Cyclical feed deprivation and refeeding fails to enhance compensatory growth in Nile tilapia, Oreochromis niloticus L.

A 12-week experiment was carried out to evaluate compensatory growth of 6.6 g Nile tilapia Oreochromis niloticus L. under three cyclical regimes of feed deprivation and refeeding. The deprivation and refeeding regimes included four cycles of 1 week of deprivation and 2 weeks of refeeding (S1F2), two cycles of 2 weeks of deprivation and 4 weeks of refeeding (S2F4) and one cycle of 4 weeks of deprivation and 8 weeks of refeeding (S4F8). A group of fish fed to satiation twice daily throughout the experiment served as control. At the end of the refeeding periods, fish deprived and refed cyclically had higher feed intake and specific growth rates (SGR), but lower body weight, than that of the control fish. There was no significant difference in feed efficiency ratio (FER) between the control and fish subjected to feed deprivation during the refeeding periods, and nitrogen retention efficiency (NRE) was not different between any two treatments throughout the experiment. At the end of the experiment, fish subjected to feed deprivation had lower body weight but similar body composition, relative to those of the control fish. No significant differences were found in final body weight, NRE and body composition between the fish subjected to different cycles of deprivation and refeeding, but the fish subjected to one cycle of deprivation and refeeding exhibited high mortality. Our results indicate that partial growth compensation induced by various cycles of feed deprivation and refeeding does not confer a huge advantage in terms of enhancing the production efficiency and reducing the nitrogen waste output in Nile tilapia farming 29–30 °C.     

Effects of low and medium levels of red alga Nori (Porphyra yezoensis Ueda) in the diets on growth,feed utilization and metabolism in intensively fed Nile tilapia,Oreochromis niloticus (L.)

A 10‐week feeding experiment was conducted in a respirometric system to evaluate the suitability of red alga Nori (Porphyra yezoensis) as a partial replacement for fish meal in intensively fed Nile tilapia. Diets were formulated to be iso‐nitrogenous and iso‐energetic and to replace 0%, 15% and 30% fish meal with Nori, P. yezoensis. No statistically significant differences in growth or feed utilization between the control diet and either Nori diet were found. Tilapia fed on Nori 15 increased their body mass by 415%, those fed the control diet by 341% and fish fed Nori 30 by 317% over the experimental period. Nori 15 fed fish showed the best feed utilization, highest metabolic growth rate and significantly lower oxygen consumption rates than the control. Both Nori supplemented groups (Nori 15: 4.1 g O₂ g^?1 protein gain and Nori 30: 3.9 g O₂ g^?1 protein gain) used less oxygen per gram of protein gain compared to fish fed the control diet (5.4 g O₂ g^?1 protein gain). Our results show that a low replacement level (15%) of fish meal with Nori improves growth and feed utilization while oxygen consumption and amount of oxygen consumed per gram protein gain are significantly decreased.     

Effect of feed colour on growth and feed utilization of Nile tilapia (Oreochromis niloticus L.) larvae and fingerlings

Two experiments were conducted to investigate the effects of feed colour on the performance of Nile tilapia (Oreochromis niloticus) larvae and fingerlings. In the first experiment, triplicate groups of newly hatched larvae (0.01 g fish⁻¹) were stocked in 40 L glass aquaria at a density of 2 fish L⁻¹. The fish were fed a test diet (400 g kg⁻¹ crude protein) with six different colours (dark blue, dark green, red, dark brown, yellow and light brown) for 60 days. The best performance and survival were achieved in fish fed on dark‐coloured diets, while light‐coloured diets (yellow and light brown) resulted in inferior performance. Dark diets also produced higher body protein than light diets. Body water, lipids and ash showed irregular trends. In the second experiment, triplicate groups of Nile tilapia fingerlings (5.30 g fish⁻¹) were stocked in 140‐L aquaria, in a recirculating indoor system. The fish were fed a test diet (350 g kg⁻¹ crude protein) with the same colours used in the larval trial, for 60 days. Growth rates, feed efficiency, survival and body composition were not significantly affected by feed colours. These results suggest that Nile tilapia larvae are visual feeders, and they prefer dark‐coloured diets to light‐coloured diets, while fingerling fish showed no preference to diet colours.     

Comparative nutritional evaluation of raw, methanol extracted residues and methanol extracts of moringa (Moringa oleifera Lam.) leaves on growth performance and feed utilization in Nile tilapia (Oreochromis niloticus L.)

The suitability of raw and methanol‐extracted moringa (Moringa oleifera Lam.) leaf meal to replace 10%, 20% and 30% of the total fishmeal‐based dietary protein in tilapia feeds was tested. Ten isonitrogenous and isocalorific feeds (35% crude protein and 20 MJ kg^?1 gross energy), denoted as diets 1 (fishmeal‐based control), 2, 3, 4 (containing 13%, 27% and 40% raw moringa leaf meal), 5, 6, 7 (containing 11%, 22% and 33% methanol‐extracted moringa leaf meal), and 8, 9, 10 (containing methanol‐soluble extracts of the raw moringa leaf meal at the same level as would have been present in diets 2, 3, 4) were prepared. Forty tilapia (16.7±2.4 g), kept individually, were fed the experimental diets (four fish per treatment) at the rate of 15 g feed per kg metabolic body weight (kg^0.8) per day. A reduction in the growth performance was observed with an increasing level of raw moringa leaf meal (diets 2–4), whereas inclusion of methanol‐extracted leaf meal (diets 5–7) had no significant (P<0.05) effect on the growth performance compared with the control (diet 1). The growth performance of fish fed diets 8–10 containing methanol extracts of the moringa leaf meal were also similar to the control. The chemical composition values of the gained weight showed that lipid accretion decreased with increased inclusion of moringa leaves, and ash content increased. Dietary moringa methanol extracts reduced protein accretion, but had no effects on lipid and ash contents compared with the control. The inclusion of raw, methanol‐extracted residues and methanol extracts of the moringa leaf meal (diets 3 and 4, 5, 6 and 7, and 8 respectively) reduced the plasma cholesterol content significantly. Similarly, a significant reduction in muscle cholesterol was observed in fish fed the diets 4, 8, 9 and 10. It was concluded that the solvent‐extracted moringa leaf meal could replace about 30% of fishmeal from Nile tilapia diets.     

A comparative study of growth and feed utilization efficiency of sex-reversed diploid and triploid Nile tilapia, Oreochromis niloticus L.

Growth performance, survival and feed utilization of diploid (2n) and triploid (3n) sex‐reversed male and female Nile tilapia were evaluated at maintenance feeding (1% body weight (BW) day^?1), fixed feeding (3% BW day^?1) and apparent satiation feeding levels in a freshwater recirculation system comprised of thirty‐six 1‐m³ concrete tanks at the Asian Institute of Technology, Bangkok, Thailand. Triploid Nile tilapia (3n) was produced by subjecting fertilized diploid (2n) tilapia eggs to heat shock. After hatching, fish were sex‐reversed to all‐male and all‐female populations by oral administration of 17 α‐methyltestosterone (60 mg kg^?1 feed) and ethynylestradiol (100 mg kg^?1 feed) respectively. There was significantly higher growth with increased ration levels in both male and female groups. There were no significant differences in final BW, specific growth rate, survival rate, feed conversion ratio and protein efficiency ratio between diploid and triploid fish. Triploids had lower gonad weights than diploids, and this was particularly evident at the satiation feeding level. Triploid fish had a significantly higher apparent net protein utilization and percentage of gutted weight than diploids at all feeding levels. Higher protein utilization efficiency of triploids might be an advantage for commercial tilapia culture but further research is necessary to make such a conclusion.     

Dietary taurine enhances growth and feed utilization in larval Nile tilapia (Oreochromis niloticus) fed soybean meal‐based diets

This study was conducted to evaluate the effects of dietary taurine on growth performance and feed utilization of Nile tilapia (Oreochromis niloticus) larvae. Four plant protein‐based, isonitrogenous (400 g kg^?1 protein), isoenergetic (19 MJ kg^?1) diets supplemented with four taurine concentrations (0.0, 5.0, 10.0 and 15.0 g kg^?1; designated as T₀, T_0.5, T₁ and T_1.5, respectively) were prepared. The diets were fed to triplicate groups of fish larvae (0.024 g average body weight), to apparent satiation, three times per day for 60 days. Larval growth rates and feed utilization efficiency were significantly improved with increasing supplemental taurine up to 10 g kg^?1 and decreased with further taurine supplementation. The quadratic regression analyses indicated that the maximum larval performance occurred at about 9.7 g kg^?1 of total dietary taurine. Fish survival was significantly lower at 15 g kg^?1 dietary taurine than at other taurine levels. Body protein significantly increased, while body moisture and ash decreased, with increasing dietary taurine up to 10 g kg^?1 and decreased with further taurine supplementation to 15 g kg^?1. Body lipid was not significantly affected by dietary taurine concentration. A number of body amino acids (tryptophan, arginine, histidine, leucine, isoleucine, valine, alanine, glycine, threonine and taurine) significantly increased with increasing supplemental taurine up to 10 g kg^?1 and then decreased with further increase in dietary taurine levels. The rest of body amino acids were not significantly affected by dietary taurine. The present results suggest that about 9.7 g kg^?1 dietary taurine is required for optimum performance of Nile tilapia larvae fed soybean meal‐based diets.     

Microwave irradiation and pelleting method affected feed chemical composition and growth performance and feed utilization of sex‐reversed Nile tilapia,Oreochromis niloticus (L.)

Microwave processing and pelleting methods were assessed to improve aquafeed quality for sex‐reversed Nile tilapia. The 2 × 3 experimental feeds were prepared with and without microwave irradiation of ingredients prior to pelleting with either a meat mincer, extruder or steam conditioner followed by a meat mincer. Five feedstuff ingredients, including fish meal, meat and bone meal, soybean meal, broken rice and rice bran, were irradiated separately at optimal times, according to the third‐order polynomial regression analysis between in vitro digestibility and microwave irradiation times (r = 0.681–0.942, P < 0.001, n = 42). The prepared feeds were studied for chemical compositions and responses in fish growth performance and feed utilization efficiency. The fish (1.57 ± 0.01 g initial weight) were fed ad libitum for 4 months. All proximate chemical compositions of experimental feeds, except protein, were influenced by microwave processing, pelleting methods or their interaction (P < 0.05). There were no significant effects from either parameter on water quality during the fish trial. Fish fed steamed microwave‐irradiated feed, mechanically pelleted with a meat mincer, showed the highest growth performance (weight gain 18.91 ± 0.73 g and specific growth rate 2.15 ± 0.26% day^?1) and feed utilization efficiency (feed conversion ratio 1.31 ± 0.05 g feed g gain^?1 and protein efficiency ratio 2.27 ± 0.08 g gain g protein^?1) compared with the other dietary groups. These findings indicate that microwave irradiation of feed ingredients prior to steam conditioning followed by mincing can improve aquafeed production quality.     

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.     

Use of cottonseed meal supplemented with iron for detoxification of gossypol as a total replacement of fish meal in Nile tilapia, Oreochromis niloticus (L.) diets

The objective of this study was to determine the effect of total replacement of fish meal by cottonseed meal (CSM) supplemented with various levels of iron in practical diets on growth performance, feed utilization, body composition and some biological and haematological parameters of Nile tilapia, Oreochromis niloticus (L.). Juvenile fish (average weight 3.78±0.1 g) were stocked in 18 glass aquariums (80 L each) at 25 fish per aquarium. Fish meal (50% of the diet) was used as the sole source of animal protein in the control diet 1. Diets 2–6 had 100% CSM (0.145% free gossypol) protein with various levels of supplemented iron (86, 486, 972, 1458 and 1944 mg Fe kg diet^?1) in diets 2–6 respectively. Diets were fed to fish twice daily at a rate of 3% of body weight during the first 12 weeks then 2% of the total fish biomass daily until the end of the experiment (30 weeks). The results of this study revealed that, groups of fish fed diets 1, 4, 5 and 6 had significantly (P≤0.01) the higher average body weight and specific growth rate than those of fish fed diet 2 (100% CSM without iron supplementation) and diet 3 (100% CSM plus 486 mg Fe kg diet^?1). The best values for feed conversion ratio, protein efficiency ratio and condition factor (K) were recorded with groups of fish fed diet 4 (100% CSM plus 972 mg Fe kg diet^?1). Red blood cell count, haematocrit and haemoglobin were increased with increasing levels of iron and significantly affected by dietary iron. Hepatosomatic index for diets 3–6 were not significantly different (P>0.05) and superior to that of diet 1 control [100% fish meal (FM)]. The gonadosomatic index of males of Nile tilapia was not influenced by CSM diets with or without iron, while females of Nile tilapia were significantly influenced with iron and the lowest values were recorded with groups of fish fed diet 2 (100% CSM without iron supplementation). Apparent digestibility coefficients of protein, fat dry matter and energy were relatively high for most diets supplemented with iron and increased by increasing iron supplementation. There were no significant differences between groups of fish fed diet 1 (100% FM) and diets 5 and 6 which contained 100% CSM with additional 1458 and 1944 mg Fe kg diet supplemental iron^?1 respectively. Proximate composition of whole body was not influenced by diet. Adding 972 mg Fe kg diet^?1 from ferrous sulphate to the CSM‐based diets that contained 972 mg free gossypol (1:1 iron to free gossypol ratio) for Nile tilapia reduce the negative effects of gossypol and improved growth performance, feed utilization and blood parameters and can totally replace fish meal in tilapia diets.     

Salmon testes meal as a functional feed additive in fish meal and plant protein‐based diets for rainbow trout (Oncorhynchus mykiss Walbaum) and Nile tilapia (Oreochromis niloticus L.) fry

Fishery processing by‐products are a large resource from which to produce fishmeal and other products for a variety of uses. In this study, testes meal (TM) produced from pink salmon processing by‐product was evaluated as a functional ingredient in aquafeeds. Nile tilapia and rainbow trout fry were fed five isonitrogenous and isoenergetic experimental diets for 4 and 9 weeks respectively. Two diets were fishmeal‐based (FM) and three were plant protein‐based (PP). Salmon TM was added to the FM and PP diets at 7% to replace 20% of fishmeal protein (FMTM and PPTM respectively). An additional control diet was prepared in which fishmeal was added to the PP diet to supply an equivalent amount of protein as supplied by TM (PPFM). Inclusion of TM in both the FM‐ and PP‐based diets resulted in higher final body weights, although differences were only significant between rainbow trout fed FM or FMTM diets. Similar differences were calculated for other indices of fish performance, e.g. specific growth rate, feed conversion ratio, protein efficiency ratio and protein retention efficiency. Feed intake was significantly higher for fish fed FMTM compared with FM in rainbow trout. For tilapia, final weights were numerically higher, but not significantly different for fish fed diets containing TM compared with non‐TM diets (FM vs. FMTM; PP vs. PPTM). Performance of trout or tilapia fed the PPFM diet did not increase compared with the PP diet. The results indicate that TM addition to both FM and PP diets increased feed intake and also increased metabolic efficiency, demonstrating that TM can be a functional ingredient in aquafeeds.     

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 positive contributions of PowerLac™ supplementation to the production performance,feed utilization and disease resistance of Nile tilapia Oreochromis niloticus (L.)

The objective of this research was to determine the optimum dietary supplementation level of a probiotic (PowerLac^?), for improving Nile tilapia Oreochromis niloticus growth performance and feed utilization, as well as enhanced protection against disease. For laboratory experimentation, a completely randomized experimental design, consisting of four treatments of a dietary probiotic (PowerLac^?, containing Lactobacillus lactis D1813) supplementation at different levels (0.25, 0.5, 1.0 and 2.0 g kg^?1), against a control (0 g kg^?1), was performed for 8 weeks (of culture period). For field experiments, three treatments of different dietary probiotic supplementation levels (0.25, 0.5 and 1.0 g kg^?1), plus a control, were employed for 22 weeks (of culture period). Under controlled experimental conditions, in the first experiment, significantly higher fish final body weight, growth and lower food conversion ratio (FCR) were achieved by treatments with dietary probiotic supplementations of 0.25 and 0.5 g kg^?1 (P < 0.05). In strong partial support of this, at field experimentation level, a dietary PowerLac^? supplementation of 0.5 g kg^?1 showed the most pronounced results, as indicated by the higher growth, and protein and lipid retention, as well as lower FCR, and reduced mortality following the Aeromonas hydrophila challenge test (P < 0.05).     

Effect of dietary protein regime during the growing period on growth performance, feed utilization and whole-body chemical composition of Nile Tilapia, Oreochromis niloticus (L.)

This study was conducted to evaluate the effect of various dietary protein regimes on growth performance, feed utilization and whole-body chemical composition of Nile tilapia, Oreochromis niloticus (L.). Twenty cages (1 m³ each) were randomly allocated to a four-replicate experiment to represent five treatments (T1–T5) where fish were randomly stocked at a rate of 50 fish (1.5–2.2 g) per cage. Fish in T1–T5 fed on a 45% crude protein (CP) diet for the first 4 weeks. In T1, T2 or T3 fish fed on 45%, 35% or 25% CP diets for the last 8 weeks respectively. In T4 fish fed 35% CP diet for the second 4 weeks followed by 25% CP diet for the last 4 weeks and in T5 fish fed 25% CP diet for the second 4 weeks followed by 35% CP diet for the last 4 weeks. Diets were offered to satiation and provided manually twice a day in the morning and in the afternoon, 6 days a week. The optimum fish growth and feed utilization were obtained at T1, T2 and T4. Protein efficient ratio and apparent protein utilization were lower at T1 and T2 than those of T3–T5. On the other hand, no significant changes in energy utilization were observed among the different treatments. There were no major changes in the carcass composition except in ash content, which was higher in T3 and T5 only. This study recommended that the dietary protein regime is an important management in tilapia culture, and the protein level could be reduced from 45% to 35% then to 25% on increasing the fish size.     

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.     

Effects of dietary arginine on growth performance,feed utilization,haematological parameters and non‐specific immune responses of juvenile Nile tilapia (Oreochromis niloticus L.)

An 8‐week feeding trial was conducted to evaluate the effects of dietary arginine on growth performance, feed utilization, haematological parameters and non‐specific immune responses of juvenile Nile tilapia (6.03 g). Five isonitrogenous and isoenergetic diets were formulated to contain graded levels of L‐arginine (8.5 g kg^?1, 11.5 kg^?1, 15.3 kg^?1, 18.8 kg^?1 and 22.4 kg^?1 dry diet) from dietary ingredients and crystalline arginine. Each diet was randomly assigned to triplicate groups of 25 juvenile fish (6.04 ± 0.02 g) three times daily (8:30, 12:30, and 17:00 hours) to apparent satiation. Results showed that the weight gain (WG) and special growth rate (SGR) increased with increasing dietary arginine levels up to 15.3 kg^?1 and remained nearly the same thereafter. Arginine supplementation had no impact on the survival, body composition and haematological parameters of tilapia. However, the immune responses (plasma nitric oxide content, total nitric oxide synthase (T‐NOS) and lysozyme activity) significantly (P < 0.05) increased with increasing dietary argentine level after stress. Quadratic regression analysis (y = ?0.7147x² + 25.986x + 147.53 R² = 0.8736) on weight gain against dietary arginine levels indicated that the optimal dietary arginine requirement was estimated to be 18.2 kg^?1 of the diet (corresponding to 6.24% of dietary protein on a dry weight basis). The present study indicates that arginine has an immunostimulatory potential to help juvenile Nile tilapia cope with stress conditions such as Streptococcus iniae infection.