Mai Kangsen

Total lipid and fatty acid composition of eight strains of marine diatoms

Fatty acid composition and total lipid content of 8 strains of marine diatoms (Nitzschia frustrula, Nitzschia closterium, Nitzschia incerta, Navicula pelliculosa, Phaeodactylum tricornutum, Synedra fragilaroides) were examined. The microalgae were grown under defined conditions and harvested at the late exponential phase. The major fatty acids in most strains were 14∶0 (1.0%–6.3%), 16∶0 (13.5–26.4%), 16∶1n−7 (21.1%–46.3%) and 20∶5n−3 (6.5%–19.5%). The polyunsaturated fatty acids 16∶2n−4, 16∶3n−4, 16∶4n−1 and 20∶4n−6 also comprised a significant proportion of the total fatty acids in some strains. The characteristic fatty acid composition of diatoms is readily distinguishable from those of other microalgal groups. Significant concentration of the polyunsaturated fatty acid 20∶5n−3 (eicosapentaenoic acid) was present in each strain, with the highest proportion in B222 (19.5%).

Effects of harvest stage on the total lipid and fatty acid composition of fourCylindrotheca strains

Four strains ofCylindrotheca (B156, B164, B196, and B200) were harvested at three phases in the growth curve and their total lipid and fatty acid composition were determined. Total lipid reached highest values in the late stationary phase in B156 (24.0%), B164 (26.6%) and B200 (17.3%), in the exponential phase in B196 (15.5%). Saturated fatty acids increased with the development of the culture in B156 and B196, and reached their highest values in the late stationary phase in B156 (41.7%) and B196 (45.1%), in the early stationary phase in B164 (45.4%) and B200 (37.6%). Monounsaturated fatty acids increased with the development of the culture in B196 and B200, and reached their highest values in the late stationary phase in B196 (32.4%) and B200 (32.8%), in the early stationary phase in B164 (31.0%) and in the exponential phase in B156 (29.3%). Polynsaturated fatty acids decreased in the later phases of the culture in B164, B196 and B200, and peaked in the exponential phase in B164 (29.5%), B196 (42.9%) and B200 (37.3%), and in the early stationary phase in B156 (32.0%).

Dietary phosphorus requirement of young abaloneHaliotis discus Hannai Ino

An experiment was performed to determine the dietary phosphorus requirement of the young abalone,Haliotis discus hannai. Five semi-purified diets were formulated to provide a series of graded levels of dietary total phosphorus (0.23%–1.98) from monobasic potassium phosphate (KH2P04). The brown alga,Laminaria japonica, was used as a control diet. Similar size abalone were distributed in a single-pass, flow-through system using a completely randomized design with six treatments and three replicates each treatment. The abalone were hand-fed to satiation with appropriate diets in excess, once daily at 17:00. The feeding trial was run for 120-d. Survival rate and soft-body to shell ratio (SB/S) were constantly maintained regardless of dietary treatment. However, the weight gain rate (WGR), daily increment in shell length (DISL), muscle RNA to DNA ratio (RNA/DNA), carcass levels of lipid and protein, soft-body alkaline phosphatase (SBAKP), and phosphorus concentrations of whole body (WB) and soft body (SB) were significantly (ANOVA, P<0.05) affected by the dietary phosphorus level. The dietary phosphorus requirements of the abalone were evaluated from the WGR, DISL, and RNA/DNA ratio respectively, by using second-order polynomial regression analysis. Based on these criteria, about 1.0%–1.2% total dietary phosphorus, i.e. 0.9%–1.1% dietary available phosphorus is recommended for the maximum growth of the abalone.

EFFECT OF LIGHT INTENSITY ON THE TOTAL LIPID AND FATTY ACID COMPOSITION OF SIX STRAINS OF MARINE DIATOMS

The effect of light intensity (1500 lx and 5000 lx) on the total lipid and fatty acid composition of six strains of marine diatomsCylindrotheca fusiformis (B211),Phaeodactylum tricornutum (B114, B118 and B221)Nitzschia closterium (B222) andChaetoceros gracilis (B13) was investigated. The total lipids of B13, B114, and B211 grown at 5000 lx were lower than those grown at 1500 lx. No evident changes were observed in B118, B221 and B222. Fatty acid composition changed considerably at different light intensity although no consistent correlation between the relative proportion of a single FA and light intensity. The major fatty acids of the 6 strains were 14∶0, 16∶0, 16∶1 (n−7) and 20∶5(n−3).Cylindrotheca fusiformis had high percentage of 20∶4n–6(9.2–10.9%). The total polyunsaturated fatty acid in all 6 strains decreased with increasing light intensity. The percentage of the highly unsaturated fatty acid eicosapentaenoic acid (EPA) decreased with increasing light intensity in all strains exceptChaetoceros gracilis.

Availability of phosphorus from selected inorganic phosphate to juvenile abalone,Haliotis discus hannai ino.

The availability of phosphorus to juvenile abalone,Haliotis discus hannai from primary, secondary and tertiary calcium phosphate, primary sodium or potassium phosphate separately or in combination was determined in a 120-day feeding trial. Seven semi-purified diets were formulated to contain relatively constant dietary phosphorus, ranging from 0.78%–0.82%. The concentrations of dietary phosphorus were presumed to be slightly below the requirement for abalone. A brown alga,Laminaria japonica, was used as a control diet. Abalone juveniles of silimar size (average weight 1.18 g; average shell length 18.74 mm) were distributed in a single-pass, flow-through system using a completely randomized design with eight treatments and three replicates each treatment. The survival ranged from 71.1% to 81.1%, and was not significantly (P>0.05) related to dietary treatment. However, the weight gain rate (41.72%–65.02%), daily increment in shell length (36.87–55.07 μm) and muscle RNA-DNA ratio (3.44–4.69) were significantly (P<0.05) affected by dietary treatment. Soft body alkaline phosphatase activity (10.9–19.8 U/g wet tissue) and carcass levels of lipid (7.71%–9.33%) and protein (46.68%–49.35%) were significantly (P<0.05) responsive to available phosphorus of the diets. Dietary treatment had significant effect (P<0.05) on concentrations of phosphorus in the whole body (WB) and soft body (SB). Apparent digestibility coefficients (45%–97%) of phosphorus were also significantly (P<0.05) different between dietary treatments. The results indicated that among these inorganic compounds, primary calcium, potassium and sodium phosphates separately or in combination could be utilized effectively by juvenile abalone as dietary phosphorus sources (availability ranging from 87%–97%). However, secondary and tertiary calcium phosphates were found to be low in availability, the values being 45% and 77%, repectively.

Effects of phytase and non-starch polysaccharide enzyme supplementation in diets on growth and digestive enzyme activity for Japanese seabass, Lateolabrax japonicus C.

A feeding experiment was conducted to investigate the effects of dietary exogenous enzymes(Phytase,non-starch polysaccharide enzymes: WX and VP) on growth,body composition and digestive enzymes activitives of Japanese seabass,Lateolabrax japonicus C.(initial weight(6.26±0.10) g).A basal diet was used as the control(Diet 1),which contained 36.1% fish meal and 18.0% compound protein source(soybean meal∶meat and bone meal∶peanut meal∶rapeseed meal=4∶3∶2∶1,and crystalline lysine,methionine and isoleucine were supplemented to simulate the essential amino acid profile of fish meal).Two other diets were supplemented with 200mg phytase and the combination of 800mg WX and 400 mg VP per kilogram diet,respectively.Each diet was fed to triplicate groups of fish in seawater floating cages(1.5m×1.5m×2.0m),and each cage was stocked with 60 fish.Fish were fed twice daily(06:00 and 18:00) to apparent satiation for 8 weeks.The water temperature fluctuated from 27.5℃ to 29.5℃,the salinity from 25‰ to 28‰ and dissolved oxygen content was above 7mg / L during the experimental period.Results showed that exogenous enzymes supplementation did not significantly influence the survival of Japanese seabass(92%—95%),but significantly improved the growth(weight gain(WG) increasing from 859.3% to 947.2% and 905.2%,specific growth rate(SGR) from 4.0 to 4.2 and 4.1%/d)(p0.01).Dietary non-starch polysaccharide enzymes did not significantly affect the carcass moisture,crude protein,crude lipid,ash and gross energy of Japanese seabass.Dietary phytase also had no influence on the carcass moisture,crude lipid and gross energy of Japanese seabass,but significant influence on the carcass crude protein and ash(p0.05).The digestive enzymes activitives in stomach and intestine of fish supplemented with exogenous enzymes showed increasing trend when supplied with exogenous enzymes compared with the control group(Diet 1).The amylase activity of stomach and intestine significantly increasing from 0.05 to 0.16 U/mg and 0.12 to 0.21 U/mg respectively by the supplementation of non-starch polysaccharide enzyme(p0.01),but no significant differences in protease and lipase were observed.Similarly,dietary supplementation of phytase significantly increased the protease activity of stomach and intestine from 0.74 to 1.02 U/mg and 1.09 to 1.71 U/mg respectively(p0.01),but no significant differences in lipase and amylase were observed.

GROWTH PROMOTION OF RED SEA BREAM, PAGROSOMUS MAJOR, BY ORAL ADMINISTRATION OF RECOMBINANT EEL AND SALMON GROWTH HORMONE

Recombinant eel GH and yeast containing chinook salmon growth hormone (reGH and rcsGH) were incorporated into gelatin and sodium alginate (reGH-GS and rcsGH-GS) or polymer matrix (reGH-HP55) to protect the hormone from proteolytic cleavage in the stomach. The diets containing reGH-GS, rcsGH-GS, reGH-HP55 and free-reGH or uncoated-rcsGH were administered to red sea bream. Feeding of reGH-GS, reGH-HP55 and rcsGH-GS diets resulted in significant increases in body weight and fork length over those of controls. These results strongly suggest that gelatin and sodium alginate as well as polymer matrix protected the hormone from proteolytic enzymes in the gastrointestinal tract to allow the bioactive hormone to enter the circulation and eventually stimulate fish growth.

饲料中添加甘氨酸可提高大黄鱼(Larimichthys crocea)的抗氧化和抗应激能力

为研究饲料甘氨酸对大黄鱼 (Larimichthys crocea) 抗氧化和抗应激反应的影响，将初始体重为 (130.35±8.37) g的大黄鱼随机分成6组，每组3个重复，每个重复 (网箱) 50尾鱼。在基础饲料中分别添加不同梯度的甘氨酸 (0、0.6%、1.2%、2.4%、4.8%和6.0%)，配制出甘氨酸实测含量分别为 (1.58%、2.15%、2.75%、3.96%、6.33%和7.51%) 的6种实验饲料。经过30 d养殖后，对大黄鱼进行拖网应激实验。结果表明，养殖实验结束后，饲料处理未对大黄鱼的存活和体成分产生显著影响。肝脏总抗氧化能力在饲料甘氨酸含量为2.75%时达到最大值，而丙二醛的含量在甘氨酸含量为3.96%时达到最小值，但与2.75%组无显著差异 (P > 0.05)。以肝脏总抗氧化能力为评价指标，根据二次曲线回归模型得出大黄鱼饲料中甘氨酸的适宜含量为3.57%。血清谷草转氨酶和谷丙转氨酶的活性均在饲料甘氨酸含量为2.75%时呈现最小值 (P < 0.05)。在拖网应激前，饲料甘氨酸含量为2.75%时，大黄鱼血清皮质醇的含量最高。在拖网应激后，该处理的大黄鱼血清皮质醇的变化幅度最小，而此时的血糖维持在较高水平。综合考虑大黄鱼的抗氧化和抗应激能力，本研究推荐大黄鱼饲料中甘氨酸的适宜含量为2.75%-3.57%。

Dietary pyridoxine requirement for juvenile cobia (Rachycentron canadum).

Vitamin B6 or pyridoxine in the form of pyridoxal phosphate participates as a prosthetic group of enzymes in a large number of metabolic reactions,particularly those associated with the metabolism of proteins and amino acids. With the success of artificial propagation and larval production,the culture of cobia becomes widely distributed in southern coastal provinces of China(especially in Guangdong and Hainan Provinces) as well as Southeast Asia. However,currently the growth of cobia heavily depends on trash fish and the development of formulated feeds for cobia is still in its infancy. The objective of this study is to detect the optimal requirement of pyridoxine in diet of juvenile cobia Rachycentron canadum.Basal diet was formulated using vitamin-free casein,gelatin and fish protein concentrate as the protein source. The graded levels of PN(0,2,4,8,16 and 32 mg/kg diet) were added to the basal diets to formulate six experimental diets containing 0.22,1.89,3.87,7.54,14.75 and 29.88 mg PN/kg diet,analyzed by HPLC,respectively. Each diet was fed to three replicate groups of cobia in 300 L tanks for 9 weeks,and each tank was stocked with 25 fish [initial weight (3.23±0.06) g]. The water salinity was from 30 to 34,temperature fluctuated from 28 to 32 ℃ and dissolved oxygen was above 7 mg/L. The results showed that specific growth rate(SGR) have an increasing trend with the increase of dietary pyridoxine(from 0.22 to 3.87 mg/kg),but no significant differences were observed among diets containing 3.87 mg/kg PN or above. The contents of PN and AST in liver of fish fed diets with 3.87 mg/kg were significantly higher than the treatments with the contents of PN lower than 3.87 mg/kg,however,there were no significant differences among diets containing 3.87-29.88 mg/kg PN. The contents of PLP and the activities of ALT of the diet containing 7.54 mg/kg PN were significantly higher than the diets containing PN7.54 mg/kg,however,no significant differences were discovered among diets containing PN7.54 mg/kg. The dietary pyridoxine requirement was estimated to be 3.09-3.26 mg/kg by the broken-line model based on the SGR,and the activities of ALT in fish liver.