Effects of Reduced Soybean‐Meal Diets Containing Moringa oleifera or Leucaena leucocephala Leaf Meals on Growth Performance,Plasma Lysozyme,and Total Intestinal Proteolytic Enzyme Activity of Juvenile Nile tilapia,Oreochromis niloticus,in Outdoor Tanks

Leaf meals are potential alternatives to soybean meal (SBM) in fish diets in developing countries because they are cheaper. Moringa oleifera (MOR) and Leucaena leucocephala (LEU) reduced nutrient digestibility of diets compared with SBM in an earlier study. However, fish raised outdoors consume natural foods, which might offset the negative effects of leaf‐meal diets. We conducted a feeding trial using mixed‐sex Nile tilapia (5.2 g) to assess performance of fish fed 36% protein diets with different concentrations of MOR and LEU leaf meals in place of SBM. Fish in static pools were fed daily to apparent satiation for 59 d. Individual weight gain (30.4–34.7 g), survival (91.8–97.3%), feed conversion ratio (FCR, 1.6–1.9), proximate composition, plasma lysozyme activity, and intestinal proteolytic enzyme activity were similar among diets. However, fish fed diets containing leaf meals had higher concentrations of n‐3 fatty acids than those fed the SBM control. Despite lower nutrient availability of the leaf‐meal diets compared with the soy diet, MOR or LEU could replace up to 30% of the SBM protein without reducing fish performance. Inclusion of poultry meal in the diets and probable nutrient supplementation from natural foods appeared to compensate for the lower nutritional value of the leaf meals compared with SBM.     

Apparent Protein and Energy Digestibility and Amino Acid Availability of Corn and Co‐products in Extruded Diets for Nile Tilapia,Oreochromis niloticus

We assessed the nutritional value of corn in extruded diets for Nile tilapia, Oreochromis niloticus, by determining the apparent digestibility coefficients of dry matter, crude protein, and gross energy, and by measuring the apparent availability coefficients (AACs) of essential and non‐essential amino acids (AAs) in several corn‐based diets. We fed 180 juvenile Nile tilapia a reference diet containing 325.8 g/kg crude protein and 4613 kcal/kg gross energy or a test diet containing a 70:30 mixture of the reference diet and a test ingredient (whole corn, corn germ, corn germ meal, corn gluten feed, or corn gluten meal). The apparent digestibility coefficients ranged from 56.3 to 96.6% (dry matter), 89.4 to 96.8% (crude protein), and 59.0 to 95.4% (gross energy). The AACs of all AAs exceeded 80% for all diets and were >90% for corn gluten meal. All ingredients showed high levels of apparent digestibility for crude protein and high AACs of AAs. Diets based on whole corn or corn gluten meal showed higher digestibility values for dry matter and gross energy, suggesting that they are preferable choices for Nile tilapia.     

Effects of extruded and pelleted diets with differing lipid levels on growth,nutrient retention and serum biochemical indices of tilapia (Oreochromis aureus × Tilapia nilotica)

This study was conducted to evaluate the effects of extruded diets and pelleted diets with varying dietary lipid levels on growth performance and nutrient utilization of tilapia. Six diets, containing three levels of lipid at 40, 60 or 80 g kg^?1 (with the supplemental lipid of 0, 20 or 40 g kg^?1, respectively), were prepared by extruding or pelleting and then fed to tilapia juveniles (8.0 ± 0.1 g) in cages (in indoor pools) for 8 weeks. The results indicated that the fish that were fed the diet with 60 g kg^?1 of lipid had a higher weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), lipid retention (LRE), energy retention (ERE), apparent protein digestibility, apparent dry matter digestibility and a lower feed conversion ratio (FCR) than those fed the diet with 40 g kg^?1 lipid in both the extruded diet and pelleted diet (P < 0.05). As the dietary lipid level increased from 60 to 80 g kg^?1, these parameters were not further improved, even digestibilities of the crude protein and dry matter decreased (P < 0.05). With the dietary lipid level increased, whole‐body lipid content significantly increased (P < 0.05), serum aspartate aminotransferase, alkaline phosphatase, total cholesterol and low‐density lipoprotein cholesterol (LDL‐C) tended to increase (P > 0.05), whereas whole‐body protein content, serum triglyceride (TG), high‐density lipoprotein cholesterol (HDL‐C) and HDL‐C/LDL‐C tended to decrease (P > 0.05). Fish fed with the extruded diets had a higher WG, SGR, hepatosomatic index (HSI), PER, protein retention (PRE), LRE, ERE, TG, apparent digestibility of protein and dry matter, as well as a lower FCR, than those fed with the pelleted diets at the same dietary lipid level (P < 0.05). These results suggested that tilapia fed with the extruded diets had a better growth and higher nutrient utilization than fish fed with the pelleted diets, when dietary lipid level ranged from 40 to 80 g kg^?1 and at dietary crude protein level was 280 g kg^?1. The optimum dietary lipid level was 60 g kg^?1 in both the pelleted and extruded diets, and extrusion did not affect dietary lipid requirement of the tilapia.     

Apparent digestibility coefficient of duckweed (Lemna minor), fresh and dry for Nile tilapia (Oreochromis niloticus L.)

Dry matter (DMD), protein (PD), ash (AD), fat (FD), gross energy (ED) and phosphorus (PhD) digestibility coefficients were determined for five different iso‐N fish diets fed to Nile tilapia (Oreochromis niloticus). The control diet contained fishmeal (35%), corn (29%), wheat (20%), wheat bran (10%), fish oil (3%), diamol (2%) and premix (1%). Partial replacement of dry matter of fishmeal, corn grain, wheat grain, wheat bran and fish oil by 20% and 40% of dry matter of duckweed, in a dry and fresh form, was performed. Diets of treatments 1 and 2 included 20% and 40% of duckweed, respectively, in a dry form. In treatments 3 and 4, tilapia received formulated diets 4 and 5 in addition to 20% and 40% fresh duckweed providing the same amount of dry matter and protein as in control. The specific growth rates (SGRs) of tilapia were 1.51±0.07, 1.38±0.03, 1.31±0.06, 1.44±0.02 and 1.33±0.05, in control and treatments 1–4. There was no significant difference between SGR for the control diet and the diet with 20% fresh duckweed, while the other treatment groups had significantly lower SGR. All the treatment diets provide good values for feed conversion ratios (FCRs) and protein efficiency ratio (PER). Dry matter of diets ranged from 61.8% in treatment 4 to 85.2% in control. All the diets have high PD (88.4–93.9%) and high‐energy digestibility (78.1–90.7%). Dry matter of duckweed were 66.8, 63.3, 45.8 and 28.3 in treatments 1 to 4 respectively. Protein values were 78.4, 79.9, 77.6 and 75.9, while ED values were 59.8, 60.9, 64.5 and 58.4 in treatments 1 to 4 respectively. Analysis of body composition shows that tilapia fed diets with duckweed contain significantly (P<0.05) higher phosphorus and protein content and significantly (P<0.05) lower lipid content. In contrast, tilapia fed control diet had a significant higher (P<0.05) dry matter content and lower ash content.     

Apparent digestibility coefficients of feed ingredients and their prediction in diets for tilapia Oreochromis niloticus×Oreochromis aureus (Teleostei, Cichlidae)

Apparent digestibility of crude protein (CP), lipid, carbohydrate, energy and fatty acids was measured in various feed ingredients fed to hybrid tilapia (Oreochromis niloticus×Oreochromis aureus) including fish and poultry meals, corn gluten, soybean meal, rapeseed meal, sunflower seed meal, wheat, corn, sorghum, barley and wheat bran. Chromic oxide was used as a non‐absorbed marker. A diet compounded from a mixture of these ingredients was then used to examine the possibility of predicting the digestibility of formulated diets. In addition, the effect of pelleting or extrusion on digestibility of a compound diet was examined. Apparent digestibility of CP ranged from 75% to 97%, lipids from 72% to 90% and energy from 39% to 89% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 32% to 80%. Digestibility of fatty acids ranged from 75% to 90% with saturated fatty acids exhibiting digestibilities lower than unsaturated fatty acids. In a full‐fat soy diet containing 19% fat, digestibility of lipids did not decrease. There were no significant differences in digestibility between a diet that was either pelleted or extruded. Tests conducted using a compound diet indicated that ingredient digestibility was additive for protein, lipids carbohydrates and energy. Diets for the hybrid tilapia may thus be formulated on the basis of digestibility of individual ingredients, for the nutrients examined in this study.     

Growth performance and feed utilization of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) and tilapia galilae Sarotherodon galilaeus (Linnaeus, 1758) fingerlings fed plant protein-based diets

This study was designed to determine the effect of complete substitution of fish meal (FM) by three plant protein sources including extruded soybean meal (SBM), extruded full‐fat soybean (FFSB) and corn gluten meal (CGM) on growth and feed utilization of Nile tilapia Oreochromis niloticus and tilapia galilae Sarothrodon galilaeus. Four isonitrogenous of crude protein (ca. 28.0%) and isocaloric (ca. 19 MJ kg⁻¹) experimental diets were formulated. The control diet (diet 1) was prepared with FM as the main protein sources. Diets 2–4, each FM control diet, were completely substituted with SBM (diet 2), FFSB (diet 3) and CGM (diet 4). l ‐lysine and dl ‐methionine were added to plant protein diets to cover the nutritional requirements of tilapia. Each treatment was allocated to three net pens and fed for 17 weeks. Nile tilapia fed the control diet showed significantly higher (P≤0.05) values for final body weight (FBW), feed intake (FI), weight gain (WG) and specific growth rate (SGR), whereas fish fed the diet with CGM achieved the lowest values. Tilapia galilae fed SBM diet recorded the highest (P≤0.05) values for growth performance. Better feed conversion ratio (FCR) for both Oreochromis niloticus and Sarothrodon galilaeus was observed when fish were fed SBM diet, whereas the worse FCR was recorded for FFSB diet. Feed utilization parameters including protein productive value (PPV), fat retention (FR) and energy retention (ER) showed significant differences (P≤0.05) for both the species fed different dietary protein sources. The present results suggest that, for Nile tilapia, both SBM and FFSB supplemented with dl ‐methionine and l ‐lysine can completely replace dietary FM. Meanwhile, S. galilaeus fed SBM diet exhibited comparable growth and feed utilization with those fish fed a fish‐meal‐based diet.     

Effects of partial and complete replacement of soybean meal with cottonseed meal on growth,feed utilization and haematological indexes for mono‐sex male Nile tilapia,Oreochromis niloticus (L.) fingerlings

The main objective of this study was to evaluate the effects of replacing soybean meal (SBM) with cottonseed meal (CSM) on the growth performance, feed utilization and haematological parameters of mono‐sex male Nile tilapia fingerlings. Five isonitrogenous diets (containing 31.82% crude protein) containing graded levels of CSM to replace SBM protein were fed to triplicate groups of fish. The diets were supplemented with lysine so that they were similar to the control diet. After a 14‐week feeding experiment, the results revealed that up to 75% of SBM could be replaced by CSM without causing a significant reduction in growth. Fish fed the diet highest in CSM had a significantly lower protein efficiency ratio and a significantly higher feed conversion ratio than fish fed the other diets. High survival was observed in all the dietary treatments, and no significant difference was observed among treatments. The apparent digestibility coefficients (ADC) of dry matter and phosphorus decreased significantly with an increase in the dietary CSM level, whereas the ADC of lipid was not affected by the dietary treatment. The hepatosomatic index and the condition factor were significantly affected by the replacement of SBM by CSM. No significant differences were detected in the moisture, lipid and ash content in whole body and muscle samples, but protein in whole‐body samples was significantly affected by the CSM levels. Significant differences were found in the haemoglobin, haematocrit, red blood cell and white blood cell contents in fish fed diets with different CSM levels. Therefore, these findings suggest that up to 41.25% CSM can be used to replace 75% of SBM protein in diets for mono‐sex male Nile tilapia fingerlings without any adverse effects on the growth performance, feed utilization, body composition and haematological indexes.     

The effect of plant protein‐based diets on apparent nutrient digestibility,growth response,egesta quantity,postprandial ammonia excretion rate and serum quality of Nile tilapia

The study assessed the effect of oilseed meal mixtures on the biological value, faecal matter output, ammonia excretion rates and serum biochemistry of Nile tilapia over 63 days. The experimental diets (PPB 1, PPB 2 and PPB 3) were formulated using four selected oilseed meals that were mixed in different protein proportions to contribute 80% of total dietary crude protein. In each diet, either one or two of the oilseed meals were the dominant protein contributor. A commercial tilapia feed was used as the control diet (CTRL). Sex‐reversed Nile tilapia fingerlings (35 g) were stocked at 20 fish per tank in a recirculation system and fed at 3% body weight of their respective diets. At the end of the study, ADCs of dry matter, crude lipid and ash were significantly (p < .05) lower in all the plant‐based diets compared with the control diet. Fish fed the control diet had significantly higher weight gain and SGR compared with the plant‐based diets. Egesta output was 127% higher in the plant‐based diets compared with the control diet. All dietary treatments exhibited a similar trend in changes in ammonia nitrogen. Nevertheless, serum metabolites levels indicated no significant differences among treatments. Although the PPBs did not affect ADC of protein and serum profile, fish growth was reduced while faecal output increased.     

Evaluation of the nutritive value of Leucaena leucocephala leaf meal, inoculated with fish intestinal bacteria Bacillus subtilis and Bacillus circulans in formulated diets for rohu, Labeo rohita (Hamilton) fingerlings

Nine isonitrogenous (35% crude protein approximately) and isocaloric (18.37 kJ g^?1) experimental diets (RLL20–BCFL40) were formulated with either raw or treated (inoculated with fish intestinal bacteria) Leucaena leucocephala leaf meal at 20%, 30% and 40% levels replacing other ingredients partially from a fish meal based reference diet (RD). Two specific strains of fish intestinal bacteria, Bacillus subtilis (isolated from Cyprinus carpio) and B. circulans (isolated from Oreochromis mossambicus) having extracellular cellulolytic and amylolytic activities, were used to inoculate Leucaena leaf meal for 15 days at 37°C. The crude fibre, cellulose and hemicellulose contents and the antinutritional factors, tannin, phytic acid and mimosine in the leaf meal decreased due to inoculation. However, free amino acids and fatty acids increased in the treated leaf meal. The response of rohu, Labeo rohita, fingerlings fed the experimental diets for 80 days was compared with fish fed a RD. Both the inclusion level and type of Leucaena leaf meal in diets significantly affected the growth performance of rohu. Fish fed diets containing inoculated Leucaena leaf meal performed better in comparison with those with the RD. On the basis of growth response, feed conversion ratio, protein efficiency ratio and apparent net protein utilization, diet formulated with 30%Leucaena leaf meal inoculated with B. circulans resulted in the best performance of rohu fingerlings followed by diet with 40%B. subtilis inoculated Leucaena leaf meal. The apparent protein digestibility (APD) was better in fish fed diets containing B. circulans inoculated leaf meal. An increasing level of raw Leucaena leaf meal was associated with a decrease in the carcass protein content of rohu fingerlings. The activity of α‐amylase increased with the increasing level of treated leaf meal in diets. Cellulase activity increased with increasing level of inclusion of raw leaf meal, and was comparatively lower in fish fed diets with treated leaf meal. Activities of protease and lipase were higher in fish fed the RD. The results showed that it is possible to incorporate Leucaena leaf meal inoculated with enzyme‐producing fish intestinal bacteria in carp diets up to 40% level of inclusion.     

The Efficacy of a Novel Microbial 6‐Phytase Expressed in Aspergillus oryzae on the Performance and Phosphorus Utilization of Cold‐ and Warm‐Water Fish: Rainbow Trout,Oncorhynchus mykiss,and Nile Tilapia,Oreochromis niloticus

The efficacy and tolerance of a novel microbial 6‐phytase were investigated in rainbow trout, Oncorhynchus mykiss, and Nile tilapia, Oreochromis niloticus. Reference diets were sufficient in available phosphorus (P). The test diet limiting in available P was supplemented with phytase at 500, 1000, or 2000 phytase units/kg feed. The enzyme was effective in increasing total P apparent digestibility coefficient in relation to increasing the dose of phytase in rainbow trout and Nile tilapia. Zinc apparent digestibility improved in relation to phytase supplementation in rainbow trout. P release due to phytase supplementation ranged from 0.06 to 0.18% P/kg feed in rainbow trout and from 0.13 to 0.26% P/kg feed in Nile tilapia. A 58‐d performance trial was conducted to evaluate tolerance of fish to phytase supplementation. Dietary treatments consisted of a basal diet without phytase or supplemented with 2000 and 200,000 phytase units/kg feed. Results indicate that this novel microbial 6‐phytase is well tolerated by fish. Significant improvements for growth as well as feed conversion ratio were observed when the phytase was fed at 2000 phytase units/kg feed. This phytase is proven efficient in releasing P from phytate and could be added when plants are used for fish meal replacement in diets for salmonid and omnivorous fish.     

Nutritional value of animal by-product meal in practical diets for Nile tilapia Oreochromis niloticus (L.) fry

Animal by-product meals (ABM) were substituted for fish meal in five experimental diets for Nile tilapia fry, Oreochromis niloticus (L), with 25%, 50%, 75% and 100% substitution. Two diets with 100% ABM were tested, one with 50:50 animal lipid:soybean oil, and the other with 100% fish oil as attractant. In general, the best growth and feeding performance was obtained with a control diet based on fish meal as the sole protein, but the results were not statistically different from those obtained with 75% and 100% ABM with soybean oil. A simple cost analysis suggested better economic efficiency when tilapia were fed with 100% ABM. It was concluded that animal by-product meal can be used as a sole protein source in commercial diets for Nile tilapia fry, without affecting growth and food utilization of the fish, improving the economics of feeding in comparison with fish meal.     

A comparative study on the apparent digestibility of selected feedstuffs in hybrid catfish (Clarias macrocephalus × Clarias gariepinus) and Nile tilapia (Oreochromis niloticus)

The apparent digestibility (AD) of dry matter (DM), organic matter (OM), crude protein (CP) and essential amino acids (EAA) in five selected feedstuffs was evaluated in hybrid catfish and Nile tilapia. The AD of DM, OM and CP in cassava leaf meal (CLM) was lower (P < 0.05) than in groundnut meal (GNM), soybean meal (SBM), sesame husk meal (SSH) and shrimp head meal (SHM). The AD of DM, OM and CP among GNM, SBM, SSH and SHM was not different (P > 0.05). The AD of most EAA was higher in SSH (P < 0.05) than in CLM, GNM, SBM and SHM. The AD of most EAA among CLM, GNM, SBM and SHM was not different (P > 0.05). The AD of DM and OM in CLM was higher (P < 0.05) in hybrid catfish than in Nile tilapia, while there was no difference in the AD of CP in CLM between fish species. The AD of DM, OM, CP and EAA among GNM, SBM, SSH and SHM did not differ between hybrid catfish and Nile tilapia. In conclusion, there were only small differences in the nutritional properties between the selected feedstuffs in both fish species. Most EAA in the selected feedstuffs were equally well utilized by hybrid catfish and Nile tilapia.     

Growth performance, feed utilization, and body composition of Nile tilapia (Oreochromis niloticus L.) fed with differently heated soybean-meal-based diets

This study was undertaken in order to determine the effect of feeding heat-treated, defatted soybean meal (SBM) on growth, feed utilization, and body composition of Nile tilapia (Oreochromis niloticus). A control diet (SBM₀) of 378 g kg⁻¹ crude protein with 18.4 kJ g⁻¹ gross energy was formulated, and three diets identical to the basal diet were autoclaved for 10, 20, or 30 min. The autoclaved diets were named SBM₁₀, SBM₂₀, and SBM₃₀, respectively. Each diet treatment was applied to triplicate groups of 30 fish (2.45 ± 0.03 g) per tank (120 l). The fish were hand fed to satiation four times daily for 45 days. At the end of the feeding trial the fish fed with the SBM₃₀ diet had significantly (P < 0.05) higher weight gain and protein efficiency ratio than those fed with the other diets. No feed-related mortality was observed during the whole experimental period. Heating SBM for 30 min reduced trypsin inhibitor activity (TIA) and increased apparent protein digestibility (APD), and indicated significant differences (P < 0.05) among various treatments. No significant differences were found in carcass moisture, lipid, and ash of fish fed with different experimental diets. An increase in the body protein content of fish fed with diet SBM₃₀ was significantly (P < 0.05) higher than in all other experimental groups. The results of this study seem to indicate that autoclaving the SBM for 30 min improved its nutritional value in practical feeds for Nile tilapia fingerlings.     

Effect of using okara meal,a by‐product from soymilk production as a dietary protein source for Nile tilapia (Oreochromis niloticus L.) mono‐sex males

The main objectives of this study was to evaluate the effect of partial and total replacement of fishmeal protein by okara meal (OM) protein in practical diets on growth performance, feed utilization and body composition of Nile tilapia (Oreochromis niloticus L.) mono‐sex males. Fish of an average initial weight of 2.67 ± 0.01 g were stocked in 15 glass aquariums (80 L each) at a rate of 15 fish per aquarium. Fishmeal protein (18% of the diet) was used as the sole source of animal protein in the control diet. Percent replacement of fish meal (FM) by OM on the basis of crude protein was as follows: 0% (control diet A), 25% (diet B), 50% (diet C), 75% (diet D) and 100% (diet E). Diets were fed to fish at a rate of 5%, and then gradually reduced to 4% of the total fish biomass daily, for a period of 12 weeks. The results revealed that the fish fed diets A (100% FM control), B (25% OM), C (50% OM) and D (75% OM) had significantly the best average body weight, weight gain g, specific growth rate (SGR % day^?1), weight gain % and feed intake g fish^?1 compared with diet E (100% OM) which had the lowest values. There were no significant differences (P > 0.05) among all experimental diets and control in terms of feed conversion ratio (FCR), protein efficiency ratio (PER) and survival rate %. Whole body protein contents for fish fed diets B, C and D were superior to the control diet. Incorporation of OM in the diets increased significantly whole body fat content. Incorporation of OM in the diets significantly increased apparent digestibility coefficient of crude protein crude fat and energy. Therefore, these findings suggest that up to 75% of FM protein can be replaced by OM protein in Nile tilapia, mono‐sex male diets.     

Effect of DL‐methionine supplementation on the success of almost total replacement of fish meal with soybean meal in diets for hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus)

This study evaluated the effects of increasing levels of methionine (Met) supplementation on the success of almost total replacement of fish meal (FM) with soybean meal (SBM) in diets for hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus). Fish were fed for 70 days a FM‐based diet (Diet1‐positive control) or SBM‐based diets supplemented with graded levels of DL‐methionine (Diet2 to Diet7). Contrast in dietary Met, concentration was created by supplementing Diet2‐negative control with 1.2 (Diet3), 2.4 (Diet4), 3.6 (Diet5), 4.8 (Diet6) or 6.0 g kg^?1 (Diet7) of DL‐Met. Specific growth rate (SGR), feed conversion ratio (FCR), and protein gain and retention efficiency (PER) improved significantly with increasing levels of dietary DL‐Met supplementation. Moreover, nonlinear regression analysis of the effects of supplementing SBM‐based diet with graded levels of DL‐Met indicated that a dietary Met + Cys level of 15.7 and 12.5 g kg^?1 diet (as fed) was required to reach 95% of maximum weight and protein gain, respectively. Supplementation of SBM‐based diet with graded levels of DL‐Met proved an effective strategy in reducing FM content in practical diets for hybrid tilapia. Data also indicate that adjustment of dietary formulas according to currently recommended Met or Met + Cys dietary concentrations is probably limiting maximum growth potential of hybrid tilapia.     

Evaluation of nutritive value of fermented de‐oiled physic nut,Jatropha curcas,seed meal for Nile tilapia Oreochromis niloticus fingerlings

Jatropha curcas seed meal was fermented with Bacillus licheniformis (LFJSM) and Bacillus pumilus (PFJSM) separately using the solid‐state fermentation. After fermentation, the crude protein and the total hydrolysed amino acid contents were increased in LFJSM and PFJSM, while fibre content, phytic acid, trypsin inhibitor and saponins were decreased. An 84‐day feeding experiment was designed for the nutritional evaluation of LFJSM and PFJSM in Nile tilapia. Seven isonitrogenous (305.47 g kg^?1 crude protein) and isocaloric (18.21 MJ kg^?1 gross energy) diets were formulated by replacing 0% (control diet), 25% (LFJSM‐25), 50% (LFJSM‐50), 75% (LFJSM‐75) and 25% (PFJSM‐25), 50% (PFJSM‐50) and 75% (PFJSM‐75) of protein from fish meal with LFJSM and PFJSM. The higher weight gain and the best feed conversion ratio were found in fish fed control diet, PFJSM‐25 and PFJSM‐50, which were insignificantly different. Apparent digestibility coefficient values of dry matter, crude protein, lipid and digestible energy reached a plateau in fish fed PFJSM‐25 and PFJSM‐50. No significant differences were found in haematocrit, haemoglobin, serum alternative complement pathway components, alanine aminotransferase and aspartate aminotransferase and triglycerides between the control diet, LFJSM‐25, LFJSM‐50, PFJSM‐25 and PFJSM‐50 treatment groups. Therefore, these findings suggest that up 50% of fish meal can be replaced by PFJSM in Nile tilapia diets.     

Utilization of genetically modified soybean meal in Nile tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> diets

The utilization of genetically modified soybean meal (GM SBM) was compared with that of non-GM SBM in Nile tilapia. Four experimental diets were formulated to include either non-GM or GM SBM at 34 or 48%, respectively. These diets were fed to juvenile Nile tilapia (49.5 g average weight) for 12 weeks. The uptake of the cauliflower mosaic virus 35S promoter fragment of the GM SBM in fish muscle was examined at 8th and 12th week. After 12th week, fish were fed the non-GM SBM diets to determine the residual span of the incorporated promoter fragment. There was no significant difference in specific growth rate or feed efficiency between GM and non-GM groups at the same inclusion level. A small number of muscles from fish receiving both levels of GM SBM diet were positive for the promoter fragment. Additionally, the promoter fragment was not detected by the second day after changing to the non-GM SBM diets. These results indicate that the utilization of GM SBM was similar to that of non-GM SBM and the promoter fragment was rarely found in fish muscles, suggesting that suitability and safety of GM SBM in Nile tilapia diet were similar to those of non-GM SBM.     

Effect of dietary probiotic Biogen® supplementation as a growth promoter on growth performance and feed utilization of Nile tilapia Oreochromis niloticus (L.)

Probiotic microbial feed supplements are gaining wide acceptance in livestock production, and may be applicable to aquaculture production systems. The present study was conducted to examine probiotic treatment in the fingerling diet of Nile tilapia Oreochromis niloticus (L.). A total of 240 of Nile tilapia fingerlings (weight ranged from 22.96 to 26.40 g) were divided into five experimental groups. The experiment was conducted for 120 days. Experimental diets were identical in all, except for the variation in probiotic levels. A probiotic (Biogen^®) was used at 0% (diet 1), 0.5% (diet 2), 1.5% (diet 3), 2.0% (diet 4) and 2.5% (diet 5) inclusion rates in the experimental diets. The growth performance and nutrient utilization of Nile tilapia including weight gain, specific growth rate, protein efficiency ratio, protein productive value and energy retention were significantly (P≤0.01) higher in the treatment receiving probiotic (Biogen^®) than the control diet. No differences were observed for moisture, ash and protein content (P≤0.01) among the experimental diets. The lowest gross energy and lipid contents were recorded for fish fed the diet containing 0.5% Biogen^® (P≤0.01). The production performance and subsequent cost–benefit analyses clearly indicated that the diets containing probiotic biogen recorded the highest net return and the lowest total cost compared with the control diet.     

Evaluation of Calanus finmarchicus copepod meal in practical diets for juvenile Atlantic halibut (Hippoglossus hippoglossus)

The copepod, Calanus finmarchicus, has potential as a new ingredient in practical feeds for marine fish. Two experiments were conducted to evaluate the nutritional value of C. finmarchicus meals when fed to juvenile Atlantic halibut. The first study determined protein, lipid and energy digestibility coefficients of four C. finmarchicus meals prepared under different processing conditions. The second study evaluated growth and nutrient utilization efficiency of juveniles fed diets containing varying proportions of fish meal, plant meals and C. finmarchicus meal. Moisture, ash, protein, lipid and gross energy contents of the C. finmarchicus meals were 28–93, 74–138, 505–648, 123–269 g kg⁻¹, and 21–26 MJ kg⁻¹, respectively. Protein, lipid and energy digestibilities of C. finmarchicus meals were 91–99%, 90–95% and 90–99%. The digestibilities significantly decreased for the Calanus meals processed at higher temperatures. During the growth study, halibut fed a diet containing 240 g kg⁻¹ C. finmarchicus meal had significantly higher weight gain and growth rate than all other groups. Nitrogen and energy retention efficiencies ranged between 35–45% and 33–43%, and were significantly higher for fish fed 160–240 g kg⁻¹ C. finmarchicus meal than for fish fed plant protein and control diets. The results indicate that growth and nutrient utilization efficiency are improved in Atlantic halibut fed diets supplemented with C. finmarchicus meal.     

Evaluation of Gambusia, Gambusia affinis, Fish Meal in Practical Diets for Fry Nile Tilapia, Oreochromis niloticus

This study was conducted to evaluate the use of gambusia, Gambusia affinis, fish meal (GFM) in practical diets for fry Nile tilapia, Oreochromis niloticus (2.11 ± 0.11 g). Six isonitrogenous diets (35%) were formulated in which GFM replaced 0.0, 10, 25, 50, 75, or 100% of the protein supplied by herring fish meal (HFM). Fish were fed one of the test diets at a feeding rate of 4% of the fish body weight 6 d a week, 2 times a day for 13 wk. Results demonstrated that fish growth increased with increasing GFM up to 75%, which produced the highest growth of the treatments. The lowest fish growth was obtained at 100% GFM. Feed intake (FI), protein efficiency ratio (PER), and apparent protein utilization (APU) increased significantly, while feed conversion ratio (FCR) decreased significantly with increasing GFM up to 75%. FI, PER, and APU decreased significantly, while FCR increased significantly for diets containing 100% GFM. There were no significant differences in moisture, protein, lipid, or ash contents in final fish body following inclusion of GFM in fish diet. There was no significant difference in the digestibility coefficient of dry matter. The digestibility coefficients of protein and gross energy for diets containing 100% GFM replacement were the lowest as compared with other GFM levels. The present study recommended that GFM is a suitable protein source in practical diets for fry Nile tilapia and could replace HFM up to 75%.