1, 27.8 ± 0.65°C and 0L : 24D photoperiod. Larvae were fed from 4 to 12 dpf with Artemia nauplii and weaned onto four different compound diets from 13 dpf within 3 days, then fed exclusively with these diets until 26 dpf. These diets contained 30 : 15, 30 : 10, 45 : 15 or 45 : 10 protein : lipid (P : L) (in % of dry matter) levels. A control group was fed Artemia nauplii until 17 dpf and weaned thereafter with the 45P : 10L compound diet. The experiment was carried out in triplicate. Results showed higher growth and survival rates and lower incidence of cannibalism in the group fed the 45P : 15L diet than in the other treatments. Differences in larval survival and growth performance were associated with the higher protein and lipid content rather than the protein : lipid ratio of this diet. When comparing diets with the same protein level, the increase in dietary lipid led to an improvement in growth, suggesting that energy from lipids spares protein for growth in P. punctifer fingerlings. An Artemia feeding period longer than 12 dpf did not improve larval growth or survival. (Resume d'auteur)

Dietary lipid and gross energy affect protein utilization in the rare minnow Gobiocypris rarus

An 8-week feeding trial was conducted to detect the optimal dietary protein and energy, as well as the effects of protein to energy ratio on growth, for the rare minnow (Gobiocypris rarus), which are critical to nutrition standardization for model fish. Twenty-four diets were formulated to contain three gross energy (10, 12.5, 15 kJ/g), four protein (20%, 25%, 30%, 35%), and two lipid levels (3%, 6%). The results showed that optimal dietary E/P was 41.7-50 kJ/g for maximum growth in juvenile rare minnows at 6% dietary crude lipid. At 3% dietary lipid, specific growth rate (SGR) increased markedly when E/P decreased from 62.5 kJ/g to 35.7 kJ/g and gross energy was 12.5 kJ/g, and from 75 kJ/g to 42.9 kJ/g when gross energy was 15.0 kJ/g. The optimal gross energy was estimated at 12.5 kJ/g and excess energy decreased food intake and growth. Dietary lipid exhibited an apparent protein-sparing effect. Optimal protein decreased from 35% to 25%-30% with an increase in dietary lipid from 3% to 6% without adversely effecting growth. Dietary lipid level affects the optimal dietary E/P ratio. In conclusion, recommended dietary protein and energy for rare minnow are 20%-35% and 10-12.5 kJ/g, respectively.

Effect of Dietary Protein and Lipid Levels on Growth and Body Composition of Spotted Halibut, Verasper variegatus

A 83-d feeding experiment was undertaken to evaluate the effects of dietary protein and lipid levels on growth and body composition of spotted halibut, Verasper variegatus (initial average weight of 93.0 ± 1.0 g). Nine diets were formulated to contain three protein levels (40, 45, and 50%), each with three lipid levels (8, 12% and 16%). Each diet was randomly fed to triplicate groups of 20 fish per tank in the indoor culture system. Results showed that the survival rate of fish was not significantly affected by protein and lipid levels (P > 0.05). Weight gain, specific growth rate (SGR), and feed intake (FI) significantly decreased with the increasing dietary lipid levels (P < 0.05). Feed efficiency significantly increased while the feed conversion ration significantly decreased with increasing dietary protein levels (P < 0.05). Weight gain, SGR, FI, and feed efficiency of fish fed 50% protein and 8% lipid were significantly higher than that of the other groups. For each level of dietary lipid, the increase in dietary protein resulted in significant increases in whole-body crude protein (CP) contents (P < 0.05); the increase in dietary lipid caused significant increases in whole-body crude lipid content and gross energy at each protein level (P < 0.05). The muscle CP, lipid, and gross energy had the same tendency. The results of this study indicated that increasing dietary lipid levels did not result in a protein-sparing effect. It could be recommended that the proper dietary protein and lipid levels of spotted halibut were 50 and 8%, respectively.

High dietary lipids elevate carbon loss without sparing protein in adequate protein-fed juvenile turbot (Psetta maxima)

This study was undertaken to determine the effects of dietary lipid levels on growth and nutrient utilization, and carbon (C), nitrogen (N) and phosphorus (P) balances in juvenile turbot (Psetta maxima) in brackish water. Four isonitrogenous diets (50 % protein) differing in dietary lipid levels from 10 to 19 by 3 % increments (named 10L, 13L, 16L and 19L, respectively) were fed to four replicate groups of fish with an initial weight of 54.4 ± 0.2 g for 9 weeks. Significantly better growth and feed conversion ratio were observed in fish fed 13L than those fed 16L and 19L. The whole body, fillet, viscera and liver dry matter and lipid levels were increased as dietary lipid was increased. Liver protein levels were lower in 16L and 19L than 10L. There was an ascending pattern in the whole-body C levels and C/N ratios with the increase in dietary lipids. No significant effect of dietary lipids on either protein efficiency ratio or N and P retentions was detected. Dietary lipids led to an increase in C losses to the environment. Overall, high dietary lipids when introduced at an adequate protein level did reduce growth and feed utilization without a protein-sparing effect and resulted in higher C losses in juvenile turbot reared, and a dietary lipid level of about 13 % seemed to be optimum.

Effects of increasing the dietary lipid levels on the growth performance, body composition and digestive enzyme activities of the teleost pejerrey (Odontesthes bonariensis)

The present study aimed at determining the growth performance, body composition and digestive enzyme activities of pejerrey (Odontesthes bonariensis) juveniles fed with graded levels of dietary lipids: 6% (L6), 10% (L10) and 25% (L25). Following a 14-week growth trial, weight increase decreased in group L6. The protein productive value increased in groups L10 and L25, whereas group L10 showed the highest lipid productive value. Hepatosomatic and mesenteric fat indexes decreased in group L6. Body protein content decreased with the increase in dietary lipids (L6>L10>L25); whereas body lipid content, and nitrogen and energy retentions were the lowest in group L6. The muscle fatty acid composition was differentially regulated by the diets except EPA, DHA and n-3 PUFA contents. The total n-6 PUFA decreased in group L6. The n-3 PUFA tended to accumulate in the muscle of the fish; group L10 exhibiting the lowest accumulation rate. The total activity of neutral lipase was stimulated in group L25 whereas the specific activity of pancreatic lipase decreased in this same group. While group L6 showed the lowest total activity of alkaline proteases, group L10 showed the highest total activity of trypsin. A decrease in the specific activity of amylase in group L25 followed the decrease in dietary starch. In summary, 25% of dietary lipids did not have additional stimulatory effects on the digestive proteases activity compared to 10%, but negatively affected pancreatic lipase and trypsin activities. Moreover, the decrease of the latter in group L25 suggests that approximately 10% of dietary lipids might support the growth of pejerrey juveniles reared in captivity.

Dietary Lipid Levels Affect Growth and Fatty Acid Profiles of Malaysian Mahseer Tor tambroides

AbstractAfter protein, the second major essential macronutrient in fish diet is lipid. This study was conducted to determine the optimum level of dietary lipid for the best growth performance of juvenile Malaysian mahseer Tor tambroides. Four isonitrogenous diets containing 40% crude protein were formulated to contain different levels of lipid (5, 10, 15, or 20% on an as‐fed basis). Cod liver oil was incorporated into the feed as the main dietary lipid source used to formulate the diets while residual oil coming from other ingredients contributed about 5% of dietary lipid. The experimental diets were labeled as L5, L10, L15, or L20 to denote the levels of dietary lipid. Fish were fed the experimental diets in triplicate groups for 63 d. Growth performance, survival rate, and daily feed intake by Malaysian mahseer significantly decreased when fed diets in which levels of dietary lipid increased from 5% to 20%. However, the growth performance did not vary significantly between fish fed the L5 and L10 diets. The increase in dietary lipid significantly increased the hepatosomatic index but did not influence the viscerosomatic index. Increasing dietary lipid levels also decreased the lipid content in the whole body composition of fish. The monounsaturated fatty acid (MUFA) and n‐3 polyunsaturated fatty acid (PUFA) contents of fish liver significantly increased with the increase of dietary lipid. The results of this study suggested that 5% dietary lipid is sufficient for the best survival rate and growth performance of juvenile Malaysian mahseer.

Effect of dietary protein and lipid levels on growth, nutrient utilization and whole‐body composition of blue gourami, Trichogaster trichopterus fingerlings

Nine semi-purified diets were prepared with three levels each of protein (300, 350 and 400 g/kg) and lipid (60, 80 and 100 g/kg) and fed ad libitum to Trichogaster trichopterus fingerlings (0.61 ± 0.03 g) in triplicate groups (10 fish/replicate) for 90 days to determine optimum dietary protein and lipid levels. Twenty-seven flow-through fibre-reinforced plastic tanks (200 l capacity each with 100 l of water) were used for rearing the fish. The dietary protein, lipid and their interactions had significant effects (p < 0.05) on weight gain, feed conversion ratio, specific growth rate, nutrient retention and digestibility, but not on hepato- and viscerosomatic indexes (p > 0.05). Dietary protein and the interaction of protein with lipid had significant effect (p < 0.05) on whole-body dry matter, lipid and energy contents, but not on protein and ash contents (p > 0.05). But, the dietary lipid had significant (p < 0.05) effect on whole-body dry matter, protein, lipid and energy contents except the ash contents (p > 0.05). For each level of dietary protein, the increase in dietary lipid resulted significant increase (p < 0.05) in whole-body lipid contents without affecting the protein and ash contents (p > 0.05). Based on better growth and dietary performances, the optimum dietary protein and lipid levels of blue gourami fingerling are 350 and 80 g/kg diet respectively.

Growth and metabolic responses of tambaqui (Colossoma macropomum) fed different levels of protein and lipid

Growth and metabolism were investigated in juvenile tambaqui (Colossoma macropomum) fed with isoenergetic diets in four treatments with protein (P) lipid (L) in g kg−1: P350L49; P301L81; P253L113 and P205L145, respectively. The experiments were carried out in the laboratory facilities. Fish growth, the intermediary metabolites (total sugar, lactate, pyruvate, ammonia, protein, fatty acids, triacylglycerols, amino acids and glycogen), and the enzyme activities of lactate dehydrogenase, malate dehydrogenase, glutamate dehydrogenase, aspartate aminotransferase and alanine aminotransferase were assayed. Fish from treatments P350L49 and P301L81 depicted the best growth. Increase in glycolytic, glycogenolytic and lipolytic activities in liver was observed following dietary lipid increase. In fish fed with high lipid levels, the energetic demand was supplied by enhancement of muscular glycogenesis and lipolysis. The plasma metabolic profile reflected the blood function on metabolites delivery to tissues underlining biochemical adaptations because of changes in the feeding. In conclusion, the increase in dietary lipid plus protein decrease resulted in (i) reduction in fish growth, (ii) augment of liver glycolysis and glycogenolysis (iii) increase in muscular glycogenesis and (iv) predominance of lipolytic metabolism.

Diet development and evaluation for juvenile abalone, Haliotis asinina Linne: Lipid and essential fatty acid levels

Experiments on diet development and evaluation for juvenile abalone, Haliotis asinina focusing on lipid and essential fatty acid (EFA) levels were conducted. Six isonitrogenous diets were formulated in Experiment 1 (E1) to contain 27% protein with lipid levels at 0, 2, 4, 6, 8, and 10%. Experiment 2 (E2) (EFA levels), used the optimum lipid level (3.59%) in E1 with EFA supplementation of 0.0, 0.2, 0.4, 0.8, and 1.6%. Abalone juveniles [mean initial weight and shell length of 0.60 ± 0.07 g and 14.70 ± 0.12 mm (E1)], [0.60 ± 0.16 g and 15.30 ± 0.73 mm (E2)] respectively, were fed these diets at 2–5% body weight in 3 replicates. Feeding trials in 90 days/experiment evaluated growth, survival, feed conversion ratio (FCR) and fatty acid composition in abalone tissues. Results showed significantly higher growth rates (ANOVA P < 0.05) with abalone fed diets with lipid levels of 2.2%, 3.6%, and 6.1% compared with those containing lipid levels of 7.6% and 9.8%. Abalone fed the lipid-free diet showed significantly the lowest growth rate among treatments. Break point analysis as a function of growth, showed optimum lipid requirement at 3.59%. Survival was high at 95–99% in both experiments. FCR values for D3 and D4 were significantly better compared to D2, D5 and D6 (E1) while no significant differences were found for D2–D6 for E2. Abalone body lipid increased with corresponding increase in dietary lipid. Addition of 18:2n−6, 18:3n−3, and n−3 HUFA showed significant improvement in weight gains up to 1.6% supplementation. Fatty acid composition of the lipid samples reflected those of the diets. Total lipid of abalone fed the lipid-free diet showed higher monoenes. Addition of EFA resulted in an increase in both n−3 and n−6 fatty acids. Lipid incorporation at 3.6% using a 1:1 ratio of CLO and SBO with EFA supplementation (1.6%) is best in juvenile abalone diet formulation.

Effects of dietary lipid levels on growth performance of marbled spinefoot rabbitfish Siganus rivulatus

The present study was carried out to evaluate the effect of dietary lipid levels on growth performance and body composition of juvenile marbled spinefoot ( Siganus rivulatus). Six iso-nitrogenous (301.0 g kg − 1 crude protein) and iso-energetic diets (16.0 MJ gross energy kg − 1 ) were formulated to contain 25, 45, 65, 85, 105, and 125 g lipid kg − 1 . Twenty juvenile fish (2.9 g ± 0.01; mean ± SE) were randomly assigned to triplicate treatments and offered the test diets three times daily to apparent satiation for 7 weeks. Survival was greater than 95% in all treatments. Fish offered the diet with the lowest lipid content (25 g kg − 1 ) exhibited lowest growth performance. No significant differences in growth performance were detected among all other treatments. However, analysis of final body weight by second order polynomial regression suggested that the dietary lipid requirement for optimal growth in juvenile marbled spinefoot is 98 g kg − 1 .There were no significant differences in condition indices (K), fillet yield and hepatosomatic index (HSI) values among treatments. Viscerosomatic index (VSI) (13.35% ± 0.42) of fish offered the diet with 125 g kg − 1 lipid was significantly greater than the VSI (10.00% ± 0.35) of fish offered the diet with 25 g kg − 1 lipid. A trend of increasing VSI with an increase in dietary lipid was obvious. Increasing dietary lipid levels beyond 85 g kg − 1 resulted in increase in whole body lipid content. No significant differences in moisture content (69.3–71.6%), protein content (13.1–14.6%), and ash content (2.8–3.2%) were observed among treatments. Based on our results, marbled spinefoot rabbitfish have low dietary lipid requirements and increasing dietary lipids increased the lipid proportion of body weight significantly.

Influence of dietary lipid/protein ratio on survival, growth, body indices and digestive lipase activity in Snakehead (Channa striatus, Bloch 1793) fry reared in re-circulating water system

Nine isoenergetic (18.5 kJ g−1) diets were formulated in a 3 × 3 factorial design to contain three protein levels (350, 400 and 450 g kg−1) for each of three lipid levels (65, 90 and 115 g kg−1), respectively, and fed twice daily for 8 weeks to fish of mean initial weight 3.34 ± 0.02 g reared in a re-circulatory water system. Temperature, pH and dissolved oxygen (DO) were maintained within the range 28–30 °C, 5.6–6.8 and 4.82–6.65 mg L−1 respectively throughout. Results show that fish survival was better in the groups fed 65 g kg−1 lipid while growth performance (% weight gain, WG; specific growth rate, SGR) and nutrient utilization (feed conversion ratio, FCR; protein efficiency ratio, PER; protein intake, PI) in the 65/450 and 90/450 g kg−1 treatments were similar and significantly (P < 0.05) higher than in fish fed the other lipid/protein ratio combinations. The body indices monitored (Hepatosomatic index, HSI and viscerosomatic index, VSI) were similar among the treatments whereas intestinal lipase activity was not significantly (P < 0.05) affected by increase in dietary lipid and protein levels. Carcass composition showed that dietary protein level affected body protein content positively in the 65 and 90 g kg−1 lipid treatments, but dietary lipid level did not affect body lipid content. A lipid/protein ratio of 65/450 g kg−1 is considered adequate for good growth performance and survival of Channa striatus fry.

Dietary lipid levels have a remarkable impact on the expression of growth-related genes in Senegalese sole (Solea senegalensis Kaup)

In Senegalese sole (Solea senegalensis Kaup), growth is negatively correlated to dietary lipid levels. To understand the molecular basis of this effect a molecular toolbox of 12 genes, including fgf6, fst, mstn1, myf5, mrf4, myod1, myod2, myog, myHC, mylc2, igf1r and insr, was developed. The expression profiles of these genes were investigated in white muscle and liver of fish fed with three dietary lipid levels (4%, 12% and 20%). The expression of igf-I and igf-II was also examined. MRFs and myosins were only expressed in the muscle and, except for myf5, the general trend was a decrease in expression with an increase in dietary lipids. Fgf6 was identified for the first time in liver and its expression augmented in hepatic tissues with increasing dietary lipid levels. A similar tendency was observed for mstn1 and igf-I. The opposite was observed for igf1r expression in muscle and liver. Myog, mrf4, mylc2 and igf1r were highly correlated with growth and nutrient utilisation indices. In addition to its practical implications, this work provides a valuable contribution towards our understanding of the genetic networks controlling growth in teleosts.