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.     

Effect of lipid levels on the reproductive performance of Snakehead murrel,Channa striatus

Present study aimed to determine the optimum dietary lipid level in snakehead murrel channa striatus broodstocks. Triplicate groups of fish were fed for 240 days with isonitrogenous experimental diets with increasing lipid levels (100, 140, and 180 g kg^?1), using fish oil and soybean oil as the lipid sources with the ratio of (1:1). Weight gain, GSI, fecundity, oocyte diameter and number of mature oocyte were found to be significantly higher in the group fed with diet containing 180 g kg^?1 lipid level. Muscle fatty acid profile showed a significant increase in LA (18:2n‐6), LNA (18:3n3), total PUFA, n‐6 and ArA (20:4n‐6) in fish fed with diet containing 180 g kg^?1 lipid. Increasing lipid level up to 180 g kg^?1 resulted in significant increase in PUFA (LA & LNA), lc‐PUFA (EPA, DHA, ArA), total PUFA, n‐3 and n‐6 series in ovary and liver of female C. striatus.     

Effects of oxidized fish oil intake on tissue lipid metabolism and fatty acid composition of channel catfish (Ictalurus punctatus)

Recent studies in terrestrial animals have shown that feeding the oxidized lipids led to a reduction in triacylglycerols (TAG) and total cholesterol (TC) in liver and plasma. However, limited information is available on the effect of oxidized lipids on lipid metabolism in fish. In this study, four diets containing 0 g kg^?1 (control: fresh fish oil), 30 g kg^?1 (low‐oxidized oil, LOO), 60 g kg^?1 (medium‐oxidized oil, MOO) and 90 g kg^?1 (high‐oxidized oil, HOO) graded oxidized oil levels with the same dietary lipid level were fed to channel catfish for 86 days. The tissue lipid metabolism and fatty acid composition of the fish were investigated after this period. The results showed that plasma and liver concentrations of TAG and TC decreased with increasing dietary oxidized oil level (P < 0.05). Decreasing liver lipoprotein lipase and hepatic lipase activities were observed with increasing dietary oxidized fish oil inclusion (P < 0.05). The liver C22:6n?3 concentrations significantly decreased with increasing dietary oxidized oil level (P < 0.05), while muscle lipid had a high proportion of polyunsaturated fatty acids. It suggests that the adverse effects of dietary oxidized oil may be induced by inhibiting lipid metabolism enzymes and, consequently, inhibition of cholesterol homoeostasis and fatty acid synthesis.     

The effects of Spirulina platensis meal on proximate composition,fatty acid profile and lipid peroxidation of rainbow trout (Oncorhynchus mykiss) muscle

This study evaluated the effects of diets containing 0, 25, 50, 75 and 100 g kg^?1 Spirulina platensis on proximate composition, fatty acid profile and lipid peroxidation of rainbow trout (Oncorhynchus mykiss). Supplementation of S. platensis did not change moisture and protein contents, but fish fed 50 and 100 g kg^?1 S. platensis had lower muscle lipid content than those fed control diet (P < 0.05). Fish fed 100 g kg^?1 of S. platensis contained lower percentages of saturated and monounsaturated fatty acid and a higher percentage of polyunsaturated fatty acid than those fed control diet (P < 0.05). The n‐3/n‐6 ratio of the fatty acid increased and muscle atherogenic and thrombogenic indices were significantly decreased as the dietary supplement of S. platensis increased. Furthermore, lipid peroxidation of the fillet significantly decreased with increasing dietary S. platensis at 4 °C and at ?20 °C (P < 0.05). The results of this study show that supplementation of S. platensis to the diet improves muscle quality of the rainbow trout.     

Effects of vitamin E supplementation on growth,lipid peroxidation and fatty acid composition of Dojo loach (Misgurnus anguillicaudatus Cantor) fingerlings

A high mortality of cultured loach during their early development has constrained loach aquaculture industry in China. The objective of this study was to evaluate the effects of dietary vitamin E (VE) supplementation on growth performance, lipid peroxidation and fatty acid composition of loach Misgurnus anguillicaudatus fingerlings. Six test diets supplemented with 0 (0E), 50 (50E), 100 (100E), 150 (150E), 200 (200E) and 500 mg kg^?1 (500E) of dl‐α‐tocopheryl acetate were fed loach fingerlings (mean initial weight 24.0 ± 0.2 mg) in triplicate for 40 days. Results showed that the fish fed diet 100E and 200E had significantly higher body weight gains and specific growth ratios and significantly lower feed conversion ratios compared with fish fed diet 0E. With the increase in dietary VE level, whole‐body VE content was significantly increased (except 500E) and thiobarbituric acid reactive substances value was significantly reduced. Increasing dietary VE level increased the percentages of 20:4n‐6 and 20:5n‐3 in neutral lipid fraction, but decreased the percentages of 20:4n‐6 and 20:5n‐3 in polar lipid fraction. In conclusion, VE requirement of loach fingerlings for optimum growth and functionally preventing lipid peroxidation was 136.1 mg kg^?1 of dry diet under the present experimental conditions.     

Conjugated linoleic acid affects growth performance,hepatic fatty acid profile and lipid metabolism in juvenile Synechogobius hasta

This study was conducted to determine the effect of dietary CLA (Conjugated linoleic acid) levels on growth performance, fatty acid profiles and lipid metabolism of liver in Synechogobius hasta. Fish were fed six diets with fish oil replaced by 0 (control), 5, 10, 15, 20 and 25 g kg^?1 CLA for 8 weeks. Weight gain, WG, and SGR (specific growth rate) tended to increase when dietary CLA levels increased from 0 to 10 g kg^?1 and then decline with further increasing dietary CLA levels to 25 g kg^?1. FCR (feed conversion ratio) showed contrary trend with WG and SGR. The reduced VSI (vicero somatic index) and increased HSI (hepatosomatic index) were observed in fish fed increasing dietary CLA levels. Whole‐body lipid content declined, but hepatic lipid content increased with increasing dietary CLA levels. Dietary CLA modified total percentages of the main groups of fatty acids in liver. Hepatic 6PGD, ME and ICDH activities increased with increasing dietary CLA levels. FAS and G6PD were very variable and not related to dietary treatments. CPT I activities showed no significant differences among the treatments. Based on second‐order polynomial regression analysis of WG and FCR against dietary CLA level, 8.7–10.1 g kg^?1 was indicated to be the optimal dietary CLA range for maximum growth and feed utilization for S. hasta.     

Effect of dietary n‐3 HUFA on growth performance and tissue fatty acid composition of gibel carp Carassius auratus gibelio

A 12‐week growth trial was conducted with gibel carp Carassius auratus gibelio (initial weight: 2.69 g) to evaluate the effects of dietary n‐3 highly unsaturated fatty acids (n‐3 HUFA) on growth performance and tissue fatty acid composition. Five diets of different n‐3 HUFA levels from 0 to 17 g kg^?1 diet were supplemented at 80 g kg^?1 dietary lipid by including fish oil (FO) at 0, 25, 50, 75 and 100% of supplemental lipid. The remainder was coconut oil. The results showed that fish fed FO₂₅ and FO₅₀ obtained highest specific growth rate and lowest with FO₀. Feed efficiency was highest at FO₁₀₀ and lowest at FO₀. Apparent digestibility coefficient of lipid increased with increasing dietary n‐3 HUFA. The fish fed FO₀ diet had the lowest thiobarbituric acid reactive substance in serum and muscle and highest moisture and lowest lipid content in viscera. Fatty acid compositions of muscle and liver were correlated with dietary fatty acids. Fish muscle concentration of 20:5n‐3 increased with increasing dietary n‐3 HUFA while the concentration of 22:6n‐3 was distinctly reduced in FO₀ group. It suggested that 4 g kg^?1 n‐3 HUFA in diet could permit gibel carp normal growth performance and provide considerable n‐3 HUFA in fish muscle. Excessive n‐3 HUFA showed impact on growth performance of gibel carp.     

Effects of dietary protein and lipid levels with different protein‐to‐energy ratios on growth performance,feed utilization and body composition of juvenile red‐spotted grouper,Epinephelus akaara

An 8‐week feeding trial was conducted to assess dietary protein and lipid levels on growth performance, feed utilization and body composition of juvenile red‐spotted grouper (7.85 ± 0.03 g fish^?1). Nine semi‐purified diets were formulated containing varying protein levels (440–520 g kg^?1, dry matter) and lipid levels (60–120 g kg^?1, dry matter). The weight gain of juvenile Epinephelus akaara was affected by dietary protein (p = .005) and its interaction with dietary lipid (p = .020). Viscerosomatic index, intraperitoneal fat ratio and whole‐body lipid level increased with increasing dietary lipid level (p < .001). Nitrogen retention was not affected by dietary protein and lipid, while lipid retention decreased with increasing dietary lipid level (p < .001). The plasma blood urea nitrogen increased with increasing dietary protein level (p = .003). This study showed that diet with 520 g kg^?1 protein and 60 g kg^?1 lipid with 30.58 mg kJ^?1 P:E provided a maximal growth for this species. Moreover, an increase in dietary lipid levels (from 60 to 90 g kg^?1) could reduce the protein requirement (from 520 to 480 g kg^?1) without affecting the growth performance, while higher fat deposition was observed in fish fed high‐lipid diets.     

Effects of dietary protein and lipid levels on growth,feed utilization and body composition in Pseudobagrus ussuriensis fingerlings

An 8‐week feeding trial was conducted to investigate the optimum dietary protein and lipid levels for growth, feed utilization and body composition of Pseudobagrus ussuriensis fingerlings (initial weight: 3.40 ± 0.01 g). Twelve diets containing four protein levels (350, 400, 450 and 500 g kg^?1 crude protein) and three lipid levels (50, 100 and 150 g kg^?1 crude lipid) were formulated. Fish were randomly allotted to 36 aquaria (1.0 × 0.5 × 0.8 m) with 25 fish to each glass aquarium. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. The results showed that weight gain and specific growth rate (SGR) decreased with increasing dietary lipid level from 50 to 150 g kg^?1 at the same dietary protein level. Fish fed the diets containing 150 g kg^?1 lipid exhibited higher feed conversion ratio (P < 0.05), lower protein efficiency ratio (PER) and nitrogen retention efficiency (NRE) relative to fish fed the diet containing 50 and 100 g kg^?1 lipid. Weight gain and SGR significantly increased with increasing dietary protein from 350 to 450 g kg^?1 at the same dietary lipid level, and even a little decline in growth with the further increase in dietary protein to 500 g kg^?1. Daily feed intake, NRE and PER were significantly affected by both dietary protein and lipid levels (P < 0.05) and tended to decrease with increasing dietary protein and lipid levels. Whole‐body protein content increased as protein levels increased and lipid levels decreased. Whole‐body lipid and muscle lipid content increased with increasing dietary lipid level, and decreased with increasing dietary protein at each lipid level. There was no significant difference in condition factor and viscerosomatic index among fish fed the diets. Hepatosomatic index was affected by dietary lipid level (P < 0.05), and increased with increasing dietary lipid level at the same protein level. These results suggest that the diet containing 450 g kg^?1 protein and 50 g kg^?1 lipid with a P/E ratio of 29.1 mg protein kJ^?1 is optimal for growth and feed utilization of P. ussuriensis fingerlings under the experimental conditions used in the study.     

Effect of dietary arachidonic acid levels on growth performance,hepatic fatty acid profile,intermediary metabolism and antioxidant responses for juvenile Synechogobius hasta

An 8‐week feeding experiment was conducted to determine the effect of dietary arachidonic acid (ARA) levels on growth performance, hepatic intermediary metabolism and antioxidant responses for juvenile Synechogobius hasta. Five isonitrogenous and isolipidic diets were formulated with arachidonic oil (containing 400 g ARA kg^?1) at inclusion levels of 0, 2, 4, 8 and 16 g kg^?1 to replace corn oil. Dietary ARA levels were 0.6, 8.6, 16.7, 32.7 and 64.8 g kg^?1 total fatty acids (FAs), respectively. Fish fed the 8.6–32.7 g ARA kg^?1 total FAs showed the highest weight gain, specific growth rate (SGR) and feed intake. By contrast, feed conversion ratio was the lowest for fish fed the 8.6–32.7 g ARA kg^?1 total FAs. Increasing ARA and total n‐6 fatty acid contents and declining linoleic acid content in liver were observed in fish fed the diet containing increasing dietary ARA levels. As a consequence, ∑n‐6/∑n‐3 ratios increased with increasing dietary ARA levels. Dietary ARA levels significantly influenced several enzymatic activities involved in hepatic intermediary metabolism, such as succinate dehydrogenase, lactate dehydrogenase, lipoprotein lipase and hepatic lipase. Superoxide dismutase activity increased with increasing dietary ARA levels. Glutathione peroxidase and catalase activities and malondialdehyde levels in liver tended to increase with increasing dietary ARA levels from 0.6 to 32.7 g ARA kg^?1 total FAs then declined when dietary ARA levels further increased to 64.8 g ARA kg^?1 total FAs. Broken‐line regression analysis of SGR against dietary ARA level indicated that optimal dietary ARA requirement for juvenile S. hasta was 10.74 g kg^?1 total FAs.     

Dietary methionine requirement of juvenile blunt snout bream (Megalobrama amblycephala) at a constant dietary cystine level

A 9‐week feeding trial was conducted to investigate the dietary methionine requirement of juvenile Megalobrama amblycephala at a constant dietary cystine level. Six semipurified diets were formulated to contain graded dietary methionine levels from 3.9 to 15.4 g kg^?1 in about 2.5 g kg^?1 increments in the presence of 2.2 g kg^?1 cystine. Results showed that specific growth rate (SGR) and protein efficiency ratio (PER) significantly increased with increasing dietary methionine levels from 3.9 to 12.4 g kg^?1 and thereafter kept stable. Maximum protein productive value (PPV), nitrogen retention efficiency (NRE) and liver weight were observed in 8.5 g methionine kg^?1 diet. Protein contents in whole fish body were positively correlated with dietary methionine level, while lipid contents were negatively correlated with it. Morphological index and hepatic glutamate‐pyruvate transaminase (GPT) activities were independent of dietary methionine levels. However, dietary methionine supplementation significantly improved haematological parameters, plasma methionine and total essential amino acid contents and hepatic glutamate‐oxaloacetate transaminase (GOT) activities. Analysis of dose response using broken‐line regression on the basis of SGR and PPV versus dietary methionine level estimated the optimum dietary methionine requirements of juvenile M. amblycephala to be between 8.5 and 8.4 g kg^?1 of diet (25.0 and 24.7 g kg^?1 of protein) in the presence of 2.2 g kg^?1 cystine, respectively. Hence, the corresponding total sulphur amino acids requirements of this species were calculated to be 10.7 and 10.6 g kg^?1 of diet (31.5 and 31.2 g kg^?1 of dietary protein).     

Effects of extruded and pelleted diets with differing lipid levels on growth,nutrient retention and serum biochemical indices of tilapia (Oreochromis aureus × Tilapia nilotica)

This study was conducted to evaluate the effects of extruded diets and pelleted diets with varying dietary lipid levels on growth performance and nutrient utilization of tilapia. Six diets, containing three levels of lipid at 40, 60 or 80 g kg^?1 (with the supplemental lipid of 0, 20 or 40 g kg^?1, respectively), were prepared by extruding or pelleting and then fed to tilapia juveniles (8.0 ± 0.1 g) in cages (in indoor pools) for 8 weeks. The results indicated that the fish that were fed the diet with 60 g kg^?1 of lipid had a higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), lipid retention (LRE), energy retention (ERE), apparent protein digestibility, apparent dry matter digestibility and a lower feed conversion ratio (FCR) than those fed the diet with 40 g kg^?1 lipid in both the extruded diet and pelleted diet (P < 0.05). As the dietary lipid level increased from 60 to 80 g kg^?1, these parameters were not further improved, even digestibilities of the crude protein and dry matter decreased (P < 0.05). With the dietary lipid level increased, whole‐body lipid content significantly increased (P < 0.05), serum aspartate aminotransferase, alkaline phosphatase, total cholesterol and low‐density lipoprotein cholesterol (LDL‐C) tended to increase (P > 0.05), whereas whole‐body protein content, serum triglyceride (TG), high‐density lipoprotein cholesterol (HDL‐C) and HDL‐C/LDL‐C tended to decrease (P > 0.05). Fish fed with the extruded diets had a higher WG, SGR, hepatosomatic index (HSI), PER, protein retention (PRE), LRE, ERE, TG, apparent digestibility of protein and dry matter, as well as a lower FCR, than those fed with the pelleted diets at the same dietary lipid level (P < 0.05). These results suggested that tilapia fed with the extruded diets had a better growth and higher nutrient utilization than fish fed with the pelleted diets, when dietary lipid level ranged from 40 to 80 g kg^?1 and at dietary crude protein level was 280 g kg^?1. The optimum dietary lipid level was 60 g kg^?1 in both the pelleted and extruded diets, and extrusion did not affect dietary lipid requirement of the tilapia.     

The effects of dietary lipid levels on performance and heat‐shock protein response of juvenile white seabass,Atractoscion nobilis

A feeding trial was conducted to study the effect of dietary lipid on growth performance and heat‐shock protein (HSP70 and HSP60) response of white seabass (WSB), Atractoscion nobilis. Five diets were formulated to contain 440 g kg^?1 protein from 300 g kg^?1 fish meal, 240 g kg^?1 soybean meal and 100 g kg^?1 soy protein concentrate with different levels of lipid: 100, 120, 140, 160 or 180 g kg^?1. At the end of the trial, heat shock response based on HSP70 and HSP60 was measured in liver and white muscle from fish at ambient temperature and temperature shock conditions. Final weight and percent gain were significantly higher for fish fed the 100 g kg^?1 lipid diet than for fish fed the rest of the diets (P ≤ 0.05). Feed conversion ratio was lowest for fish fed the 100 g kg^?1 lipid diet. The HSP70 and HSP60 responses were positively correlated to dietary lipid levels following temperature shock. At ambient temperature, HSP60 and HSP70 responses in muscle and HSP60 response in liver increased with dietary lipid level. Temperature shock significantly increased the HSP response of fish in all treatments. Results of this study demonstrated that a moderate (110–120 g kg^?1) level of dietary lipids would be recommended for production diets but a higher dietary lipid level may be required for optimal stress tolerance.     

Combined effects of dietary mannan‐ and fructo‐oligosaccharide on growth indices,body composition,intestinal bacterial flora and digestive enzymes activity of regal peacock (Aulonocara stuartgranti)

A 56‐d feeding trial was conducted to investigate the effect of dietary mannan‐oligosaccharides (MOS) and fructo‐oligosaccharide (FOS) on growth indices, body composition, intestinal bacterial community and digestive enzymes activity of regal peacock. A total of 240 fish were randomly distributed to 15 experimental units (40‐L aquariums) of 16 fish each. These replicates were randomly assigned to one of five treatments in a 2 × 2 + 1 factorial arrangement. The treatments were control diet (no MOS and FOS), diet A (2 gkg^?1 MOS + 1.5 g kg^?1 FOS), diet B (2 g kg^?1 MOS + 3 g kg^?1 FOS), diet C (4 g kg^?1 MOS + 1.5 g kg^?1 FOS) or diet D (4 g kg^?1 MOS + 3 g kg^?1 FOS). The results showed that feeding diet C increased specific growth rate and protein efficiency ratio and decreased feed conversion ratio compared with control diet. Higher intestinal trypsin activity and increased Lactobacillus counts were observed in fish fed diets B and C. All diets significantly elevated body protein deposition and intestinal amylase activity compared to the control diet. In conclusion, the diet supplemented with 4 g kg^?1 MOS + 1.5 g kg^?1 FOS was advantageous over other MOS + FOS‐supplemented diets, with respect to growth performance and health benefits of regal peacock.     

Growth,feed utilization and body composition of juvenile Manchurian trout,Brachymystax lenok (Pallas) fed different dietary protein and lipid levels

A 10‐week feeding trial with four dietary protein levels (400, 450, 500 and 550 g kg^?1 crude protein) and two dietary lipid levels (80 and 160 g kg^?1 crude lipid) was conducted to assess optimum dietary protein and lipid levels for the growth, feed utilization and body composition of juvenile Manchurian trout (initial weight 11.80 ± 0.15 g). Fish were fed twice daily (08:30 and 16:30 h) to apparent satiation. The results showed that fish fed the diet with 500 g kg^?1 protein and 80 g kg^?1 lipid had the highest growth and feed efficiency. However, fish fed the diet with 450 g kg^?1 protein and 160 g kg^?1 lipid showed comparable growth to that of the fish fed diet 5 (500/80) and had higher protein efficiency ratio (PER), nitrogen retention (NR) and energy retention (ER) than other groups (P < 0.05). Growth, PER, NR and ER of fish fed the 160 g kg^?1 lipid diet was significantly higher (P < 0.05) than that of fish fed the 80 g kg^?1 lipid diet at 400 and 450 g kg^?1 protein diet, whereas these values showed an opposite trend at 500 and 550 g kg^?1 protein diet, and the lowest PER, NR and ER was found by fish fed the 400 g kg^?1 protein diet with 80 g kg^?1 lipid. Fish fed diets with 400 g kg^?1 protein had lower feed intake (FI) than that of other groups. Feed intake of fish fed 80 g kg^?1 lipid level was significantly lower than that of fish fed 160 g kg^?1 lipid diet at 400 g kg^?1 protein (P < 0.05), while no significant differences were observed at 450, 500 and 550 g kg^?1 protein‐based diets. Contrary to moisture content, lipid content of whole body and muscle increased significantly (P < 0.05) with increasing lipid levels. The results of this study indicated that the diet containing 450 g kg^?1 protein and 160 g kg^?1 lipid, with a P/E ratio of 23.68 g protein MJ^?1 would be suitable for better growth and feed utilization of juvenile Manchurian trout under the experimental conditions and design level used in this study.     

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.     

Effects of dietary protein and lipid levels on growth, feed conversion and body composition in rohu, Labeo rohita (Hamilton), fingerlings

Twelve experimental diets (D‐1 to D‐12) in a 4 × 3 factorial design (four protein levels: 250, 350, 400 and 450 g kg^?1 and three lipid levels: 50, 100 and 150 g kg^?1) were formulated. Carbohydrate level was constant at 250 g kg^?1. Rohu fingerlings (average wt. 4.3 ± 0.02 g) were fed the experimental diets for 60 days in three replicates at 2% BW  day^?1. Weight gain (%), specific growth rate (% day^?1) and feed gain ratio (FGR) indicated that diets containing 450 g kg^?1 protein and 100 or 150 g kg^?1 lipid (diets D‐11 and D‐12) resulted in best performance, although results were not significantly different from those of diet D‐9 (400 g kg^?1 protein and 150 g kg^?1 lipid). Protein efficiency ratio was highest with diets D‐6 (350 g kg^?1 protein and 150 g kg^?1 lipid) and D‐9 (400 g kg^?1 protein and 150 g kg^?1 lipid) (P > 0.05) and declined with higher and lower protein diets at all levels of lipid tested. Elevated lipid level (50, 100 or 150 g kg^?1) did not produce better FGR in diets containing 400 and 450 g kg^?1 dietary protein (P > 0.05). The combined effects of protein and lipid were evident up to 400 g kg^?1 protein. Growth and FGR showed consistent improvement with increased lipid levels from 50 to 150 g kg^?1 at each protein level tested except with diets containing 450 g kg^?1 protein. Apparent nutrient digestibility (for protein, lipid and energy) did not show significant variation among different dietary groups (P > 0.05). Whole body protein and lipid contents increased significantly (P > 0.05) with dietary protein level. The results of this study indicate that rohu fingerlings are adapted to utilize high protein in diets with varying efficiency. The fish could utilize lipid to spare protein but there is no significant advantage from this beyond the dietary protein level of 350–400 g kg^?1 in terms of growth and body composition.     

Effects of varying protein and lipid levels and protein‐to‐energy ratios on growth,feed utilization and body composition in juvenile Nibea diacanthus

A two‐factor experiment was designed to determine the suitable dietary protein and lipid levels for juvenile Nibea diacanthus. Nine extruded pellet diets were formulated to contain three levels of protein (420, 470 and 520 g kg^?1) and three levels of lipid (70, 110 and 150 g kg^?1). Each diet was randomly fed to triplicate groups of 25 juvenile N. diacanthus (initial weight 12.12 ± 0.23 g) for 8 weeks in net cages. The results showed that weight gain rate (WGR), specific growth rate, final body weight and energy retention were significantly influenced by the dietary protein and lipid levels‐. The highest WGR (982.5g kg^?1.) of N. diacanthus was found in the group with dietary protein and lipid of 520 and 150 g kg^?1. Feed intake and feed efficiency were significantly impacted by the dietary protein levels. An interactive effect between dietary protein and lipid on the protein retention and protein efficiency ratio was observed. There were no significant differences in condition factor and survival among all treatments. Hepatosomatic index and viscerasomatic index of N. diacanthus were positively related with dietary lipid levels, but negatively with dietary protein levels. Crude protein, crude lipid, ash, moisture and energy contents of the whole body, muscle and liver were influenced by dietary protein and lipid levels. Moreover, total essential amino acid pattern of the muscle was correlated to those of dietary protein. Total protein concentration in the serum was affected by dietary protein and lipid levels. Meanwhile, both serum cholesterol and triglyceride concentrations increased with increasing dietary lipid levels. These results demonstrate that the diet containing 470 g kg^?1 protein and 110 g kg^?1 lipid is optimal for juvenile N. diacanthus and analysis of WGR by quadratic regression indicated that the estimated optimal protein‐to‐energy ratio for juvenile N. diacanthus was 24.53 mg protein kJ^?1.     

Effects of dietary lipid level on growth performance,body composition and digestive enzymes activity of juvenile sea cucumber,Apostichopus japonicus

A feeding trial aimed to determine the effects of dietary lipid level on growth performance, body composition and digestive enzymes activity of juvenile sea cucumber, Apostichopus japonicus. Diets with six crude lipid levels (1.9, 13.8, 29.1, 43.6, 59.6 and 71.6 g kg^?1) were fed to sea cucumbers (initial weights 0.65 ± 0.01 g) at a density of 30 juveniles, once a day. After 60 days, body weight gain (BWG), specific growth rate (SGR), feed intake (FI) and protein efficiency ratio (PER) decreased with increasing dietary lipid levels. The sea cucumbers fed 1.9 g kg^?1 crude lipid showed significantly higher (P < 0.05) BWG than those of the sea cucumbers fed 59.6 and 71.6 g kg^?1 crude lipid. Intestinal protease and lipase activities generally increased with increasing dietary lipid levels. Eicosapentaenoic acid (EPA) content of body walls generally increased with increasing dietary lipid levels. Docosahexaenoic acid (DHA) content of body walls reached the maximum value at a dietary lipid level of 13.8 g kg^?1. N‐3 highly unsaturated fatty acid content followed the same pattern of DHA. According to the growth performance and body composition of sea cucumbers, it can be indicated that the optimum dietary lipid level for juvenile sea cucumbers is between 1.9 and 13.8 g kg^?1.     

Effect of dietary lipid and protein levels with different protein to energy ratios on growth performance,feed utilization and body composition of Rutilus frisii kutum (Kamenskii, 1901) fingerlings

A 3 × 5 factorial design including three lipid levels (100, 130 and 180 g kg^?1 diet, based on dry matter) and five dietary protein levels (370, 420, 470, 520 and 570 g kg^?1 diet, based on dry matter) was conducted to investigate the optimum dietary lipid and protein requirements for Rutilus frisii kutum fingerlings. Triplicate groups of 80 kutum (500 ± 60 mg initial weight) were stocked in 250‐l tanks and fed to apparent satiation thrice daily for 8 weeks. The results showed that the growth performance and feed utilization were significantly (P < 0.05) affected by dietary protein and lipid levels. Weight gain, specific growth rate and feed conversion ratio of kutum improved significantly with increasing protein level from 370 to 470 g protein kg^?1 diet, but there was a significant decrease in growth parameters with increasing protein level from 470 to 570 g protein kg^?1 diet. Also, the higher values of weight gain, specific growth rate and better feed conversion ratio were observed for fish fed diets containing 130 g kg^?1 lipid diet. The results of this study showed that diet containing 420 g kg^?1 protein and 130 g kg^?1 lipid with a P:E ratio of 19.22 mg protein kJ^?1 of gross energy is optimal for kutum fingerlings.