Effects of dietary lipid sources on growth performance,lipid metabolism and antioxidant status of juvenile Russian sturgeon Acipenser gueldenstaedtii

Six isonitrogenous and isoenergetic diets were used to test the influence of lipid source on growth performance, antioxidant status and lipid metabolism of juvenile Russian sturgeon, Acipenser gueldenstaedtii. Each diet was supplemented with 90 g kg^?1 of lipid from each of six sources including fish oil (FO), beef tallow (BT), sunflower oil (SO), linseed oil (LO) and equal combinations of FO + SO + BT (FSB) or LO + SO + BT (LSB). After 56 days, fish fed LSB demonstrated highest weight gain, specific growth rate and lowest hepatosomatic index among all groups. The n‐6 polyunsaturated fatty acids (PUFAs) in the whole fish were highest in the SO group, and n‐3 PUFAs were highest in fish fed LO. The fish fed FO contained highest n‐3 highly unsaturated fatty acids. Triglyceride in the serum of fish fed LSB was lowest, but was not significantly different from that in the SO group. Triglyceride in the serum of fish fed FO and BT was highest among all groups. Lipase, malate dehydrogenase and lipoprotein lipase activities were highest in fish fed LSB. Serum malondialdehyde in fish fed LSB was significantly lower than in fish fed FO or SO, but no significant differences were found among fish fed LSB, BT, LO or FSB. Fish fed LSB showed higher catalase activity and total antioxidant capacity than fish fed FO or FSB. This study indicates that linseed, sunflower oil and BT mixed oil are a suitable lipid source and can benefit growth performance and antioxidation in juvenile sturgeon.     

Effects of dietary lipid source on fatty acid composition,expression of genes involved in lipid metabolism and antioxidant status of grass carp (Ctenopharyngodon idellus)

This study determined the effect of different lipid sources on growth, feed use, lipid metabolism and antioxidant status of grass carp (Ctenopharyngodon idellus). Juvenile fish (56.9 ± 4.7 g) were divided into four triplicate groups and fed diets containing 30 g/Kg of fish oil (FO), olive oil (OO), peanut oil (PO) and linseed oil (LO), respectively, for 60 days. Weight gain and feed conversion ratio were not significantly different between the dietary groups, but we observed changes in the fatty acid composition of muscle and intraperitoneal fat reflecting the fatty acid profile of the dietary lipid source. In the hepatopancreas, the highest mRNA level of fatty acid translocase CD36 (FAT/CD36) and carnitine palmitoyl transferase (CPT‐1A) was both observed in the FO group. In muscle, the expression of FAT/CD36 and CPT‐1A in the LO group was significantly higher than that in other groups, except for CPT‐1A in the PO group. In addition, the lowest and highest content of malondialdehyde in serum was observed in OO and FO groups, respectively. In summary, dietary lipid source altered the fatty acid composition, potential uptake (FAT/CD36) and oxidation (CPT‐1A) of fatty acids, and antioxidant status of grass carp, which should be considered when selecting a lipid source.     

Effects of dietary fish oil replacements with three vegetable oils on growth,fatty acid composition,antioxidant capacity,serum parameters and expression of lipid metabolism related genes in juvenile Onychostoma macrolepis

Five isonitrogenous and isoenergetic diets with soybean oil (SO), linseed oil (LO), algae oil from Schizochytrium sp. (AO), mixed oil (MO, SO:LO:AO = 1:1:1) and fish oil (FO; control group) were selected to feed juvenile Onychostoma macrolepis (initial weight 1.86 ± 0.07 g) for eight weeks. The results showed that in the LO and FO groups fish grew best. There was no significant difference in specific growth rate (SGR) and feed efficiency (FE) between the MO and FO groups (p > .05). The highest contents of 18:2n‐6, 18:3n‐3 and 22:6n‐3 in liver and muscle were found with the SO, LO and AO groups, respectively (p < .05). There appeared the highest malondialdehyde (MDA) content and the lowest superoxide dismutase (SOD) activity in the fish liver of the AO group. There appeared the highest concentrations of serum glucose (GLU), cholesterol (CHOL) and triglycerides (TG) in the SO group. The expressions of lipid anabolism genes were significantly up‐regulated by dietary SO and LO (p < .05). The expressions of lipid catabolism genes were significantly higher with the AO, MO and FO groups (p < .05). This study recommended that LO or MO as a better vegetable oil source for juvenile O. macrolepis.     

饲料脂肪水平对俄罗斯鲟幼鱼生长、血液生化指标及抗氧化性能的影响

以鱼油、豆油、亚麻籽油等比例混合,配成脂肪含量分别为5.45%(L1)、7.00%(L2)、10.44%(L3)、14.37%(L4)、16.34%(L5)、18.91%(L6)及20.15%(L7)的等氮饲料,饲喂俄罗斯鲟(Acipenser gueldenstaedtii)幼鱼[(6.20±0.02)g]8周。实验结果表明,L3组的终末体质量、增重率最大,但与L2组间无显著差异(P0.05),L3组的蛋白质效率显著高于其它组(P0.05),且饲料系数最低。L6和L7组终末体质量、增重率和蛋白质效率显著低于L2和L3组(P0.05)。将幼鱼的增重率与饲料脂肪水平进行回归分析,得出俄罗斯鲟幼鱼在饲料脂肪水平为10.69%时生长最佳。随着饲料脂肪水平的升高,各组鱼的肝体比和体粗脂肪有上升趋势,其中肝体比在饲料脂肪含量大于14.37%时显著增大(P0.05)。血清中的甘油三酯、胆固醇含量也随脂肪水平升高而显著提高(P0.05),提示脂肪过高会影响俄罗斯鲟幼鱼的生长,降低蛋白质效率,导致脂肪在体内的过量积蓄。L7组鱼血清中高密度脂蛋白胆固醇含量最高,而L1组鱼的低密度脂蛋白胆固醇含量最高。肝脏脂蛋白酯酶活性随饲料脂肪水平的提高而升高,脂肪酸合成酶活性则随脂肪水平升高而降低,提示饲料脂肪水平的提高会促进鱼体脂肪的分解代谢。肝脏丙二醛含量和超氧化物歧化酶活性均随着饲料脂肪水平的提高显著升高(P0.05),表明脂肪含量过高会导致脂质过氧化,引发机体抗氧化酶活性的升高。综合俄罗斯鲟幼鱼的生长、血液指标及抗氧化性能,建议生产中将幼鱼的饲料脂肪水平控制在7.00%~10.69%。     

Effects of dietary protein and lipid levels on growth performance,fatty acid composition and antioxidant‐related gene expressions in juvenile loach Misgurnus anguillicaudatus

Dojo loach (Misgurnus anguillicaudatus) is one of the most important cultured freshwater fish in several East Asian countries. However, a little information is available in its nutritional requirements. Thus, this study was conducted to evaluate the effects of feeding varying levels of dietary protein and lipid on growth, fatty acid composition and antioxidant‐related gene expressions in juvenile loach. Six practical diets at three levels of protein (30%, 40% and 50%) and two levels of lipid (6% and 12%) were fed to loach juveniles (initial weight 0.40 g) in triplicated groups (20 fish per replicated) for a period of 8 weeks. Results showed that regardless of lipid level, body weight gain of fish was significantly increased with incremental dietary protein level. Meanwhile, feed conversion ratio was significantly decreased by dietary protein levels, and the lowest value was observed in fish fed dietary protein levels of 50%, regardless of dietary lipid level. Moreover, the percentage of 22:6n‐3 in viscera was significantly increased by different protein levels. The expression level of catalase was significantly increased with incremental dietary protein level with both lipid levels. Meanwhile, the expression level of hepatic nuclear factor erythroid 2‐related factor 2 (Nrf2) was downregulated with incremental dietary protein level with 6% of lipid level, but the expression was upregulated with incremental dietary protein level with 12% of lipid level. In conclusion, these data suggested that 6% lipid and 50% protein in diet was optimal for loach during early development stage.     

Effect of dietary iron (Fe) levels on growth performance,hepatic lipid metabolism and antioxidant responses in juvenile yellow catfish Pelteobagrus fulvidraco

This study was conducted to determine effects of dietary Fe levels on growth performance, hepatic lipid metabolism and antioxidant response for juvenile yellow catfish Pelteobagrus fulvidraco. Yellow catfish were fed six isonitrogenous and isolipidic diets containing Fe levels of 16.20, 34.80, 54.50, 76.44, 100.42 and 118.25 mg/kg for 8 weeks. Weight gain (WG) and specific growth rate (SGR) increased with dietary Fe levels from 16.20 to 54.50 mg/kg diet and then plateaued over the level. Feed conversion rate (FCR) was highest and protein efficiency rate (PER) was lowest for fish fed the lowest Fe levels of diet. Fe contents in whole body and liver increased with increasing dietary Fe levels. Hepatic lipid content was lowest, but mRNA levels of carnitine palmitoyltransferase (CPT‐1) and peroxisome proliferator‐activated receptor α (PPARα) were highest for fish fed 54.50 mg Fe/kg diet. Fish fed adequate dietary Fe levels reduced hepatic malondialdehyde (MDA) level and increased activities of antioxidant enzymes Superoxide dismutase (SOD), Catalase (CAT) and GS. Based on the broken‐line regression analysis of WG against dietary Fe levels, optimal dietary Fe requirement for yellow catfish was 55.73 mg Fe/kg diets. Fe‐induced changes in MDA levels and antioxidant enzymatic activities paralleled with the change in hepatic lipid content, suggesting the potential relationship between oxidative stress and hepatic lipid accumulation in yellow catfish.     

Effect of oil source on growth performance,antioxidant capacity,fatty acid composition and fillet quality of juvenile grass carp (Ctenopharyngodon idella)

This study was conducted to evaluate the dietary use of vegetable oil sources in grass carp (Ctenopharyngodon idella). Fish were fed diets having the same lipid level from fish oil (FO), palm oil (PO), rapeseed oil (RO), soybean oil (SO) or linseed oil (LO). The results showed that dietary vegetable oils significantly decreased the feed utilization and a significantly lower growth was observed in SO group, while palm oil showed no effect on the growth performance. Dietary vegetable oils suppressed intestinal digestion by inhibiting the activities of digestive enzymes. Vegetable oils significantly elevated the activities of lipase, hepatic lipase and total lipase in liver, and a phenomenon of intense lipid accumulation emerged in liver of PO and SO groups. Furthermore, linseed oil significantly decreased plasma antioxidant capacity, whereas no significant difference was found between RO and FO groups. Dietary vegetable oils caused a significantly lower EPA and DHA in muscle, and further influenced fillet quality through an increase in cohesiveness, gumminess, chewiness and/or springiness, together with a decrease in hardness. Overall, our results indicated that rapeseed oil may be a suitable alternative oil source for grass carp from a point of growth, feed conversion ratio, antioxidative capacity and hepatic histology.     

Effects of dietary tea polyphenols on growth,immunity and lipid metabolism of juvenile black carp Mylopharyngodon piceus

An 8‐week feeding experiment was aimed to investigate the effect of dietary tea polyphenols (TP) on growth, immunity and lipid metabolism in juvenile black carp Mylopharyngodon piceus (initial weight 5.90 ± 0.03 g). Tea polyphenols were added at different levels (0, 25, 50, 100 and 500 mg/kg; TP₀, TP₂₅, TP₅₀, TP₁₀₀ and TP₅₀₀). The results are as follows: the highest specific growth rate (SGR) and condition factor (CF) and activity of trypsin (TRS) of intestine in TP₅₀, but SGR and activities of lipase (LPS)and TRS of intestine and content of whole body crude protein in TP₅₀₀ were remarkably lower than TP₀. Compared with TP₀, content of serum superoxide dismutase (SOD) and glutamic oxalacetic transaminase (GOT) remarkably increased (p < .05), but contents of glutathione (GSH), glutathione peroxidase (GSH‐Pox), malondialdehyde (MDA), triglyceride (TG) and low‐density lipoprotein cholesterol (LDL‐C) were significantly decreased (p < .05), content of cortisol was remarkably lower in TP₅₀ and TP₁₀₀ (p < .05), expression of growth hormone (GH) and melanocortin 4 receptor (MC4R) in liver and GH in muscle were remarkably up‐regulated in TP₅₀, but expression of apolipoprotein A‐1 (ApoA1), GH and MC4R of intestine, ApoA1 of liver and MC4R of muscle in TP₅₀₀ were remarkably down‐regulated, contents of complement 3 (C3), complement 4 (C4), high‐density lipoprotein cholesterol (HDL‐C) and LDL‐C were significantly reduced in TP₅₀₀ (p < .05). In conclusion, TP could improve growth performance and oxidative capacity on juvenile black carp, and its optimal dosage was 50 mg/kg.     

Effects of conjugated linoleic acid on growth,body composition,antioxidant status,lipid metabolism and immunity parameters of juvenile Chu's croaker,Nibea coibor

A‐56 days feeding trial was conducted to evaluate the growth performance, feed utilization, biochemical composition, antioxidant status, lipid metabolism and immunity parameters of Chu's croaker Nibea coibor fed diets supplemented with different levels of conjugated linoleic acid (CLA): 0% (control), 0.5%, 1%, 1.5% and 2%. Each diet was randomly assigned to triplicate groups of 25 fish (initial body weight: 12.8 ± 0.1 g) in 15 floating cage. Weight gain (WG) and specific growth rate (SGR) were not significantly affected. 2% of dietary CLA led to significant lower lipid content in both whole body and liver (p < .05). Muscle lipid content was significantly lower in fish fed 1.5% and 2% CLA (p < .05). Saturated fatty acid (SFA) increased while monounsaturated fatty acid (MUFA) decreased with increasing dietary CLA in tissues (p < .05). Increasing CLA significantly promoted hepatic lipase (HL), lipoprotein lipase (LPL), serum lysozyme (LSZ) and immunoglobulin M (IgM) while decreased serum triglyceride (TG) in both liver and serum (p < .05). Liver Superoxide dismutase (SOD), catalase (CAT) and total antioxidant capacity (t‐AOC) increased while malondialdehyde (MDA) decreased (p < .05). Our study shown that Chu's croaker can successfully incorporate CLA in tissues up to 2% dietary lipid without growth inhibition, and that CLA increased fish quality due to the increased parameters of lipid metabolism, specific immunity, hepatic antioxidant and CLA accumulation, and the reduction of tissue fat deposition.     

Effects of different dietary lipid sources on tissue fatty acid composition,serum biochemical parameters and fatty acid synthase of juvenile mud crab Scylla paramamosain (Estampador 1949)

A 6‐week study was conducted to determine the effects of different lipid sources in pelleted diets on juvenile mud crab Scylla paramamosain. Five isonitrogenous and isolipidic diets containing 8% level of fish oil (FO), lard (LD), safflower oil (SO), perilla seed oil (PO) or mixture oil (MO; V_FO:V_SO:V_PO = 1:1:1), and a live food of marine bivalve Potamocorbula rubromuscula as the control diet (CF), were fed to groups of 25 juvenile crabs (average initial weight 7.4 g, carapace width 3.5 cm) in triplicate. The results showed that crabs fed MO had the highest survival (P < 0.05). The moisture content was significantly higher in crabs fed LD, SO and PO (P < 0.05). Crabs fed SO exhibited the lowest crude protein and lipid (P < 0.05). Ash contents were obviously lower in LD group (P < 0.05). Highest total lipid in the hepatopancreas and muscle was in LD and FO group respectively. Glucose, total cholesterol and low‐density lipoprotein were higher while high‐density lipoprotein was lower (P < 0.05) in LD group. Tissue fatty acid compositions were consistent with those in diets. FO and MO diets had the same depression effect like CF on fatty acid synthase activity and mRNA expression in the hepatopancreas. The results of this study indicated that FO and mixed oil are suitable for preparation of pelleted diets with better effects for juvenile S. paramamosain compared with live food, and the ratio of n‐6/n‐3 fatty acids in pelleted diets must be <1.     

Effects of dietary linolenic acid on growth,fatty acid composition,immune function and antioxidant status of juvenile blunt snout bream,Megalobrama amblycephala

A nine‐week feeding trial was performed to determine the dietary linolenic acid (LNA; 18:3n–3) requirements of juvenile blunt snout bream. Six iso‐nitrogenous, semi‐purified diets were prepared with different concentrations of LNA (0–25 g/kg). Dietary LNA had no significant effects on survival rate. However, final fish weight, weight gain (WG), specific growth rate (SGR) and feed efficiency ratio (FER) increased with increasing dietary LNA concentrations up to 20 g/kg. Dietary LNA increased muscle LNA and total n‐3 polyunsaturated fatty acid (PUFA) contents, but decreased total saturated fatty acid content. Fish fed 20 g/kg LNA had the highest plasma alkaline phosphatase activity, total protein, albumin and white blood cell count levels. Additionally, fish fed 20 g/kg LNA had higher triglyceride levels than control fish. Plasma glucose increased with increasing dietary LNA concentrations. Superoxide dismutase and glutathione peroxidase activities significantly increased with increasing dietary LNA concentrations up to 15 g/kg. Based on SGR and FER, the optimal dietary LNA requirements of juvenile blunt snout bream were 17.5 and 15.6 g/kg respectively.     

Effects of dietary lipid levels on growth performance,whole body composition and fatty acid composition of juvenile gibel carp (Carassius auratus gibelio)

We evaluated the effects of dietary lipid levels on the growth, whole body composition and fatty acid composition of juvenile gibel carp (Carassius auratus gibelio). Triplicate groups of 120 juvenile Carassius auratus gibelio (average weight: 2.05 g) were fed four isonitrogenic diets formulated with lipid levels of 1.4% (low), 6.1% (control), 11.6% (medium) and 21.1% (high) for 60 days. Weight gain in the 11.6% lipid group was significantly higher than that in the other groups (P < 0.05). The feed conversion ratio decreased and protein efficiency ratio increased (P > 0.05) as dietary lipid levels increased. N‐3 polyunsaturated fatty acids (PUFA) were not detected in faeces. The whole body lipid contents of 11.6% and 21.1% lipid level groups were significantly higher than that of the 1.4% and 6.1% lipid level groups (P < 0.05). The content of whole body n‐3 PUFA in the 21.1% lipid level group enhanced significantly (P < 0.05). The whole body contents of eicosapntemacnioc acid (EPA) and docosahexaenoic acid (DHA) in the 21.1% lipid level group were the highest (P < 0.05). These results indicated that high dietary lipid levels (21.1%) inhibit weight gain and promoted fat and n‐3 PUFA deposition in juvenile Carassius auratus gibelio, which led to liver damage. A dietary lipid level of 11.6% was determined to be optimal for growth performance of juvenile Carassius auratus gibelio.     

Effects of dietary supplementation with coconut oil on the growth,fatty acid profiles and some lipid metabolism relative gene expressions of orange‐spotted grouper Epinephelus coioides

This study investigated the effects of coconut oil as a dietary supplement on the growth, lipid metabolism and related gene expressions of juvenile orange‐spotted grouper Epinephelus coioides. Coconut oil at concentrations of 0, 10, 30 and 50 g/kg was used to replace dietary lipids in a basal diet containing 150 g/kg lipids. The four experimental diets were, respectively, fed to triplicate groups of juvenile groupers (initial weight: 8.53 ± 0.13 g) in a recirculating system for 8 weeks. Fish fed the diet containing 50 g/kg coconut oil exhibited lower (p < .05) weight gain than did fish fed the diet containing 30 g/kg coconut oil; however, no significant differences in weight gain were observed between fish fed diets containing 0 and 10 g/kg coconut oil. Hepatic carnitine palmitoyltransferase‐1, fatty acid synthase, fatty acid elongase, fatty acid desaturase and peroxisome proliferator‐activated receptor gamma gene expressions were all the highest in fish fed the diet containing 10 g/kg coconut oil. Fish fed the coconut oil‐free basal diet demonstrated upregulated gene expression of neuropeptide Y. The results suggest that dietary supplementation with 10 g/kg coconut oil exerted beneficial effects on lipid metabolism by E. coioides.     

Effects of dietary fish oil replacement by various vegetable oils on growth performance,body composition and fatty acid profile of juvenile Malaysian mahseer,Tor tambroides

The current study was carried out to investigate the effects of replacing dietary fish oil with different vegetable oil sources and ratios on the growth performance and tissue fatty acid profiles of juvenile Tor tambroides. Three different vegetable oils (sunflower oil, linseed oil and palm oil) were used in two different substitution ratios (50% and 100%). A diet without replacement (100% fish oil) was used as a control. Triplicate groups of T. tambroides juveniles (5.0 ± 0.4 g) were fed the test diets for 9 weeks. The highest weight gain was observed in fish fed palm oil diets that, of course, were reared in aquaria. There was a significant effect (P < 0.05) of the percentage of fish oil replacement on the liver weight after controlling for the effect of fish weight (P < 0.05). The viscera weight significantly increased (P < 0.05) in fish on vegetable oil diets, and its highest amount observed among fish fed palm oil diets. Vegetable oil inclusion significantly reduced eicosapentaenoic acid and docosahexaenoic acid (DHA) concentrations in both muscle and liver of fish except for fish on 50% palm oil diet that had similar liver DHA content with those on control diet.     

Effects of different dietary lipid sources on growth performance,antioxidant enzyme activities and biochemical composition of juvenile swimming crab,Portunus trituberculatus

An 8‐week feeding trial was conducted to evaluate the effects of dietary lipid sources on growth performance, antioxidant enzyme activities and biochemical composition of juvenile swimming crab Portunus trituberculatus of initial weight 2.34 ± 0.08 g. Four different diets were formulated to contain fish oil (FO), soybean oil (SO), linseed oil (LO) or palm oil (PO). The highest final body weight, weight gain, specific growth rate and molting frequency were observed in crabs fed the FO diet. Crabs fed the SO diet showed higher glutathione peroxidase, superoxide dismutase (SOD) and catalase (CAT) activities in both serum and hepatopancreas than those fed the FO diet. The lowest malondialdehyde concentration in hepatopancreas and serum were occurred at crabs fed the SO diet. Crabs fed the LO diet had significantly higher SOD and CAT activities in hepatopancreas compared with those fed the FO diet. Crabs fed the PO diet had the highest activities of fatty acid synthase and carnitine palmitoyltransferase 1 activities in hepatopancreas among all treatments. Fatty acid compositions both in hepatopancreas and muscle reflected those of diets. Overall, these findings demonstrated that physiological–biochemical characteristics and lipid metabolism were significantly regulated by different dietary lipid sources. Moreover, dietary SO and LO supplementation could improve antioxidant ability.     

Growth,antioxidant capacity,intestine histology and lipid metabolism of juvenile red claw crayfish,Cherax quadricarinatus,fed different lipid sources

Five dietary lipid sources (fish oil, soybean oil, palm oil, rapeseed oil and linseed oil) were evaluated in juvenile red claw crayfish, Cherax quadricarinatus, based on the response of growth, antioxidant capacity, intestine histology, whole‐body composition, fatty acid nutrition and lipid metabolism. Crayfish were fed in quadruplicate net cages for 8 weeks. Crayfish fed diets with fish oil, soybean oil and linseed oil obtained significantly higher weight gain and specific growth rate than those fed the other two diets. Survival, condition factor and hepatosomatic index were not significantly affected by lipid sources. Lipid sources also do not affect the whole‐body composition of crayfish. Serum SOD, T‐AOC and GSH‐PX activities of crayfish fed the palm oil and rapeseed oil diets had a significantly lower value than those fed other diets. The minimum concentrations of MDA have been observed in crayfish fed the soybean oil diet. The activity of ACC in the hepatopancreas of crayfish fed the linseed oil diet showed the highest value, and the CPT‐1 activity was not significantly affected by different lipid sources. Crayfish fed the soybean oil diet showed significantly higher TC and TG contents in hepatopancreas than those fed other diets. Crayfish fed linseed oil diet had a significantly higher percentage of EPA, C18:3n?3 and Σn?3 PUFA in muscle than those fed other treatments. Most of the fatty acid compositions in the hepatopancreas had a close correlation to fatty acid compositions in diets. All findings in this study indicate that soybean oil is the advantageous lipid source for juvenile C. quadricarinatus which can reflect in satisfactory growth performance, antioxidant capacity and fatty acid nutrition of edible tissues.     

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.     

饲料脂肪水平对白甲鱼幼鱼形体指数、脂肪沉积和脂肪代谢酶活性的影响

实验评价了不同饲料脂肪水平对白甲鱼形体指数、脂肪沉积和脂肪代谢酶活性的影响。选用初始均质量(0.78±0.05)g的白甲鱼幼鱼900尾,随机分成6个实验组,每组3个重复,每个重复50尾实验鱼,分别饲喂添加0%(对照组)、2%、4%、6%、8%和10%的豆油,设计出脂肪水平为2.83%、4.52%、6.68%、9.14%、11.35%和14.07%的6种等氮(蛋白质含量为40%)等能(总能为16.30 MJ/kg)的实验饲料,养殖时间为60 d。结果表明,随着饲料脂肪水平的升高,白甲鱼幼鱼肥满度(CF)先升后降的变化趋势,且脂肪水平为9.14%时最大,为2.64%,但饲料脂肪水平为6.68%～14.07%时差异不显著(P>0.05),肝体指数(HSI)随饲料脂肪水平的升高呈上升趋势,脏体指数(VSI)则随饲料脂肪水平的升高呈略微上升趋势(P>0.05);白甲鱼幼鱼肌肉和肝脏中脂肪的含量易受饲料脂肪水平的影响。随着饲料脂肪水平的升高,肌肉和肝脏脂肪含量均呈上升趋势,饲料脂肪水平对饲料氮的沉积量无明显影响(P>0.05),能量沉积量则在饲料脂肪水平为14.07%时最高,氮和能量的沉积率随饲料脂肪水平的升高呈先升后降的变化趋势,且分别在饲料脂肪水平为11.35%和9.14%时达到最大,脂肪的沉积量随饲料脂肪水平的升高而升高,但脂肪沉积率则随饲料脂肪水平的升高而逐渐降低(P<0.05);白甲鱼幼鱼肠道脂肪酶活性呈先升后降的变化趋势,且在脂肪水平为9.14%时最大,为296.03 U/g,脂蛋白酯酶、肝脂酶和总酯酶活性则呈先升后降并逐渐趋于稳定,均在饲料脂肪水平为9.14%时达到最高;脂肪合成酶则呈逐渐降低的趋势(P<0.05)。说明适当的饲料脂肪水平可以提高饲料营养物质的利用率,但过高的脂肪水平(11.35%及以上)将使白甲鱼肝脏脂肪沉积增多,不利于鱼类健康生长。     

Effects of dietary fish oil substitution with blending vegetable oils on growth performance,antioxidant enzyme activities and tissue fatty acid composition of juvenile swimming crab,Portunus trituberculatus

An 8‐week feeding trial was conducted to evaluate the effects of replacement of fish oil (FO) with blending vegetable oils (VOs) on growth performance, antioxidant enzyme activities and fatty acid composition in tissue of swimming crab Portunustrituberculatus. Five isonitrogenous and isolipidic diets were formulated to contain VOs (colza oil: palm oil: linseed oil = 4:2:1) to replace 0 (the control diet), 250, 500, 750 and 1000 g/kg of FO (defined D0, D25, D50, D75, D100). Three hundred juvenile swimming crabs (initial weight 2.34 ± 0.08 g) were randomly stocked and sorted into 300 individual rectangle plastic baskets in three cement pools. Each treatment has three replicates, one replicate has 20 swimming crabs, and each diet fed 60 crabs distributed in 60 baskets. The results indicated that crabs fed the control diet showed significantly higher survival, final body weight, per cent weight gain (PWG), specific growth rate and moulting frequency, crude protein and crude lipid contents in muscles than those fed the D75 and D100 VO diets (p < .05). Crabs fed the D25 VO diet showed significantly higher concentration of triglyceride, low‐density lipoprotein cholesterol and total protein, activities of superoxide dismutase, catalase and glutathione peroxidase (GSH‐Px) in haemolymph than those fed the control diet (p < .05). Fatty acid composition in hepatopancreas was positively correlated with dietary composition. In summary, based on the PWG, the optimal replacement of FO with VOs was estimated to be 250 g/kg. These findings demonstrated that swimming crabs make better use of FO than VOs.