Use of White Fat as a Replacement for Squid Liver Oil in Practical Diets for Surubim Pseudoplatystoma coruscans

The effect of dietary lipid on culture performance, fatty acid composition of carcass, and the liver polar lipid of surubim fingerlings Pseudoplatystoma coruscans was investigated. Five isonitrogenous (46.5% crude protein) and isolipidic (19% crude lipid) diets were formulated with squid liver oil (SLO) and white fat (pig lard-PL) as lipid sources. Diet 1 was supplemented with 12% SLO, diet 2 with 8% SLO and 4% PL, diet 3 with 6% SLO and 6% PL, diet 4 with 4% SLO and 8% PL, and diet 5 with 12% PL. Fish were fed to apparent satiation over a 64-d feeding trial. No statistically significant difference ( P >0.05) was observed in growth performance of fish. In contrast, fatty acid profile of fish carcass and liver polar lipid fraction was affected ( P 0.05) by dietary fatty acid composition. Palmitic (16:O) and the oleic (18:1n-9) acids were the major saturated and monoene fatty acids respectively found in fish carcass, independent of the lipid source in the diets. The total amount of saturated and monoene fatty acids was significantly higher ( P 0.05) in the carcass of the fish fed diets 4 and 5, than in the other fish. The concentration ( P 0.05) of eicosapentaenoic and docosahexaenoic acids and the n-3/n-6 ratio in fish carcass and in polar lipid fraction of liver increased in direct proportion to the level of squid liver oil in diet. Results of this experiment clearly demonstrated that both squid liver oil and pig lard have a positive nutritive value for surubim and that it is possible to increase the n-3 to n-6 ratio in favor of n-3, without loss in the growth performance, feeding fish with a diet containing a lipid source rich in this fatty acid.     

Fasting and refeeding lead to more efficient growth in lean pacu (Piaractus mesopotamicus)

We evaluated whether body fat content affects the energetic metabolism and growth in pacu submitted to daily feeding, fasting and refeeding. For 15 days, fish were fed different diets to obtain lean and fat conditions, and then subjected, for 20 days to: (1) continuously feeding (control), or (2) fasting for 15 days and refeeding for 5 days. Blood (glucose, triglycerides, cholesterol, non‐esterified fatty acids and total protein) and tissue (liver lipid and glycogen, muscle lipid and mesenteric fat) metabolic indicators, and growth performance parameters (weight gain, specific growth rate, daily feed intake and feed conversion ratio) were measured. Fasting led both lean and fat pacu to make notable use of their energy reserves, through glycogenolysis and lipolysis, reflected in reduced blood glucose and triglycerides, liver glycogen and muscle lipid levels. Lipolysis was confirmed by the high levels of non‐esterified fatty acids, especially in fat pacu. Refeeding led to higher plasma glucose and liver lipid in lean fish. Muscle fat increased in fat fish but was not restored in lean fish, while mesenteric fat index (MFI) remained the same in fat fish and increased in lean fish. Although refeeding occurred only for 5 days, lean fish grew more and were more efficient at utilizing food (higher weight gain and better feed conversion ratio). In conclusion, our results suggest that fat pacu have higher glycogenic and lipogenic abilities, and the higher deposition of lipids in fish does not mean higher availability of energy for growth when compensatory growth is stimulated by refeeding after fasting.     

Effects of background color on growth performances and physiological responses of scaled carp (Cyprinus carpio L.) reared in a closed circulated system

Growth performances and physiological responses of Cyprinus carpio after long-term (14 weeks) background color adaptation were investigated. Six groups of ten individuals each (initial body weight 116 g) were reared in black, green and white tanks (two replicate groups for each color). At the end of the experiment, blood (cortisol, glucose, haematocrit, cholesterol, triglycerides, total lipids, osmolality, electrolytes, pCO₂, pH), liver (total lipids, glycogen, hepatosomatic index) and growth (body weight, specific growth rate, food conversion ratio, condition factor, proximate carcass composition) parameters were determined. Plasma cortisol levels in white-adapted carp were significantly (P<0.05) lower than those in black, while in green-adapted fish did not differ significantly from those in both other counterparts. White-adapted carp showed the highest specific growth rate and the lowest food conversion ratio, whereas black-adapted fish exhibited the opposite pattern. In addition, mean (%) increase of body weight in white-adapted carp was 4.66 and 3.58% higher than that in black- and green-adapted fish, respectively. Furthermore in white-adapted carp, blood pCO₂ and pH were significantly higher and lower, respectively, than those obtained in black- and green-adapted fish. In black-adapted carp, liver total lipid levels were significantly lower, and plasma total lipid levels were significantly higher, than those in white- and green-adapted fish. No significant variations were observed in the other parameters. It is concluded that different background colors may lead to different growth performances of scaled carp depending upon rearing conditions.     

黑龙江鲤、荷包红鲤及其杂种血液学指标比较研究

本文对黑龙江鲤、荷包红鲤及其杂交鲤幼鲤的血液中红细胞数、血红蛋白、比溶及血糖、血清总蛋白、胆固醇和总脂等指标进行了测定。并比较了二个亲本和杂交种在上述指标的差异。黑龙江鲤的血液各项指标均高于荷包红鲤。杂交鲤的血液指标红细胞数低于双亲,但胆固醇和总脂二项高于双亲而其它指标均低于黑龙江鲤而高于荷包红鲤,从脂类代谢方面反映了杂交鲤适应低温能力。这可能受黑龙江鲤的影响,表现出偏母本效应。     

Evaluation of carbohydrate/lipid ratios on growth and metabolic response in tropical gar (Atractosteus tropicus) juvenile

Five experimental diets with different carbohydrates/lipid ratio (CHO:L, 0.75, 1.28, 2.10, 2.52, 4.63) were formulated. Fish were randomly assigned by triplicate (10 fish per tank, 0.50 ± 0.01 g). Growth was registered every 15 days until end of the experiment (45 days). Samples were taken for analysis of chemical carcass composition, blood chemistry, glycogen and lipid liver content, digestive and metabolic enzyme activities. Results showed that survival, growth performance parameters and plasma glucose were not affected by treatments (p > 0.05). Lipids of carcass and liver, as well as triglycerides and plasma cholesterol increase significantly as CHO:L ratio decreased. While an inversely proportional tendency was observed for carcass protein and liver glycogen (p < 0.05). Digestive enzymes did not show significant differences among treatments (p > 0.05). Finally, Hexokinase (HK), glucokinase (GK), phosphoenol pyruvate carboxykinase (PEPCK) and fructose‐1,6‐biphosphase (FBPase) showed high regulation by carbohydrates up to the CHO:L ratio of 2.10 (p < 0.05), while pyruvate kinase (PK) activity was not significantly affected by the CHO:L ratio. By the other side, glucose‐6‐phosphate dehydrogenase (G6PD) tends to significantly increase as the CHO:L ratio increases. We conclude that A. tropicus fry have a high capacity to utilize carbohydrates substituting lipids as energy source in balanced diets.     

Carbohydrate molecule size affects the metabolic and digestive dynamics of jundiá (Rhamdia quelen)

This experiment was conducted to study the effects of carbohydrates with different molecular sizes on growth performance, feed utilization and composition, activity of digestive enzymes, plasma and hepatic metabolites of jundiá (Rhamdia quelen). Triplicate groups of jundiá (4.08 ± 0.005 g) were stocked in 12 tanks with stocking density of 25 individuals per tank and fed for 40 days with four isonitrogenous diets (37%) and isocaloric diets (3,200 kcal/kg) containing fructose (FRU), sucrose (SUC), maltodextrin (MALDEX) or corn starch (CS). The results showed no significant differences for growth variables and digestive enzymes. Fish whose diet received maltodextrin showed higher levels of deposited body fat and hepatosomatic index. Moreover, the above‐mentioned treatment resulted in lower concentrations of glucose and cholesterol in the plasma of jundiá, higher levels of triglycerides, and lower reserves of glucose and liver glycogen. However, fish fed the starch‐based diet presented higher moisture content, crude protein deposition, and body protein retention coefficient. In that same treatment, the jundiá presented higher levels of plasma glucose and liver protein. In conclusion, the efficiency of using digestible carbohydrates in iso‐nutritional diets for jundiá depends on the size of their molecular structure. The corn starch was the best dietary carbohydrate source for jundiá, based on feed utilization and composition and greater synchronicity between energy utilization and protein synthesis.     

Hatching success of walleye embryos in relation to maternal and ova characteristics

Abstract – Understanding how maternal and ova traits influence offspring quality is a key issue in both ecological research and fish culture. We examined the survival and size at hatch of walleye embryos in relation to a suite of maternal and ova traits in laboratory incubation trials involving two native walleye populations. Ova were analysed for size, lipid content, fatty acid composition, soluble protein content and size composition, and mineral (Ca, Co, Cu, Fe, Mg, Mn and Zn) content. Embryonic survival (egg hatching success) varied most consistently with respect to spawning date and maternal age. Embryonic survival increased with maternal age, but other indices of maternal health, such as condition (residual mass at length) or somatic lipid content, did not account for significant amounts of variation. Indices of ova total lipid content, fatty acid composition and mineral composition explained significant variation in embryonic survival not accounted for by maternal age and spawning date, whereas indices of protein content and composition generally explained less variance. Both larval mass and length at hatch were primarily determined by ovum size, but length at hatch was also related to some aspects of ova fatty acid and mineral composition.     

Dietary carbohydrate and growth,body composition and heat increment in rainbow trout (Salmo gairdneri)

A study was conducted to determine growth, body composition and heat increment (HI) of rainbow trout reared on isonitrogenous high digestible carbohydrate (HC) and high fat (HL) diets at 15°C. Trout reared on the HC diet had a significantly lower final body weight and carcass lipid content and a significantly higher feed:gain ratio and carcass protein content than trout reared on the HL diet after 12 weeks on the test diets. The lower carcass lipid composition indicates that trout do not readily convert dietary carbohydrates into fat. HI of trout reared on the HC diet was significantly higher than that of fish reared on the HL diet. Considering the poor utilization of dietary carbohydrates as an energy source and the apparently low conversion of dietary glucose into fat, the cause of the higher HI associated with the HC diet is not completely understood. However, it is possible the elimination of excess dietary glucose is an energy dependent process resulting in an increased heat production which would partly account for the increased HI. Furthermore, if the HC diet is a low net energy diet, then the metabolism and utilization of dietary and tissue proteins (amino acids) for energy by the trout may also be partly responsible for the increased HI of the trout reared on the HC diet.     

Influence of dietary protein levels on growth performance, carcass composition and liver lipid classes of juvenile Spinibarbus hollandi (Oshima)

A feeding trial was conducted to investigate the influence of dietary protein levels on growth performance, carcass proximate composition and liver lipid classes of juvenile Spinibarbus hollandi (Oshima), a cyprinid fish. White fish meal was the primary protein source in the study. Eight experimental diets containing 13–55% crude protein were fed to three replicate groups of six fish weighing nearly 8.5 g each for 10 weeks. Both percentage weight gain and feed efficiency ratio increased significantly with increasing dietary protein levels up to 31%, but there was no further increase for protein levels from 31% to 55%. Application of broken‐line regression analysis to the percentage weight gain provided an estimate of 32.7±1.5% dietary protein for maximum growth. The protein efficiency ratio and productive lipid value were inversely correlated with dietary protein level. The hepatosomatic index and the viscerosomatic index were also inversely related to dietary protein level. The carcass protein of fish fed lower protein diets was significantly lower than that of the fish fed higher protein diets. Carcass lipid content decreased with increasing dietary protein levels, whereas moisture was inversely related to lipid content. Both liver glycogen and liver lipid contents decreased with increasing dietary protein levels. Triglyceride was the major component in the liver lipid, and the amount of triglyceride deposited in the liver also decreased with dietary protein levels. The results indicated that both carcass proximate composition and liver lipid class of juvenile Spinibarbus hollandi were affected by dietary treatments.     

Effects of Reduced Levels of Dietary Protein and Menhaden Fish Meal on Production,Dressout, and Biochemical Composition of Phase III Sunshine Bass Morone chrysops ♀× M. saxatilis ♂ Cultured in Earthen Ponds1

The responses of phase III sunshine bass Morone chrysops ♀× M. saxatilis ♂ to diets containing reduced levels of menhaden fish meal (30–10%, dry weight) and crude protein (40–36%, dry weight) were evaluated in two separate experiments. Reductions in fish meal were compensated by increase in dietary soybean meal, a meat and blood meal product, and additional amounts of a 1:1 catfish oil:menhaden oil mixture sprayed on as a top dressing. Fish were cultured in earthen ponds and fed commercially manufactured, extruded diets to apparent satiation. In Experiment 1, dietary crude protein was reduced from 40 to 36% and the menhaden fish meal ingredient was reduced from 30 to 15% (dry weight). The mean weight of fish stocked into each pond ranged from 144 to 188 g, the stocking density was 8641/ha, and the duration of the growout was 172 d. In Experiment 2, both dietary treatments contained 40% crude protein (dry weight) and either 30% or 10% menhaden fish meal. The mean weight of fish stocked into each pond ranged from 42 and 77 g, the stocking density was 8,500/ha, and the duration of the growout was 175 d. Simultaneous reductions in dietary menhaden fish meal and crude protein resulted in significant decreases in all production indices except survival and percent weight increase. Weights of filet, carcass, liver and intraperitoneal fat, expressed as a percent of total body weight, were not significantly different. A 66% reduction in dietary menhaden fish meal while the crude protein level was maintained at 40% did not significantly affect growth, production, and weights of filet, carcass, liver and intraperitoneal fat, expressed as a percent of total body weight, and represents a 6% decrease in the cost of feed. In both experiments, levels of protein, lipid, moisture, and ash of the whole body and the filet were not significantly different. Fatty acid composition of the filet and livers from fish fed the control and experimental diets in Experiment 2 were highly comparable. The comparable level of performance of fish fed diets believed to be deficient in HUFA suggests that the dietary levels reported to be required may not be totally applicable to diets formulated for pond culture.     

膨化与非膨化饲料对大规格草鱼生长、体成分及部分生理生化指标影响

以商业配方为基础,配制膨化饲料和非膨化饲料饲喂初始体重（394.96±13.21g）草鱼（Ctenopharynodon idellus）120天,旨在对比这两种饲料对其生长、体成分及部分生理生化指标的影响。养殖试验在水库网箱（2m×2m×2m）中进行,每个处理组3个重复,每个重复30尾鱼。实验结果表明,与非膨化料组相比,膨化饲料组草鱼成活率和增重率显著提高（P＜0.05）,饵料系数显著降低（P＜0.05）,增重成本显著降低（P＜0.05）;肥满度、肝体比、脏体比和肠体比显著升高（P＜0.05）;鱼体血清血糖、甘油三酯、总固醇和过氧化氢酶显著升高（P＜0.05）;胰蛋白酶、淀粉酶和脂肪酶显著降低（P＜0.05）;肝脏谷丙转氨酶（GPT）显著升高,谷草转氨酶（GOT）显著降低（P＜0.05）;鱼体成分中水分和灰分无显著差异（P>0.05）,粗脂肪显著升高、粗蛋白显著降低（P＜0.05）。综上所述,与非膨化饲料相比,饲喂膨化饲料可使大规格草鱼生长性能和养殖效益提高,但会鱼体肥满度和粗脂肪含量提高。     

Fatty Acid Composition of Muscle, Liver, and Depot Fat of Wild and Cultured Common Snapping Turtles Chelydra serpentina

Abstract This study was conducted to compare the fatty acid composition of muscle, liver, and depot fat of common snapping turtles Chelydra serpentina from the wild with those of captive common snapping turtles fed a diet of known fatty acid composition. Total lipid from each tissue was separated by thin-layer chromotography, methylated, and analyzed by gas chromatography/mass spectrometry. The fatty acid composition of total lipid, polar lipid, and nonpolar lipid in muscle and depot fat of wild and captive turtles exhibited greater variability than liver polar lipid. Cultured turtles contained significantly lower levels of linolenic and arachidonic acids in liver polar lipid than wild turtles. Total n-9 fatty acids were significantly higher in whole-lipid and nonpolar fractions of muscle, liver, and depot fat of cultured turtles indicating de novo synthesis. Total polyunsaturated fatty acids were significantly lower in total lipid of muscle tissue from cultured turtles. Total polyunsaturated fatty acids were significantly lower in both depot fat and liver nonpolar lipid of cultured turtles, but did not differ (P > 0.05) in the polar lipid fractions of cultured and wild turtles.     

Effects of six alternative lipid sources on growth and tissue fatty acid composition in Japanese sea bass (Lateolabrax japonicus)

Ten-week experiment was carried out on Japanese sea bass (5.87 ± 0.02 g) to study the effects of replacement of fish oil with six alternative lipid sources: pork lard, PL; beef tallow, BT; poultry fat, PF; soybean oil, SO; corn oil, CO; and a mixed-fat (MF: tallow, 60%; soy oil, 20%; fish oil, 20%) on growth performance and fatty acid (FA) composition in fillet and liver. Seven isoenergetic and isonitrogenous experimental diets were formulated, containing 10% of added lipid. Fish oil was used in control diet, which was substituted by 50% with the alternative lipid sources in the other six diets.

Weight gain (WG), specific growth rate (SGR), Feed conversion ratio (FCR) feed intake and hepatosomatic index (HSI) of fish fed the experimental diets were not significantly different (P > 0.05). Protein efficiency ratio (PER) in fish fed the PF diet were significantly lower than those of fish fed SO and CO diets. Significant differences in carcass moisture and lipid contents of carcass and liver were observed among fish fed the dietary treatments. Generally, the fatty acid composition of fish fillets and livers reflected the dietary FA composition.     

Effect of dietary mirex and PCB (Aroclor 1254) on thyroid activity and lipid reserves in rainbow trout Salmo gairdneri Richardson

Abstract. Rainbow trout were fed diets contaminated with either PCB (Aroclor 1254, 500 μg/g dry food) or Mirex (500 μg/g dry food). There was no apparent effect of PCB on thyroid histology or on serum thyroid hormone levels. Mire effected significant reductions in serum T₄ ( P <0.05) and T₃ levels ( P <0.01) without apparent change om the histological appearance of the thyroi. Liver weights and total liver lipid content were significantly ( P <0.001) greater in PCB fed fish compared with controls as was the carcass lipid content ( P <0.01). Mirex had no apparent effect on liver size or liver lipid content but there was a decline in carcass lipid content ( P <0.02) which persisted 25 days after returning Mirex-fed fish to the control diet ( P <0.05).     

Blood chemistry profile as indicator of nutritional status in European seabass (Dicentrarchus labrax)

This study was carried out to establish biochemical parameters with potential diagnostic value to assess the nutritional status of healthy seabass. For that purpose, triplicate groups of seabass juveniles were submitted to different feeding protocols: fed for 14 days; fed for 7 days followed by 7 days of fasting or fasted for 14 days. At the end of the trial, body, liver and viscera were randomly sampled for proximate composition analysis. Blood was also collected and the following plasma parameters were analyzed by standard clinical methods: glucose; cholesterol; triglycerides; protein; inorganic phosphorus; calcium; magnesium; alkaline phosphatase (ALP); aspartate aminotransferase; lactate dehydrogenase; creatine phosphokinase and lipase. No major effect of feed deprivation on body composition, visceral index, perivisceral and hepatic lipid content were observed, whereas hepatosomatic index and hepatic glycogen were reduced. Previous feeding conditions strongly influenced the plasma parameters in seabass. Comparatively to the fed group, plasma glucose, cholesterol and calcium levels were reduced after 2 weeks of fasting while plasma triglycerides, protein, inorganic phosphorus and ALP attained minimum levels after 1 week of fasting. Overall, enzymatic activity parameters showed higher variability than biochemistry parameters. In conclusion, during short-term starvation (<14 days) hepatic energy depots were extensively mobilized while perivisceral and body lipids reserves were preserved. Among measured parameters, plasma protein, triglycerides, inorganic phosphorus and ALP seem to have potential as predicative diagnostic tools to assess the nutritional status of seabass and may be useful to monitor feeding practices in aquaculture. Further studies are, however, required to extend results of this study to other fish size classes.     

不同饵料比对黄鳝生长及生理生化指标的影响

以冰鲜鱼与配合饲料5个不同比例饵料饲养黄鳝（Monopterus albus）14周,设定配合饲料所占比例分别为0%、25%、50%、75%、90%,研究不同饵料比处理对黄鳝生长、体成分及部分血清生理生化指标的影响。结果显示,各处理组黄鳝增重率、成活率均无显著差异（P〉0.05）;粗蛋白及粗脂肪含量随饵料中配合饲料比例增大呈先升高、后降低的趋势,且均以90%配合饲料组最低;而各组体灰分和水分差异不显著（P〉0.05）;各处理组黄鳝的血清谷草转氨酶（GOT）、谷丙转氨酶（GPT）、甘油三酯、总胆固醇及血糖有显著差异（P〈0.05）;与完全投喂冰鲜鱼（0%组）相比,其它各处理组血清GOT和GPT显著降低;75%配合饲料组血清GOT、GPT（50%组除外）、总胆固醇均为所有处理组最低;表明黄鳝投喂以25%冰鲜鱼和75%配合饲料的混合饵料为宜。     

Sex-based differences in fatty acid composition of adult walleye

Differences in reproductive strategies of male and female fishes are presumably accompanied by differences in nutrient allocation and predicted to lead to divergence in body composition between the sexes. We compared patterns of variation in fatty acid profiles of lipids extracted from ova, liver, muscle and visceral fat between mature male and female walleye (Sander vitreus) sampled from two wild spawning stocks. Fatty acid profiles differed significantly among body tissues in both males and females, with the strongest contrast between muscle and visceral fat. Significant differences in fatty acid composition between the sexes were found in liver, muscle and visceral fat tissues. Variation among sexes and populations was greater in liver than in the other tissues. Female livers had lower relative abundances of palmitic acid (PA, 16:0) and oleic acid (OA, 18:1(n-9)), and higher relative abundances of arachidonic acid (ARA, 20:4(n-6)), eicosapentaenoic acid (EPA, 20:5(n-3)) and docosahexaenoic acid (DHA, 22:6(n-3)) compared to male livers. In addition, female muscle had higher relative abundance of OA and lower relative abundance of DHA compared to male muscle. Our results illustrate the differential effects of reproductive demands on the biochemical composition of males and females and have implications for the analysis of fatty acid profiles in studies of wild fish populations.     

越冬对黄鳝(Monopterus albus)机体生化组成及部分血清生化指标的影响

以初始体重为(118.42±4.38) g的黄鳝(Monopterus albus)为研究对象,研究越冬对黄鳝机体生化组成及部分血清生理生化指标的影响。实验结果显示,与越冬前相比,1) 越冬后黄鳝全鱼、肝脏和肌肉组成显著改变,越冬后鱼体粗脂肪含量显著下降(P<0.05),鱼体水分和粗灰分含量显著升高(P<0.05),肝体比和肝糖原含量极显著降低(P<0.01),肝脏粗脂肪含量显著升高(P<0.05),肌肉中总氨基酸和必需氨基酸含量极显著升高(P<0.01),肌肉中饱和脂肪酸含量极显著降低(P<0.01),多不饱和脂肪酸含量显著升高(P<0.05);2) 越冬后黄鳝血清甘油三酯、葡萄糖和总蛋白含量以及血清氨基酸发生显著改变,越冬导致黄鳝血清甘油三酯、葡萄糖含量显著降低(P<0.05),总蛋白含量极显著升高(P<0.01),黄鳝血清中总氨基酸和必需氨基酸含量显著下降(P<0.05),但越冬对血清总胆固醇和尿素氮含量、谷草转氨酶和谷丙转氨酶活力无显著影响。上述结果表明,越冬期间黄鳝营养物质消耗以肝糖原和鱼体脂肪为主,越冬后肌肉氨基酸和脂肪酸组成显著改变。     

不同糖脂比对建鲤幼鱼生长、体组成、消化及糖酵解能力的影响

本试验研究了饲料中不同糖脂比对建鲤幼鱼生长、体组成、消化及糖酵解的影响。试验共配制6组等氮等能的半纯合饲料,对应糖脂比分别为2.3,3.0,4.0,5.6,7.7和12.1。将鱼饱食投喂8周,每日投喂3次。试验结果表明,当饲料糖脂比从2.3升高至7.7时,增重率、特定生长率、蛋白质效率和蛋白保留率均显著升高(P < 0.05);而当糖脂比进一步升高时,其均呈下降趋势,但差异不显著(P > 0.05);饲料系数的变化趋势与其相反。建鲤幼鱼的脏体比以及全鱼、胴体和肝脏脂肪含量随着饲料糖脂比的降低均显著升高(P < 0.05),而全鱼、胴体和肝脏的蛋白质含量无显著差异(P > 0.05)。肠道淀粉酶活性随着糖脂比的升高显著升高(P < 0.05),而脂肪酶的变化趋势则相反(P < 0.05)。此外,血糖和胰岛素水平、肝糖原含量及肝脏葡萄糖激酶和丙酮酸激酶活性随饲料糖脂比的升高均显著升高(P < 0.05),血液中总胆固醇和甘油三酯含量则随着糖脂比的降低显著升高(P < 0.05)。根据二次回归模型得出,在等氮等能的饲料条件下,建鲤幼鱼最适宜的糖水平和脂肪水平分别为38.21%和4.69%,对应的糖脂比为8.14。     

Effect of Dietary Protein Concentration and Feeding Rate on Weight Gain,Feed Efficiency,and Body Composition of Pond-Raised Channel Catfish Ictalurus punctatus1

Two experiments were conducted in earthen ponds to evaluate the effect of dietary protein concentration and feeding rate on weight gain, feed efficiency, and body composition of channel catfish. In Experiment 1, two dietary protein concentrations (28% or 32%) and four feeding rates (≤ 90. ≤ 112, ≤ 135 kg/ha per d, or satiation) were used in a factorial arrangement. Channel catfish Ictalurus punctatus fingerlings (average size: 27 g/fish) were stocked into 0.04-ha ponds at a rate of 24,700 fish/ha. Fish were fed once daily at the predetermined maximum feeding rates for 282 d (two growing seasons). In Experiment 2, three dietary protein concentrations (24, 28, or 32%) and two feeding rates (≤ 135 kg/ha per d or satiation) were used. Channel catfish (average size: 373 g/fish) were stocked into 0.04-ha ponds at a rate of 17,300 fish/ha. Fish were fed once daily for 155 d. In both experiments, five ponds were used for each dietary treatment. Results from Experiment 1 showed no differences in total feed fed, feed consumption per fish, weight gain, feed conversion ratio (FCR), or survival between fish fed diets containing 28% and 32% protein diets. As maximum feeding rate increased, total feed fed, feed consumption per fish, and weight gain increased. There were no differences in total feed fed, feed consumption per fish, or weight gain between fish fed at ≤ 135 kg/ha per d and those fed to satiation. Fish fed the 28% protein diet had a lower percentage carcass dressout and higher percentage visceral fat than fish fed the 32% protein diet. Dietary protein concentrations of 28% or 32% had no effect on fillet protein, fat, moisture, and ash. Feeding rate did not affect FCR, survival, percentage carcass dressout, or fillet composition, except fillet fat. As feeding rate increased, percentage visceral fat increased. Fish fed at ≤ 90 kg/ha per d had a lower percentage fillet fat than fish fed at higher feeding rates. In Experiment 2, dietary protein concentration or maximum feeding rate did not affect total feed fed, feed consumption per fish, weight gain, FCR, or survival of channel catfish. Feeding rate had no effect on percentage carcass dressout and visceral fat, or fillet composition. This was due to the similar feed consumption by the fish fed at the two feeding rates. Fish fed the 24% protein diet had lower carcass dressout, higher visceral fat and fillet fat than those fed the 28% or 32% protein diet. Results from the present study indicate that both 28% and 32% protein diets provide satisfactory fish production, dressed yield, and body composition characteristics for pond-raised channel catfish fed a maximum rate of 90 kg/ha per d or ahove.