Growth and energy budget in young grass carp, Ctenopharyngodon idella Val., fed plant and animal diets

Young grass carp held under laboratory conditions were fed either duckweed or tubificid worms. Food consumption ( C ), faecal production ( F ), excretion ( U ), metabolism ( R ) and growth ( G ) were estimated for fish fed both diets. Fish fed tubificid worms had higher growth rates than those fed duckweed, in terms of wet weight, dry matter, protein, lipid and energy. Fish fed duckweed consumed more wet and dry matter than did the fish fed tubificids, but rates of protein and lipid consumption were lower. The energy budget was estimated to be 100C = 9 F + 8 U + 61 R + 22 G for fish fed tubificids, and 100C = 35 F + 5 U + 51 R + 9 G for fish fed duckweed. Linear relationships existed between specific growth rate in wet weight and rate of food absorption (consumption minus faecal production) in dry matter, protein or energy. Food type did not have a significant effect on these relationships. It was concluded that differences in growth rate between grass carp fed different diets were mainly caused by differences in absorption rate.     

Growth and reproductive performance of the Asian catfish Clarias macrocephalus (Gunther) fed artificial diets

Four natural ingredient diets similar in nutrient composition (crude protein = 42–44%; P/E ratio = 115–120 mg/kcal) but different in protein sources, were formulated and fed to hatchery-reared catfish to measure the relative performance of the catfish fed alternative broodstock diets. The control feed was a combination of fish-by-catch and commercial fish pellets. In trial I, growth of the catfish was slow over a 36-week period, but some fish became gravid. Diets 1, 2, and 3 and the control feed were tested in trial II. Growth of fish did not differ significantly (P > 0.05) and female fish in all treatments became gravid. For fish induced to spawn from April to August (1994), hatching rate showed significant differences among treatments (P < 0.05). Relative fecundity, fertilization and hatching rates, and production of 3-day-old larvae were significantly different among fish induced to spawn in November (1994) when another incubation setup was used. Among the diets, diets 2 and 3 best enhanced reproductive performance of the catfish.     

Lactation in mice fed endophyte-infected tall fescue seed

This study was conducted to assess the effects of endophyte-infected Acremonium coenophialum tall fescue (KY-31) seed (80% infected) on lactation in CD-1 dams and suckling performance of pups as measured by pup survival and growth rates. Twenty-four pairs of mature CD-1 mice were randomly allocated to four dietary treatments: 1) 100% mouse chow ad libitum; 2) 40% endophyte-infected tall fescue seed and 60% mouse chow (w/w); 3) reduced intake (100% chow), adjusted daily to the intake level of Treatment 2; and 4) 60% infected tall fescue seed and 40% chow. The mice were preconditioned on their respective diets for 100 d prior to 96 h of cohabitation between pairs of males and females. At parturition the litters were removed, and each dam was given a litter of six pups of equal weight, size and sex ratio to suckle for 15 days. All pups given to all the dams were born to other mice that were not part of the study and had not been exposed to endophyte-containing diets. Dams and litter weights were measured daily for 15 consecutive days. The combined body weight measurements of litters from dams fed the tall fescue containing diets (Treatments 2 and 4) were significantly lower (2.07 +/- 0.41 g/d) than that of litters from dams fed the chow containing diets (Treatments 1 and 3) during the suckling trial (P<0.05). Similarly, nine of ten (90%) dams fed the chow containing diets maintained five or more pups (5.5 +/- 0.2) throughout the study as compared to five of nine (55.6%) dams fed the tall fescue containing diets that maintained less than five pups (4.5 +/- 0.2).     

Survival and changes in growth of juvenile tench (Tinca tinca L.) fed defined diets commonly used to culture non-cyprinid species

The study is an attempt to evaluate the feasibility of intensive tench culture using non‐specific diets as a preliminary step to check the acclimatization of the species under intensive rearing systems. Five‐month‐old juvenile tench were reared in recirculating systems at mean water temperatures of 22°C for 75 days. Fish fed with four different commercial diets (trout starter, trout first feeding, sea‐bass and eel), showed significantly higher final weights than the fish fed either eel or sea‐bass diets. Initial weight for all treatments was 2.3 ± 0.53 g. Final weight for the commercial diet groups was 3.56 ± 0.4 g, compared with the remaining groups that reached 2.09 ± 0.47 g (P < 0.05). Significantly higher survival rates were observed in the eel and sea‐bass groups (84.7 and 51.5%, respectively) than in either of the trout diet groups (38%). Specific growth rates (1.26 vs –0.18) and condition factor (1.26 vs 0.93) were also higher than those fed with salmonid diets (P < 0.05). Results obtained in this study indicate that regardless of the species’ slow growth, when compared with other cyprinids, final growth rates and survival of tench fed exclusively on sea‐bass or eel diets can be considered satisfactory. It must be pointed out that these promising results were obtained at lower temperatures than previous studies of tench in culture systems. The use of belt feeders did not show improvement in growth compared with manually fed fish when trout diets were used.     

A dietary dairy/yeast prebiotic and flaxseed oil enhance growth,hematological and immunological parameters in channel catfish at a suboptimal temperature (15°C)

Channel catfish raised in the southern United States require two growing seasons to reach market size. Growing seasons are separated by a cool period of about 3 months when feed intake and growth are greatly reduced. A cool-weather feeding strategy to improve feed intake, growth or health of catfish might improve survival and reduce the time needed to achieve market size. We conducted a feeding trial with channel catfish at a suboptimal temperature (15°C) to determine the effects of supplementing diets with either a dairy/yeast prebiotic or flaxseed oil (high in 18:3n-3) compared with a control with soybean oil (high in 18:2n-6). The trial was conducted in recirculating systems with 1140-l tanks containing 100 fish each (mean initial weight 61.4 g±0.43 s.e.m.). A 28%-protein basal diet was supplemented with 20 g/kg cellulose and 20 g/kg soybean oil (SBO, control), 20 g/kg cellulose and 20 g/kg flaxseed oil (FLAX) or 20 g/kg of a dairy/yeast prebiotic and 20 g/kg soybean oil (PREB). Fish were fed once daily to satiation and weighed every 3 weeks to track growth. Hematology, non-specific immune responses, proximate and fatty acid composition of muscle were determined to assess diet effects. Catfish-fed FLAX or PREB had higher weight gain, feed consumption and lysozyme activity than fish fed SBO. Total n-3 fatty acids in muscle were higher in fish fed SBO or FLAX than those fed PREB. Total n-6 long-chain polyunsaturated acids were higher in muscle of fish fed PREB than those fed SBO. Fatty acids in the PREB and SBO diets were similar, so the PREB appeared to increase elongation and desaturation of n-6 fatty acids in muscle. Flaxseed oil and the dairy/yeast prebiotic both have potential to increase catfish performance at a low temperature.     

Effects of feeding on survival, cannibalism, growth and feed conversion of African catfish, Clarias gariepinus (Burchell) in concrete tanks

Daily feeding rates of 0, 2, 4, 6, 8 and 10% of body weight to juvenile (average weight 0.64–65.4 g) catfish, Clarius gariepinus, for 112 days had significant effects on survival, cannibalism, growth and feed conversion ratio (FCR). Survival was significantly higher in fish fed at 6–10% of body weight than those fed at 2–4%. Mortality was mainly caused by cannibalism, being significantly higher in underfed (2–4%) fish than in fish fed at the 6–10% level. A feeding level above 6% did not further reduce cannibalism. The best growth performance was recorded for the fish fed at 8–10% body weight, followed by the fish fed at 4–6%; poorest growth was found for those fed at the 2% level. FCR significantly increased from 2–4% (FCR, 1.14–1.13) to 6, 8 and 10% (FCR, 1.37, 2.18, 2.98, respectively). The results of this study suggest that the optimum feeding rate of juvenile catfish with an average initial weight of about 0.64 g and grown to a size of about 64 g is at 6% body weight per day.     

Growth, fat content and fatty acid profile of South American catfish, surubim (Pseudoplatystoma fasciatum) juveniles fed live, commercial and formulated diets

South American catfish, barred surubim ( Pseudoplatystoma fasciatum ) juveniles (117.6 ± 11.8 mg individual weight; 28.3 ± 2.5 mm total length) were fed various diets: one live ( Tubifex worms), two commercial (Aglo Norse and Bio Kyowa), and one semi-purified formulated diet (75% peptide based protein) over a 2-week period. Fish fed the Aglo Norse diet showed the highest growth performance, but cannibalism also was very high (42%). Fish fed peptide based formulated diet demonstrated the lowest growth rate, with no cannibalism. The highest survival was achieved with fish fed Tubifex worms (100%). Lipid level in the whole body of the fish fed four different experimental diets did not differ significantly, averaging 3.6 ± 0.7%. Fatty acid composition of neutral and phospholipid fractions of whole body lipids of fish reflected the fatty acid composition of the diets. The high level of 20:4 n -6 in Tubifex worms resulted in a high level of this fatty acid in the tissue of fish fed this diet. It remains uncertain how high survival and no cannibalism is related to dietary lipids/fatty acids. In all cases, the increasing ratio of n -3 HUFA (highly unsaturated fatty acids)/ n -6 HUFA in phospholipid fractions suggested the elongation and desaturation of 18:3 n -3 to 22:6 n -3 via 20:5 n -3. Moreover, in respect to the 20:4 n -6 levels in the diets, an increase in the concentration of this fatty acid in phospholipid fraction suggests that South American catfish can transform linoleate into arachidonate.     

黄颡鱼饲料中添加谷胱甘肽降低藻毒素毒性作用的研究

通过60d的生长实验研究饲料中不同含量的谷胱甘肽(GSH)对黄颡鱼(Pelteobagrus fulvidraco Richardson)摄食含蓝藻粉饲料后的毒性保护作用。共配制6种近似等氮等能(粗蛋白45%,总能19.5kJ/g)的实验饲料。以不添加蓝藻粉、不添加GSH的饲料组作为正对照,其他5种饲料均添加7.5%的藻粉,微囊藻毒素(Microc ystins,MCs)含量约为58μg/g,GSH添加量分别为:0(负对照)、200、500、800和1400mg/kg。实验结果表明,第1至第30天时,负对照组与正对照组实验鱼的摄食率无显著性差异(P>0.05)。第31至第60天时,负对照组实验鱼的摄食率显著高于正对照和其他GSH添加组(P0.05),但各GSH添加组肾脏中GSH显著低于正对照而高于负对照(P<0.05)。200、500和800mg/kg GSH添加组肝脏和肌肉中丙二醛(MDA)含量显著低于负对照(P<0.05)。在整个实验期间,随着饲料中GSH含量的增加,肝脏、肾脏、全肠和肌肉中微囊藻毒素含量先显著下降,当GSH添加量为500和800mg/kg时达到稳定,直至GSH添加量为1400mg/kg时显著上升。根据对黄颡鱼增重,肝脏和肌肉中MDA的含量以及组织中毒素的分析,在饲料中添加500-800mg/kg GSH可以有效缓解黄颡鱼饲料中微囊藻毒素的毒性。       

Growth response of African catfish,Clarias gariepinus (B.), larvae and fingerlings fed protease‐incorporated diets

African catfish, Clarias gariepinus (B.), is one of the promising freshwater fish species in African aquaculture but the expansion of its farming needs more production of its larvae. The use of live food organisms at first feeding for larvae is still obligatory. That increases the cost of larvae production. Hence, the incorporating of exogenous enzymes especially protease in artificial microdiets may provide affordable alternatives for enhancing the larvae performance. The present study was carried out to evaluate the growth and survival of larvae or fingerlings of African catfish fed artificial diets incorporated with different protease levels. Four artificial diets were formulated and enriched with protease enzyme at levels of 0.0, 750, 1,000, and 1,250 unit/kg diet; after that diets were made into crumbles (100–200 µm diameter). After absorption of the yolk sac, diets were offered to fish larvae (3.6 ± 0.2 mg) in triplicates as a starter feed up to apparent satiation every two hours for 30 days. In another treatment, fish larvae were fed on newly hatched Artemia nauplii (2,500 Artemia/L) as a starter food. In another experiment, African catfish fingerlings (10.1 ± 1.6 g) were fed on the same diets up to satiation twice a day for 2 months. It was noticed that the dietary protease improved larval growth and survival but not as Artemia nauplii did where fish larvae fed on Artemia nauplii showed highest growth and survival followed by those fed a diet enriched with 1,250 unit/kg diet of protease. The mortality of larvae fed protease‐enriched diets as well as the control diet was occurred mostly at the first week reaching its maximum at the third week. The poor growth was observed with fish larvae fed the control diet. Meanwhile, catfish fingerlings fed protease‐enriched diets showed higher growth over those fed the control diet. The larvae survival (11.0%–41.7%) was enhanced by increasing protease levels and it was lower than that of fingerlings (95.6%–100.0%). Furthermore, protein retention and digestibility were significantly improved with protease supplementation over the control diet especially at a level of 1,000 unit/kg diet. As compared with the previous studies, live food should be used in larvae rearing for the first week after that a starter diet enriched with protease at levels of 1,250 unit/kg diet should be used. In case of fish fingerlings, the dry diets should be enriched with 1,100 unit/kg diet to improve diet digestibility and subsequently enhance their growth.     

Intensive culture of grass carp, Ctenopharyngodon idella, in circular tanks

Fingerling grass carp ( Ctenopharyngodon idella ) were cultured in 380 1 circular fiberglass tanks at stocking densities of 0.53, 1.06, 1.59 and 2.11 fish/1. Fish were fed duckweed ( Lemna minima ) to satiation. Fish grew from 2.7 g to a maximum mean weight of 72.7 g in 88 days. Fish stocked at 0.53 fish/1 grow more rapidly than those stocked at higher densities. Mean daily consumption rates were strongly correlated with oxygen levels and when oxygen levels dropped below 4 mg/1 consumption was reduced approximately 40%. High biomass, growth, and survival rates obtained during this study indicate grass carp are well suited for intensive tank culture.     

Replacement value of hatchery waste meal for fish meal in layer diets

An experiment was conducted in which hatchery waste meal (HWM) replaced fish meal (protein for protein) in layer diets at 0%, 33%, 66% and 100% levels. Both feed and protein intake were superior on HWM diets. The highest hen-day production of 73.97% was obtained on diet 2 in which 33% of fish meal was replaced with HWM. Egg weight and egg length were also superior on HWM diets. All birds fed on HWM diets had thicker egg shells (0.33 mm) than did those fed on the control diet, fish meal diet (0.32 mm). Results obtained for yolk weight were statistically different (P < 0.05). Highest values for yolk weight (16.91 g) and albumen weight (40.93 g) were recorded for birds fed with diet 4 in which 100% fish meal was replaced with HWM. HWM can replace fish meal completely in layer diets without adverse effect on egg quality characteristics.     

Use of soybean flour (dehulled, solvent-extracted soybean) as a fish meal substitute in practical diets for African catfish, Clarias gariepinus (Burchell 1822): growth, feed utilization and digestibility

Growth and digestibility trials were conducted using African catfish, Clarias gariepinus (Burchell 1822): (1) to obtain apparent digestibility coefficient (ADC) values for capelin fish meal, soybean flour and corn meal; (2) to formulate diets based on ADC values of the protein feedstuffs; and (3) to evaluate the effects of replacing 25%, 50% and 75% of fish meal in control diets with soybean flour on growth, feed utilization efficiency and carcass composition. Supplemental methionine was added to the diet formulation in which soybean flour replaced 75% of the diet. Diets were formulated (400 g digestible protein kg⁻¹ and 15 kJ digestible energy g⁻¹ dry diet) and fed to catfish fingerlings (13.1 ± 0.5 g) to apparent satiation twice daily for 70 days. The protein and energy digestibilities of fish meal and soybean flour were high (>90% and >80%, respectively; P < 0.05). At 75% fish meal replacement with soybean flour (without methionine supplementation), growth and feed utilization efficiency indicators were depressed compared with other diet treatments which had a similar (P > 0.05) growth and feed utilization efficiency to those fed the control diet. The carcass compositions of catfish in all diets were similar (P > 0.05) and the liver histology of catfish fed any of the diets showed no alterations. The results obtained indicate that 50% of fish meal protein in practical catfish diets can be replaced with soybean flour and that catfish can effectively utilize supplemental methionine, thereby allowing up to 75% of the dietary fish meal protein to be replaced by soybean flour.     

Dietary influences on product quality in African catfish (Clarias gariepinus)

In this trial a full-sib family of Clarias gariepinus was raised under standard conditions in a warmwater recirculation system. The fish were divided into two experimental groups of 1200 individuals each and were raised in separate tanks. The groups were fed two experimental diets differing in crude protein (group I 40% and group II 52% DM) and crude fat (group I 8% and group II 13% DM). Gross energy was 21.3 and 22.1 MJ/kg. Slaughtering of 100 fish per group (50 males, 50 females) took place after two experimental periods. Besides the significant effect of the diets on body weight and size, a higher degree of corpulence was observed in group II. Tissue and organ percentages were not influenced, except a higher intestinal fat deposition in intensively fed fish. This group also showed a higher carcass weight. More expressed differences between both feeding alternatives were observed in physical and chemical flesh quality criteria. In group I texture of flesh was firm and water-binding-capacity was significantly increased in group II. The appearance of the filet was affected by the diet. Intensively fed catfish showed a tendency to a lighter and more yellowish colour. The chemical composition of the flesh indicated a significant increase of dry matter caused by higher protein and fat contents in this group. A strong influence of sex and fattening age on inner and outer product quality was evident. High fat and protein content of the diet has a certain influence on product quality in African catfish. It can be concluded that there is a clear effect of diet on quantitative criteria with a tendency to higher slaughtering yields in intensively fed catfish.     

The effects of surimi and pelleted diets on the laboratory survival, growth, and feeding rate of the cuttlefish Sepia officinalis L.

The effects of feeding a prepared surimi diet (fish-based) and a prepared pelleted diet (shrimpbased) on the survival, growth and feeding rate of the cuttlefish Sepia officinalis L. were evaluated during a 45-day experiment. One hundred and twenty juveniles of laboratory cultured cuttlefish (74.5 ± 12.36 g) were divided into three treatments and were fed thawed shrimp (control), pellets or surimi. Survival rates on these diets were 95.0%, 67.5% and 22.5%, respectively. Preliminary data indicated that the low survival of cuttlefish fed surimi may have been caused by low levels of copper in their blood (131 vs 244 μg/ml) since copper is required for their respiratory blood pigment, hemocyanin. Instantaneous growth rates were 2.71 % body weight BW/day for cuttlefish fed raw shrimp, 0.33% BW/day for cuttlefish fed pellets, and 0.54% BW/day for cuttlefish fed surimi. The feeding rate of cuttlefish fed shrimp was high (6–8% BW/day). The feeding rate on pellets increased with time (from < 1 to 3% BW/day) but never reached the level for raw shrimp. The feeding rate on surimi increased to equal the rate for raw shrimp during days 1–30 (8 to 9% BW/day) and thereafter decreased (<4% BW/day). In conclusion, there was a major distinction between the palatability of a prepared diet and the ability of that diet to support growth. Surimi was highly palatable but resulted in poor survival, suggesting low nutritional quality. In contrast, pellets were less palatable but produced maintenance growth. Development of practical surimi diets will require supplementation of the surimi with soluble micro- and macronutrients.     

Growth, body composition and hepatic tyrosine aminotransferase activity in cortisol-fed channel catfish, Ictalurus punctatus Rafinesque

Metabolic consequences of chronic elevation of cortisol in the diet of yearling channel catfish, Ictalurus punctatus , were studied. Cortisol was incorporated into the diet in concentrations of 1, 10, 50 and 100 μg/g of food. This diet was offered at 3% of the body weight per day for 10 weeks. Fish were individually weighed and measured at 2-week intervals and feeding rates were adjusted. Body weight, liposomatic index and condition factor were significantly lower and food conversion was significantly higher in fish fed 50 or 100 μng cortisol/g of food when compared with controls. The hepatosomatic index of fish fed cortisol at the rate of 100 μg/g of food decreased significantly. Specific activity of hepatic tyrosine aminotransferase was significantly higher at the two highest cortisol doses. Long-term cortisol administration can reduce growth and condition factor by activating gluconeogenic mechanisms in which lipids and amino acids, rather than carbohydrates, are used for energy production. The metabolic effects of exogenous cortisol in this study offer an explanation for the decreased growth of fish under conditions that activate the secretion of endogenous cortisol.     

饲料脂肪水平对瓦氏黄颡鱼生长及脂蛋白脂酶基因表达的影响

研究采用脂肪水平分别为4.7%、7.9%、10.9%、15.4%、18.9%的五种等氮配合饲料饲喂瓦氏黄颡鱼早期幼鱼,进行了为期30d的生长实验,探讨了瓦氏黄颡鱼早期幼鱼的脂肪需求。并克隆了瓦氏黄颡鱼脂蛋白脂酶(LPL)cDNA序列片段,采用实时荧光定量PCR研究了饲料脂肪水平对肝脏LPL基因表达水平的影响。结果表明,饲料脂肪水平从4.7%增加到10.9%显著促进了瓦氏黄颡鱼早期幼鱼的生长(P<0.05)。饲料脂肪水平显著影响了实验鱼的鱼体体成分,随着饲料脂肪水平的升高,鱼体干物质和脂肪含量显著增加而蛋白含量显著下降(P<0.05)。高脂诱导了瓦氏黄颡鱼肝脏LPL基因表达,摄食15.4%、18.9%这两组较高脂肪水平的实验鱼肝脏LPLmRNA表达水平显著升高(P<0.05)。根据特定生长率通过折线回归分析得出瓦氏黄颡鱼早期幼鱼最适脂肪水平为11.2%。       

食物中多氯联苯PCB 126对南方鲇的致死效应及代谢胁迫的研究

于2007年10－12月,为探讨食物中多氯联苯126（3,3′,4,4′,5-pentachlorobiphenyl, PCB 126）对南方鲇（Silurus meridionalis Chen）的致死效应及代谢胁迫作用,将72尾南方鲇幼鱼分为6个实验组,配制PCB 126含量分别为0、50、100、200、400和800 μg/kg的6组饲料,采用室内养殖系统,在（27.5±0.2）℃水温条件下以3％BW/d的日粮水平单尾喂养8 周。观测结果表明：PCB 126含量为0、50和100 μg/kg的饲料组在实验期间无实验鱼死亡,至实验结束时的PCB 126总摄入量分别为0、30.56和66.66 μg/kg;而200、400和800 μg/kg的饲料组有实验鱼死亡,半致死时间（Median lethal time, LT50）分别为34d、16d和11d,与饲料中PCB 126水平呈负相关,至半致死时PCB 126总摄入量分别为90.18、92.05和94.11 μg/kg,三者间无显著差异,但均显著高于无实验鱼死亡饲料组的PCB 126总摄入量（p<0.05）;肝指数（Hepatosomatic index , HSI）及静止代谢率随饲料中PCB 126水平的增加而升高;在无实验鱼死亡的饲料组,肝线粒体代谢耗氧率和细胞色素c氧化酶（Cytochrome c oxidase , CCO）活性随饲料中PCB 126水平的增加而升高,而在有实验鱼死亡的饲料组,肝线粒体代谢耗氧率和CCO活性则随饲料中PCB 126水平的增加而呈下降趋势。本研究提出,PCB 126对南方鲇的致死临界累计摄入量在92 μg/kg左右;PCB 126对南方鲇在整体水平表现为使静止代谢增强的胁迫效应,但在肝线粒体水平表现为低浓度使其代谢耗氧率增强,这应当是该种鱼应对多氯联苯类污染物的一种生理调节结果,而高浓度的PCB 126则使肝脏功能受到不可耐受的损害,不能对胁迫做出进一步的代谢调节。     

再投喂鱼油对瓦氏黄颡鱼肌肉脂肪酸组成的影响

为研究植物油替代鱼油对瓦氏黄颡鱼（Pelteobagrus vachelli）生长及肌肉脂肪组成的影响及重投喂鱼油对瓦氏黄颡鱼肌肉脂肪酸组成的影响,实验以大豆油分别替代饲料中的0（FO）、50（S1）、75（S2）和100%（SO）的鱼油配制等氮、等能的颗粒饲料,每组设置3个平行,养殖80d后,再投喂鱼油30d。结果表明,饲料中添加豆油不会显著影响瓦氏黄颡鱼的增重率、肝体指数和体成分（P>0.05）。随着饲料中大豆油含量的增加,S2和SO组肌肉中C18:1n-9、C18:2n-6和单不饱和脂肪酸比例显著增加（P < 0.05）,而C20:5n-3,C22:5n-3及n-3/n-6比例显著下降（P < 0.05）。再投喂鱼油30d后,SO组肌肉中C18:3n-6、C20:4n-6、Σ n-9、Σ n-6和S2组中C18:1n-9、Σ n-6比例显著下降（P < 0.05）,而S2和SO组肌肉中Σn-3多不饱和脂肪酸、C20:5n-3和C22:5n-3比例显著增加（P < 0.05）。在生产中,可采用先植物油饲料、后鱼油饲料的养殖方式提高瓦氏黄颡鱼肌肉品质（增加有益人类健康的多不饱和脂肪酸）。     

Dietary sodium alginate administration affects fingerling growth and resistance to Streptococcus sp. and iridovirus, and juvenile non-specific immune responses of the orange-spotted grouper, Epinephelus coioides

The percent weight gain (PWG) and feeding efficiency (FE) of fingerling orange-spotted grouper, Epinephelus coioides, fed diets containing sodium alginate at 1.0 and 2.0 g kg(-1) were calculated on the 2nd, 4th, 6th, and 8th weeks after feeding. Survival rates of the fingerling grouper against Streptococcus sp. and an iridovirus, and non-specific immune parameters such as alternative complement activity (ACH50), lysozyme activity, natural haemagglutination activity, respiratory bursts, superoxide dismutase (SOD) activity, and phagocytic activity of juvenile grouper were also determined when the fish were fed diets containing sodium alginate at 0.5, 1.0, or 2.0 g kg(-1). The PWG and FE of fish were better when the fish were fed diets containing sodium alginate at 1.0, and 1.0 and 2.0 g kg(-1), respectively. The PWG and FE of fish fed the 0, 1.0 and 2.0 g kg(-1) sodium alginate-containing diets after 8 weeks were 271.0%, 454.4% and 327.8%, and 0.61, 0.72 and 0.68, respectively. Fish fed a diet containing sodium alginate at the level of 2.0 g kg(-1) had a significantly higher survival rate than those fed the control diet after challenge with Streptococcus sp. and an iridovirus causing an increase of survival rate by 25.0% and 16.7%, respectively, compared to the control group. The ACH(50) level of fish fed the sodium alginate-containing diets at 2.0 g kg(-1) was significantly higher than those fed the 1.0 g kg(-1) sodium alginate diet and control diet after 12 days, and had increased to 1.9-fold, compared to those fed the control diet. The lysozyme activity, phagocytic activity, respiratory bursts, and SOD level of fish fed the sodium alginate-containing diets at 1.0 and 2.0 g kg(-1) were significantly higher than those fed the control diet after 12 days, and had increased to 1.97- and 1.68-fold, 1.35- and 1.50-fold, 1.63- and 1.81-fold, and 1.23- and 1.31-fold, respectively, compared to those fed the control diet. We therefore recommend dietary sodium alginate administration at 1.0 and 2.0 g kg(-1), respectively, to promote growth and enhance immunity and resistance against Streptococcus sp. and an iridovirus.     

Dietary lipid requirement on non-specific immune responses in juvenile grass carp (Ctenopharyngodon idella)

This study aimed to evaluate the dietary lipid requirement and its effects on liver oxidative status and non-specific immune responses of juvenile grass carp (Ctenopharyngodon idella). Purified diets with five dietary lipid levels (0%, 2.5%, 5%, 7.5% and 10%, fish oil/corn oil = 1:1) were each fed to triplicate groups of grass carp (mean initial weight: 6.57 ± 0.01 g) in a recirculating rearing system maintained at 27.5 ± 0.5 °C for 10 weeks. Percent weight gain was highest (P < 0.05) with 5% lipid and lowest in fish fed the lipid free control diet. Feed efficiency (FE) and protein efficiency ratio (PER) in fish followed the same pattern of percent weight gain. Fish fed with lipid containing diets had better non-specific immune response indexes (e.g. phagocytic activity, plasma peroxidase and lysozyme activity) and low-level of liver oxidation status than fish fed with the control diet. But excess dietary lipid supplement would bring over metabolic burden to liver. After the feeding trial, fish were challenged by Aeromonas hydrophila. Fish fed control diet obtained significantly (P < 0.05) lower survival rate. The survival rate was highest with 7.5% lipid. The results of this study indicated that proper dietary lipid supplementation enhanced the immune response of grass carp and improved the survival rate in the bacterial challenge, but excess dietary lipid may elevate liver oxidation rates of grass carp. Analysis by second-order regression of percent weight gain indicated that the optimal dietary lipid level in juvenile grass carp (6.6–35.5 g) is about 6.5%.