黑水虻幼虫培养基替代豆粕对吉富罗非鱼生长、体组成和血清生化指标的影响

在实用饲料(含豆粕35.0%,豆粕粗蛋白质含量为47.7%)的基础上,用黑水虻幼虫培养基分别替代0(G0)、15%(G15)、30%(G30)、45%(G45)的豆粕,配制成4种等氮(31%),等脂(6%)的实验饲料,以研究罗非鱼(Oreochromis niloticus)饲料中黑水虻幼虫培养基替代豆粕的可行性。将400尾初始体重为(2.30±0.02)g的罗非鱼随机分成4组(每组设4个重复,每个重复25尾),其中以饲喂G0实验饲料的组为对照组,实验期为8周。结果显示:黑水虻幼虫培养基替代豆粕对罗非鱼增重率、饵料系数、存活率影响不显著。与G0组相比,各替代组罗非鱼全鱼粗蛋白、灰分、水分含量差异不显著,但随着替代量的增加,全鱼粗脂肪含量显著降低,G45组全鱼粗脂肪含量显著低于对照组。黑水虻幼虫培养基替代豆粕对罗非鱼肥满度影响不显著,但肝体比随着替代量的增加显著降低,在30%的替代量时差异达到显著水平。与G0组相比,各替代组罗非鱼血清白蛋白、球蛋白、血糖、甘油三酯、胆固醇、谷丙转氨酶、谷草转氨酶以及尿素含量差异不显著。由以上研究结果得出,在豆粕用量为35%的基础饲料中,黑水虻幼虫培养基可替代豆粕用量的45%而不影响罗非鱼生长,黑水虻幼虫培养基在基础饲料中的添加量为34.6%,占饲料总蛋白质含量的23.69%;黑水虻幼虫培养基可显著降低罗非鱼全鱼粗脂肪含量以及肝体比。     

Effects of black soldier fly (Hermetia illucens) larvae meal protein as a fishmeal replacement on the growth and immune index of yellow catfish (Pelteobagrus fulvidraco)

A 65 days feeding trial was conducted to evaluate the potential of black soldier fly larvae (BSFL) as a fish meal (FM) protein alternative in the diet of yellow catfish. Fish meal protein was replaced with BSFL meal protein at 0% (control), 13%, 25%, 37%, 48%, 68%, 85% and 100%. Compared with the control group, increased growth performances (e.g. weight gain rate increased by 21.7%) and immune indexes (e.g. serum lysozyme activity increased by 6.8%) of yellow catfish fed with diets in which a maximum of 48% FM protein was replaced by BSFL meal protein was determined. The diet in which 25% FM protein was replaced by BSFL meal protein resulted in the greatest growth performances (e.g. weight gain rate increased by 29.1%) and immune indexes (e.g. serum lysozyme activity increased by 31.9%) as well as the lowest feed conversion ratio (0.9) among all diets tested. No significant differences in survival rate, body indexes or composition were determined among all treatments. Therefore, BSFL meal protein has the potential to partially replace FM protein in the diet of yellow catfish, and it may also enhance the immunocompetence of the fish.     

Growth,nitrogen gain and indispensable amino acid retention of pacu (Piaractus mesopotamicus,Holmberg 1887) fed different brewers yeast (Saccharomyces cerevisiae) levels

A feeding‐and‐digestibility trials were carried out to evaluate the efficacy of replacing fishmeal with brewers yeast Saccharomyces cerevisiae in diets of pacu, Piaractus mesopotamicus, juveniles. The feeding trial was conducted during 54 days with 450 fish (26.6 ± 1.7 g) testing six isonitrogenous (270 g kg^?1 crude protein) and isoenergetic (19 MJ kg^?1 crude energy) diets, with increasing yeast level to replace 0 (control), 30, 35, 50, 70 or 100% of dietary fishmeal. Growth performance and feed utilization increased with increasing dietary yeast level until 50% fishmeal replacement. Protein retention efficiency was higher in fish fed 35 and 50%. Protein digestibility and the fillet hue (the red/green chromaticity) were not significantly different among all treatments. Nitrogen gains were significantly improved in fish fed 35% replacement diet compared to fish fed the control diet. The retentions of indispensable amino acids tended to increase with increasing dietary yeast levels, with maximum retention at 35–50%. On the basis of our results, replacing 50% fishmeal by yeast in pacu diets successfully improved feed efficiency and growth performance, and reduced nitrogen losses, thereby reducing the nitrogen outputs from fish farms.     

Apparent digestibility coefficients of several protein sources,and replacement of fishmeal by porcine meal in diets of Japanese seabass,Lateolabrax japonicus,are affected by dietary protein levels

A digestibility and a growth trial were conducted in this study respectively. Firstly, the apparent digestibility coefficients (ADC) of nutrients and energy in meat and bone meal, porcine meal (PM), hydrolysed feather meal, poultry by‐products meal, fishmeal (FM), soybean meal and spray‐dried blood meal were determined. In experiment 2, an 8‐week growth trial was conducted to evaluate the effects of the substitution of FM by PM under the digestible ideal protein concept at two protein levels in the diets of Japanese seabass, Lateolabrax japonicus. A FM‐based control diet (FM diet; FM: 320 g kg^?1, crude protein: 434.9 g kg^?1, crude lipid: 124.6 g kg^?1) and three other diets were formulated to contain 115 g kg^?1 PM and only 160 g kg^?1 FM. Two diets were formulated on a crude protein basis without (PM diet) or with (PMA diet) essential amino acid (EAA) supplementation respectively. A low‐protein diet was designed (LPMA diet, crude protein: 400.9 g kg^?1, crude lipid: 96.3 g kg^?1) with the same level of FM and PM but with the same digestible protein/ digestible energy and EAA profile as the FM diet. The results showed that nitrogen and total amino acid digestibility of the tested ingredients were ranged from 85.6% to 95.5% and from 87.6% to 95.5% respectively. Apparent digestibility coefficients of protein for FM and PM were 91.2% and 95.9% respectively. In the growth trial, the weight gain rate and feed conversion ratio of fish fed the PMA diet did not show a significant difference from those of the control group, but were significantly higher than those of the PM and LPMA groups (P<0.05). Growth was related linearly to lysine and methionine intakes. It was shown that PM could be utilized in the Japanese seabass diet up to 115 g kg^?1 to replace about 160 g kg^?1 of FM protein under an ideal protein profile. Essential amino acid deficiency (diet PM) or a lower protein level despite having an ideal amino acid profile (diet LPMA) could not support the optimal growth of Japanese seabass.     

Evaluation of amaranth (Amaranthus caudatus L.) and quinoa (Chenopodium quinoa) protein sources as partial substitutes for fish meal in Litopenaeus vannamei grow‐out diets

Two groups of isonitrogenous diets formulated by replacing 15%, 25%, 35% and 45% of fish meal protein by amaranth meal and quinoa meal were used to evaluate the performance of Litopenaeus vannamei. Growth showed significant reduction (P < 0.05) in the group of shrimp fed with amaranth diets, with diet A15 showing the best specific growth rate (SGR = 2.81% day^?1), but after the control diet AQ0 (3.07% day^?1). Diet A15 had significantly (P < 0.05) the best digestibility of dry matter (79.7%) and protein (88.4%) without differences compared to control diet AQ0 (75.1% and 85.2%). Replacement with quinoa meal at any level tested did not significantly affect (P > 0.05) the shrimp growth performance. Shrimp fed with quinoa diets showed better SGR (3.05% day^?1) than those shrimp fed with amaranth (2.56% day^?1). No differences in feed conversion ratio appeared in either of the protein sources, but quinoa diets presented a better average (3.13) than amaranth diets (4.01). The apparent digestibility of dry matter and protein for quinoa diets was similar for all diets, but they were statistically different (P < 0.05) from the control diet. We conclude that quinoa meal can replace fishmeal up to 45%, whereas it can be replaced with amaranth meal up to 15%, without adverse effects on growth and survival.     

Growth performance,nutrient digestibility and lipase activity in juvenile rainbow trout (Oncorhynchus mykiss) fed fat powder in diet containing emulsifiers (cholic acid and Tween‐80)

This research was conducted to investigate the effects of two dietary emulsifiers on nutrient digestibility and lipase activity in rainbow trout (Onchorhyncus mykiss). A basal rainbow trout diet containing fat powder supplemented with 10 and 5 g kg^?1 of cholic acid, and 20 and 40 g kg^?1 of Tween‐80. Control diet contained no emulsifiers with fat powder was replaced by fish oil. Each diet was randomly assigned to 1,500‐L tanks in triplicate. Juvenile rainbow trout with an initial weight of 27.32 ± 2.03 g were randomly distributed in the experimental tanks. The results showed that growth parameters did not change by the addition of the two emulsifiers (p > .05). Total triglyceride content was significantly higher in control fish fed diet containing fish oil (p < .05), while serum cholesterol content showed no significant differences among treatments (p > .05). Control diet resulted in a higher fat digestibility than those of other experimental diets. However, protein and ash digestibilities in diet containing emulsifier were higher than those of the control diet. Control group showed the lowest lipase activity, whereas 20 g kg^?1 Tween‐80 diet caused the highest lipase activity among treatments (p < .05). In conclusion, it seems that a higher lipase activity induced by the emulsifiers could not compensate for the negative impacts of fat powder on the experimental diets.     

Effects of replacing soybean meal with rubber seed meal on digestive enzyme activity,nutrient digestibility and retention in tilapia (Oreochromis niloticus × Oreochromis aureus)

A feeding trial was conducted to evaluate the effects of replacing soybean meal (SBM) with rubber seed meal (RSM) on digestive enzyme activity, nutrient digestibility and retention in juvenile tilapia (Oreochromis niloticus × Oreochromis aureus). Five isonitrogenous and isoenergetic diets were formulated with 0 (control), 100, 200, 300 and 400 g kg⁻¹ RSM replacing graded levels of SBM respectively. Each diet was randomly assigned to triplicate groups of 30 fish (initial average weight 5.2 g) per aquarium in a rearing system maintained at 29 ± 1°C for 8 weeks. The hepatic protease and lipase activities gradually decreased with increasing dietary RSM level, but no significant differences were observed among the low inclusion level (0–200 g kg⁻¹) groups. The apparent digestibility coefficients of dry matter, crude protein, crude lipid and ash showed a similar trend as the hepatic protease and lipase activities. The retentions of protein and individual essential amino acid (except lysine, threonine and leucine) in fish fed diet with 200 g kg⁻¹ RSM were similar to those in fish fed the control diet. These results indicate that dietary RSM inclusion level up to 200 g kg⁻¹ did not markedly affect the digestive enzyme activity, nutrient digestibility and retention in tilapia, whereas these were depressed by the inclusion of 400 g kg⁻¹ RSM.     

Growth and nutrient utilization of Murray cod Maccullochella peelii peelii (Mitchell) fingerlings fed diets with varying levels of soybean meal and blood meal

Abstract The Australian native freshwater fish Murray cod, Maccullochella peelii pellii (Mitchell), currently supports a fledgling inland aquaculture industry, which is thought to have considerable growth potential. The aim of this study was to evaluate the suitability of two alternate protein sources [blood meal (BM) and defatted soybean meal (SBM)] as substitutes for fish meal at various levels of inclusion in diets for juvenile Murray cod. The growth performance of juvenile Murray cod in response to nine isonitrogenous and isocalorific diets (50% protein, 14% lipid, 20.2 kJ g^?1) consisting of a control diet in which protein was supplied from fish meal, and test diets in which the fish meal protein was substituted at levels of 8%, 16%, 24%, and 32% with BM or SBM was evaluated from a 70‐day growth experiment. The per cent apparent dry matter (% ADC_dm) and percentage protein digestibility (% ADC_p) of the test diets were also determined using Cr₂O₃ as a marker. Survival in all the SBM dietary treatments was high but that of fish on the BM dietary treatments was significantly (P < 0.05) lower than in all the other dietary treatments. Specific growth rate (% day^?1) of Murray cod fed SBM incorporated diets ranged from 1.63 ±  0.06 to 1.78 ±  0.10 and even at the highest level tested (32% of the dietary protein from SBM) was not significantly different (P > 0.05) from the fish fed the control diet (1.65 ±  0.09). Feed conversion ratios of the SBM dietary treatments ranged from 1.36 ±  0.08 to 1.45 ±  0.07. The protein efficiency ratios and protein conversion efficiencies of Murray cod in the soybean meal treatments were also good and for a majority of the SBM diets were better than those for the control diet. Per cent ADC_dm and ADC_p of the SBM diets tested ranged from 70.6 ±  1.46 to 72.3 ±  1.81% and 88.6 ±  0.57 to 90.3 ±  0.17%, respectively, and was not significantly different (P > 0.05) from the control diet (% ADC_dm 74.3 ±  1.63; % ADC_p 91.3 ±  0.55). The reasons for significantly poor survival and growth of Murray cod reared on BM incorporated diets, and relatively poor digestibility of these diets are discussed. The study shows that for Murray cod diets in which fish meal protein is substituted up to 32% performance or carcass composition is not compromised.     

Influence of dietary black soldier fly (Hermetia illucens Linnaeus) pulp on growth performance,antioxidant capacity and intestinal health of juvenile mirror carp (Cyprinus carpio var. specularis)

This study was conducted to investigate whether dietary supplementation of black soldier fly (Hermetia illucens Linnaeus) pulp (BSFP) affects growth performance, antioxidant capacity and intestinal health of juvenile mirror carp (Cyprinus carpio var. specularis). A total of 270 juvenile mirror carp (13.68 ± 0.02 g) were randomly allotted to five dietary treatments, BSFP0, BSFP25, BSFP50, BSFP75 and BSFP100, in which BSFP was included in the basal diet at 0, 43.7, 87.3, 131 and 174.7 g/kg, respectively. Then, fish were fed to apparent satiation for 8 weeks. Fish growth performance and nutrient utilization were not different among the five groups (p > .05). Increasing BSFP dietary content significantly decreased whole‐body lipid content but increased kidney index (p < .05). The general relative intestine length was significantly higher in the BSFP100 group than the BSFP0 group (p < .05). Increasing BSFP dietary content significantly increased serum catalase activity and decreased malonaldehyde content (p < .05). The intestinal villus height, villus area and muscle layer thickness were significantly lower in the BSFP100 group than the BSFP0 group (p < .05). No significant differences in the activity of intestinal trypsin, lipase and amylase were observed among all groups (p > .05). In conclusion, this study indicated that BSFP at the level below 131 g/kg could be added in diet of juvenile mirror carp without any negative effect on growth performance and intestinal health. Dietary BSFP inclusion at low levels decreased the whole‐body lipid content and increased the antioxidant activity of juvenile mirror carp.     

Effect of replacing fishmeal with canola meal on growth and nutrient utilization in kuruma shrimp Marsupenaeus japonicus (Bate)

A feeding trial was conducted to assess the nutritional values of canola meal as a substitute for fishmeal in diets for kuruma shrimp using five isocaloric diets (190 kJ kg^?1) prepared by replacing 0%, 10%, 20%, 30% and 40% of fishmeal protein with canola meal protein in CM0, CM10, CM20, CM30 and CM40 diets respectively. Triplicate groups of juveniles (0.19 g) were fed the respective diets for 60 days in tanks. At the end of trial, weight gain (%) and specific growth rate (% day^?1) were not significantly (P > 0.05) different among shrimp fed CM0, CM10 and CM20 diets. However, growth was significantly (P < 0.05) decreased in shrimp fed CM30 and CM40 diets. As with growth performance, feed intake, feed conversion ratio and protein efficiency ratio were also decreased (P < 0.05) in CM30 and CM40 groups. Whole body dry matter, methionine and proline were significantly decreased with canola meal substitution levels. In general, retention efficiency of protein and indispensible amino acids were decreased as canola meal increased in diets. It may be concluded that 20% fishmeal protein can be successfully replaced with canola meal, while supplementation of amino acids or blending with complementary proteins could facilitate higher fishmeal replacements in kuruma shrimp diets.     

脱脂亮斑扁角水虻幼虫粉替代鱼粉对黄颡鱼幼鱼生长性能、营养素沉积率、血清生化指标和消化酶活性的影响

为研究脱脂亮斑扁角水虻幼虫粉(DBSFLM)替代鱼粉对黄颡鱼幼鱼生长性能、营养素沉积率、血清生化指标和消化酶活性的影响,本实验选用平均体质量为(1.67±0.01) g的黄颡鱼幼鱼480尾,随机分为4个处理组,分别投喂基础饲料(T0)和实验饲料[脱脂亮斑扁角水虻幼虫粉分别替代鱼粉20%(T20)、40%(T40)和60%(T60)],每个处理组3个重复,每个重复40尾鱼,养殖8周。结果显示,随着DBSFLM替代量的增加,黄颡鱼生长呈先增加后降低的趋势;T20组的终末均重、增重率和特定生长率最高,且显著高于T60组;实验组T20和T60的摄食量显著高于对照组和T40组;实验组的腹脂指数、灰分和钙沉积率呈下降趋势,其中T60组的腹脂指数、T40和T60组的灰分和钙沉积率达到显著水平;与对照组T0相比,实验组的肥满度、脏体比、肝体比、肠体比和胃体比、蛋白质、脂肪和磷沉积率及黄颡鱼体蛋白、体脂肪和灰分均没有显著差异;血清胆固醇和甘油三脂显著降低,高密度/低密度脂蛋白胆固醇显著升高,实验组T40的胃蛋白酶活性有增加趋势、肠道胰蛋白酶活性显著增加。研究表明,在本实验条件下,脱脂亮斑扁角水虻幼虫粉替...     

Effect of replacing dietary fish meal with black soldier fly larvae meal on growth and fatty acid composition of Jian carp (Cyprinus carpio var. Jian)

To explore the effect of replacing dietary fish meal (FM) with black soldier fly (Hermetia illucens) larvae meal (BSFLM) on growth and body composition of Jian carp (Cyprinus carpio var. Jian), the FM in basal diet of Jian carp was replaced by 0, 35, 70, 105 and 140 g/kg BSFLM respectively to form five isonitrogenous and isolipidic diets. A total of 300 Jian carp (10.1 ± 1.6 g) were randomly divided into five groups (triplicate per group) and fed five diets, respectively. After 56 days of feeding, growth and body composition of fish were determined. Results showed that serum maleic dialdehyde, total antioxidant capacity, 18:1n‐9, 18:2n‐6, 20:5n‐3 and 22:6n‐3 in fish significantly decreased and 12:0, 14:0 and 16:0 significantly increased with increasing replacement of BSFLM. The growth, biological parameters, proximate composition, amino acid composition and serum biochemical parameters of Jian carp were not affected by the replacement of BSFLM. In conclusion, up to 140 g/kg BSFLM (100% replacement of FM) can be included in diets of Jian carp without unfavourable effects on growth while decreasing n‐3 highly unsaturated fatty acid (HUFA) composition in body of fish, suggesting that BSFLM could be used after nutrient enrichment with n‐3 HUFA to bring active effects on fish quality.     

Alternative protein sources in diets for Japanese flounder Paralichthys olivaceus (Temminck and Schlegel): II. Effects on nutrient digestibility and digestive enzyme activity

An 8‐week feeding trial was conducted to compare the effects of dietary protein sources on nutrient digestibility and digestive enzyme activity. Four experimental diets were formulated to contain one of the following as the sole protein source: fish meal (FM), fish protein concentrate (FPC), soy protein concentrate (SPC) and soy protein isolate (SPI). Each diet was randomly assigned to triplicate aquaria stocked with 25 Japanese flounder (Paralichthys olivaceus) each. The dry matter, crude protein and energy digestibility and individual amino acid availability of the SPC‐based diet were significantly lower than those of the other diets. The crude lipid digestibility of soy protein‐based diets was significantly lower than that of the FM‐based diet. The pepsin/protease activity was significantly higher in fish fed fish protein‐based diets compared with fish fed soy protein‐based diets. The lipase activity in fish fed the SPI‐based diet was the highest among the dietary treatments. These results indicate that P. olivaceus can effectively digest the protein from FPC and SPI (but not SPC) as well as FM. The low protein digestibility and amino acid availability of the SPC‐based diet may be related to the non‐protein compounds present in SPC, whereas the low‐lipid digestibility of soy protein‐based diets may contribute to the undigested soy protein fractions and/or the alcohol‐soluble components.     

Digesta characteristics in relation to nutrient digestibility and mineral absorption in Nile tilapia (Oreochromis niloticus L.) fed cereal grains of increasing viscosity

Soluble non-starch polysaccharides (NSP) present in cereal grains may affect performance of Nile tilapia through changes in digesta characteristics. The objective of this study was to investigate whether dietary cereal grains of increasing viscosity induce changes in digesta viscosity, dry matter and volatile fatty acids (VFA) and if these changes explain differences in nutrient digestibility and mineral absorption. Four experimental diets were formulated by adding 40% grains to a basal diet to obtain a range of dietary viscosities, increasing in the order of maize, barley, wheat and rye. The diets were assigned to 16 tanks with 40 fish (mean weight 70 g) each. Digesta viscosity increased with increasing grain viscosity (P < 0.001), whereas digesta dry matter decreased with increasing grain viscosity (P < 0.05). No significant differences were found among diets in total concentration and type of VFA. Nutrient digestibility was not significantly correlated with digesta viscosity. Of all nutrients, only starch digestibility was significantly negatively correlated with digesta dry matter in the middle intestine (r = − 0.57; P = 0.03). Absorption of sodium was significantly negatively correlated with digesta viscosity in all intestinal segments (r = − 0.76 to − 0.82; P < 0.001) and positively correlated with digesta dry matter in all intestinal segments (r = + 0.60 to + 0.67; P < 0.05), except for the proximal intestine (P = 0.18). Of the other minerals, potassium and magnesium absorption were positively correlated with digesta dry matter in the distal (r = + 0.56; P = 0.03) and proximal (r = + 0.54; P = 0.04) intestine, respectively. Phosphorus absorption was significantly negatively correlated with dry matter in the stomach (r = − 0.55; P = 0.03), middle (r = − 0.58; P = 0.02) and distal (r = − 0.54; P = 0.04) intestine. In conclusion, viscous cereal grains induce increases in digesta viscosity and decreases in digesta dry matter in Nile tilapia. These changes do not explain differences in nutrient digestibility among diets, but seem more related to differences in mineral absorption. The strong negative correlations between digesta viscosity and sodium absorption suggest negative effects of dietary viscous grains on intestinal water balance.     

Digesta viscosity, nutrient digestibility and organ weights in African catfish (Clarias gariepinus) fed diets supplemented with different levels of a soluble non-starch polysaccharide

The objective of the present study was to investigate if dietary soluble non‐starch polysaccharides (NSP) increase digesta viscosity, reduce nutrient digestibility and increase organ weights in African catfish. The fish (mean weight 80 g) were fed diets supplemented with the soluble NSP guar gum at three levels, 0 g kg^?1 (GG0), 40 g kg^?1 (GG4) and 80 g kg^?1 (GG8). Guar gum inclusion significantly increased digesta viscosity in the proximal (GG0: 1.7 centipoise or cP; GG4: 84.9 cP; GG8: 98.3 cP) and distal (GG0: 1.9 cP; GG4: 109.8 cP; GG8: 66.4 cP) intestine. Apparent digestibility coefficients (ADC) were significantly lower for the GG8 diet than the GG0 diet (dry matter: 52% versus 69%; protein: 77% versus 90%; ash: 41% versus 54%; energy: 60% versus 77%). The ADC of dry matter and energy were significantly lower for the GG4 diet than the GG0 diet. The relative growth rate of metabolic weight (14.5–15.4 g kg^?0.8 day^?1) and feed conversion ratio (0.8) did not differ between diets. Fish fed the GG8 diet had a significantly higher somatic stomach index than GG0 fish (0.71% versus 0.65% body weight). The intestinal somatic index tended to increase with increasing guar gum supplementation (GG0: 1.08%; GG4: 1.23%; GG8: 1.59%). In conclusion, high digesta viscosities in the guar gum fed fish may explain the observed reduced nutrient digestibilities and increases in digestive organ weights.     

Effect of phytic acid and phytase on feed intake, growth, digestibility and trypsin activity in Atlantic salmon (Salmo salar, L.)

In the majority of experiments, the effects of phytic acid (with or without phytase) are not separated from the effects of adding plant meals containing phytic acid. A 12‐week experiment was conducted with Atlantic salmon (28.9 g) to determine the separate and combined effects of phytic acid and phytase on feed intake, trypsin activity, digestibility and growth. Diets were prepared without phytic acid and phytase; with 2000 U phytase kg^?1 diet; with 10 g sodium phytate kg^?1 diet; and with 10 g sodium phytate and 2000 U phytase kg^?1 diet. The basal diet contained sufficient phosphorus and other minerals to meet salmonid requirements. The addition of phytic acid had no significant effect on feed intake or weight gain, it significantly (P < 0.05) reduced protein digestibility although there was no reduction in trypsin activity. Phytase inclusion neutralized the effect of phytic acid on protein digestibility. Phytase had no effect on feed intake but significantly enhanced growth whether included with or without phytic acid. Feed efficiency ratio was significantly improved for fish fed the diet containing both phytase and phytic acid but not separately. The significance of this experiment was to separate the direct effects of phytase and the direct effects of phytic acid, added in a pure form, from effects due to other components in ingredients containing phytic acid.     

Growth, digestibility and nutrient utilization of rainbow trout (Oncorhynchus mykiss) and European sea bass (Dicentrarchus labrax) juveniles fed different dietary soybean oil levels

A shortage of marine raw ingredients, such as fish oil, is predicted in the near future. The use of suitable alternative lipid sources, such as vegetable oils, is crucial for sustainable growth of the aquaculture sector. Three isonitrogenous (50% Crude Protein) and isoenergetic (19 kJ g⁻¹) diets, in which fish oil was gradually replaced by soybean oil (0, 25 and 50% of the oil fraction) were tested for 12 weeks, using European sea bass (Dicentrarchus labrax) and rainbow trout (Oncorhynchus mykiss) juveniles. No dietary effects (p>0.05) on growth performance, feed conversion, digestibility or body composition were observed with either species. The results obtained suggest the inclusion of soybean oil up to 50% of the dietary lipid is possible, in diets for sea bass and/or rainbow trout juveniles.     

Bio‐Ag reutilization of distiller's dried grains with solubles (DDGS) as a substrate for black soldier fly larvae,Hermetia illucens,along with poultry by‐product meal and soybean meal,as total replacement of fish meal in diets for Nile tilapia,Oreochromis niloticus

A feeding trial was conducted in a closed system with Nile tilapia, Oreochromis niloticus, juveniles (mean initial weight, 2.66 g) to examine total replacement of menhaden fish meal (FM) with distiller's dried grains with solubles (DDGS), which had been used as substrate for the production of black soldier fly larvae, Hermetia illucens, in combination with soybean meal (SBM) and poultry by‐product meal (PBM), with or without supplementation of the amino acids (AA) DL‐methionine (Met), L‐lysine (Lys) and a commercial non‐amylaceous polysaccharide enzyme (Enz) product. Fish were fed seven isoenergetic [available energy (AE) = 4.0 kcal g^?1 of diet] and isonitrogenous (350 g kg^?1 protein as‐fed basis) practical diets formulated with equivalent digestible protein levels. Diet 1 was formulated to be similar to a commercial, high‐quality, tilapia diet containing 200 g kg^?1 FM. Diets 2–5 were formulated as a 2 × 2 factorial to replace FM with similar contributions from DDGS (45%), PBM (25%) and SBM (2.1–2.9%), but to differ in supplementation of AA and/or Enz preparation. Diets 6 and 7 were formulated to investigate the effects of a 2/3 and 1/3 reduction, respectively, in DDGS contribution to the replacement protein mix, with concomitant increases in SBM, with respect to diet 3, and were balanced with Lys and Met. After 6 weeks, growth responses were slightly attenuated (P ≤ 0.05) and average daily intake (ADI) and feed conversion ratio (FCR) were slightly higher in tilapia fed DDGS diets 2–5 compared to those of fish fed the FM control diet 1. Growth responses were not significantly affected by the presence or absence of AA or Enz (diets 2–5), or the level of DDGS (diets 3, 7 and 6). Whole‐body proximate composition was not different among treatments. Amino acid profiles of fish fed DDGS diets were not significantly different from those of fish fed the FM control. Evidence of interaction between AA and Enz supplementation was detected in whole‐body amino acid concentrations such that AA content was higher with AA or Enz addition alone, but lower when both were added to the diet. Results suggest that DDGS replacement of FM in tilapia diets can be substantial when diets are formulated on a digestible protein basis and DDGS is combined with highly digestible animal (PBM) and plant proteins (SBM).     

The effects of dietary protein levels with amino acid supplementation on the growth performance,haematological profile and histology of meagre (Argyrosomus regius) in two different size classes

A 12‐week feeding trial was conducted to estimate the effects of supplemented amino acids (lysine and methionine) with different dietary protein levels on growth, haematology and liver histology in meagre (Argyrosomus regius) at two different sizes: fingerling (15.2 g) and juvenile (44.4 g). Six practical diets were prepared, and three of these practical diets were formulated with 40 (P40), 44 (P44) and 48% (P48) crude protein without supplementation of amino acids. Other three diets having same protein levels were supplemented with lysine and methionine (P40AA, P44AA and P48AA) to bring these amino acids level up to that estimated to be at the least in the 48% protein diet. Final mean weight (FMW) and specific growth rate (SGR) of P48AA in fingerlings were higher than that of 40AA. According to FMW and SGR of juveniles, there was interaction found between dietary protein levels and the supplementation of amino acids. The FMW and SGR of meagre fed P44AA were higher than that of fish fed the other diets, except fish fed the P48. Economic profit index, packed cell volume and haemoglobin for juvenile meagre were significantly improved with the dietary protein level and amino acid supplementation. The liver tissues of the P48 group in both sizes displayed better structure compared with the other groups. In conclusion, dietary crude protein content of practical diets for juvenile meagre could be reduced from 48% to 44% by adding essential amino acids with an enhancement in growth, health and economic profit.     

Growth performance,muscle and liver composition,blood traits,digestibility and gut bacteria of beluga (Huso huso) juvenile fed different levels of soybean meal and lactic acid

The objective of this study was to assess the effects of fishmeal (FM) replacement with 0, 350 or 700 g/kg soybean meal (SBM) in combination with the supplementation of lactic acid (LA; 0, 10 or 20 g/kg) in the diets of juvenile beluga sturgeon (Huso huso; 700 ± 30 g). Nine isonitrogenous (400 g/kg protein) and isoenergetic (18 MJ/kg) diets were fed to beluga ad libitum, three times a day, for 60 days. The results showed that replacing FM with SBM without LA significantly reduced fish growth; on the other hand, LA supplementation had positive effects on fish fed diets that FM was replaced by SBM (p < .05). Increasing SBM in the diet altered the fatty acid profiles of the fish, reducing long‐chain polyunsaturated fatty acids and the n‐3/n‐6 fatty acids. High amounts of SBM (700 g/kg) caused reductions in the haematocrit, glucose and cholesterol levels in the blood (p < .05). In addition, the digestibility of protein, fat, dry matter and phosphorus was reduced when replacing FM with SBM, however, adding LA to the diets increased fish performance (p < .05), and this improvement was sharper in 2% LA groups. The number of LA bacteria increased significantly with the dietary supplementation of LA (p < .05). Based on these results, replacing 350 g/kg of FM with SBM and adding 20 g/kg LA to their feed do not negatively affect the biological and physiological indices of beluga.