Effect of replacing fish meal with soybean meal on growth,feed utilization and nitrogen and phosphorus excretion of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to evaluate the effects of replacing fish meal with soybean meal (SBM) on growth, feed utilization, and nitrogen (N) and phosphorus (P) excretion of juvenile Pseudobagrus ussuriensis (initial average weight 0.50 ± 0.00 g). Seven isonitrogenous and isolipidic diets were formulated to contain SBM to replace fish meal protein at 0% (S0), 10% (S10), 20% (S20), 30% (S30), 40% (S40), 50% (S50) and 60% (S60) respectively. To investigate the effects of supplementation with crystalline amino acid to balance diet S60, one diet was formulated to add 0.30% methionine (SM60). The results showed that there was no significant difference in weight gain among fish fed S0, S10, S20, S30 and S40 diets, however, a significant reduction in this variable occurred when 50% and 60% of fish meal protein was replaced by SBM (P < 0.05). Apparent digestibility coefficients of dry matter, crude protein and phosphorus of diets were affected by dietary SBM levels. N and P excretion indicate that fish meal replacement by SBM led to an increase in N excretion, but led to a reduction in P excretion. No differences were detected in growth, feed utilization and N and P excretion between fish feed diets S60 and SM60. The results of this study show that 40% of fish meal protein could be replaced by SBM in diets of juvenile P. ussuriensis without having a significant negative effect on growth or feed efficiency, but that higher dietary SBM levels reduce fish performance.     

Effect of replacing fish meal with meat and bone meal on growth,feed utilization and nitrogen and phosphorus excretion for juvenile Pseudobagrus ussuriensis

The effect of replacing fish meal (FM) with meat and bone meal (MBM) in diets for juvenile Pseudobagrus ussuriensis was evaluated in a 90‐day feeding trial. Six isonitrogenous (crude protein, 430 g/kg) and isolipidic (crude lipid, 74 g/kg) diets were formulated to contain MBM to replace FM at 0 (S0), 200 (S20), 400 (S40), 600 (S60), 800 (S80) and 1000 g/kg (S100), respectively. The results showed that there was no significant difference in weight gain (WG) among fish fed S0, S20 and S40 diets. However, a significant reduction in WG occurred when 600, 800 and 1000 g/kg FM protein was replaced by MBM (p < .05). Similar trends were observed in specific growth rate and protein efficiency ratio. Apparent digestibility coefficients (ADC) of protein and dry matter of the diets S80 and S100 were significantly lower than those of the other diets. The ADC of phosphorus significantly reduced with the increase in dietary MBM level. Nitrogen and phosphorus excretion increased with the increasing dietary MBM level. Protease, lipase and amylase activities of the diets S80 and S100 were significantly lower than those of the other diets (p < .05). The results of this study showed that the optimum dietary MBM replacement level was 34.3% according to broken‐line model based on WG against dietary MBM replacement level.     

Effects of supplementing methionine hydroxy analogue in soybean meal and distiller's dried grain-based diets on the performance and nutrient retention of rainbow trout [Oncorhynchus mykiss (Walbaum)]

Two experiments were conducted to evaluate the effects of supplementing methionine hydroxy analogue (MHA) on the performance, body composition, and nutrition retention of rainbow trout. In experiment 1, a 2×4 factorial arrangement with two MHA supplemental levels (with and without) and four fish meal replacement levels (25%, 50%, 75%, and 100%, replaced with soybean meal (SBM) and wheat gluten) was used. A fish meal diet was included as a control. Results showed that fish meal replacement levels had significant effects on fish weight gain (WG), feed conversion ratio (FCR), body moisture, crude protein, crude fat, and ash (P<0.05). In experiment 2, a fish meal reference diet and seven other diets were made using SBM and distiller's dried grain with solubles supplemented with 0, 0, 0.55, 1.1, 1.65, 2.2, and 2.75 g MHA kg^?1 diet to replace 50% of fish meal. WG, FCR, and apparent retention of crude protein and phosphorus were significantly improved in rainbow trout fed the diet containing 1.65 g MHA kg^?1 diet compared with fish fed an equivalent diet without MHA.     

Effects of diets containing a bacterial protein meal on growth and feed utilisation in rainbow trout (Oncorhynchus mykiss)

Triplicate groups of rainbow trout with initial weight 361 g were fed either a fish meal based control diet or diets containing 9, 18 or 27% bacterial protein meal (BPM) or 9% of an autolysate (AU) of the BPM. No significant treatment effects were found on specific growth rates (SGR), feed intake, feed efficiency ratio (FER), or retention of nitrogen, amino acids or energy. The apparent digestibility coefficients (ADC) of nitrogen, energy and most indispensable amino acids decreased when BPM was included in the diet. The ADC of lipid, sum of amino acids, arginine, lysine, threonine and most of the dispensable amino acids were reduced at 27% BPM inclusion compared to the control, 9% and 18% BPM diets. None of the ADC estimated was different in the 9% AU diet compared to the 9% BPM diet. The loss of nitrogen and energy in faeces per kg gain increased as the dietary BPM or AU levels increased, and the energy used for activity and maintenance was higher in fish fed the 27% BPM diet than in fish fed the other diets (P < 0.05). There were no significant differences in the urea concentrations in plasma, liver and muscle, whereas the uric acid level in plasma was elevated in trout fed the 27% BPM diet. Histological evaluation of tissue from the stomach, pyloric caeca, mid-intestine and distal intestine did not reveal any diet-related morphological changes.In conclusion, no significant differences in growth and feed efficiency were found in the rainbow trout fed diets containing up to 27% BPM, and the AU did not increase fish performance compared to the BPM. Based on the data from this study, at levels up to 27% dietary inclusion, BPM is a good replacement for fish meal in diets for rainbow trout.     

Effect of dietary zinc supplementation and phytase pre-treatment of soybean meal or corn gluten meal on growth, zinc status and zinc-related metabolism in rainbow trout, Oncorhynchus mykiss

Rainbow trout, Oncorhynchus mykiss, were fed diets containing untreated or phytase-treated soybean meal and corn gluten meal with or without 50 mg supplemental zinc kg–1 to determine if dietary phytate caused a zinc (Zn) deficiency. Fish fed diets containing untreated soybean meal and corn gluten meal without supplemental Zn (basal diet) showed no signs of a Zn deficiency after 170 d of weight gain. Weight gain, carcass protein content, total bone Zn, and alkaline phosphatase and carboxypeptidase B activities were not significantly altered in fish fed the basal diet. Dietary phytate removal and supplemental dietary Zn were not required to prevent Zn deficiency in rainbow trout fed a plant-based diet. Although bone Zn concentrations were reduced in fish fed the basal diet, total bone Zn increased in all fish regardless of dietary treatment. Future assessments of Zn status of fish should be based on changes in Zn-dependent metabolism or total bone Zn rather than on bone Zn concentration.     

Partial replacement of soybean meal with Methylobacterium extorquens single‐cell protein in feeds for rainbow trout (Oncorhynchus mykiss Walbaum)

A feeding trial was conducted with juvenile rainbow trout (15–16 g initial weight) to assess the effects of including single‐cell protein (SCP) produced from Methylobacterium extorquens in trout feeds. Three isonitrogenous and isoenergetic diets were produced: a control diet and two experimental diets containing 5% or 10% bacterial protein meal replacing soybean meal. Triplicate tanks, each containing 35 fish, were fed each diet to apparent satiation in a constant‐temperature (15°C), flow‐through tank system for 12 weeks. No statistically significant differences in final fish weight or other fish growth parameters were observed. Similarly, feed efficiency parameters showed no significant differences among groups. Nutrient retention indices (protein, fat, energy) were relatively high and similar among fish in each dietary treatment group, as were whole body proximate compositions. Fish survival was high, with a small but statistically significant increase for the 10% SCP diet. Overall, results demonstrate that SCP from M. extorquens is a safe and effective alternative protein for rainbow trout diets at the low inclusion levels tested. Slightly lower weight gain in fish fed the 10% SCP diet was largely due to lower feed intake, suggesting that adding palatability‐enhancing ingredients to feeds may allow higher levels of M. extorquens SCP to be used without compromising fish growth.     

Utilization of combined extruded soybean and corn gluten meals as feed ingredients for juvenile rainbow trout,Oncorhynchus mykiss diet

In this study, feeding experiment and subsequent digestibility trial were performed to investigate the utilization of extruded soybean meal (SBM) and corn gluten meal (CGM) as feed ingredients for juvenile rainbow trout. Plant ingredients have undergone extrusion at low temperature (100°C, LT) or high temperature (150°C, HT) for 30 s. Four isonitrogenous (44%, crude protein) and isolipidic (14%, crude lipid) diets were formulated. Control diet is fishmeal based while a combined (1:1) non‐extruded SBM and CGM for NE diet, LT SBM and LT CGM for LT diet and HT SBM and HT CGM for HT diet. Two hundred forty rainbow trout juveniles (7.8 g average body weight) were randomly divided into 12 rectangular 60 L glass aquaria and offered four different diets in triplicate. Fish were fed at satiation twice a day, six days a week for 12 weeks. Phosphorus in phytic acid level of extruded ingredients decreased through extrusion cooking. Final weight, weight gain, SGR and PER of fish fed HT diet were significantly (p < .05) higher than those fed with NE diet. Apparent digestibility coefficient for protein of LT and HT diets is significantly higher than of NE diet. The results of this study demonstrated that HT extruded SBM and CGM are suitable feed ingredients for rainbow trout diet without compromising fish growth, feed utilization and fish body composition.     

Effect of partial replacement of dietary fish meal by soybean meal with betaine attractant supplementation on growth performance and fatty acid profiles of juvenile rainbow trout (Oncorhynchus mykiss)

This study was conducted to investigate the effects of dietary incorporation of soybean meal for fish meal replacement and supplementation of betaine as an attractant on growth performance and fatty acid profiles of rainbow trout (Oncorhynchus mykiss). Juvenile trout were fed practical diets, with increasing soybean levels and betaine supplementations. The experimental diets consisted of a control diet with fish meal as the sole protein source (control) and no attractant, 25% soybean‐1% betaine diet (SBM25‐B1), 50% soybean‐2% betaine diet (SBM50‐B2), and 50% soybean‐0% betaine diet (SBM50‐B0). Average body weight was 12.69 ± 0.16 g at the beginning of experiments. Following 54 days feeding programme with experimental diets, average body weights reached 47.45 ± 1.22 g, 58.11 ± 1.77 g, 56.34 ± 1.87 g and 53.76 ± 1.74 g in the control, SBM25‐B1, SBM50‐B2 and SBM50‐B0 groups respectively. As compared with control treatment, significant differences were observed in weight gain, specific growth rate and feed intake of 1% betaine treatment at 25% soybean‐meal‐incorporated diet (p < .05), but no differences were observed in feed conversation ratio and survival rates (p > .05). Compared with the control treatment, betaine‐supplemented groups had significantly higher total saturated fatty acid contents (p < .05). On the other hand, the control treatment showed a significantly higher level of monounsaturated fatty acid than the betaine‐supplemented groups (p < .05). Significant differences were observed in fatty acid profile of 1% betaine‐supplemented group (p < .05) compared with the control. Present findings revealed that 1% betaine supplementation with dietary incorporation of soybean meal at 25% level positively influenced growth performance, feed utilization and fatty acid profiles of rainbow trout juveniles.     

Replacing the substitute—Guar meal as an alternative for non‐genetically modified soybean meal in the nutrition of rainbow trout (Oncorhynchus mykiss,Walbaum, 1792)

Soybean meal (SBM) is widely used in aqua feed products. In the European Union, only non‐genetically modified (non‐GM) SBM is accepted. However, global production of non‐GM soybeans is declining and is limiting its utilization in aqua feeds. Therefore, non‐GM SBM alternatives are required. In this study, guar meal was evaluated as a substitute for non‐GM SBM in test feeds for rainbow trout (Oncorhynchus mykiss). Fish (initial weight of 57 ± 10.1 g) were stocked to 12 experimental tanks of a freshwater recirculation system with a stocking density of 6 kg/tank (500 L). Fish were organized in triplicate groups and received isonitrogenous and isocaloric experimental feeds designated as control and test feeds 1–3, where 0, 50, 100 and 150 g/kg feed of non‐GM SBM was replaced by guar meal. During the experimental test period of 56 days, fish were fed twice a day until apparent satiation. Compared to the control group, daily feed intake of test feeds 1–3 was significantly increased by guar meal inclusion. No significant differences in feed conversion ratio and specific growth rate were detected among all the treatments. Furthermore, guar meal inclusion did not affect protein efficiency ratio. However, protein productive value was significantly impaired when guar meal incorporation was above 100 g/kg feed. In accordance with the affected protein productive value, the crude protein content of the proximate whole fish body declined significantly. In contrast, condition factor, hepatosomatic index, slaughter yield and fillet yield provided no significant differences between the experimental groups. In conclusion, this study demonstrated that non‐GM SBM could be entirely replaced by guar meal without affecting the general performance of fish and suggests guar meal as an appropriate alternative for non‐GM SBM in the nutrition of rainbow trout.     

Effects of dietary supplements on the availability of minerals in fish meal; preliminary observations

Preliminary studies were conducted to determine if several feed supplements with the potential to improve dietary mineral availabilities in fish meal had any measurable effect in fish feeds. In the first study with rainbow trout, 11 supplements were tested: citric acid; sodium citrate; potassium chloride; sodium chloride; histamine dihydrochloride; EDTA disodium salt; sodium bicarbonate; a mixture of amino acids; ascorbic acid; a mixture of inositol and choline; and cholecalciferol. Apparent availability of calcium, phosphorus, magnesium, sodium, iron, manganese and strontium in fish meal-based diets was determined using both yttrium oxide (Y₂O₃) and chromium oxide (Cr₂O₃) as inert dietary markers. Apparent availability was expressed as the fractional net absorption (%) of minerals from diets. After a 7-day acclimation period with test diets, fecal samples were collected for five consecutive days using passive collection systems. Apparent availability of calcium, phosphorus, magnesium, iron, manganese and strontium was increased by citric acid supplementation. Apparent availability of manganese also was increased by EDTA and sodium citrate. The other supplements had no measurable effect on the apparent availability of minerals in fish meal. In the second study, the effect of supplemental citric acid was further investigated using monogastric (rainbow trout) and agastric fish (goldfish). Fish were fed for 5 weeks (rainbow trout) or 3 weeks (goldfish) with fish meal-based diets containing either 0% (control), 2% or 5% citric acid on a dry basis. Feces were collected by settling and by stripping. Apparent availabilities of calcium and phosphorus were greatly affected by citric acid supplementation in rainbow trout but not in goldfish. Phosphorus levels in feces of fish fed a diet with 5% citric acid were approximately half of that of fish fed the control diet (0% citric acid) in the rainbow trout trial. This pattern was consistent during the 5-week feeding trial. A dietary supplement of citric acid as high as 5% did not reduce feed intake or appetite of rainbow trout. Conversely, this level of dietary acidification led to a marked reduction of feed intake in goldfish. Dietary supplementation of citric acid at 2% level did not reduce feed intake of goldfish; however, this level of dietary acidification had little effect on the apparent availability of major minerals in fish meal-based diet. Levels of non-fecal excretion of calcium and phosphorus, inorganic phosphorus in urine, and citric acid in feces were increased in rainbow trout fed 5% citric acid. The pH values of the feces and urine were decreased in rainbow trout fed citric acid. Plasma bicarbonate, plasma calcium and phosphorus, and blood pH of rainbow trout tended to increase by a 5% dietary supplementation of citric acid. The soluble inorganic phosphorus content increased in the diets and decreased in the feces of rainbow trout by supplementing the diet with 5% citric acid. Feces samples of rainbow trout collected by stripping provided similar availability values to data collected by settling for most elements except sodium, which had negative values in all dietary treatments.     

Evaluation of solid‐state fermented protein concentrates as a fish meal replacer in the diets of juvenile rainbow trout,Oncorhynchus mykiss

We evaluated four fermented protein concentrates (FPCs) as a fish meal replacer in juvenile rainbow trout, Oncorhynchus mykiss. Ten diets were formulated to contain low‐temperature fish meal (LT‐FM), Vietnam fish meal (VT‐FM) and four types of FPCs as fish meal replacers (FPC‐A, B, C & D) at 30% and 50% FM replacement levels. FPC‐A was a mixture of solid‐state fermented soybean meal (SBM) and corn gluten meal (CGM) with Bacillus subtilis; FPC‐B was pretreated acid‐hydrolysed FPC‐A; FPC‐C and FPC‐D were FPC‐A + 2% shrimp soluble extract (SSE) and FPC‐B + 2% SSE, respectively. Triplicate groups of fish (average 15.4 g) were fed one of the experimental diets for 8 weeks. At the end of the feeding trial, fish fed the LT‐FM, FPC‐B, FPC‐C and FPC‐D diets showed significantly higher growth performance at 30% FM replacement than those of fish fed the FPC diets at 50% FM replacement. Fish fed 30FPC‐B, 30FPC‐C and 30FPC‐D diets showed higher weight gain (WG) than fish fed 30FPC‐A diet. Haematological parameters showed no clear trends among the experimental groups. Superoxide dismutase, lysozyme and myeloperoxidase activities were found to be higher in fish fed the LT‐FM, FPC‐A, FPC‐B, FPC‐C and FPC‐D diets at 30% FM replacement than in fish fed the FPC diets at 50% FM replacement. Antinutritional factors such as α‐ and β‐conglycinin, glycinin, trypsin inhibitors or zein were absent in FPC compared with SBM and CGM. Intestinal villi length and muscular thickness were significantly reduced in fish fed the VT‐FM and FPC diets at 50% FM replacement compared to fish fed the LT‐FM and FPC diets at 30% FM replacement. The results show that FPC‐B, FPC‐C, FPC‐D could replace up to 30% of LT‐FM in juvenile rainbow trout.     

Dietary microbial phytase supplementation and the utilization of phosphorus, trace minerals and protein by rainbow trout [Oncorhynchus mykiss (Walbaum)] fed soybean meal-based diets

Effects of thermal and enzymatic treatments of soybean meal on apparent absorption of total phosphorus, phytate phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, manganese, strontium and zinc were examined using rainbow trout, Oncorhynchus mykiss (Walbaum), as the test species. Absorption of the test nutrients was estimated using yttrium as an inert non-absorbable indicator. Thermal treatments (microwaving, dry roasting, steam heating, cooking) had no measurable effect on the apparent absorption of phosphorus and other minerals. Phytase supplementation increased the apparent absorption of phosphorus, nitrogen (protein), ash, calcium, magnesium, copper, iron, strontium and zinc in low-ash diets containing soybean meal, but had little effect in high-ash diets containing both soybean and fish meal. In low-ash diets, the apparent absorption of phosphorus increased in accord with the level of phytase added to the diet, from 27% (no phytase added) up to 90% (phytase added, 4000 units kg⁻¹ diet) or 93% (predigested with phytase, 200 units kg⁻¹ soybean meal). In high-ash diets, dietary acidification with citric acid decreased the effect of phytase, whereas in low-ash diets, acidification markedly increased the effect of the enzyme. Excretion of phosphorus in the faeces of fish fed a low-ash diet containing phytase-treated soybean meal was 0.32 g per kg diet consumed, a 95%−98% reduction compared with phosphorus excretion by fish consuming commercial trout feeds.     

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.     

Effects of dietary phosphorus and lipid levels on utilization and excretion of phosphorus and nitrogen by rainbow trout (Oncorhynchus mykiss). 1. Laboratory-scale study

Nutritional strategies to reduce both phosphorus (P) and nitrogen (N) excretion relative to growth of rainbow trout were tested in a 2 × 3 factorial experiment. The two factors were `dietary P level' and `dietary lipid level.' Reduction in dietary P from 14 to 8 g kg^–1 dry diet was achieved by partial substitution of dietary fish meal with a combination of full-fat soyabean meal, corn gluten and spray-dried blood meal. Triplicate tanks of 35 rainbow trout per tank were fed experimental diets for 16 weeks and grew from approximately 40 to 250 g, in 15 °C spring water. All tanks were fed the same percent biomass per day. Diets were isonitrogenous, and dietary energy varied with dietary lipid. Diet digestibility data and results of the experiment were used to construct N and P budgets for the fish fed the various diets. A reduction in dietary fish meal from 500 to 200 g kg^–1 dry diet, corresponding to a reduction in dietary P from 14 to 8 g kg^–1 dry diet, resulted in >50% reductions in both solid and dissolved P waste, but did not affect growth, feed efficiency ratio (FER) or sensory characteristics of rainbow trout. Increasing dietary lipid from 170 to 310 g kg^–1 dry diet led to higher growth rate and FER, and lower total N waste relative to weight gain, but did not change protein retention. Increasing dietary lipid level increased deposition of lipid in whole bodies of rainbow trout, and resulted in discernible differences in sensory characteristics of trout fillets.     

添加晶体或包膜DL-蛋氨酸对利用豆粕替代花鲈饲料中鱼粉的影响

通过8周生长实验检验了添加晶体或包膜DL-蛋氨酸对利用豆粕替代花鲈饲料中鱼粉的影响,以确定添加DL-蛋氨酸对提高饲料鱼粉替代水平的作用。对照饲料鱼粉水平为40%。采用2×4实验设计,按等蛋白替代原则分别用豆粕替代对照组饲料中鱼粉的40%（L）和80%（H）;在每个鱼粉替代水平上,分别添加晶体DL-蛋氨酸（A）、包膜DL-蛋氨酸（B）、晶体DL-蛋氨酸和包膜材料（C）以及按1:1比例配制的B和C的混合物（D）。配成8种等氮、等脂肪的实验饲料（LA、LB、LC、LD、HA、HB、HC和HD）。饲料LA、LB、LC和LD含24%鱼粉,并分别添加0.5% A、1.3%B、1.3%C或1.3%D;饲料HA、HB、HC和HD含8%鱼粉,并分别添加0.7% A、1.8% B、1.8% C或1.8% D。实验鱼初始体质量为（6.0 ± 0.1）g。实验结果表明,饲料鱼粉替代水平显著影响花鲈增重（WG）、摄食率（FI）、饲料系数（FCR）、饲料氮沉积效率（NRE）、饲料氮废物排放量（TNW）、肝体比（HSI）以及全鱼水分和粗脂肪含量;DL-蛋氨酸剂型可显著影响饲料磷废物排放量（TPW）。当添加的DL-蛋氨酸剂型相同时,WG和NRE随饲料鱼粉替代水平增加而下降,而FCR和TNW增加;在相同饲料鱼粉替代水平下,添加晶体或包膜DL-蛋氨酸未导致花鲈WG、FCR、NRE、CF、HSI、鱼体组成、TNW和TPW出现显著差异。上述结果显示,通过添加豆粕可将花鲈饲料中鱼粉含量降低至24%,而添加晶体或包膜DL-蛋氨酸不能进一步提高利用豆粕替代饲料鱼粉的水平。     

Effect of nucleotides supplementation to low‐fish meal feed on long‐chain polyunsaturated fatty acid composition of juvenile rainbow trout Oncorhynchus mykiss

A feeding trial was conducted to evaluate the effect of nucleotides supplementation to low‐fish meal feed on growth and fatty acid composition of rainbow trout. Six isonitrogenous (42% crude protein) and isolipidic (18% crude lipid) diets were formulated containing fish meal and plant ingredients as main protein sources. The control diet was a basal diet without supplementation of nucleotides, and five experimental diets were prepared by supplementing one of the five different nucleotides in the form of 5′‐monophosphate (0.15%), that is inosine (IMP), adenosine (AMP), guanosine (GMP), uridine (UMP) and cytidine (CMP) onto basal diet. Two hundred forty juvenile rainbow trout with an initial average body weight 9.8 g were randomly distributed into twelve aquaria. After 15 weeks of feeding period, growth performance and feed utilization of rainbow trout were not significantly different among dietary treatments. Dietary GMP, UMP and CMP tended to accumulate crude lipid in the muscle and whole fish body. Moreover, dietary GMP, UMP and CMP significantly increased hepatic 18:3n‐3 and long‐chain homologue 18:4n‐3 and 20:4n‐3 contents. Hepatic 18:2n‐6 content showed also increase in fish fed GMP, UMP and CMP diets, but decreased in long‐chain homologue 20:3n‐6 and 20:4n‐6 contents. Decrease in 20:4n‐6, 20:5n‐3 and 22:6n‐3 contents was also found in the muscle of fish fed IMP, GMP and CMP diets. The present study clearly showed that there was no positive effect of dietary nucleotides on growth of fish, but dietary nucleotides particularly GMP, UMP and CMP altered polyunsaturated fatty acid composition of rainbow trout.     

Soybean meal and wheat flour,proper dietary protein sources for optimal growth of snail (<Emphasis Type="Italic">Semisulcospira coreana</Emphasis>)

A 10-week feeding experiment was conducted to determine the proper dietary protein source for optimal growth performance of juvenile snails, Semisulcospira coreana. Sixteen isonitrogenous (31% crude protein) and isocaloric (4.2 kcal/g DM) experimental diets (designated as FM, F-FM, SBM, F-SBM, WF, F-WF, SSM, F-SSM, SCR, F-SCR, UP, F-UP, FWP, F-FWP, MIX and F-MIX) were formulated to contain 41% fish meal, 42% fermented fish meal, 59% soybean meal, 55% fermented soybean meal, 55% wheat flour with 26% fish meal, 55% fermented wheat flour with 29% fish meal, 50% sesame seed meal with 10% fish meal, 50% fermented sesame seed meal with 11% fish meal, 55% soya-curd residue or fermented soya curd residue with 25% fish meal, 50% Undaria powder or fermented Undaria powder with 24% fish meal, 50% freshwater plant with 29% fish meal, 50% fermented freshwater plant with 28% fish meal, a mixture of 8% soybean meal, 10% wheat flour, 8% sesame seed meal, 8% soya-curd residue, 8% Undaria powder and 8% freshwater plant with 17% fish meal, and 50% the fermented mixture with 16% fish meal, respectively, as dietary protein sources. Juvenile snails (average weight, 32 ± 0.7 mg) were randomly distributed in forty-eight 25-L aquaria (16 L water each) in a flow-through system at a density of 130 snails per aquarium. Three replicate groups of snails were fed one of the experimental diets ad libitum once per day for 10 weeks. At the end of the feeding experiment, survival of snails was above 98% and not significantly different among the dietary treatments. The best final body weight was observed in snails fed the SBM and WF diets. There were no significant differences in final body weight of snails fed the F-SBM, WF, F-WF and MIX diets, but the value was higher than that of snails fed the FM, F-FM, FWP and F-FWP diets. The lowest value was observed in snails fed the SSM, F-SSM, SCR and F-SCR diets. Whole body protein and lipid contents of snails varied with dietary protein sources. Amino acid composition of whole body was altered by dietary protein sources. The results of the present study indicate that dietary protein sources significantly influence proximate and amino acid composition, and growth performance of snails. Fermentation with ferminpan instant brown yeast does not improve nutritional quality of the protein sources, and soybean meal and wheat flour in combination with fish meal could be potential protein sources in feeds for juvenile snails.     

Effects of phytase pretreatment of soybean meal and phytase-sprayed in diets on growth, apparent digestibility coefficient and nutrient excretion of rainbow trout (Oncorhynchus mykiss Walbaum)

Rainbow trout were fed a diet containing phytase-sprayed and phytase-pretreated soybean meal with different phytase levels. The single factor random block design was used to analyze the effects on rainbow trout of dietary phytase supplementation on growth performance, nutritional ingredient digestibility and nutrient excretion. After 90 days, the results showed that feed conversion ratio (FCR) and protein efficiency ratio (PER) were significantly improved and specific growth rate (SGR) was not affected by spraying phytase, but SGR, FCR and PER were not significantly improved by phytase pretreatment. A digestibility trial conducted after the feeding trial showed that apparent digestibility coefficient (ADC) of diet protein and minerals was increased with phytase supplementation. However, there was a negative effect of phytase on the ADC of lipid. The excretion experiment showed that the supplementation of phytase resulted in decreased nutrient excretion in feces, but lipid excretion was slightly increased with phytase supplementation. In addition, the results of P excretion and ADC of P analyzed by t-test showed that phytase pre-treatment method should be a more rational method than the spraying method. The results of SGR, ADC of P and P excretion analyzed by quadratic regression indicated that 2,000–3,000 U/kg levels by the spraying method could be a rational range of phytase supplementation, and about 1,000 U/kg should be an optimal level by the pretreatment method. Thus, use of phytase in rainbow trout feeds can have economic and environmental benefits.     

Effect of partial fish meal replacement by soybean meal on the growth performance and biochemical indices of juvenile Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

A feeding trial was conducted to investigate the effect of partial fish meal (FM) replacement by dietary soybean meal (SBM) on the growth and protein and lipid metabolism of the juvenile Japanese flounder. Four isonitrogenous and isolipidic diets (Diets 1–4) were formulated containing 47% protein and 9% lipid with different SBM inclusion (Diet 1, 11%; Diet 2, 16%; Diet 3, 24%; and Diet 4, 41%). The fish were fed to satiation twice daily for a feeding period of 56 days. The weight gain rate (WGR) and protein efficiency ratio of fish fed Diet 4 were significantly lower than those fed Diets 1, 2, and 3, and feed conversion ratio in the group fed Diet 4 was significantly higher than that in the groups fed Diets 1, 2, and 3. Hepatosomatic indices showed the similar trend as WGR, and the value (1.75%) for Diet 1 was significantly lower than that (1.96–2.2%) for other diets. There were no differences in whole body moisture, crude protein, crude lipid, and ash content among all treatments. With increasing dietary SBM level, serum triglyceride (TG), cholesterol (CHO), and low-density lipoprotein cholesterol (LDL-C) concentrations increased, whereas the serum total protein (TP) and high-density lipoprotein cholesterol (HDL-C) concentrations decreased. Compared with Diet 1, the serum TG, CHO, and LDL-C concentrations of fish fed Diet 4 significantly increased by 78, 37, and 36%, respectively, while the TP and HDL-C concentrations decreased by 14 and 33%, respectively. No significant differences in condition factor, blood urea nitrogen concentration, and alanine and aspartate aminotransferase activities were observed among the dietary treatments. These results indicated that dietary SBM inclusion above 24% could adversely affect the growth and protein and lipid metabolism of Japanese flounder.     

Total fish meal replacement with canola protein isolate in diets fed to rainbow trout (Oncorhynchus mykiss W.)

The potential of canola protein isolate (CPI) as fish meal alternative in diets for rainbow trout was evaluated. Apparent digestibility coefficients (ADCs) for protein from a fish meal‐based reference diet (89.2 ± 1.1%) and CPI (84.6 ± 1.8%) were determined by indirect marker method in a digestibility experiment. ADC of dietary dry matter was slightly lower for the reference diet (62.5 ± 4.7%), but not significantly different to the CPI test diet (65.9 ± 3.1%). In a subsequent growth trial, 20 fish (initial weight 31.5 ± 0.5 g) were stocked into each of 15 experimental tanks of a freshwater flow‐through system. Fish were organized in triplicate groups and received experimental diets with 0%, 25%, 50%, 75% and 100% of fish meal replaced with CPI on the basis of digestible protein (designated as Control, I25, I50, I75, I100 respectively). At the end of a 70‐day feeding period, growth performance, feed intake and feed conversion ratio of treatment groups receiving diets I25, I50 or I100 were similar to the control group, while fish fed diet I75 showed significantly higher weight gain caused by improved feed conversion. The tested CPI was therefore identified to be a highly valuable fish meal alternative, not negatively affecting diet palatability, feed intake and feed efficiencies.