Effect of dietary protein and lipid level on metabolic utilization of diets by european sea bass (Dicentrarchus labrax) juveniles

Two trials were performed with sea bass juveniles to study the effect of dietary protein (trial I) and lipid (trial II) levels on the metabolic utilization of diets at 25 °C. The effect of water temperature (18 and 25 °C) on metabolism was also tested in trial I. For that purpose, oxygen consumption and ammonia excretion were measured both in fed and in 9-days starved fish. In trial I, diets were formulated to be isoenergetic (GE: 19.4 kJ g^–1) and to have 36, 42, 48 and 56% protein; in trial II, diets were formulated to be isonitrogenous (48% protein) and to have 12, 18, 24 and 30% lipid. In trial I, feed intake (g kg^–1 day^–1), and daily ammonia excretion and oxygen consumption significantly increased with water temperature. However, when expressed relatively to intake there was no significant effect of temperature on ammonia excretion (% N intake) or heat production (% GE intake). Heat increment of feeding (% GE intake) was neither affected by diet composition nor by water temperature. The relative contribution of protein catabolism to total energy expenditure significantly increased with dietary protein level, but was not affected by water temperature. In trial II, both daily ammonia excretion and oxygen consumption were inversely correlated to dietary lipid levels. Nitrogen excretion, heat production, heat increment of feeding, non-fecal losses (% intake) and the relative contribution of protein to total energy expenditure were also inversely related to dietary lipid levels. Results of this study indicate that the main effect of water temperature was to modify feed intake, not the metabolic utilization of diets. Indeed, expressed relatively to nitrogen or energy intakes, both nitrogen and energy budgets were not significantly affected by water temperature. A decrease of dietary protein to energy ratio, by modifying either dietary protein or lipid levels, spared protein utilization for metabolism, and this effect was essentially due to a decrease of non-fecal nitrogen excretion and of the heat increment of feeding.     

Essential fatty acid enrichment of cultured rotifers (Brachionus plicatilis, Müller) using frozen-concentrated microalgae

There is a growing interest in preserving microalgal preparations to maintain constant properties over a long period. The aim is to ensure sufficient delivery of essential fatty acids (and other key nutrients) to mollusc and crustacean larvae and to zooplankton used as live prey in the first feeding of fish larvae. For example, the rotifer Brachionus plicatilis has to be enriched with polyunsaturated fatty acids (PUFA) prior to fish feeding. We used four microalgal species [ Isochrysis galbana (T-ISO), Chaetoceros muelleri (CHGRA), Pavlova lutheri (MONO), and Nannochloropsis sp.] both as fresh culture or in a frozen-concentrated form to enrich rotifers. Overall, rotifers had similar relative fatty acid levels when fed the frozen-concentrated or fresh microalgal diets. The levels of 20:4n-6, 22:6n-3, and 20:5n-3 between B. plicatilis and the microalgal diets were linearly correlated. The fatty acid 20:4n-6 was the most readily assimilated: the content found in rotifers reached half the level measured in the microalgal diets. Our results indicate that both the fresh and frozen-concentrated forms of the four microalgal species can be used to enrich PUFA levels in rotifers. Further experiments should be conducted to test if assimilation differs when rotifers are enriched with mono- or multispecific microalgal preparations.     

Seasonal variations in muscle growth dynamics and selected quality attributes in Atlantic halibut (Hippoglossus hippoglossus L.) fed dietary lipids containing soybean and/or herring oil under different rearing regimes

Atlantic halibut (Hippoglossus hippoglossus), 1630 ± 510 g at the start of the experiment were reared in tanks for 1 year and subjected to three different environmental regimes; Continuous light and Constant temperature (CC), Natural light and Constant temperature (NC) or Natural light and Ambient temperature (NA). Two diets were fed, where 50% of the dietary lipids were either herring oil or soybean oil supplemented. The fish were sampled in May, August and November the first year, and February and May the following year. The CC groups grew better than the NC and NA groups from May to November, and as a result had a significantly (p < 0.05) higher weight by the end of the experiment. This difference did however not affect muscle fibre size distribution, or the chosen muscle quality attributes texture, fat content, water or fat loss of the fillet. These quality attributes were influenced by season and body weight, whereas diet had no significant effect. The NA group had lower fat content of the fillet than the other environmental regimes in August, November and May_end, and fat content increased with increasing fish weight. Water and fat losses were lowest in November and February. The diet influenced the fatty acid profile of the musculature; the triacylglycerol fraction reflecting the dietary treatment while the polar fraction was less influenced by diet. The hardness of the fillet was not influenced by the environmental regimes, but by season, and hardness was at its lowest in August, and increased towards the following spring. The muscle fibre distribution varied only with season, and neither treatment nor diet had any effect on the muscle growth dynamics. Recruitment of new fibres seemed mainly to occur during winter, signified by maximum occurrence of fibres < 500 μm² by the end of the experiment in May.     

Effects of different dietary lipid sources in the diet for Pangasius nasutus (Bleeker, 1863) juveniles on growth performance,feed efficiency,body indices and muscle and liver fatty acid compositions

Four isonitrogenous (300 g kg^?1 crude protein), isoenergetic (21 kJ g^?1) experimental diets were formulated to contain fish oil (FO), soybean oil (SBO), crude palm oil (CPO) and linseed oil (LO), respectively, as the lipid sources, added at 120 g kg^?1 of crude lipid each. The diets were fed by hand to triplicate groups of Pangasius nasutus (Bleeker, 1863) juveniles (mean weight 10.66 ± 0.04 g), to apparent satiation twice daily for 12 weeks. Fish survival rate was 100% among all the treatments. Growth performance (DGR) was similar among fish fed the SBO, CPO and LO diets, but was significantly (P < 0.05) higher in the CPO compared to fish fed the control (FO) diet. Fish fed SBO and CPO diets also recorded significantly (P < 0.05) higher intraperitoneal fat compared to fish fed the control, whereas fish fed the LO diet did not significantly differ from the other treatments. Muscle and liver fatty acid profile of fish from all the treatments generally mirrored the composition of the diets fed and the major fatty acids recorded were 18:3n‐3 and 18:2n‐6 in the tissues of fish fed the LO and SBO treatments, respectively. Results of this study suggests that P. nasutus fed diets containing vegetable oils (especially CPO and SBO) produce better growth performance, without compromising fish survival and feed efficiency compared with those fed a diet containing only FO.     

Influence of one selected Tisochrysis lutea strain rich in lipids on Crassostrea gigas larval development and biochemical composition

Effects of a remarkably high overall lipid Tisochrysis lutea strain (T+) upon gross biochemical composition, fatty acid (FA), sterol and lipid class composition of Crassostrea gigas larvae were evaluated and compared with a normal strain of Tisochrysis lutea (T) and the diatom Chaetoceros neogracile (Cg). In a first experiment, the influence of different single diets (T, T+ and Cg) and a bispecific diet (TCg) was studied, whereas, effects of monospecific diets (T and T+) and bispecific diets (TCg and T+Cg) were evaluated in a second experiment. The strain T+ was very rich in triglycerides (TAG: 93–95% of total neutral lipids), saturated FA (45%), monounsaturated FA (31–33%) and total fatty acids (4.0–4.7 pg cell^?1). Larval oyster survival and growth rate were positively correlated with 18:1n‐7 and 20:1n‐7, in storage lipids (SL), and negatively related to 14:0, 18:1n‐9, 20:1n‐9, 20:4n‐6 and trans‐22‐dehydrocholesterol in membrane lipids (ML). Surprisingly, only the essential fatty acid 20:5n‐3 in SL was correlated positively with larval survival. Correlations suggest that physiological disruption by overabundance of TAG, FFA and certain fatty acids in larvae fed T+ was largely responsible for the poor performance of these larvae. ‘High‐lipid’ strains of microalgae, without regard to qualitative lipid composition, do not always improve bivalve larval performance.     

Abundance and origins of plasma lipids in sexually maturing female coho salmon Oncorhynchus kisutch (Walbaum) in culture

Coho salmon Oncorhynchus kisutch are semelparous spawners with highly synchronized oocyte growth. Plasma was collected from maturing female fish and plasma lipids were quantified by lipoprotein class. Stable ¹³C isotopes were employed to investigate the origins of plasma lipids. Plasma lipoproteins were partitioned into the very low density (VLDL), low density (LDL), high density (HDL) and very high density (VHDL) lipoprotein classes. Lipids from all lipoprotein classes increased between the lipid droplet and early vitellogenesis stages of oocyte growth and VHDL lipids continued to increase through mid vitellogenesis (P < 0.05). During vitellogenesis, total plasma lipid concentrations were similar to the sum of lipoprotein lipids (P = 0.51). Plasma vitellogenin determined by an ELISA method was very well correlated with VHDL lipid during vitellogenesis (R² = 0.91, n = 15). In general, the δ¹³C values of plasma lipids reflected that of feed (exogenous) and muscle (endogenous) lipids when feed and muscle δ¹³C values were similar, and were intermediate when differences existed between the two lipid sources. With one exception, the δ¹³C values of lipids from all lipoprotein classes within a plasma sample were similar. Results indicate that during sexual maturity, lipids from all plasma lipoprotein classes originate from a common pool of exogenous and endogenous lipids.     

Nutrient evaluation of rotifers and zooplankton: feed for marine fish larvae

The objective of this study was to examine the biochemical composition of intensively reared rotifers after enrichment with three commonly used enrichment media, Multigain, Ori‐Green and DHA‐enriched freshwater algae Chlorella, using standard enrichment protocols at a local cod larvae producer and compare it with that of natural zooplankton from Lofilab AS, a cod larvae producer using semi‐intensive rearing techniques. Unenriched rotifers were analysed to examine whether the enrichment procedures were successful in increasing the content of essential nutrients to level requirements for marine fish larvae. Neither total lipids nor proteins were affected by enrichment. Unenriched rotifers were significantly lower in highly unsaturated fatty acids (HUFAs) and significantly higher in linoleic acid (LA, C18:2, n‐6), than were zooplankton. Enrichment with Chlorella and Multigain increased the HUFAs significantly, while they were slightly reduced after enrichment with Ori‐Green. Total amino acids and mineral content were unaffected by enrichment. Zooplankton was rich in taurine and selenium, whereas rotifers were devoid of it, both prior to and after enrichment. Using zooplankton as a reference for the nutritional requirements of marine fish larvae, results from this study demonstrate that enrichment media currently in use are not effective for enhancing the nutritional quality of rotifers.     

Lipid droplet distribution of immature canine oocytes in relation to their size and the reproductive stage

This study investigated the distribution of lipid droplets (LD) in immature canine oocytes in relation to their size and the reproductive stage. Oocytes were collected from the ovaries of bitches at different estrous stages, divided according to their size (110‐120 µm; >120 µm), and stained with Nile Red to detect lipid droplet distribution. At the follicular phase most of the oocytes displayed a diffuse pattern of LD distribution, whereas at anestrus and luteal phase oocytes showed LD mainly in a peripheral/ perinuclear LD distribution. A significantly higher intensity of LD has been recorded in the oocytes > 120 µm compared to those of smaller size (110 ‐ 120 µm) at all stages of the estrous cycle. At follicular phase, oocytes > 120 µm displayed LD intensity similar to that of oocytes > 120 µm at luteal phase and higher compared to the oocytes of the other groups.     

三七生境研究进展

目的探究三七茎和叶水提物对高脂饮食小鼠血脂血糖参数的影响以及对高脂饮食诱导的肝损伤和胰岛素抵抗的影响。方法30只7~8周龄雄性C57BL/6J小鼠,随机均分为3大组：对照组（CON）、三七茎水提物组(PNS)和三七叶水提物组(PNL)。三七茎和叶水提物以5 g/L的量溶于自来水,灭菌后供小鼠自由饮用,小鼠饲喂高脂饲料16周,每周定时称量小鼠体质量、测定小鼠空腹血糖。小鼠处死前1周测定胰岛素耐量(ITT),解剖时取血浆测定甘油三酯(TG)、总胆固醇(CHOL)、高密度脂蛋白(HDL-C)、低密度脂蛋白(LDL-C)、谷草转氨酶(AST)和谷丙转氨酶(ALT)水平,取小鼠皮下脂肪、附睾脂肪和肝脏称质量,同时对肝脏进行拍照。结果三七茎和叶水提物对小鼠体质量和脂肪系数没有显著影响(P>0.05),但能够显著降低高脂饮食小鼠的TG、CHOL、LDL-C、AST和ALT等参数(P<0.05),对高脂饮食诱导的脂肪肝也有明显的改善作用。此外,还能够在一定程度上改善胰岛素敏感性。结论三七茎和叶水提物能显著改善高脂饮食饲养小鼠的血脂血糖参数。     

不同动物油脂对大鼠血糖血脂及血液相关因子的影响研究

研究羊油、猪油、牛油、马油4种油脂对大鼠血糖、血脂及血液相关因子的影响研究。130只雄性健康SD大鼠随机分为对照组、羊油脂组、猪油脂组、牛油脂组和马油脂组共5组。各油脂组再分为高（2mL／100g体重）、中（1mL／100g体重）、低（0．5mL／100g体重）剂量3个灌胃组,对照组灌胃纯净水（1mL／100g体重）。灌胃56d后,测定各组动物体重、内脏脂肪重量、血糖（GLU）、血脂4项[高密度脂蛋白（HDL-C）、低密度脂蛋白（LDL-C）、胆固醇（TC）、甘油三酯（TG）3的变化以及脂代谢相关血液因子[血浆胰岛素（INS）、瘦素（LEP）、一氧化氮（NO）、超氧化物歧化酶（SOD）和丙二醛（MDA）]的变化。结果表明,与对照相比,4种油脂对大鼠的体重、LEP、NO影响不明显（P〉0．05）;4种动物油脂的高剂量组以及猪油脂和马油脂的中剂量组均能显著增加内脏脂肪的重量（P〈0．05）;羊油脂中剂量组、马油脂高剂量和中剂量组的GLU值均极显著升高（P〈0．01）;羊油脂高剂量组HDL—C水平显著升高（P〈0．05）,猪油脂高剂量组HDL—C水平极显著升高（P〈0．01）;牛油脂高剂量组LDL—C水平显著升高（P〈0．05）;牛油脂和马油脂的各剂量组TC水平均极显著升高（P〈0．01）;仅羊油脂高剂量组TG水平显著升高（P〈0．05）;马油脂的高、中剂量组的血浆INS水平极显著降低（P〈0．01）;羊油脂和猪油脂的各剂量组MDA水平均极显著升高（P〈0．01）;牛油脂和马油脂的各剂量组SOD水平均极显著升高（P〈0．01）;4种油脂对大鼠的体重、血浆LEP、血浆NO没有明显影响;灌服猪油脂对大鼠GLU水平影响不明显;灌服高剂量羊油脂可明显升高大鼠血液HDL-C和TG水平;猪油脂主要表现为升高HDL-C水平;而牛油脂和马油脂各剂量组则可极显著升高血浆总胆固醇。羊油脂和猪油脂均能升高大鼠的MDA水平;牛油脂和马油脂均能升高大鼠的SOD水平,推测牛油脂和马油脂具有抗氧化的作用。