Growth performance and metabolic utilization of diets including starch,dextrin, maltose or glucose as carbohydrate source by gilthead sea bream (<Emphasis Type="Italic">Sparus aurata</Emphasis>) juveniles

The effect of dietary carbohydrate complexity on growth, feed utilization and activity of selected key liver enzymes of intermediary metabolism were studied in gilthead sea bream juveniles. Four isonitrogenous (50% crude protein) and isolipidic (16% crude lipids) diets were formulated to contain 20% of pregelatinized maize starch, dextrin, maltose or glucose. Triplicate groups of fish (117 g initial weight) were fed each diet to near satiation during 6 weeks. No effect of dietary carbohydrate on growth was noticed. Feed efficiency was lower in fish fed the glucose diet than the maltose and dextrin diets. The lowest protein efficiency ratio was observed in fish fed the glucose diet. Six hours after feeding, glycemia was higher in fish fed the glucose diet than the maltose and starch diets. Liver glycogen content was unaffected by dietary carbohydrate complexity. Hepatic glucokinase (GK) activity was higher in fish fed the glucose and the maltose diets, while higher pyruvate kinase (PK) activity was recorded in fish fed the glucose diet than in fish fed the starch diet. Fructose-1,6-bisphosphatase (FBPase) and glucose-6-phosphate dehydrogenase (G6PD) activities were higher in fish fed the starch diet compared to dextrin and glucose diets. Data suggest that dietary glucose and maltose are more effective than complex carbohydrates in enhancing liver glycolytic activity. Dietary glucose also seems to be more effective than starch in depressing liver gluconeogenic and lipogenic activities. Overall, dietary maltose, dextrin or starch was better utilized than glucose as energy source by gilthead sea bream juveniles.     

Effects of dietary carbohydrate sources on the growth performance and hepatic carbohydrate metabolic enzyme activities of juvenile cobia (Rachycentron canadum Linnaeus.)

An 8-week feeding trial was conducted to evaluate the effect of dietary carbohydrate sources on the growth performance and hepatic carbohydrate metabolic enzyme activities of juvenile cobia. Six experimental diets were formulated to contain 20% glucose, sucrose, maltose, dextrin, corn starch and wheat starch respectively. The results indicated that fish fed the wheat starch and dextrin diets showed significantly better weight gain, specific growth rate and protein efficiency ratio compared with those fed the other diets. However, fish fed the glucose diet had a significantly lower survival and condition factor than those fed the other diets. There were significant differences in the total plasma glucose and triglyceride concentration in fish fed diets with different dietary carbohydrate sources. Haematocrit, haemoglobin, red blood cell and leucocytes were significantly affected by the dietary carbohydrate sources. The activities of glucose-6-phosphate dehydrogenase (G6PD), 6-phosphofructokinase (PFK) and fructose-1,6-bisphosphatase (FBPase) were significantly affected by the dietary carbohydrate sources, while fish fed the glucose diet showed higher G6PD, PFK and FBPase activities than those fed the other diets. These data indicated that dextrin and wheat starch were the most optimal carbohydrate sources for juvenile cobia.     

Hepatic enzyme adaptation to different dietary carbohydrates in juvenile tilapiaOreochromis niloticus xO. aureus

The influence of two carbohydrates, starch and glucose, on hepatic enzyme activities of juvenile tilapia,Oreochromis niloticus xO. aureus, were investigated. Fish were fed either starch or glucose diet solely for 12 weeks or fed either starch or glucose diet for the first 6 weeks and then switched the diet each other for the last 6 weeks. Fish fed only the starch diet gained more (p < 0.05) body weight, had better feed conversion, higher protein deposition and energy retention values than fish fed the glucose diet. These parameters generally decreased in fish when the starch diet was fed first and then switched to the glucose diet, or increased in fish when the glucose diet was fed first and then switched to the starch diet. The starch — fed fish had higher body lipid content than glucose — fed fish. Body lipid decreased in fish transferred from the starch to glucose diet orvice versa when fish were transformed from the glucose to the starch diet. Hepatic hexokinase, phosphofructokinase, and glucose-6-phosphatase activities in fish were not affected by the different dietary regimes. Malic enzyme (ME), glucose-6-phosphate dehydrogenase (G-6-PD) and phosphogluconate dehydrogenase (PGD) activities were higher in the fish fed the starch diet than in those fed the glucose diet. Changing the diet from starch to glucose decreased ME, G-6-PD and PGD activities, whereas, changing the diet from the glucose to the starch increased these enzyme activities in fish liver. These results suggest that lipogenic enzyme activity can adapt to dietary carbohydrates in the fish liver.     

Effects of Dietary Carbohydrate Source and Level on Growth,Feed Utilization,and Body Composition of the Humpback Grouper,Cromileptes altivelis (Valenciennes)

Six diets were formulated to contain corn starch, tapioca starch, or dextrin at 10% and 20% inclusion levels and fed to humpback grouper fingerlings to apparent satiation for 10 weeks. Growth and feed utilization efficiency of humpback grouper were not affected by dietary carbohydrate source and level. Only slightly higher growth was observed in fish fed 20% dietary carbohydrate compared to the fish fed 10% carbohydrate irrespective of carbohydrate source. Body indices and whole body proximate composition of fish in the present study were generally independent of diet, except that muscle lipid of fish fed diets with 7.6% lipid and 20% carbohydrate was significantly lower than the other groups. In view of the lower price and local availability of tapioca starch compared to corn starch and dextrin, tapioca starch is the preferred source of starch in practical diets for humpback grouper.     

Effects of high carbohydrate and high lipid diets on growth,body composition and glucose metabolism in southern catfish at two temperatures

The effects of high carbohydrate and high lipid diets on the growth, body composition and glucose metabolism in the southern catfish were determined at 17.5 °C and 27.5 °C. At each temperature, the feeding rate, specific growth rate and protein productive value decreased with increasing dietary carbohydrate (P<0.05). Feed efficiency and protein efficiency ratio were lower in the fish fed a high dietary carbohydrate diet at 17.5 °C, but were not significantly different between diets at 27.5 °C. Plasma glucose and activities of pyruvate kinase and glucose‐6‐phosphate dehydrogenase were higher in fish reared at 27.5 °C than those reared at 17.5 °C, and within each temperature, they were higher in fish fed the high‐carbohydrate diet. Hepatosomatic index was higher in fish fed the high‐carbohydrate diet than those fed the high‐lipid diet at 27.5 °C, but no significant difference was found at 17.5 °C. The results indicate that higher temperatures enhance glycogen deposition and lipogenous enzyme activities when fed with a high‐carbohydrate diet; thus, at higher temperatures, this fish uses carbohydrate more efficiently for protein sparing.     

饲料中不同蛋白质和淀粉水平对斜带石斑鱼生长性能和肝脏相关代谢酶活性的影响

为了探讨饲料蛋白质和碳水化合物对斜带石斑鱼的互作效应,实验采用3×3因子设计,配制蛋白质水平(P)为38%、45%和52%,淀粉水平(S)为10%、20%和30%的9种实验饲料,分别饲喂斜带石斑鱼56 d。结果显示,38%粗蛋白与10%淀粉饲料组(38P/10S饲料组)增重率显著低于其他各组,52P/10S组增重率最高,但与45P/20S、45P/30S、52P/20S组差异不显著。增加饲料蛋白质或淀粉水平显著增加饲料效率、鱼体蛋白质与脂肪含量及肝糖原肝脂含量,而降低摄食率和鱼体水分含量。增加饲料蛋白质水平降低蛋白质效率,但增加淀粉水平却增加蛋白质效率及肝体比与脏体比。饲料蛋白质水平和淀粉水平对鱼体灰分含量无明显影响。肝中肝酯酶、脂蛋白酯酶、脂肪酸合成酶、谷丙转氨酶和谷草转氨酶活性均随蛋白质或淀粉水平的升高呈显著上升趋势。增加饲料蛋白质水平显著降低肝中葡萄糖-6-磷酸酶活性,而增加肝中苹果酸酶活性,但对肝中葡萄糖激酶、丙酮酸激酶、磷酸果糖激酶、磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸脱氢酶活性没有明显影响。增加饲料淀粉水平显著增加肝中葡萄糖激酶、丙酮酸激酶、磷酸果糖激酶、葡萄糖-6-磷酸脱氢酶和苹果酸酶活性,但显著降低磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸酶活性。上述结果显示,斜带石斑鱼的生长和肝脏代谢明显受饲料蛋白质和淀粉水平的影响,其中,糖代谢酶活性受淀粉水平的影响较大,而受饲料蛋白质水平的影响较小,斜带石斑鱼生长适宜的饲料蛋白质和淀粉水平分别为45%和20%。     

Effects of dietary glucose and starch levels on the growth,haematological indices and hepatic hexokinase and glucokinase mRNA expression of juvenile mirror carp (Cyprinus carpio)

The effect of the different dietary carbohydrate types and levels on growth performance, haematological indices and hepatic hexokinase (HK) and glucokinase (GK) genes expression involved in control of glucose metabolism, was studied in juvenile mirror carp (Cyprinus carpio). Two carbohydrates (glucose and starch) diets with two levels (250 and 500 g kg^?1) were fed to triplicate groups of 35 fish for 60 days. The best weight gain rate and specific growth rate were observed in fish fed with 250 g kg^?1 glucose diet and 500 g kg^?1 starch diet (P < 0.05). Fish fed with 500 g kg^?1 glucose showed low feed utilization, with the highest food conversion ratio and the lowest protein efficiency ratio (P < 0.05). Hepatosomatic index was significantly higher in fish fed with glucose diets and the 500 g kg^?1 starch diet compared to 250 g kg^?1 starch. CHOL, HDL‐C and LDL‐C were significantly highest in fish fed with 500 g kg^?1 starch than all other diets (P < 0.05). Hepatic GK mRNA expression level and activity were positively related to glucose and starch levels (P < 0.05). Correlation analysis showed that hepatic glycogen concentration was increased by dietary carbohydrate content (P < 0.05). These results suggest that GK may play a major role in the postprandial glucose utilization in juvenile mirror carp.     

Growth,Feed Utilization,and Glycemic Response in European Sea Bass,Dicentrarchus labrax,Juveniles Fed Carbohydrate of Different Complexities

The effect of dietary carbohydrate complexity on growth, feed utilization, and glycemia was studied in European sea bass juveniles. Four isonitrogenous (50% crude protein) and isolipidic (15% crude lipids) diets were formulated to contain 20% pregelatinized maize starch (PGS diet), dextrin (DEX diet), maltose (MAL diet), or glucose (GLU diet). No effect of dietary carbohydrate complexity on growth was noticed. Feed efficiency and protein efficiency ratio were lower in fish fed the GLU diet than in the other groups, whereas the opposite was observed for feed intake. Plasma glucose peaked 3–4 h after feeding in fish fed the MAL and GLU diets, whereas in fish fed the PGS and DEX diets the peak was reached 5–6 h after feeding. Peak plasma glucose concentration (13 mmol/L) was higher in fish fed the GLU diet than the other diets (9 mmol/L). Shorter hyperglycemia duration was observed in fish fed the MALT and GLU diets (6 h) than the PGS and DEX diets (10 h). Complex carbohydrates delayed plasma glucose concentration peak compared with simple sugars, whereas the opposite was observed for hyperglycemia duration. Overall, dietary maltose, dextrin, and starch were apparently better utilized as energy source than glucose by European sea bass juveniles.     

饲料中三种不同碳水化合物对大黄鱼生长性能和肝脏糖代谢关键酶活性的影响

为研究饲料中添加3种不同的碳水化合物对大黄鱼生长性能、饲料利用以及糖代谢关键酶活性的影响,进行为期8周的生长实验和持续24 h的饥饿实验。以葡萄糖、小麦淀粉和糊精这3种碳水化合物作为糖源,设计3组等氮等脂(48%粗蛋白和12%粗脂肪)的饲料。选用初始体质量为(8.51±0.02)g的大黄鱼450尾,随机分为3组(每组3个重复,每个重复50尾)。养殖实验结束后进行饥饿实验,分别在饥饿实验开始后的0、1、3、5、7、9、11和24 h取样。结果显示,小麦淀粉组和糊精组大黄鱼的增重率和特定生长率显著高于葡萄糖组,且这2个饲料组的饲料系数显著低于葡萄糖组。糊精组大黄鱼的肝体比显著高于其余2组大黄鱼的肝体比。饲料中添加3种不同碳水化合物对大黄鱼成活率、脏体比和肥满度无显著性影响。葡萄糖组和小麦淀粉组大黄鱼血糖含量在饥饿1 h后都开始显著上升,葡萄糖组高血糖水平持续至少10 h;小麦淀粉组3 h显著下降至初始水平左右,未达到高血糖水平;糊精组大黄鱼血糖含量随着时间的推移持续升高,在11 h达到最大值,高血糖水平持续4 h。饲料中添加3种不同碳水化合物对大黄鱼血清胰岛素和肝糖原含量有显著性影响。小麦淀粉对大黄鱼肝脏葡萄糖激酶(GK)活性的升高有诱导作用。大黄鱼摄食3种不同碳水化合物饲料后鱼体血糖水平升高,但糖异生关键酶如葡萄糖-6-磷酸酶(G6Pase)、果糖-1,6-二磷酸酶(FBPase)和磷酸烯醇式丙酮酸羧激酶(PEPCK)的活性并不降低。饲料中添加葡萄糖和小麦淀粉对大黄鱼肝脏丙酮酸激酶(PK)活性有显著性影响。研究表明,大黄鱼利用结构复杂的多糖(如小麦淀粉和糊精)的能力要高于单糖(如葡萄糖),3种不同碳水化合物对大黄鱼血糖调节及糖酵解和糖异生途径关键酶活性的影响存在差异。     

黄鳍鲷幼鱼对几种不同糖源的利用

本研究用来评价黄鳍鲷幼鱼对饲料中葡萄糖、麦芽糖、糊精、玉米淀粉和预糊化玉米淀粉的利用。本试验饲料为6种等氮(粗蛋白:45%,干重)等脂(粗脂肪:9%,干重)的半纯化饲料,其中对照组糖源为纤维素。每种饲料设3个平行。试验鱼初始体重为(3.57±0.13)g(平均值±均差)。试验鱼饲养在含18个水族箱的循环系统中。水温保持在(27±1)℃。试验周期为8周。本试验用来评价黄鳍鲷幼鱼对饲料中不同糖源利用的指标为生长指标、饲料效率、蛋白质效率和肝脏的6-磷酸葡萄糖脱氢酶、苹果酸脱氢酶、异柠檬酸脱氢酶和葡萄糖-6-磷酸脱氢酶。试验结果表明,黄鳍鲷幼鱼体增重、特定生长率、肝体比、肠系膜脂肪体比、饲料效率、蛋白质效率、肝脂肪合成有关酶活性和全鱼、肌肉、肝脏组成均受到饲料中不同糖源的显著影响。预糊化玉米淀粉和麦芽糖组比其它糖源组显著具有更好的体增重和特定生长率,但与对照组没有显著性差异。黄鳍鲷幼鱼生长和体增重与饲料中糖源的复杂性没有相关性。饲喂预糊化淀粉和对照饲料鱼的饲料效率和蛋白质效率显著比其它组高。饲料中糖的添加增加了黄鳍鲷幼鱼的肝体比,但对照组肝体比与糊精组,玉米淀粉组没有显著性差异。预糊化玉米淀粉组肠系膜脂肪体比比其它饲料组要高。结论:基于体增重和特定生长率为指标,饲料中添加25%预糊化玉米淀粉和麦芽糖可以提高黄鳍鲷幼鱼的生长。另外,玉米淀粉预糊化显著提高了黄鳍鲷对玉米淀粉的利用。     

Water temperature does not affect protein sparing by dietary carbohydrate in Senegalese sole (Solea senegalensis) juveniles

The effect of dietary protein reduction balanced by an increase in carbohydrate (starch) level on growth performance, feed utilization and intermediary metabolism of Senegalese sole juveniles was evaluated at two temperatures, 12 and 18°C. For that purpose two isolipidic (16% lipids) diets were formulated to contain 550gkg^?1 protein and 90gkg^?1 starch (diet HP:LC), and 450gkg^?1 protein and 200gkg^?1 starch (diet LP:HC). Each experimental diet was fed to triplicate groups of 20 fish (initial body weight: 15.9g) within each temperature. Diets had no effect on growth and feed utilization. Temperature affected growth but not feed efficiency, with fish growing more at 18°C. Fatty acid synthetase and glutamate dehydrogenase activities were higher at 12°C than at 18°C while activity of the other measured enzymes was not affected by water temperature. Glucokinase and malic enzyme activities were lower while fructose 1,6‐bisphosphatase activity was higher in fish fed the HP:LC diet. Our data suggest that protein can be reduced from 550 gkg^?1 to 450 gkg^?1 by increasing starch level in high lipid diets for Senegalese sole juveniles without affecting overall performance. A reduction in protein content through an increase in dietary starch decreases hepatic gluconeogenesis. Increasing temperature from 12°C to 18°C improves fish growth but does not affect feed efficiency.     

Effects of Amylopectin/Amylose Starch Ratio on Growth, Body Composition and Glycemic Response of Sunshine Bass Morone chrysops × M. saxatilis

Manipulation of the ratio of amylopectin (α‐[1,4] and α‐[1,6] linked glucose) to amylose (α‐[1,41 linked glucose) starches in the carbohydrate fraction of the diet has been used to improve carbohydrate and lipid metabolism in mammalian models. A 10‐wk feeding trial was conducted to determine the effect of dietary amylopectin/amylose ratio on growth and composition of growth of advanced sunshine bass (Morone chrysops × M. saxatilis) fingerlings (60 g, initial weight). Fish were fed cold‐pelleted, semipurified, isonitrogenous (35% crude protein), isocaloric (3.6 kcaVg protein), isolipidic (5%) diets containing 25% carbohydrate. The carbohydrate fraction of the diets was composed of either glucose, dextrin, 100% amylopectin/0% amylose, 70% amylopectin/30% amylose, or 30% amylopectin/70% amylose. Diets differing in ratios of amylopectin/amylose were achieved by adjusting the proportion of high‐amylopectin (100% amylopectin) to high‐amylose (70% amylose) corn starch. Diets were fed to fish in quadruplicate 76‐L tanks (seven fish/tank) connected to a brackish water (5‐7%v) recirculating culture system with biofiltration. Weight gain ranged from 195 to 236% of initial weight (60 g) and was significantly greater (P < 0.1) for fish fed diets containing 25% carbohydrate as dextrin or as 70% amylose and significantly lower in fish fed diets in which carbohydrate was composed of 30% amylose, 100% amylopectin, or glucose. Feed efficiency ranged from 0.52 to 0.61 and was higher in fish fed the diet containing the highest concentration of amylose and lower in fish fed the diet containing glucose. Hepatosomatic index was highest (2.71) in fish fed the diet containing glucose and lowest (1.401.45) in fish fed diets containing high‐amylose cornstarch. Intraperitoneal fat ratio was distinctly lower in fish fed diets containing some amylose as compared to those fed diets without amylose. Liver lipid was significantly lower (4.8%) in fish fed the diet containing glucose and almost twice as high (7.3‐8.9%) in fish fed the diets containing any starch. Glycogen content of the liver decreased from approximately 12% in fish fed the diet containing glucose to 5% in fish fed the diets containing amylose. Muscle proximate composition and ratio were unaffected by the dietary treatments. Fasting levels (15 h) of blood glucose in fish reared for 10 wk on the diet containing glucose were significantly elevated (5.5 mmol/L) when compared to fasting levels of those that had been reared on diets containing starch (3.4‐1.1 mmol/L). Fish fed the diet containing glucose exhibited maximum blood concentrations (14.6 mmoVL) 4 h postprandial then rapidly declined to nearly fasting levels within 8 h postprandial. In contrast, maximum plasma glucose concentrations in fish fed diets containing starch were roughly half (6.8‐8.1 mmol/L) those of fish fed the diet containing glucose. Blood glucose in fish fed diets containing dextrin or predominantly amylopectin starch remained elevated longer than that of fish fed diets containing glucose or predominantly amylose starch. Glycemic response appeared to decrease with increasing dietary amylose content. These data suggest that feeding diets in which a greater portion of the starch is amylose may be a useful strategy for improving carbohydrate use in sunshine bass.     

Temperature and dietary carbohydrate level effects on performance and metabolic utilisation of diets in European sea bass (Dicentrarchus labrax) juveniles

This study aimed to evaluate the effect of temperature and dietary starch level on growth performance, nutrient utilisation, whole-body composition and activity of selected hepatic intermediary metabolism enzymes in European sea bass juveniles. An experimental diet was formulated to contain 46% crude protein, 12% crude lipids and 30% pregelatinized starch (diet 30GS); two other diets were formulated to include the same levels of all ingredients as diet 30GS except for the pregelatinized starch, which was included at 20% (diet 20GS) or 10% (diet 10GS). Diets were assigned to triplicate groups of 25 fish (initial weight: 15 g) at two water temperatures (18 and 25 °C) for 10 weeks. Group receiving diet 30GS was fed to apparent satiation and groups fed diets 20GS and 10GS were pair-fed according to group fed diet 30GS, so that each group ate the same amount of all nutrients except for carbohydrates. At the end of the trial, growth rate, feed efficiency and protein efficiency ratio were higher at 25 than at 18 °C. Dietary starch level did not affect growth or N utilisation. Feed efficiency was inversely related to dietary starch level. Whole-body lipids and energy content were higher at 25 °C and increased with dietary starch levels. Whole-body protein and ash content were also higher at 25 °C but were not affected by dietary starch level. Liver glycogen, HSI and VI increased with dietary starch level. ADC of starch was higher at 25 °C and within each temperature decreased with increasing dietary starch levels. ADC of protein was neither affected by temperature nor dietary starch levels. Data on enzyme activities showed that hexokinase (HK) but not glucokinase (GK) was affected by temperature. Dietary starch level affected the activities of glucokinase and glucose-6-phosphate dehydrogenase (G6PD) but not of the others enzymes tested (HK, PK, FBPase and GDH).     

Effect of supplemental dietary chromium and vanadium on the utilization of different carbohydrates in tilapia, Oreochromis niloticus×O. aureus

Diets containing 40% glucose or starch with either 2 ppm chromium (Cr), 2 ppm vanadium (V) or without either supplement were fed to tilapia, Oreochromis niloticus×O. aureus, to investigate the effect of Cr and V on carbohydrate utilization. Each diet was fed to three aquaria with 18 fish/aquarium in a recirculating, filtered rearing system for 8 weeks. Results indicated that weight gain, protein and energy deposition were significantly (P<0.05) higher in fish fed the starch diet than in those fed the glucose diet. Chromium supplementation significantly increased the weight gain, energy deposition and liver glycogen content in fish fed the glucose diet. Delayed plasma glucose plateau and significantly higher body lipid content were observed in fish fed the glucose diet with Cr than in those without the Cr supplementation.     

不同小麦淀粉和脂肪水平对大黄鱼的生长性能、饲料利用及糖代谢关键酶活力的影响

为探讨饲料中添加不同小麦淀粉和脂肪水平对大黄鱼幼鱼生长、饲料利用以及糖代谢关键酶活力的影响,进行了为期8周的生长实验。设计了3个小麦淀粉水平(5%、10%和30%)和2个脂肪水平(5%和10%)的3×2的两因子实验,配制了6种等氮的饲料,分别喂养平均体质量为(6.75±0.12)g的大黄鱼幼鱼。结果显示,饲料中小麦淀粉和脂肪水平对大黄鱼增重率(WG)、特定生长率(SGR)、饲料效率(FE)、成活率(SR)、肝体比(HSI)和肥满度(CF)无显著交互作用,对脏体比(VSI)有显著交互作用。在同一脂肪水平下,淀粉水平为30%组WG和SGR显著高于10%淀粉组。不同小麦淀粉和脂肪水平对肝糖原含量无显著交互作用,而对肌糖原含量有显著交互作用,在饲料脂肪水平为5%时,30%小麦淀粉水平下的肝糖原含量显著高于10%和20%淀粉水平,10%淀粉水平下的肌糖原含量显著高于20%和30%淀粉水平;在脂肪水平为10%时,10%淀粉水平下的肝糖原含量显著高于20%和30%淀粉水平,而30%小麦淀粉水平下的肌糖原含量显著高于10%和20%淀粉水平。小麦淀粉和脂肪水平对血清中谷丙转氨酶(ALT)、谷草转氨酶(AST)、总胆固醇(TC)和葡萄糖(GLU)含量无显著交互作用,对总蛋白(TP)和甘油三酯(TG)交互作用显著。不同小麦淀粉和脂肪水平对肝脏脂肪酶活性有显著的交互作用,对淀粉酶活性无显著交互作用;同一脂肪水平下,脂肪酶的活性随着淀粉水平的升高而升高,同一饲料淀粉水平下,饲料脂肪水平为10%组的脂肪酶活性显著高于5%组。不同小麦淀粉和脂肪水平对肝脏丙酮酸激酶(PK)的活性有显著的交互作用,而对葡萄糖激酶(GK)、磷酸果糖激酶(PFK)、磷酸烯醇式丙酮酸羧激酶(PEPCK)、1,6-二磷酸果糖酶(FBPase)和6-磷酸葡萄糖酶(G6Pase)的活性均无显著交互作用。研究表明,当饲料脂肪水平为5%时,大黄鱼能够通过调节糖酵解关键酶活性及肝糖原含量来维持血糖平衡,改善对小麦淀粉的利用能力;而当脂肪水平为10%时,大黄鱼对小麦淀粉的利用能力降低。     

The specific dynamic action of southern catfish, <Emphasis Type="Italic">Silurus meridonalis</Emphasis> Chen,fed diets containing either raw or precooked corn starch or glucose

The growth performance of carnivorous southern catfish (Silurus meridionalis) was lower when fed a diet containing glucose as a carbohydrate source than when fed one containing starch. To test whether this decreased growth performance was partly due to higher metabolic costs induced by the fast assimilation of dietary glucose, the postprandial metabolic responses of southern catfish juvenile (36.7 ± 1.9 g) fed diets containing either raw or pre-cooked corn starch and glucose were investigated at 27.5°C. The peak metabolic rate of fish fed a raw corn starch diet was significantly higher than that of fish fed precooked corn starch and glucose diets (P < 0.05). The specific dynamic action (SDA) coefficients (energy expended on SDA as a percentage of energy content of the meal) of fish fed raw or precooked corn starch diets were significantly higher than that of fish fed a glucose diet (P < 0.05). The postprandial metabolic rate of fish fed a raw starch diet displayed a classic response – increased metabolic rate immediately after feeding, followed by a decreased metabolic rate several hours after feeding – as has been documented earlier in this species. However, the postprandial metabolic rate of fish fed a glucose diet had two alternating cycles of increasing and decreasing metabolic rate, which has not been reported previously. This bimodal pattern of the SDA curve was also found in a subsequent experiment in which purified d-glucose (0.1 g dry mass) was packed into sections of grass carp (Ctenopharyngodon idellus) intestine (0.05 g dry mass). The results suggest that the digestibility and absorption speed of the dietary carbohydrate has a significant effect on postprandial metabolic response in juvenile southern catfish. The results of this study may provide useful data in terms of the utilization of dietary carbohydrates by carnivorous fishes.     

Effects of dietary amylose/amylopectin ratio on growth performance,feed utilization,digestive enzymes,and postprandial metabolic responses in juvenile obscure puffer Takifugu obscurus

The effect of dietary amylose/amylopectin (AM/AP) ratio on growth, feed utilization, digestive enzyme activities, plasma parameters, and postprandial blood glucose responses was evaluated in juvenile obscure puffer, Takifugu obscurus. Five isonitrogenous (430 g kg^?1 crude protein) and isolipidic (90 g kg^?1 crude lipid) diets containing an equal starch level (250 g kg^?1 starch) with different AM/AP ratio diets of 0/25, 3/22, 6/19, 9/16 and 12/13 were formulated. Each experimental diet was fed to triplicate groups (25 fish per tank), twice daily during a period of 60 days. After the growth trial, a postprandial blood response test was carried out. Fish fed diet 6/19 showed best growth, feed efficiency and protein efficiency ratio. Hepatosomatic index, plasma total cholesterol concentration, liver glycogen and lipid content, and gluconokinase, pyruvate kinase and fructose-1,6-bisphosphatase activities were lower in fish fed highest AM/AP diet (12/13) than in fish fed the low-amylose diets. Activities of liver and intestinal trypsin in fish fed diet 3/22 and diet 6/19 were higher than in fish fed diet 9/16 and diet 12/13. Activities of liver and intestinal amylase and intestinal lipase, and starch digestibility were negatively correlated with dietary AM/AP ratio. Fish fed diet 3/22 and diet 6/19 showed higher plasma total amino acid concentration than fish fed the other diets, while plasma urea nitrogen concentration and activities of alanine aminotransferase and aspartate aminotransferase showed the opposite trend. Equal values were found for viscerosomatic index and condition factor, whole body and muscle composition, plasma high-density and low-density lipoprotein cholesterol concentrations, and activities of lipase and hexokinase and glucose-6-phosphatase in liver. Postprandial plasma glucose and triglyceride peak value of fish fed diet 12/13 were lower than in fish fed the low-amylose diets, and the peak time of plasma glucose was later than in fish fed the other diets. Plasma glucose and triglyceride concentrations showed a significant difference at 2 and 4 h after a meal and varied between dietary treatments. According to regression analysis of weight gain against dietary AM/AP ratio, the optimum dietary AM/AP ratio for maximum growth of obscure puffer was 0.25. The present result indicates that dietary AM/AP ratio could affect growth performance and feed utilization, some plasma parameters, digestive enzyme as well as hepatic glucose metabolic enzyme activities in juvenile obscure puffer.     

Metabolic fitness and growth performance in tropical freshwater fish Labeo rohita are modulated in response to dietary starch type (gelatinized versus non‐gelatinized) and water temperature

This study investigated the modulating effect of temperature variation on the metabolic status and growth performance of tropical freshwater fish, Labeo rohita, when reared with starch‐based gelatinized (G) or non‐gelatinized (NG) diet. Fish were either maintained at ambient water temperature (26 °C) or exposed to 32 °C for 1 week, and then subjected to 26 °C for 4 weeks. Both groups were fed with isoproteinous (300 g kg^?1) diets containing G or NG starch. A significant interaction was evident between increased metabolic activity due to the short‐term exposure to higher temperature and starch type on growth performance, feed efficiency and protein retention. Dietary starch type and water temperature interactions were more effective in modulating the hepatic glucokinase and pyruvate kinase responses than that of hexokinase. Hepatic aspartate amino transferase and alanine amino transferase activities were augmented at low temperature in NG starch fed group. Overall, our findings indicate that enzyme activities are enhanced due to the short‐term exposure to higher temperature (32 °C). This elevated temperature lasted for 3 weeks after exposure during which NG starch tended to support the growth.     

Effects of dietary blend of fish oil with corn oil on growth and non-specific immune responses of grouper, Epinephelus malabaricus

A growth trial was conducted to investigate the effects of fish oil and corn oil on the growth and non‐specific immune responses of juvenile grouper, Epinephelus malabaricus. Five semi‐purified diets were supplemented with 40 g kg⁻¹ of either fish oil (F4), corn oil (C4) or blend of fish oil with corn oil at ratio of 3 : 1 (F3C1); 1 : 1 (F2C2) and 1 : 3 (F1C3). Each diet was fed to triplicate groups of grouper (mean initial weight: 10.26 ± 0.14 g) in a recirculating rearing system for 8 weeks. Weight gain and feed efficiency of fish fed the F4, F3C1 and F2C2 diets were the highest (P < 0.05), followed by fish fed the F1C3 diet, and the lowest in fish fed the C4 diet. Fish fed the C4 diet had a lower survival rate than fish on other dietary treatments. Fatty acid composition of liver and muscle in fish generally reflected the composition of the diet. Leukocyte superoxide anion (O⁻₂) production ratio was the highest in fish fed the F3C1 and F2C2 diets, followed by fish fed the F4 and F1C3 diets, and the lowest in fish fed the C4 diet. Fish fed the F3C1 and F2C2 diets had higher plasma lysozyme activities than fish fed the F4 and C4 diets. Plasma alternative complement activity was higher in fish fed the F3C1, F2C2 and F1C3 diets than fish fed the F4 and C4 diets. These results suggest that grouper fed diets with 3 : 1 or 1 : 1 of fish oil to corn oil ratio had similar growth to the fish fed diet with fish oil. Blend of fish oil with corn oil in diet significantly enhanced non‐specific immune responses of grouper when the fed diet contained fish oil as the only lipid source.     

Effect of guar gum on glucose and lipid metabolism in white sea bream Diplodus sargus

The aim of this study was to assess the role of soluble non-starch polysaccharide (guar gum) on white sea bream Diplodus sargus, glucose and lipid metabolism. A control diet was formulated to contain 40 % crude protein, 14 % crude lipids and 35 % pregelatinized maize starch, and three other diets were formulated similar to the control diet except for guar gum, which was included at 4 % (diet GG4), 8 % (diet GG8) or 12 % (diet GG12). Diets were fed to the fish for 9 weeks on a pair-feeding scheme. Guar gum had no effect on growth performance, feed efficiency, glycaemia, cholesterolaemia and plasma triacylglyceride levels. Hepatic glucokinase and pyruvate kinase activities, liver glycogen content and liver insulin-like growth factor-I gene expression were not affected by dietary guar gum, while fructose-1,6-bisphosphatase activity was lower in fish fed guar gum–supplemented diets. Hepatic glucose-6-phosphate dehydrogenase activity was higher in fish fed diets GG4 and GG8 than in the control group. Overall, data suggest that in contrast to mammals guar gum had no effect on white sea bream glucose utilization and in lowering plasma cholesterol and triacylglyceride levels. However, it seems to contribute to lower endogenous glucose production.