Effects of dietary lipid levels on growth,feed utilization,digestive tract enzyme activity and lipid deposition of juvenile Manchurian trout,Brachymystax lenok (Pallas)

Six isoproteic diets were designated to evaluate the effects of dietary lipid levels (from 70 to 270 g/kg) on the growth performance, feed utilization, digestive tract enzyme activity and lipid deposition of juvenile Brachymystax lenok (average initial weight 0.54 ± 0.04 g). Each diet was fed to triplicate tanks (30 fish per tank) in an indoor closed recirculating system for 9 weeks. Final body weight and weight gain were highest in fish fed 190 g/kg diet and lowest in fish fed the 70 g/kg diet. Specific growth rate of fish fed with 190 g/kg diet was significantly higher than those fed with 70 and 270 g/kg diets (p < .05). Protein efficiency ratio of fish fed with 70 g/kg diet was significantly lower than the 110–230 g/kg treatments and was not significantly different from the 270 g/kg treatment. Fish fed with 270 g/kg diet had significantly higher hepatosomatic index and viscerosomatic index than those fed with 70–190 g/kg diets (p < .05). Intraperitoneal fat ratio and the whole‐body lipid content had a trend to increase with increase in dietary lipid level. Muscle crude lipid content increased up to 190 g/kg with increase in dietary lipid level. Lipid retention decreased with increase in dietary lipid level, while no significant differences in protein intake and retention levels were observed in fish among all treatments. Lipase activity of the mixture of pyloric caeca and foregut in fish fed 190 and 230 g/kg diets was significantly higher than those fed 70 and 110 g/kg diets. Midgut and hindgut lipase activities of fish were significantly higher than those fed the 190 and 230 g/kg diets. In conclusion, based on the second‐order polynomial model of WG and FCR, this study suggested that 173.8–195.0 g/kg dietary lipid levels were appropriated for B. lenok.     

Influence of dietary fish oil concentration and finishing duration on beneficial fatty acid profile restoration in sunshine bass Morone chrysops ♀ x M. saxatilis ♂

Considerable feed savings may be realized by reducing the fish oil (FO) content of aquafeeds used during grow-out, but fatty acid (FA) profile of the resultant seafood will be altered. By feeding a FO-rich finishing feed prior to harvest, fillet levels of beneficial long-chain polyunsaturated FA (LC-PUFA) can be partially or completely restored. We evaluated the use of linseed oil (LO) as a partial substitute for FO, and assessed the relative impacts of grow-out feed FO concentration and finishing duration on production performance and fillet fatty acid (FA) composition of sunshine bass. Fish were raised on feeds containing 33 or 67% FO during the grow-out period, and then finished with a 100% FO finishing feed for 4 or 8 weeks before harvest; for comparison, a control group was fed the 100% FO feed throughout the entire 20-week trial. Production performance was unaffected by the dietary formulations or feeding schemes, however, fillet FA varied among treatment groups. Increased consumption of LO, whether by increased dietary concentrations or longer feeding periods, resulted in elevated levels of LO-associated medium-chain polyunsaturated FA, specifically 18:3n-3; increased consumption of FO had the same effect on tissue levels of FO-associated LC-PUFA such as 20:5n-3 and 22:6n-3. Finishing had a significant restorative effect on fillet LC-PUFA content (LC-PUFA in finished groups ranged from 64-87% of control levels compared to 50-71% in unfinished groups), however, with the exception of 22:6n-3, 8 weeks of finishing was still insufficient to completely restore fillet LC-PUFA content to control levels, regardless of grow-out feed. We observed fillet levels of LC-PUFA to be essentially a function of total FO consumption, and FA profile change to be relatively well-described by simple dilution modeling. However, further research is needed to unequivocally demonstrate the relative merits of continuous vs. periodic provision of FO-rich aquafeeds.     

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

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

不同脂肪源日粮补充维生素E对罗氏沼虾生长、免疫及肉品质的影响

本研究旨在完善罗氏沼虾（）饲料配方,降低罗氏沼虾饲料成本。研究采用3×2双因素设计,配制6组饲料,分别包含鱼油（fish oil,FO）、豆油（soybean oil,SO）、菜籽油（rapeseed oil,RO）三种脂肪源;200 mg/kg（200VE）和600 mg/kg（600VE）两个维生素E（VE）水平。养殖实验在温室水泥池中进行,每个处理3个重复,养殖期8周,每天定点定量投喂3次。结果显示,相对于FO组,SO和RO组增重率、特定生长率显著升高,饵料系数显著下降（>0.05）。对于血淋巴抗氧化指标,在相同VE水平下,FO组血淋巴总抗氧化能力（T-AOC）和超氧化物歧化酶（SOD）活性均显著低于SO和RO组,谷胱甘肽过氧化物酶（GPX）活性均显著高于SO和RO组（<0.05）。在相同脂肪源下,600VE可显著提高FO组T-AOC活性,RO组GPX活性以及SO和RO组SOD活性（>0.05）。对于血淋巴生理生化指标,谷草转氨酶（AST）、总蛋白（TP）、白蛋白（ALB）和甘油三酯（TC）受日粮影响显著（<0.05）。此外,日粮脂肪源和VE水平对肉质也有显著影响。其中,SO组肌肉鲜度和滋味强度较高;RO组鱼腥味较低;FO组肌肉亮度较高,气味强度较低。在200 mg/kg VE水平下,FO组肌肉硬度、胶黏性、耐咀性、黏性和回复性显著高于植物油组（<0.05）,而对肌肉蒸煮损失和滴水损失无显著影响（>0.05）。上述结果表明,相对于鱼油,豆油和菜籽油等植物油是罗氏沼虾更优质的脂肪源,VE在以鱼油为单一脂肪源的饲料中有一定的促生长和缓解应激的作用,且脂肪源和VE均显著影响肌肉品质。本研究结果将为降低鱼油在罗氏沼虾饲料中的使用提供数据支持。     

Nutritional regulation of gene expression and enzyme activity of phosphoenolpyruvate carboxykinase in the hepatic gluconeogenesis pathway in golden pompano (Trachinotus ovatus)

Phosphoenolpyruvate carboxykinase (PEPCK) is known to exist as mitochondrial (PEPCK‐M) and cytosolic isoforms (PEPCK‐C). They are involved in glucose production and play vital roles in regulating glucose homeostasis. This study aimed to (1) clone and characterize PEPCK‐C cDNA from golden pompano fish (Trachinotus ovatus), which are known to have poor utilization of dietary carbohydrates, and (2) analyze the regulation of its expression by varying dietary carbohydrate‐to‐lipid ratios and nutritional status. A full length golden pompano PEPCK‐C cDNA fragment of 2,652 bp was cloned, which contains an open reading frame of 1,875 bp encoding 624 amino acids and shows a high homology to cobia (Rachycentron canadum) PEPCK‐C sequence (92% similarity). The analysis of tissue distributions of PEPCK‐C mRNA showed that a high abundance of PEPCK‐C was expressed in golden pompano liver, followed by kidney; while lower expression levels were found in the heart and intestine. In liver, PEPCK is under the regulation of dietary composition and nutritional status at the enzymatic and molecular levels. Our results indicate that PEPCK‐C plays a modulating role in the adaptation of hepatic gluconeogenesis to different nutrient conditions. Thus, the absence of molecular inhibition of gluconeogenic PEPCK gene expression in rainbow trout (Oncorhynchus mykiss) and gilthead sea bream (Sparus aurata), which can at least partially account for their poor utilization of dietary carbohydrate, is specific to these species and is not observed in golden pompano. Further studies that examine, at the enzymatic and molecular levels, other key enzymes involved in hepatic glucose metabolism are necessary to understand the poor utilization of carbohydrates in golden pompano.     

水产动物锌营养生理及其与脂类代谢相关研究进展

锌是水产养殖动物必需的微量元素,维持着水产动物正常生长、发育和营养代谢等功能.为了深入解析锌调控水产动物营养物质代谢的机制,本文综述了水产动物饲料锌需求量及其影响因素、锌稳态调控系统中的关键蛋白(锌转运蛋白ZnTs和ZIPs家族、MTs和MTF-1)的结构特征和功能,锌对水产动物脂类代谢和沉积的影响以及相关机理的研究进...     

The influence of a dietary lipid source on growth, muscle fatty acid composition and erythrocyte osmotic fragility of hybrid tilapia

An 8-week feeding trial was conducted to determine the effects of various dietary lipids on the growth, tissue proximate composition, muscle fatty acid composition and erythrocyte osmotic fragility of red hybrid tilapia, Oreochromis sp. Five isonitrogenous and isoenergetic semipurified diets were supplemented with 10% of either cod liver oil (CLO), sunflower oil (SFO), crude palm oil (CPO), crude palm kernel oil (CPKO), or a combination of 5% CLO with 5% palm fatty acid distillates (PFAD), respectively. There were no significant effects (P > 0.05) of diet on growth but fish fed the CLO diet showed a significantly (P< 0.05) poorer feed efficiency ratio compared to fish fed the CPO diet. Lipid deposition in fish muscle was mostly similar among fish fed the various diets but bone ash was significantly higher in fish fed the CPO and CPKO diets. Muscle lipids of fish fed palm oil-based diets did not increase in saturated fatty acids content but showed significantly lower polyunsaturated fatty acid (PUFA) concentrations compared to fish fed the CLO diet. The concentrations of individual PUFA in muscle lipids were strongly influenced by dietary PUFA concentrations. Dietary lipids did not markedly affect the structural integrity of erythrocyte membranes but the erythrocytes of tilapia fed the CPO diet were slightly more resistant to osmotic lysis. It was concluded that palm oil products, especially CPO, could be successfully used in the diet of hybrid tilapia based on its availability, cheaper costs and its potential ability to enhance oxidative stability due to its low PUFA content and high natural concentrations of antioxidants.     

皮氏蛾螺肌肉营养成分分析与评价

采用生化手段对皮氏蛾螺肌肉中营养成分进行检测与分析。结果表明:皮氏蛾螺肌肉中水分含量为75.78%,蛋白质含量为15.70%,脂肪含量为0.50%,灰分含量为1.50%。皮氏嫂螺肌肉氨基酸总含量为58.21 g/100 g,共检测出17种氨基酸:半胱氨酸(Cys)含量最高,含量为11.35 g/100 g,其次是精氨酸(Arg)、天冬氨酸(Asp)和甘氨酸(Gly),组氨酸(His)含量最低,含量为0.39 g/100 g。共检测到6种呈味氨基酸,分别为天冬氨酸(Asp)、丝氨酸(Ser)、谷氮酸(Glu)、甘氨酸(Gly)、丙氨酸(Ala)及脯氨酸(Pro)。呈味氨基酸(DAA)总量为23.07 g/100 g。共检测出25种脂肪酸,其中包括9种饱和脂肪酸(SFA),16种不饱和脂肪酸(UFA)。在所有脂肪酸中,二十碳五烯酸EPA(C20:5i3)含量最高,达19.75%;而十五碳一烯酸(C15:1)含量最低,仅0.26%。     

Beneficial effects on growth,haematic indicators,immune status,antioxidant function and gut health in Juvenile Nile tilapia (Oreochromis niloticus) by dietary administration of a multi‐strain probiotic

The present study was conducted to administer a commercial multi‐strain probiotic (MP), Yilibao (Bacillus velezensis:Bacillus cereus:Lactobacillus casei = 2:2:1), in Nile tilapia, Oreochromis niloticus. In terms of aerobic Bacillus spp. counts, we produced five diets containing 0, 0.34, 1.68, 3.36 and 6.72 g/kg of MP dry product (Control, T1, T2, T3, T4). Seven hundred and fifty tilapia juveniles (13.26 ± 0.01 g) distributed into 25 tanks in five replications were fed their diet for eight weeks. Results showed that fish fed T3 and T4 diets displayed significantly higher final body weight and weight gain (p < .05). Further, all MP‐treated fish exhibited remarkably decreased plasma lipid profiles (cholesterol, triglycerides) (p < .05) and fish fed T3 and T4 diets displayed significantly higher plasma myeloperoxidase activity and complement C3 content (p < .05). Additionally, fish fed T3 and T4 diets exhibited significantly promoted total antioxidant capacity, glutathione peroxidase activity, glutathione level and declined malondialdehyde content in the plasma and/or liver (p < .05). Moreover, significantly elevated chymotrypsin activity, villus height and intraepithelial lymphocytes counts were found in fish fed T3 and T4 diets (p < .05). As fish fed T3 and T4 diets surpassed the other treatments in growth, immune–antioxidative status and gut health, the recommended dose for tilapia is 3.36–6.72 g/kg.