The effect of dietary protein source on growth and carcass composition in juvenile Australian freshwater crayfish

A feed trial was conducted for 12 weeks on juvenile Australian freshwater crayfish (Cherax destructor) (mean weight (SE) 0.82 (0.02)g) maintained on five isoenergetic diets with a protein content of 30%. Diets differed in the primary source of protein used, with meat, snail, soybean, yabby, and zooplankton meals comprising the major protein ingredient, varying from 56–60% of total protein. Mean percentage weight gain per day ranged from 7.57% (yabby meal diet), to 9.42% (snail meal diet). No significant difference occurred in mean weight, percentage weight gain, specific growth rate (%), or survival among diets. A maximum size of 16.44g was attained on the yabby meal diet. Largest mean weight was 8.27g on the snail-based diet. Food conversion ratios were all good, with a minimum value of 0.95 recorded for the snail-based diet. Initial food consumption per day was approximately 5% of mean animal weight, decreasing to around 2.4%, and is collectively described by a power curve. Protein retention ranged from 29.57% in the zooplankton meal diet to 41.15% in the snail-based diet. Carcass composition was influenced by feed type, with the most marked difference occurring in carapace colour. Animals fed the zooplankton-based pellets developed the strongest pigmentation. Recommendations are made for including certain protein-based ingredients in manufactured yabby diets.     

Partial and total replacement of fish meal with soybean meal and brewer's grains with yeast in practical diets for Australian red claw crayfish Cherax quadricarinatus

Three feeding studies were conducted to evaluate the effects of total replacement of fish meal (FM) with a combination of soybean meal (SBM) and brewer's grains with yeast (BGY) in diets for two separate strains of juvenile Australian red claw crayfish. In Experiment 1, three practical diets were formulated to be isonitrogenous (40% protein) and isocaloric (4.0 kcal available energy/g diet) and contained either 25%, 10%, or 0% fish meal. Variable percentages of SBM (35%, 46.8%, and 79.8%, respectively) and BGY-35 (0%, 30%, and 5%, respectively) replaced the fish meal. In Experiments 2 and 3, four practical diets were formulated to be isonitrogenous (40% protein) and isocaloric (4 kcal available energy/g diet) containing 24% or 0% fish meal. Diet 1 contained 24% fish meal, 23% SBM, and 0% BGY-35. A variable percentage of SBM (56.75%, 47.75%, and 40.75%, respectively) and BGY-35 (10%, 20%, and 30%, respectively) replaced the fish meal in the remaining three diets.

In Experiment 1, after 8 weeks, juvenile red claw fed all three diets had no significant difference (P>0.05) in final weight, percentage weight gain, or survival, which averaged 7.90 g, 3848%, and 83%, respectively. In Experiment 2, after 8 weeks, juveniles fed all four diets had no significant difference in final weight, percentage weight gain, or specific growth rate which averaged 11.46 g, 977%, and 3.08%/day, respectively. Percentage survival was not significantly different among treatments and averaged 79%. In Experiment 3, after 8 weeks, juvenile red claw fed all four diets had no significant difference in final weight, percentage weight gain, or specific growth rate which averaged 16.22 g, 457%, and 2.34%/day, respectively. Percentage survival was not significantly different among treatments and averaged 98%.

These results indicate that fish meal and shrimp meal can be totally replaced with soybean meal and BGY in diets for juvenile red claw crayfish. This may allow for less expensive diets by red claw producers, which may increase profitability.     

Effects of different feed stimulants on freshwater crayfish (Procambarus clarkii), fed diets with or without partial replacement of fish meal by biofeed

The feeding trials were carried out with freshwater crayfish (Procambarus clarkii) to evaluate the three feed stimulants betaine (Bet), squid extract (SE) and squid meal (SM) upon fish meal (FM) diets or biofeed (BF) diets in which FM were partially replaced by BF. Results showed the three feed stimulants had no significant effect on growth. By the relative concentration of markers in the faeces and diets, the preference for each diet was estimated, and the best stimulant was the mixture of Bet, SE and SM. As FM replaced by BF increased, added with the mixture, the relative weight gain showed an increasing trend, but decreased significantly by 30% replacement. With the substitution increasing, trypsin activities increased, whereas decreased too upon 30% substitution. Less than 30% replacement, there was no significant effect on muscle proximate composition, intestine amylase activities and serum haemocyanin contents, except the drop of lipid. The results indicated that the mixture of Bet, SE and SM could perform well as a feed stimulant. And with the addition of the mixture, FM in the diet could make about no more than 20% saving without any adverse effects.     

Production of Australian freshwater crayfish in earthen-based systems using pelleted diets and forage crops as food

Juvenile Cherax destructor (commonly called theyabby) were cultured in earthen-based ponds and tanks for 70–105d, and were fed pellets and/or a forage crop of the perennialwhiteclover, Trifolium repens. Three supplementary feedingstrategies were evaluated. Yabby growth on pellets consistently exceeded (by67–159%) that obtained on clover. Base-line yields for extensiveproduction systems are around 400 kg ha^–1. Thesupplementary addition of T. repens produced yields of 635kg ha^–1 (in ponds) to 1086 kgha^–1 (in tanks). The sequential addition of cut-cloverto tanks stimulated growth to levels approaching those achieved on pellets.Yabbies stocked into ponds at 17 m^–2 and fed 33%protein pellets for 100 d, resulted in a yield of 1117 kgha^–1.Pellet inputs at a rate of 129–249 g m^–2(dry matter) and 38–83 g m^–2 (protein) over70–100 d resulted in acceptable growth and feed utilisationindices. Clover inputs of 534–682 g m^–2 (asdry matter) or 84–177 g m^–2 (as protein)produced reasonable growth rates but poor feed utilisation indices. Aconsiderable quantity of the dry matter and protein content of clover waseitherinefficiently utilised or directed into other production pathways. In tanks,clover inputs from 113–296 g m^–2 (drymatter) and 24–54 g m^–2 (protein) weresufficient to maintain high growth rates for 4 weeks, while in ponds, inputs of21 g m^–2 (dry matter) and 4.3 gm^–2 (protein) were sufficient for 3 weeks. During theearly weeks of production no growth advantage was gained by providing pelletstoanimals cultured in forage-based systems. Forage depletion occurred after3–4 weeks and was probably a major growth limiting factor.     

Effect of replacing fish meal with soybean meal on growth, feed utilization and carcass composition of cuneate drum (Nibea miichthioides)

The effect of replacing fish meal with soybean meal (SBM) in practical feeds for cuneate drum was evaluated in an 8-week net pen trial. The cuneate drum fingerlings (initial body weight 29.8 ± 1.3 g fish^− 1) were fed six isonitrogenous and isocaloric feeds containing 39% digestible protein and 16 MJ kg^− 1 digestible energy. The control feed was formulated to contain 40% herring meal, whereas in the other five feeds SBM was included at 11.3, 22.5, 33.8, 45.0 and 56.3% to replace 20, 40, 60, 80 or 100% of the fish meal. There were no significant differences in feed intake between fish fed the control feed and feeds in which SBM replaced 20 to 80% of the fish meal, but fish fed the fish meal free feed had higher feed intake than the other treatments. Weight gain linearly declined with the decrease of fish meal level. Final body weight (FBW) of fish fed the feeds in which SBM replaced 20% of the fish meal did not significantly differ from fish fed the control feed. Replacing 40 to 100% of the fish meal resulted in lower FBW and nitrogen retention efficiency (NRE), and higher feed conversion ratio (FCR) than those of fish fed the control feed. Fish fed the feeds in which SBM replaced 60 to 100% of the fish meal had lower condition factor and hepatosomatic index than those of fish fed the control feed. No significant differences in carcass protein content was found among the treatments, but fish fed the feeds in which SBM replaced 60 to 100% of the fish meal had higher moisture and lower lipid content in carcass than those of fish fed the control feed. Results of the present study appear to indicate that cuneate drum has a limited ability to utilize SBM as a protein source in practical feeds.     

豆粕替代鱼粉对牛蛙生长、体组成、消化酶活力及肝脏生化指标的影响

为减少牛蛙饲料鱼粉使用量以降低养殖成本,研究了豆粕替代饲料中不同比例的鱼粉对牛蛙的生长性能、体组成、肠道消化酶活力和肝脏生化指标的影响。用豆粕分别替代0%、20%、40%、60%、80%和100%的鱼粉配制出6种等氮等能的实验饲料,每组饲料设3重复,养殖牛蛙60 d。结果显示,豆粕替代鱼粉对牛蛙摄食率、成活率、肝体指数、脏体指数、蛙体水分和灰分含量、蛙腿肌肉组成以及肝脏丙二醛含量的影响不显著;豆粕100%替代鱼粉显著降低牛蛙增重率、特定生长率、饲料系数、蛋白质效率、蛋白质累积率;随豆粕替代鱼粉比例的提高,牛蛙的肥满度和后腿指数呈下降趋势,替代100%鱼粉显著降低牛蛙肥满度,替代60%鱼粉显著降低牛蛙后腿指数;替代80%鱼粉显著降低牛蛙全体粗蛋白的含量;牛蛙全体粗脂肪含量随替代鱼粉比例的提高呈上升的趋势,替代100%鱼粉组粗脂肪含量最高;随着替代比例的提高,牛蛙肠道蛋白酶的活力显著降低,而肠道淀粉酶和脂肪酶活力显著提高。豆粕替代鱼粉显著影响肝脏超氧化物歧化酶和过氧化氢酶活力,其中超氧化物歧化酶活力最低值出现在替代80%鱼粉组,过氧化氢酶活力最低值出现在替代100%鱼粉组。基于以上实验结果,建议牛蛙饲料中豆粕可替代鱼粉的比例为60%~80%。     

豆粕替代鱼粉对青鱼幼鱼生长及生理生化指标的影响

以初始体重(5.90±0.01)g的青鱼(Mylopharyngodon piceus)为研究对象,用豆粕替代不同水平鱼粉,配制5种等氮等能的实验饲料,分别为30%鱼粉(对照组)、25%鱼粉、20%鱼粉、15%鱼粉和15%鱼粉+晶体氨基酸,试验持续8周。结果显示:当鱼粉含量为15%时,其增重率、特定生长率、肌肉鲜味氨基酸含量和总氨基酸含量显著低于对照组,而饲料系数则显著高于对照组,添加晶体氨基酸对青鱼生长无显著改善;各处理组间甘油三酯(TG)、总蛋白(TP)、总胆固醇(TC)含量及谷丙转氨酶(ALT)活性无显著差异,但15%鱼粉组和15%鱼粉+晶体氨基酸组的青鱼的血糖含量和谷丙转氨酶活性显著高于对照组。结果表明,青鱼幼鱼实用饲料中鱼粉含量以不低于20%为宜,添加晶体氨基酸对青鱼幼鱼的生长无改善作用。     

豆粕替代鱼粉对红螯螯虾幼虾生长、肌肉组成和消化酶活力的影响

为探讨红螯螯虾幼虾的饲料豆粕替代鱼粉的适宜替代量,配制5种不同替代水平(0、40%、60%、80%和100%)的等氮等能饲料,饲喂初重(0.53±0.06)g的红螯螯虾幼虾8周,测定其生长性能、肌肉组成、肝胰腺消化酶活力及抗氧化活力。结果显示,豆粕替代鱼粉对螯虾存活率没有显著影响;与对照组相比,豆粕替代鱼粉的替代量为40%~80%时,红螯螯虾幼虾的增重率和特定生长率没有显著变化;替代量为100%时,螯虾增重率和特定生长率显著下降,螯虾肌肉的蛋白质含量呈现一定程度的下降;豆粕替代鱼粉对螯虾肌肉的脂肪和灰分含量没有显著影响;随着替代量的增加,螯虾肝胰腺胰蛋白酶活力呈现下降的趋势,当替代量为100%时,胰蛋白酶活力显著下降;豆粕替代鱼粉对螯虾肝胰腺脂肪酶、淀粉酶和超氧化物歧化酶(SOD)活力均没有显著影响;替代量为100%时,螯虾肝胰腺总抗氧化活力(T-AOC)显著下降。结果表明,豆粕替代鱼粉的替代量为40%~80%时,对螯虾的生长性能、肌肉组成、消化酶活力和抗氧化活力均没有显著影响,替代量为100%时,显著抑制螯虾的生长、胰蛋白酶活力和T-AOC。根据本试验结果,建议红螯螯虾幼虾饲料中豆粕替代鱼粉的替代量为80%。     

Effects of dietary substitution of soya bean meal for fish meal on consumption, growth, and metabolism of juvenile giant freshwater prawn, Macrobrachium rosenbergii

A 42‐day study was conducted where prawns (0.32 g) were fed diets where 0, 20, 50, 75 and 100 g (100 g)^?1 of fish meal was replaced by soya bean meal (SBM). Feed intake was not significantly affected by inclusion of SBM, while specific growth rate and conversion efficiency decreased with increasing dietary SBM. Standard metabolic rate was significantly affected by dietary soya bean level, and was the highest in the 75 g (100 g)^?1 SBM group. Carcass dry matter, crude fat and energy value declined with increasing SBM inclusion. SBM, without supplementation of amino acids or other additives, was not suitable as a major protein source in freshwater‐prawn diets.     

Incisor ridge modification of the mandibles in freshwater crayfish, Astacus leptodactylus

The differences in the ridge structure of the mandibles of different size Astacus leptodactylus (32–80 mm carapace length, CL) were investigated. The results showed that a modification occurs with an increase in size in the incisor ridge of mandibles in A. leptodactylus. The results also showed that A. leptodactylus possesses four different types of ridge structure in the mandibles. These are: (1) Incisor ridge with big teeth (dentate crenate), (2) Blade-like incisor ridge with numerous small teeth, (3) Blade-like ridge (toothless), (4) Blunt ridge. In conclusion, it is thought that the incisor ridge modification of the mandibles may cause the difference in the food choice of different size A. leptodactylus, because, crayfish possessing different ridge structures of the mandible may probably feed on different type of food.     

饲料低蛋白、高脂肪和高消化能对斑点叉尾鮰

为了探讨高脂肪条件下不同的蛋白和能量水平对斑点叉尾鮰生长及体组成的影响,试验设2个蛋白水平(22%,28%),2个脂肪水平(10.0%,14.0%),2个消化能水平(12.56 kJ/g,14.23 kJ/g),共8组,分别为P28L10E14.23,P28L14E14.23,P22L10E14.23,P22L14E14.23,P28L10E12.56,P28L14E12.56,P22L10E12.56和P22L14E12.56。试验饲料配方使用鱼粉和豆粕调节蛋白含量,混合油脂(鱼油∶玉米油=1∶1)调节脂肪含量,α-淀粉、次粉和麸皮调节消化能含量,并以微晶纤维素为填充物,每组3个重复,每个重复20尾鱼(141.5?1.0) g。饲养60 d后,进行生产性能测定,并采集组织样本,测定相关指标。结果表明,鱼体末重(FW)、增重率(WG)、特定生长率(SGR)和饵料系数(FCR)不受饲料蛋白、脂肪和消化能单一营养水平影响(P>0.05);但与饲料蛋白、脂肪和消化能三者的交互作用(P<0.01)有关。胴体蛋白、脂肪含量与饲料脂肪和消化能水平相关(P<0.05)。由此可见,饲料过高脂肪和消化能对斑点叉尾鮰没有额外的促生长作用;饲料蛋白水平达到22%时,即可满足140~300 g斑点叉尾鮰的营养需要;饲料中22%的蛋白、10%的脂肪、12.56 kJ/g的消化能即可满足斑点叉尾鮰仔鱼的生长需要,同时又能保证其正常生理机能,建议可在实际生产配方中作参考值。     

豆粕替代鱼粉对点篮子鱼生长性能的影响

以豆粕替代鱼粉配置5组等氮(35%)等能(19.00 MJ/kg)饲料,豆粕∶鱼粉替代比分别为0∶1(D₁)、1∶2(D₂)、1∶1(D₃)、2∶1(D₄)、1∶0(D₅),研究豆粕蛋白对体重(104.64±2.76) g点篮子鱼生长性状、体成分、生物学指标的影响,从而确定点篮子鱼饵料中最佳的动植物蛋白比。试验在室内圆锥形孵化桶中进行,分5个处理,每个处理3个重复,每个重复25尾鱼。49 d养殖试验结果表明,饲料中豆粕含量对点篮子鱼生长有显著影响,特定生长速率(SGR)、增重率(WG)、摄食率(FI)与替代比成负相关,对照组(D₁)［11.87(100 g)/d］FI显著高于全豆粕组(D₅)［5.81(100 g)/d］。饲料系数(FCR)与替代比成正相关,D₅组FCR高达2.97。饲料中豆粕含量水平对肌肉粗蛋白与水分含量无显著影响,对全鱼粗蛋白和脂肪影响显著,粗蛋白在D₅组取得最小值19.11%。肝脏蛋白含量随饲料中豆粕含量增加呈先增加后降低趋势,高豆粕含量组肝脏脂肪含量显著低于低豆粕组。蛋白替代对点篮子生物学指标影响较小。综合考虑SGR、FCR、FI等指标,点篮子鱼饲料中豆粕替代鱼粉比不宜大于1∶2。但从肌肉营养品质方面考虑,替代比可以达到2∶1。     

蟋蟀粉替代鱼粉对黄颡鱼幼鱼生长性能、肌肉氨基酸组成和血清生化指标的影响

为研究蟋蟀(Gryllus bimaculatus)粉替代鱼粉对黄颡鱼(Pelteobagrus fulvidraco)幼鱼生长性能、肌肉成分和血清生化指标的影响,以黄颡鱼幼鱼[(2.0±0.13) g]为研究对象,分别使用蟋蟀粉替代0 (对照组)、15%、30%、45%和60%的鱼粉配制成5组等氮等能的实验饲料,分别记为T0、T15、T30、T45和T60组。实验幼鱼在室内循环水系统进行为期10周的养殖实验。结果显示,随着蟋蟀粉替代量的增加,黄颡鱼幼鱼生长呈先增加后降低的趋势;T30组的终末均重(FBW)、增重率(WGR)和特定生长率(SGR)最高,且均显著高于T0组;T30组的饲料系数(FCR)显著低于T0和T15组;T30的肝体比(HSI)显著高于T0和T15,而与T45和T60组无显著差异。与T0组相比,各替代组的脏体比(VSI)、摄食量(FI)、肥满度(CF)和成活率(SR)均无显著差异。黄颡鱼幼鱼肌肉必需氨基酸(EAA)含量中,T60组肌肉中精氨酸(Arg)和缬氨酸(Val)含量显著高于T0组;且蟋蟀粉替代不同比例的鱼粉对黄颡鱼幼鱼肌肉中的总呈味氨基酸(TFAA)含量均未产生显著影响。T30、T45和T60组血清中的葡萄糖(GLU)含量显著高于T0组;相反,其总胆固醇(TCHO)含量显著低于T0组。在本研究条件下,蟋蟀粉替代不同比例的鱼粉不影响黄颡鱼幼鱼的生长性能和肌肉氨基酸含量,且能增加血清GLU和降低TCHO含量,以30%的蟋蟀粉替代鱼粉比例能生长最佳,且优于对照组。本研究对揭示蟋蟀粉在黄颡鱼饲料中替代鱼粉应用的可行性、为今后昆虫蛋白源在水产饲料中的开发提供科学依据。     

饲料蛋白水平对方格星虫稚虫生长和体组成的影响

以初始体重为39.20±0.24mg的方格星虫稚虫为实验对象,分别饲喂蛋白水平为25.21%、29.87%、35.03%、40.67%、45.47%、50.12%、55.29%、60.38%、64.85%的9种等能微颗粒饲料56d,研究饲料蛋白水平对方格星虫稚虫生长和体组成的影响。结果表明,饲料蛋白水平对方格星虫稚虫的生长性能有显著影响(P<0.05)。随着饲料中蛋白水平的提高,稚星虫的增重率和特定生长率都呈先增后降的趋势,当饲料蛋白水平为45.47%时,稚星虫增重率和特定生长率均达到最大值,二次曲线回归分析确定当增重率达到极值时,饲料蛋白水平为46.79%;对稚星虫体组成成分的分析表明,饲料蛋白水平对方格星虫稚虫体组成中脂肪和蛋白质的含量影响显著(P<0.05),稚星虫体蛋白含量随着饲料蛋白水平的上升有显著升高的趋势,64.85%组稚星虫体蛋白含量最高,显著高于其他各蛋白水平组(P<0.05)。体脂肪含量随着饲料蛋白水平的上升有降低的趋势,64.85%组稚星虫的体脂肪含量最低,显著低于25.21%、29.87%、35.03%和40.67%组(P<0.05)。饲料蛋白水平对稚星虫体灰分含量没有显著影响(P>0.05)。以增重率为评价指标时,方格星虫稚虫对饲料中蛋白的适宜需求量为46.79%。     

Effects of soybean meal based diet on growth performance, gut histopathology and intestinal microbiota of juvenile rainbow trout (Oncorhynchus mykiss)

Effects of soybean meal (SBM) based diet on growth performance, histology of the intestinal epithelium and on the gut microbiota of juvenile rainbow trout (Oncorhynchus mykiss) were investigated on two trials lasting for 8 weeks (Trial I) and 18 weeks (Trial II). The microbiological characterization was done both with conventional plating techniques, biochemical profiling and length heterogeneity analysis of PCR amplified 16S rDNA (LH-PCR).Typical histological changes were found after 18 weeks of SBM feeding (Trial II). Mean height of simple foldings were significantly higher within the group fed with fish meal (FM) based diet. These changes were not, however, reflected in the appearance, behavior and weight gain of the fish, although the feed conversion rate (FCR) was higher, compared to fish fed with the traditional FM feed.In both SBM and FM groups the counts of cultivable intestinal bacteria dropped within the first 4 weeks of feeding (Trial I). Subsequently, the bacterial numbers increased in the FM group, but not in the SBM group by the 8th week of the trial. The LH-PCR data suggested also that diet-related qualitative changes in the microbiota had occurred (Trial II). The main identified bacteria were mainly representatives of the genera Aeromonas, Sphingomonas and Chryseomonas, and among the lactic acid bacteria, Lactococcus and Lactobacillus.Future research will be directed to the identification and eventual elimination the SBM-associated factors involved in the inflammatory responses and unfavorable FCR, in particular by modifying the intestinal microbiota.     

家蝇蛆粉替代鱼粉对凡纳滨对虾生长、抗氧化和免疫指标的影响

设计6种等氮等能的试验饲料,以评价不同比例的家蝇蛆粉替代鱼粉对凡纳滨对虾幼虾生长性能、抗氧化以及非特异性免疫指标的影响。选用960尾体质量为(0.56±0.03)g的凡纳滨对虾随机分为6组,分别投喂用家蝇蛆粉替代鱼粉的6种饲料,替代比例(等蛋白替代)分别为0、20%、40%、60%、80%和100%,记为G0、G20、G40、G60、G80和G100。45 d的养殖试验结果显示,G20~G60组凡纳滨对虾的增重率(WGR)与对照组相比差异不显著(P>0.05),G80、G100组WGR显著降低(P<0.05)。除G40组外,各替代组凡纳滨对虾的特定生长率(SGR)均显著低于对照组(P<0.05)。G100组摄食量(FI)显著低于其它各组(P<0.05)。当替代水平不超过60%时,家蝇蛆粉对凡纳滨对虾的饲料系数(FCR)、蛋白质效率(PER)、蛋白质沉积率(PPV)和肝胰指数(HSI)影响不显著(P>0.05);随替代水平的继续增加,FCR和HSI显著升高,PER和PPV显著降低(P<0.05)。替代组对虾肥满度(CF)和存活率(SR)均不同程度的高于对照组,但差异不显著(P>0.05)。随家蝇蛆粉替代水平的增加,全虾粗蛋白、钙(Ca)和总磷(P)含量显著升高(P<0.05),粗脂肪含量显著降低(P<0.05),干物质和灰分含量差异不显著(P>0.05)。各替代组对虾血清和肝胰腺超氧化物歧化酶(SOD)活性、血清丙二醛(MDA)含量与对照组相比差异不显著(P>0.05),G80和G100组肝胰腺MDA含量显著高于对照组(P<0.05)。血清酚氧化酶(PO)活性随家蝇蛆粉替代量的增加而显著降低,其中G20组显著高于其它各组(P<0.05)。肝胰腺碱性磷酸酶(AKP)活性随添加量的增加而显著降低(P<0.05)。家蝇蛆粉替代鱼粉对凡纳滨对虾的血细胞总数(THC)、血清一氧化氮(NO)含量、AKP活性和肝胰腺PO活性、NO含量影响不显著(P>0.05)。     

Effects of feeding rate on growth, feed utilizationand body composition of a tropical bagrid catfish

A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P > 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P > 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.     

Effects of fishmeal replacement by feather meal in practical diets for juvenile crayfish (Pacifastacus leniusculus Dana,Astacidae)

The aim of this study was to evaluate different replacement levels of fishmeal (FM) by feather meal (FeM) on survival and growth of juvenile crayfish (Pacifastacus leniusculus). An 80‐day experiment was conducted with stage 2 juveniles from the onset of exogenous feeding. Four practical diets (500 g kg^?1 protein) differing in the level of replacement of FM protein by FeM protein were prepared: 0% (control diet), 15% (8.2% dietary FeM), 25% (13.7% dietary FeM) or 35% (19.2% dietary FeM). Each diet was tested on grouped or individually isolated crayfish. Crayfish fed the control diet or 15% replacement achieved the highest survival (average of grouped and isolated: 88.2%) and growth (grouped and isolated: 13.58 mm carapace length, 523.2 mg weight) and the lowest feed conversion ratio (average of grouped and isolated: 1.11). Final growth of isolated crayfish was significantly higher than that of grouped crayfish for all diets. This study provides the first data on the substitution possibilities of FM by FeM in diets for freshwater crayfish. An 8.2% of FeM (15% replacement of FM protein) can be included in extruded diets for juvenile P. leniusculus during the first 80 days of intensive rearing without impairing growth or feed conversion.     

Effects of fish meal replacement with animal protein blend on growth performance,nutrient digestibility and body composition of juvenile Chinese soft‐shelled turtle Pelodiscus sinensis

An 8‐week feeding trial was conducted to evaluate the potential of partial replacement of fish meal with rendered animal protein blend (APB) [meat and bone meal (MBM): expanding blood meal (EBM) = 4 : 1] in the diet of juvenile Chinese soft‐shelled turtle Pelodiscus sinensis. Seven isonitrogenous and isoenergetic practical diets replacing 0%, 10%, 20%, 30%, 40%, 50% and 60% fish meal protein by APB were formulated. Weight gain, feed efficiency, protein efficiency and the apparent digestibility coefficients (ADCs) of dry matter and gross energy in the experimental diets all exhibited no significant difference (P > 0.05) when dietary fish meal was replaced for 0–40%, but decreased significantly (P < 0.05) with further increasing substitution levels. However, relative feed intake, ADC of lipid as well as the contents of whole‐body moisture, protein, lipid and ash all showed little differences (P > 0.05) among all the treatments. Nitrogen retention and the ADCs of protein and most amino acids all decreased significantly (P < 0.05) when fish meal was substituted by more than 30%. The results indicated that fish meal in the practical diet of juvenile Chinese soft‐shelled turtle could be replaced by 30–40% using a combination of MBM and EBM without negative effects on growth performance, nutrients digestibility and body composition.