氧化油脂对斑点叉尾鮰生长、体色和抗氧化能力的影响

为考察正常及氧化鱼油、豆油、混合油脂(鱼油﹕豆油=1﹕1)对斑点叉尾鮰(Ictalurus punctatus)生长性能、体色和肝脏抗氧化能力的影响, 设计6组等氮等脂饲料, 分别添加6%鱼油、6%豆油、3%鱼油+3%豆油、6%氧化鱼油、6%氧化豆油、3%氧化鱼油+3%氧化豆油, 饲喂6组初始体重(150.5±4.2 g)的斑点叉尾鮰8周, 每组3个重复, 每个重复14尾鱼。结果表明, 摄食6%鱼油、6%豆油、3%鱼油+3%豆油饲料的斑点叉尾鮰在增重率、饲料系数、肌肉组成、体色和肝脏抗氧化指标上均无显著差异(P>0.05); 摄食3组氧化油脂饲料后, 鱼体增重率和肌肉粗脂肪含量降低(P<0.05), 饲料系数和背部、尾部皮肤b*(黄度值)增加(P<0.05), 肝脏丙二醛(MDA)和血清谷丙转氨酶(ALT)、谷草转氨酶(AST)、总胆红素(TBIL)和直接胆红素升高(DBIL)(P<0.05), 肝脏超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、还原型谷胱甘肽降低(GSH)(P<0.05), 而肌肉色度值(L*、a* 、b*)和肌肉水分、粗蛋白质、灰分含量无显著差异(P>0.05)。以上结果表明, 6%氧化油脂(鱼油、豆油或混合油脂)导致斑点叉尾鮰生长性能下降、皮肤黄度增加、肝脏抗氧化能力受损; 豆油可替代斑点叉尾鮰饲料中鱼油的使用, 而不会对生长产生负面影响。     

Growth and product quality of European eel (Anguilla anguilla) as affected by dietary protein and lipid sources

A 12‐week feeding trial was undertaken to evaluate the effects of partial replacement of marine raw materials in the diet with soybean meal and beef tallow on growth and product quality of European eel (Anguilla anguilla). Based on growth, feed efficiency and chemical composition, soybean meal was found to be an unsuitable ingredient for eel diets as a substitute for fishmeal (25% on a protein basis), probably because of the low digestibility of its carbohydrate content. However, beef tallow can be used to replace 50% of fish oil without reduction in growth, provided that digestible carbohydrates are present in the diet. No major effects of protein and lipid sources in the diet were found on fillet chemical composition. Sensory analysis revealed no significant differences between fish fed the control and the experimental diets, with the exception of salty taste which was significantly higher in fish fed combined soybean meal and beef tallow compared with fish fed the control diet.     

Nutrient digestibility and intestinal enzyme activity of Clarias batrachus (Linn.) juveniles fed on dried fish and chicken viscera incorporated diets

A feeding trial was conducted for 56 days to study the effect of replacement of fish meal by dried fish and chicken viscera, and a combination of oil cakes, in the diet of Clarias batrachus juveniles. The nutritional values of these by-products were studied through a digestibility experiment. No significant difference in nutrient digestibility was observed in different diets. Even 19.59% lipid in the diet of catfish did not affect the nutrient digestibility. Both amylolytic and proteolytic enzymes in the intestine of juveniles were studied. A decreased protease activity due to replacement of animal protein by plant protein and a decreased (P < 0.01) aspartate aminotransferase (ASAT) activity could be observed after inclusion of 22% of dried fish viscera in the diet of the catfish. Though body lipid content increased in fish fed a high level of lipid, fat-free body composition did not vary among the fish fed on different diets.     

Effects of dietary soybean protein levels on energy budget of the southern catfish, Silurus meridionalis

Energy budgets were calculated for the southern catfish, Silurus meridionalis, fed diets replacing 0%, 13%, 26%, 39%, 52% and 65% fish meal protein with soybean meal (SBM) protein with or without methionine supplementation to apparent satiation at 27.5 °C. With increasing dietary soybean protein levels (SPL), the feed energy lost in feces, excretion and metabolism increased, while that available for growth decreased (P < 0.05). When 0.12% or 0.26% methionine at 39% SPL was added to reach that in body carcass or the control group (0% SPL), no significant differences were found in each component of energy budgets. When 0.21% or 0.33% methionine at 52% SPL was added to reach the content of methionine in body carcass or the control group, energy spent on growth increased, but that on excretion and metabolism decreased (P < 0.05). These results suggested that the differences in growth rate among the southern catfish fed the diets with different SPL were due to decreasing absorption rate, increasing excretion and metabolism with increasing dietary SPL. The most important factor limiting the use of soybean protein was the imbalance of essential amino acids, which resulted in more energy spent on metabolism and excretion, less energy on growth. Supplementation of methionine produced a relatively better amino acid profile and subsequently improved the utilization of soybean protein at high SPL, which resulted in less energy used for metabolism or lost in excretion and more energy available for growth.     

Use of soybean flour (dehulled, solvent-extracted soybean) as a fish meal substitute in practical diets for African catfish, Clarias gariepinus (Burchell 1822): growth, feed utilization and digestibility

Growth and digestibility trials were conducted using African catfish, Clarias gariepinus (Burchell 1822): (1) to obtain apparent digestibility coefficient (ADC) values for capelin fish meal, soybean flour and corn meal; (2) to formulate diets based on ADC values of the protein feedstuffs; and (3) to evaluate the effects of replacing 25%, 50% and 75% of fish meal in control diets with soybean flour on growth, feed utilization efficiency and carcass composition. Supplemental methionine was added to the diet formulation in which soybean flour replaced 75% of the diet. Diets were formulated (400 g digestible protein kg⁻¹ and 15 kJ digestible energy g⁻¹ dry diet) and fed to catfish fingerlings (13.1 ± 0.5 g) to apparent satiation twice daily for 70 days. The protein and energy digestibilities of fish meal and soybean flour were high (>90% and >80%, respectively; P < 0.05). At 75% fish meal replacement with soybean flour (without methionine supplementation), growth and feed utilization efficiency indicators were depressed compared with other diet treatments which had a similar (P > 0.05) growth and feed utilization efficiency to those fed the control diet. The carcass compositions of catfish in all diets were similar (P > 0.05) and the liver histology of catfish fed any of the diets showed no alterations. The results obtained indicate that 50% of fish meal protein in practical catfish diets can be replaced with soybean flour and that catfish can effectively utilize supplemental methionine, thereby allowing up to 75% of the dietary fish meal protein to be replaced by soybean flour.     

Lecithin essay in the diet of young Penaeus vannamei (Crustacea: Decapoda)

The effect of different lecithin sources and presentations on growth, food conversion ratio and survival of P. vannamei (290 mg +/- 0.02) was studied. The bioassay was designed in order to compare different dietary levels and different quality of lecithin. Squid lecithin, crude soybean (7%), deoiled soybean lecithin (3.48%) in combination with fish oil or squid neutral lipids, in a partially dilapidate formula. The isoenergetic diets were fed ad libitum to four replicate groups (tanks) of 15 shrimps each (5 x 4 x 15), during 28 days. The result of the bioassay with the partially dilapidate formulas was; the best growth rate (191%) and FCR (1.69 +/- 0.041) were obtained with the diet containing 7% of soybean crude lecithin as the unique lipid source. Followed by the diet countering 3.94% deoiled lecithin and 2.42% Menhaden oil (172% and 2.03 +/- 0.054 respectively). As expected, the worst results were obtained without the dietary lecithin 121% and 2.42 +/- 0.129). Crude soybean lecithin alone covered the phospholipid and neutral lipids requirements as well as the combination of deoiled soybean lecithin with fish or squid oil.     

Linolenic acid supplementation in the diet of European catfish (Silurus glanis): effect on growth and fatty acid composition

In an 18‐week treatment, the effect of linolenic acid on European catfish (Silurus glanis L.) growth indicators was investigated as to weight gain, feeding coefficient (FCR value), specific growth rate (SGR value), protein efficiency ratio (PER value), productive protein value (PPV) and survival rate. Concurrently, the fishmeat chemical composition was also investigated. The experiment was organized into four groups, each divided into three subgroups. Stocked in each of 12 cages were 30 × 1‐year‐old catfish, with individual weights ranging from 148.5 to 151.5 g/ind. All fish were given standard feed for European catfish which contained 45% protein. The first batch, control group (C), received no additional linolenic acid. Linolenic acid was added to the feed of the second (E₁), third (E₂) and fourth group (E₃), at 0.5, 1.0 and 1.5%, respectively. Growth indicator improvement was best in the E₂ group fed the 1% linolenic acid, whereby the fish weight gain was 12.6% higher and the feeding coefficient 12.9% lower, while SGR, PER and PPV values were 6.1, 12.0 and 15.8% better than the control group. Growth indicators were also significantly (P < 0.01) improved in the three groups receiving additional linolenic acid in comparison to the control group. Moreover, this addition positively affected fishmeat quality by increasing meat protein content from 18.04% (C) to 18.79% (E₃). The total unsaturated fatty acid content also increased from 65.07% (C) to 69.82% (E₃), and the total saturated fatty acid content decreased from 31.36% (C) to 26.50% (E₃); consequently, the ratio of unsaturated to saturated fatty acids increased from 2.07% (C) to 2.63% (E₃). It can be concluded that the addition of 1% linolenic acid to standard catfish feed has beneficial effects on fish growth indicators and meat quality.     

4 种不同脂肪源对太平洋鲑生长和体组成的影响

在日粮中添加11.5%的4 种不同来源脂肪饲养180 尾初始重约为110g 的太平洋鲑(Oncorhynchus spp.)于水泥池中56d。实验分4 组,每组3个平行池,每池15尾鱼。研究日粮中4 种不同来源脂肪对淡水养殖太平洋鲑生长性能、体组成与品质的影响。4 组脂肪源分别为鱼油(实验1 组)、大豆油(实验2 组)、大豆磷脂(实验3 组)和玉米油(实验4 组)。实验表明:(1) 实验各组太平洋鲑存活率相似,但大豆磷脂组的特定生长率显著好于鱼油组、大豆油组和玉米油组(P0.05)。大豆磷脂组、大豆油组和玉米油组的饲料效益显著好于鱼油组(P< 0.05); (2) 大豆油组、大豆磷脂组和玉米油组太平洋鲑肠系膜脂肪与肝脏脂肪含量不同程度低于鱼油组,而肌肉中脂肪含量不同程度低于鱼油组; (3) 实验各组太平洋鲑肝脏脂肪、肌肉脂肪和肠脂中总多不饱和脂肪酸组成基本相似,但玉米油组、大豆磷脂组和大豆油组太平洋鲑总n-3 多不饱和脂肪酸比例较鱼油组显著下降,而总n-6 系多不饱和脂肪酸比例显著提高(P<0.05);(4) 玉米油组、大豆磷脂组和大豆油组太平洋鲑血浆中脂肪分解酶、甘油三酯和高密度脂蛋白指标较鱼油组不同程度上升;(5) 实验各组太平洋鲑解剖组织学检查未见异常病理变化。实验结果表明,淡水养殖条件下,太平洋鲑日粮中脂肪以添加大豆磷脂的生长性能最好,大豆油、玉米油和鱼油效果相似,添加玉米油、大豆磷脂和大豆油均不影响太平洋鲑健康状况和品质。       

Effect of dietary carbohydrate-to-lipid ratios on growth and feed utilization in Chinese longsnout catfish (Leiocassis longirostris Günther)

An 8‐week growth trial was carried out in a semi‐recirculation system at 26 ± 0.5°C to investigate the optimal dietary carbohydrate‐to‐lipid (CHO:L) ratio for carnivorous Chinese longsnout catfish (Leiocassis longirostris Günther). Triplicate tanks of fish were assigned to each of five isocaloric and isonitrogenous diets with different carbohydrate‐to‐lipid ratios (0.75, 1.48, 1.98, 2.99 and 5.07). The results showed that a higher specific growth rate (SGR) and feed rate (FR) were observed in the fish fed diet ratios of 1.98 CHO:L (P < 0.05). Overloading dietary carbohydrate (5.07 CHO:L ratio) caused skeletal malformations. Apparent digestibility of dry matter (ADC_d) significantly increased with dietary CHO:L ratio (P < 0.05), while significantly higher apparent digestibility of protein (ADC_p) and apparent digestibility of energy (ACD_e) was observed only in the 1.98 CHO:L group (P < 0.05). Whole body contents of dry matter, lipid and energy significantly increased as the CHO:L ratio decreased (P < 0.05). The hepatosomatic index (HSI) was highest at 1.98 CHO:L ratio (P < 0.05). Highest dietary CHO:L ratio resulted in lower liver glycogen, liver lipid, plasma glucose and plasma triacylglycerol (P < 0.05), whereas there was no significant difference in plasma total cholesterol (P > 0.05). High dietary CHO:L ratio caused pathological changes in fish morphology and liver histology. Based on maximum growth, the optimal carbohydrate‐to‐lipid ratio was 1.98 for Chinese longsnout catfish.     

Growth performance and body composition in response to dietary protein and lipid levels in Nile tilapia (Oreochromis niloticus Linnaeus, 1758) subjected to normal and temporally restricted feeding regimes

A factorial experiment was designed to examine the effect on compensatory growth (CG) of Nile tilapia Oreochromis niloticus fed diets containing different protein and lipid levels under normal and temporally restricted feeding regimes. Four diets were formulated to contain either 30% or 36% crude protein, and 5% or 11% crude lipid. Triplicate replicates of each treatment were assigned to 24 150‐L tanks (20 fish/tank density). Fish (mean initial weight ± SD = 8.79 ± 0.34 g) were then fed either the normal feeding regime (thrice daily to apparent satiation) or the restricted regime (1 day feed deprivation followed by 3 days of feeding to apparent satiation) over a 44‐days study period. Fish receiving a diet under the restricted regime achieved weight gains (WG) comparable to fish consuming the diet containing 30% protein and 5% lipids under the normal feeding regime. Fish maintained on the restricted feeding regime exhibited reduced feed intake (FI), WG, feed efficiency ratio (FE), protein efficiency rate (PER) and hepatosomatic index versus fish on the normal feeding regime, except WG in fish fed the diet with 30% protein and 5% lipids. However, the resultant FI (85%~94%) was higher than the excepted 75% intake when fish were subjected to the restricted regime. Feeding 11% lipid diets led to improved FI, WG, FE, and PER compared to feeding the 5% lipid diets. Increased FI, WG, and FE, but reduced PER were observed in fish fed with 36% protein versus fish fed 30% protein. Fish receiving the 36% protein diets had lower whole‐body moisture and ash contents, but elevated whole‐body protein and lipid contents compared to those receiving the 30% protein diets. Whole‐body moisture contents were lower, but whole‐body protein, lipid and ash contents were higher in fish fed 11% lipid diets than in fish fed 5% lipid diets. There was an increase in whole‐body moisture content, but a decrease in protein and lipid content in response to the restricted feeding regime. Ash content was not affected by the feeding regime. The present study shows that Nile tilapia fed diets subjected to a restricted feeding regime exhibited growth comparable to those fed the diet at 30% protein and 5% lipid levels under a normal feeding regime. This positive effect was more pronounced in diets at a high protein level or in a combination of high protein and lipid levels.     

Effect of soybean oil and glucose on sophorose lipid fermentation by Torulopsis bombicola in continuous culture

The effect of soybean oil and glucose on the growth of Torulopsis bombicola and sophorose lipid production in continuous culture was investigated. As the dilution rate in 100 g/l glucose and 100 g/l soybean oil medium was increased, the dry cell weight and sophorose lipid concentration decreased. Sophorose lipid productivity, however, was maximum at a dilution rate of 0.03 h⁻¹. The cell yield from glucose and the sophorose lipid production from soybean oil were approximately constant regardless of the dilution rate. The specific consumption rate of soybean oil was closely related to the specific production rate of sophorose lipid. These results suggest that soybean oil was used only for sophorose lipid production whereas glucose was used only for cell mass and maintenance. When the soybean oil concentration was varied at fixed dilution rate in 100 g/l glucose medium, a high concentration of soybean oil was found to inhibit sophorose lipid production. Received: 9 January 1997 / Received revision: 5 March 1997 / Accepted: 13 April 1997     

Stacking of a stearoyl‐ACP thioesterase with a dual‐silenced palmitoyl‐ACP thioesterase and ∆12 fatty acid desaturase in transgenic soybean

Soybean (Glycine max (L.) Merr) is valued for both its protein and oil, whose seed is composed of 40% and 20% of each component, respectively. Given its high percentage of polyunsaturated fatty acids, linoleic acid and linolenic acid, soybean oil oxidative stability is relatively poor. Historically food processors have employed a partial hydrogenation process to soybean oil as a means to improve both the oxidative stability and functionality in end‐use applications. However, the hydrogenation process leads to the formation of trans‐fats, which are associated with negative cardiovascular health. As a means to circumvent the need for the hydrogenation process, genetic approaches are being pursued to improve oil quality in oilseeds. In this regard, we report here on the introduction of the mangosteen (Garcinia mangostana) stearoyl‐ACP thioesterase into soybean and the subsequent stacking with an event that is dual‐silenced in palmitoyl‐ACP thioesterase and ?12 fatty acid desaturase expression in a seed‐specific fashion. Phenotypic analyses on transgenic soybean expressing the mangosteen stearoyl‐ACP thioesterase revealed increases in seed stearic acid levels up to 17%. The subsequent stacked with a soybean event silenced in both palmitoyl‐ACP thioesterase and ?12 fatty acid desaturase activity, resulted in a seed lipid phenotype of approximately 11%–19% stearate and approximately 70% oleate. The oil profile created by the stack was maintained for four generations under greenhouse conditions and a fifth generation under a field environment. However, in generation six and seven under field conditions, the oleate levels decreased to 30%–40%, while the stearic level remained elevated.     

Effects of dietary whole and defatted Arthrospira platensis (Cyanobacterium) on growth,body composition and pigmentation of the yellow catfish Pelteobagrus fulvidraco

The cyanobacterium Arthrospira platensis is regarded as a potential future source of food for humans due to its superior nutritional value compared with many conventional crops. An 8-week feeding trial was conducted to evaluate nutritional and pigmentation effects of whole A. platensis, defatted A. platensis and its lipid extracts in diets for the yellow catfish Pelteobagrus fulvidraco. Four percent whole A. platensis (AP4), 0.4% A. platensis lipid extracts (AL0.4), and 4% defatted A. platensis (AR4) were used as experimental diets, and a diet without any A. platensis was as the control diet (AP0). The AP4 and AL0.4 groups had no effects on the growth performance and feed utilization in yellow catfish; however, the AR4 group was significantly lower than the AP0 group in terms of specific growth rate and feed efficiency (P < 0.05). AP4 and AL0.4 groups significantly increased the body protein of fish (P < 0.05). The skin color was significantly improved in the AP4 and AL0.4 groups, as well as the fish skin and plasma lutein contents (P < 0.05). Correlations between skin color and the lutein contents in liver and muscles were weak, whereas the correlations between skin color and the lutein contents in skin and plasma were significant and strong. The results suggest that whole A. platensis and its lipid extracts can be functional additives to improve whole body protein and skin color of fish, while defatted A. platensis showed no advantage in yellow catfish diets.

     

Effects of dietary l-tryptophan and lighting conditions on growth performance of European sea bass (Dicentrarchus labrax) juveniles reared in a recirculating water system

The aim of the present study was to investigate possible stressful effects on European sea bass Dicentrarchus labrax reared under constant darkness (0L‐24D) and to examine the possible anti‐stressful effect of dietary tryptophan (TRP) supplementation. Juvenile European sea bass (initial body weight 4.23 ± 0.032 g) were reared for 10 weeks under 0L‐24D and 12L‐12D and fed either a commercial diet (0.47% TRP) or the same diet supplemented with L‐TRP (2.47% TRP). Results showed that lighting conditions had no significant effect on fish growth, while a depressive effect by the TRP supplementation was obvious. All fish populations reared under 0L‐24D exhibited reduced body protein, lipid and ash content and increased food consumption. Reduced body lipids, food consumption and nutrient utilization were observed in TRP‐supplemented fed fish, along with lower liver lipids. Dietary TRP enrichment significantly lowered liver saturated and monounsaturated acids and increased poly‐ and highly‐unsaturated fatty acids, especially in combination with 0L‐24D. These changes were also considerably reflected in carcass fatty acid composition.     

饲料脂肪水平对瓦氏黄颡鱼生长及脂蛋白脂酶基因表达的影响

研究采用脂肪水平分别为4.7%、7.9%、10.9%、15.4%、18.9%的五种等氮配合饲料饲喂瓦氏黄颡鱼早期幼鱼,进行了为期30d的生长实验,探讨了瓦氏黄颡鱼早期幼鱼的脂肪需求。并克隆了瓦氏黄颡鱼脂蛋白脂酶(LPL)cDNA序列片段,采用实时荧光定量PCR研究了饲料脂肪水平对肝脏LPL基因表达水平的影响。结果表明,饲料脂肪水平从4.7%增加到10.9%显著促进了瓦氏黄颡鱼早期幼鱼的生长(P<0.05)。饲料脂肪水平显著影响了实验鱼的鱼体体成分,随着饲料脂肪水平的升高,鱼体干物质和脂肪含量显著增加而蛋白含量显著下降(P<0.05)。高脂诱导了瓦氏黄颡鱼肝脏LPL基因表达,摄食15.4%、18.9%这两组较高脂肪水平的实验鱼肝脏LPLmRNA表达水平显著升高(P<0.05)。根据特定生长率通过折线回归分析得出瓦氏黄颡鱼早期幼鱼最适脂肪水平为11.2%。       

Effect of dietary fish oil replacement with palm oil on growth performance,hematology and liver anti‐oxidative enzymes of juvenile Japanese flounder Paralichthys olivaceus (Temminck & Schlegel, 1846)

A 60‐day feeding trial was conducted to evaluate the effects of dietary palm oil supplements on growth performances, hematology, liver anti‐oxidative enzymes and air exposure resistance of Japanese flounder, Paralichthys olivaceus (initial weights 2.56 ± 0.01 g). Five diets were tested wherein the dietary fish oil was replaced by palm oil at: 0% (Control), 20% (20%), 40% (40%), 50% (50%) and 60% (60%). After the feeding trial, the 20% dietary palm oil was shown to provide similar growth rates and feed efficiency with no negative effects compared to the control group (P > 0.05). Significantly lower growth rates and feed utilization were found in fish fed higher than 40% palm oil in the diet (P < 0.05). Except for total serum protein, the blood parameters, liver anti‐oxidative enzymes, stress resistance and proximate compositions of Japanese flounder were not altered, even with dietary palm oil up to 60% of the lipid source (P > 0.05). According to the present results, palm oil is a valuable lipid source substitute in Japanese flounder diets; around 20–40% fish oil can be replaced with palm oil with no negative effects.     

黑水虻虫油替代豆油对黄颡鱼幼鱼生长、血清生化指标和肝脏脂滴面积的影响

试验旨在研究黑水虻(Hermetia illucens L.)虫油替代饲料中豆油对黄颡鱼(Pelteobagrus fulvidraco)幼鱼生长性能、血清抗氧化能力、炎症因子及肝脏脂滴面积的影响。以豆油为对照组(T0), 虫油分别替代20%(T20)、40%(T40)、60%(T60)、80%(T80)、100%(T100)的豆油, 配置6种等氮等脂的试验饲料。选取初始体重为(2.12±0.01) g 的黄颡鱼幼鱼840尾, 随机分为6组, 每组4个重复, 每个重复35尾, 养殖56d。结果表明: 黑水虻虫油替代豆油对黄颡鱼幼鱼的末均重、增重率、特定生长率、饲料系数、存活率、摄食率均无显著影响(P>0.05); 各组间黄颡鱼肥满度、腹脂指数、脏体比、肝体比无显著差异(P>0.05); 全鱼粗蛋白、粗脂肪、水分、灰分、钙、磷含量无显著差异(P>0.05); 黑水虻虫油替代豆油对饲料的干物质、蛋白质、脂肪、磷及能量的表观消化率未产生显著影响(P>0.05), 但T60和T80组钙的表观消化率显著高于T100组(P<0.05), 与对照组相比差异不显著(P>0.05)。各组间黄颡鱼幼鱼血清白蛋白、低密度脂蛋白胆固醇、甘油三酯、谷丙转氨酶、谷草转氨酶、尿素氮、球蛋白、乳酸脱氢酶、血糖、总蛋白差异不显著(P>0.05), 但高密度脂蛋白胆固醇含量则随着替代比例的增加先上升后下降, T60组和T80组显著高于对照组(P<0.05)。各组间黄颡鱼幼鱼血清中抗超氧阴离子和丙二醛含量, 过氧化氢酶、超氧化物歧化酶活性无显著差异(P>0.05); 与对照组相比, 各处理组血清肿瘤坏死因子-α浓度无显著性差异(P>0.05); 当黑水虻虫油替代比例超40%时, 各处理组血清中抗炎因子白介素-10和促炎因子白介素-6及白介素-8的浓度均显著高于对照组(P<0.05)。油红O染色显示, 黑水虻虫油替代豆油对肝脏脂滴面积无显著影响(P>0.05)。综上所述, 黑水虻虫油完全替代豆油对黄颡鱼幼鱼生长性能、形体指标、体成分、营养物质表观消化率和抗氧化指标无显著影响, 以生长性能为评价指标, 当黄颡鱼幼鱼基础饲料中添加4%豆油时, 黑水虻虫油完全替代豆油。     

Absorption of food in Heterotis niloticus (Cuvier) (pisces: osteoglossidae) from a small tropical man-made lake in Ibadan, Nigeria

The protein, carbohydrate and lipid contents of the food ingested and their absorption in the intestine of Heterotis niloticus inhabiting a small man-made lake; Awba Lake, in Ibadan were investigated.The ingested food had mean total protein, mean total carbohydrate and mean total lipid contents of 53.0%, 28.8% and 15.5% of the organic content, respectively. Calculated percentages absorbed were 56.4–72.7% (mean — 64.9%) total protein, 32.2–50.8% (mean — 40.3%) total carbohydrates and 71.9–87.3% (mean = 78.3%) lipid.Absorption mostly occurred in the fore-gut (the first one-third of the intestine) and least in the hind-gut (the last one-third of the intestine). Different sizes of fish showed different dietary protein, carbohydrate and lipid contents. Absorptive capacity for these components of the food also varied with fish size.     

Growth performance and metabolic response of juvenile grouper Epinephelus moara (Temminck & Schlegel, 1842) fed low dietary protein and high lipid levels

Nine test diets were formulated at three low levels of crude protein (P; 35%, 40% or 45%) and three high levels of crude lipid (L; 9%, 12% or 15%) to investigate whether Epinephelus moara differs in the nutrient requirements from any of the other closely‐related grouper species, and if there are any indications that a further decrease in protein with increasing dietary lipid would induce a higher protein‐sparing effect. Fish (20.34 ± 0.82 g/ind) were distributed among 27 experimental cages (100 cm diameter, 80 cm depth), with 20 fish per cage and three replicates for each test diet. The experiment was conducted over an 8‐week period at a temperature of 23.9–25.7°C. Weight gain and specific growth rate (SGR) tended to increase either with an increase in dietary protein level (at the same lipid level) or with the increase in dietary lipid level (at the same protein level, except at the 45% protein level). The highest weight gain and SGR occurred in fish fed the diet P45/L12. The serum cholesterol, high‐density lipoprotein‐cholesterol (HDL‐C) and low‐density lipoprotein‐cholesterol (LDL‐C) contents in fish were significantly increased as the dietary lipid increased. The increase of dietary protein significantly decreased the activities of serum and hepatic alanine aminotransferase (ALT) as well as aspartate aminotransferase (AST). Hepatic fatty acid synthase (FAS) activity significantly increased with the decrease of dietary protein and lipid levels (p < .05). However, lipoprotein lipase (LPL) activity showed an inverse trend compared to FAS. Hepatic glutamate dehydrogenase (GDH) activity significantly increased with the increase in the dietary protein level. In conclusion, the results reveal that growth performance and metabolic responses of E. moara are dependent on dietary protein and lipid levels, and that protein‐sparing action can be induced by increasing the dietary lipid. To support the feeding and growth of juvenile E. moara under the present conditions, 45% protein and 12% lipid are adequate.     

Growth performance and body composition of sub-yearling Persian sturgeon, (Acipenser persicus, Borodin, 1897), fed different dietary protein and lipid levels

In order to evaluate the protein and energy requirement of Persian sturgeon (Acipenser persicus) sub‐yearlings, eight experimental diets containing two protein levels (40% and 45%) and four lipid levels (10%, 15%, 20% and 25%) were tested. Sturgeons (W₀ = 136.8 g) were fed the experimental diets to satiation four times daily for 150 days, resulting in a final mean weight of 375.8 g. Growth was significantly affected by lipid content of the diets. At 40% protein level, weight gain and specific growth rate (% per day) were significantly improved (P < 0.05) by increasing the dietary lipid (energy) content. Protein efficiency ratio (PER) was significantly affected by different dietary treatments for each dietary protein level tested, reaching a mean value of 3.58 in fish fed high lipid diets and a PER of 2.77 in low lipid diets. Results obtained in the present study suggest that the optimum dietary protein content for Persian sturgeon is 40%, with an estimated optimum protein‐to‐energy ratio of 18–20 mg kJ⁻¹.