The effect of vitamin A supplementation in broodstock feed on reproductive performance and larval quality in Penaeus chinensis

The effect of feeding four semi‐purified diets A1, A2, A3, A4, containing different vitamin A acetate levels 0, 20, 40, 60 mg kg^?1 diet, respectively, on fecundity, egg hatching rate, larval survival rate and vitamin A content in eggs of Chinese shrimp (Penaeus chinensis) broodstock was compared with a fresh clam diet (control) in a 60‐day feeding trial. The broodstock shrimp fed the diet with 60 mg kg^?1 vitamin A acetate added exhibited significantly higher fecundity (P < 0.01). Hatching rate was highest with diet A4 (P < 0.05), whereas hatching rates were similar fed diets A1, A2, A3. Increasing levels of vitamin A in broodstock diet resulted in improvement in larval quality. The vitamin A levels in shrimp eggs from broodstock fed with diet A4 were higher compared with those from broodstock fed with diet A1, A2 (P < 0.01). The fecundity and hatching percentages were positively correlated with the vitamin A content in eggs in the present study. The results of this study showed that higher level of vitamin A in broodstock diet may have positive effects on fecundity and larval quality in P. chinensis.     

Effect of dietary protein and lipid levels and protein–energy ratio on growth indices, feed utilization and body composition of freshwater prawn, Macrobrachium rosenbergii (de Man 1879) post larvae

A grow‐out experiment was designed to determine the effect of different dietary protein, lipid levels and protein–energy (P:E) ratio on growth performance and feed utilization of the freshwater prawn, Macrobrachium rosenbergii post larvae (PL) culture in pond net enclosures (hapa, 3.75 m^?3 each) for 12 weeks (84 days). The experimental treatments were assigned in triplicate. Six test diets were formulated to contain three different protein levels (300, 350 and 400 g kg^?1 diet) and two lipid levels (100 and 140 g kg^?1 diet) in a factorial manner (3 × 2) to provided six different dietary P:E ratio: 16, 17, 18, 19, 20 and 21 mg CP kJ^?1 g^?1). The result showed that the highest significant (P≤0.05) survival rate, growth indices and feed utilization were observed for M. rosenbergii PL fed a diet with a P:E ratio of 17 mg CP kJ^?1 g¹, whereas, the lowest value was recorded for prawns fed a diet with a P:E ratio of 20 mg CP kJ^?1 g^?1. Whole body contents of protein and lipid were highest (P≤0.05) when fed diets with 21 and 17 mg CP kJ^?1 g^?1 respectively. Concerning dietary protein levels, the highest (P≤0.05) values for survival and growth indices were observed for PL fed a diet containing 300 g kg^?1 diet protein. The same trend was observed for PL fed a diet with 100 g kg^?1 diet lipid level, irrespective of dietary protein levels. A diet containing 300 g kg^?1 protein and 100 g kg^?1 lipid with a dietary P:E ratio of 17 mg CP kJ g^?1 is recommended to stimulate growth performance and nutrients utilization efficiency of M. rosenbergii PL.     

Protein content and amino acid composition of eggs and endotrophic larvae from wild and captive fed sea urchin Paracentrotus lividus (Echinodermata: Echinoidea)

Knowledge on the biochemistry of proteins and amino acids (AA) of eggs and larvae of echinoids is scarce and the possibility to modify their profiles by diet manipulations is unknown. The protein content of eggs, prisms and pre‐plutei and the amino acid composition of eggs of Paracentrotus lividus from captive broodstock fed prepared diets were analysed and compared with the ones obtained from wild broodstock. Diets differed on protein source (fish or soy meals) and on protein content (10–40% dry weight – DW). Total and soluble protein content of both eggs and larvae was higher than 400 g kg^?1 DW and 200 g kg^?1 DW respectively. Glycine was the most abundant free AA. Very few differences were found among P. lividus eggs and larvae biochemical parameters, suggesting that their AA composition can hardly be changed by broodstock diet manipulations.     

Effects of dietary protein and energy levels on spawning performance of Nile tilapia (Oreochromis niloticus) broodstock in a recycling system

The effects of dietary protein and energy level on spawning performance of Nile tilapia broodstock and hatchability of their eggs were studied. Nine diets containing three protein (30, 35 and 40%) and three energy (14.6, 16.7 and 18.8 MJ GE/kg) levels were prepared. The diets were fed to duplicate groups of broodfish (average weight of 60.5 ± 4.6 g for males and 39.4 ± 3.1 g for females) at 2–3% of their body weight, twice a day, for 150 days. At low protein level (30%), time to first spawning was significantly longer than at 35 and 40% protein levels, and increased with increasing dietary energy (decreasing protein-to-energy (P/E) ratio). At 35 and 40% protein levels, time to first spawning was not affected by dietary energy. Inter-spawning intervals (ISI) showed irregular patterns in relation to dietary protein and energy, however, at 40% protein the females tended to spawn at shorter intervals, regardless of dietary energy. Spawning performances, including total number of spawnings per tank, number of spawnings per female, absolute fecundity and average number of eggs per spawn, were all significantly lower (P < 0.05) at 30% CP than at higher protein levels. At all protein levels, increasing dietary energy from 14.6 to 18.8 MJ GE/kg (and decreasing P:E ratio) resulted in a significant decrease in fish fecundity. Egg size was not significantly affected by dietary protein and energy. At all energy levels, egg hatchability increased with increasing dietary protein levels (P < 0.05). Eggs produced from broodstock fed 30 and 35% CP, exhibited significantly lower hatchability (P < 0.05) and needed less time for hatching and yolk-sac absorption, and resulted in lower larval length than those fed a 40% protein diet. However, increasing energy level at each dietary protein level did not significantly affect these parameters. These results revealed that the best spawning performance of Nile tilapia broodstock reared in a recycling system was achieved at 40% dietary protein and 16.7 MJ GE/kg, with a P/E ratio of 23.6 g/MJ.     

Maturation performance, offspring quality and lipidcomposition of Macrobrachium rosenbergii femalesfed increasing levels of dietary phospholipids

The effects of increasing levels of dietaryphospholipids (PL) on the reproductive performance,egg and larval quality, and lipid composition offemales of the freshwater prawn Macrobrachiumrosenbergii were investigated. Three isolipidic dietscontaining similar amounts of highly unsaturated fattyacids but varying levels of PL (0.8, 2.4 and 4.6%)were fed during 180 days to three groups of eightfemales originating from Thai ponds. No significantdifferences were observed for fecundity, egg size andhatchability, starved larvae size, and size, survivaland tolerance to stress of 8 day-old larvae.Similarly, no major differences in the lipidcomposition of the midgut gland, ovaries and muscletissue of females could be detected. Results indicatethe lack of need of dietary supplementation of PL forM. rosenbergii broodstock, as previouslyreported for earlier life stages. It is suggested thatthe basal level of 0.8% dietary PL was sufficient tomeet the dietary demands of the prawn broodstock. ThePL requirements of M. rosenbergii broodstock, ifany, may be satisfied in commercial feeds through theinclusion of ingredients containing some phospholipidsendogenously.     

Effects of variable feed allowance with constant energy and ratio of energy to protein in a diet for constant protein input on the growth of common carp Cyprinus carpio L.

An 11‐week feeding trial was conducted to evaluate the effects of dietary protein and/or energy levels on growth, feed efficiency and proximate composition of juvenile (average weight: 21.5 g) common carp (Cyprinus carpio L.) fed various diets based on constant daily protein input. Five experimental diets were prepared. One group of diets (diets 1, 2 and 3) contained three crude protein (P) levels (35%, 40% and 45%) with a constant gross energy (GE) of 3.8 kcal g^?1 diet. The second group of diets (diets 4 and 5) were formulated to contain a GE of 4.3 or 4.9 kcal g^?1 diet and 40% or 45% protein levels, respectively, where GE/P was constant at 10.8 kcal g^?1 protein. Fish receiving diet 1 served as the control; they were hand‐fed to visual satiety. Feed allowance for diets 2 and 4 was 87.5% of the control. Feed allowance for fish receiving diets 3 and 5 was 77.8% of the control. Thus, all tanks received the same daily protein input. When gross energy in the diets was constant, 3.8 kcal g^?1 diet, weight gain of fish fed diet 2 at 87.5% satiation was significantly higher than that of fish fed diet 3 at 77.8% of satiation. When the GE/P in the diets was constant, 10.8 kcal g^?1 protein, weight gain of fish fed diet 1 was significantly higher than that of fish fed diet 5 at 77.8% satiation. The feed efficiency ratio (FER) for diets 2–5 was significantly higher than for diet 1 at constant GE and GE/P, and this improved linearly as dietary protein levels increased. The protein efficiency ratio (PER) for diet 2 was significantly higher than for diet 3 at constant GE. However, PER was not significantly different at constant GE/P. Protein retention of fish fed diet 2 was significantly higher than that of fish fed diet 3 at constant GE. Protein retention of fish linearly decreased at constant GE/P. The energy efficiency ratios (EER) for diets 2 and 3 were significantly higher than for diet 1 at constant GE. Moisture and protein contents of the whole body of fish were not significantly different at constant GE, but they decreased linearly at constant GE/P. The lipid content of fish fed diet 1 was significantly lower than that of fish fed diet 2 at constant GE, and body lipid content linearly increased at constant GE/P. These results indicate that growth and feed efficiency for common carp fed a 40% protein diet with 3.8 kcal g^?1 diet GE at 87.5% satiation rate was superior to those for the fish fed either a 35% protein diet with 3.8 kcal g^?1 diet GE at 100% satiation rate or a 45% protein diet with either a 3.8 or 4.9 kcal g^?1 diet GE at 77.8% satiation rate.     

Growth and carcass composition of giant freshwater prawn, Macrobrachium rosenbergii (De Man), fed different isonitrogenous and isocaloric diets

A feeding experiment was conducted for 135 days to observe the effect of different isonitrogenous (35% crude protein) and isocaloric (385 kcal) diets on the growth and carcass composition of giant freshwater prawn, Macrobrachium rosenbergii ( De Man 1879 ). Three experimental diets (ED1, ED2 and ED3) were prepared using locally available ingredients. These diets differed mainly in terms of percent contribution of major protein sources such as fish meal, soybean meal, groundnut oil cake and mustard oil cake. Experimental diets were evaluated against a commercial diet, which served as the control (CD). Juveniles 1.87–2.44 g in size were stocked at a population density of 40 000 ha⁻¹ and fed thrice daily at 10% in the beginning and reducing gradually to 7% and 5% of the body weight during the experimental period. No significant differences (P>0.05) in the growth performance were observed; however, a significantly (P<0.05) higher yield (721.9 kg ha⁻¹ 135 days⁻¹) was recorded for prawn fed with control diet, followed by experimental diet 2 (676.5 kg ha⁻¹ 135 days⁻¹, having soybean meal as a major protein source). The survival ranged between 63.8% and 77.7%, with different diets showing significantly higher survival. The apparent feed conversion ratio values of diets ranged between 3.15 and 3.49, with experimental and control diets showing non‐significantly lower AFCR values. At the end of the experiment, representative specimens from each treatment were collected and their carcass composition was measured. Analysis of variance showed that carcass protein and total carbohydrate contents were significantly (P<0.05) higher in prawns fed on a fish–soybean meal‐based diet (ED3) and a control diet. The total lipid contents of prawns, however, did not differ significantly among the various dietary treatments. The results of our study suggest that the experimental diets could be used effectively for M. rosenbergii without compromising growth and flesh quality.     

Effects of varying dietary protein levels on growth, reproductive performance, body and egg composition of rohu, Labeo rohita (Hamilton)

A 360‐day feeding trial was conducted to observe the influence of varying levels of dietary protein on growth, reproductive performance, body and egg composition of rohu, Labeo rohita. Twenty fish (40.4 ± 0.24 cm; 852 ± 4.9 g), stocked in outdoor concrete tanks (200 m²), in duplicate, were fed diets with varying levels (200, 250, 300, 350 and 400 g kg^?1) of crude protein exchanged with carbohydrate to apparent satiation, twice daily, at 09:00 and 17:00 h. Higher (P < 0.05) weight increment was discernible in fish fed dietary protein ≥300 g kg^?1. Gonadosomatic index was comparable (P > 0.05) among fish of different dietary groups except those fed 200 g kg^?1 protein diet which produced least values. Egg diameter remained unaffected (P > 0.05) by variations in levels of dietary protein. Relative fecundity was maximum (P < 0.05) in fish fed 250 and 300 g kg^?1 protein diets. With the exception of fish fed 200 g kg^?1 protein diet, fertilizability (%) remained unaffected (P > 0.05) by variations in dietary protein level. Hatchability (%) followed the trend of variations almost similar to that of fertilizability. Proximate composition of muscle and eggs varied significantly (P < 0.05) with dietary protein levels. For broodstock L. rohita, a dietary protein level of 250 g kg^?1 was found optimum with regard to its reproductive performance, egg quality and composition.     

Effects of dietary protein level on spawning performance of Nile tilapia (Oreochromis niloticus) broodstock reared at different water salinities

Effects of dietary protein level and water salinity on spawning performance of Nile tilapia broodstock and growth of their larvae were studied. Four isocaloric (400 kcal/100 g) diets containing 25%, 30%, 35% and 40% crude protein were prepared. The diets were fed to broodfish (25.7 g) reared at three water salinities (0‰, 7‰ and 14‰) at a female/male ratio of 3:1, to satiation twice a day for 195 days. The size at first maturation increased with increasing dietary protein at all salinities. At 25% and 30% protein levels, broodstock reared at 0‰ reached their sexual maturity at bigger sizes than those reared at 7‰ and 14‰. At 0‰, spawning intervals were not significantly affected by dietary protein levels. At 7‰ and 14‰, spawning intervals significantly decreased with increasing dietary protein level. Spawning frequency and number of eggs per spawn were increased with increasing dietary protein level. The total number of spawnings per female and absolute fecundity were better in fish fed 40% protein in freshwater than at 7‰ and 14‰ salinity. The relationship of dietary protein and water salinity on egg size was significant, but showed irregular patterns. The chemical composition of broodstock muscles, eggs and fry were not significantly affected by dietary protein and water salinity, except for body water and crude protein of broodstock which were significantly affected; but showed irregular trends. At each water salinity, egg hatchability was linearly increased with increasing dietary protein level. Eggs produced from broodstock fed 25% protein at 7‰ and 14‰ needed more time for hatching and yolk-sac absorption and resulted in poorer larval weight than those reared in freshwater. Fry growth was improved with increasing protein level at all salinities. This result revealed that 40% dietary protein is required for optimum spawning performance of Nile tilapia reared at 0‰, 7‰ and 14‰ salinity. It also indicated that spawning performance and larval growth were better in freshwater than at 7‰ and 14‰.     

Effects of Dietary Protein and Energy Levels on Growth and Body Composition of Juvenile Flounder Paralichthys olivaceus

A feeding trial of three protein levels (30, 40 and 50%) and two energy levels (300 and 400 kcal/100-g diet) factorial design with three replications was carried out to investigate the proper dietary protein and energy levels for the growth of juvenile flounder Paralichthys olivaceus . Weight gain of fish tended to improve with increasing dietary protein level. Weight gain of fish fed either the 40% or 50% protein diet with 300 kcal/100-g diet was significantly higher ( P < 0.05) than with 400 kcal/100-g diet. The best weight gain was obtained from fish fed the 50% protein diet with 300 kcal/100-g diet. Feed efficiency tended to improve with increasing dietary protein level. However, dietary energy level had no significant effect on feed efficiency of fish fed the 30% or 50% protein diet, but that of fish fed the 40% protein diet with 300 kcal/100-g diet was significantly higher than with 400 kcal/100-g diet. Protein retention tended to increase as dietary protein level increased and energy level decreased. Lipid content of fish fed the diet containing 400 kcal/100-g diet was significantly higher than that of fish fed the diet containing 300 kcal/100-g diet at all protein levels. Fatty acid compositions such as linoleic acid, EPA (20:5n-3) and DHA (22:6n-3) offish were directly affected by dietary lipid (squid liver oil and/or soybean oil) used for energy source. Based on the above results, it can be concluded that the proper dietary protein and energy levels for the growth of juvenile flounder are 50% and 300 kcal/100-g diet, respectively.     

Dietary Protein Requirement of Juvenile Cachara Catfish,Pseudoplatystoma reticulatum

Cachara, Pseudoplatystoma reticulatum, is a high commercial value carnivorous catfish in Brazil, but whose dietary protein requirement is still unknown. Aiming to determine this requirement, groups of 15 juveniles (16.08 ± 1.13 g) were fed isoenergetic diets (4600 kcal/kg gross energy) with increasing levels of crude protein (30, 35, 40, 45, 50, and 55%). After 60 d, regression analysis revealed a quadratic effect (P < 0.05) of increasing dietary crude protein concentration on growth variables. The highest weight gain and specific growth rate as well as the best feed conversion were shown by fish fed the 50% crude‐protein diet. Similarly, protease activities were significantly higher (P < 0.05) in fish fed 50% crude protein. However, the highest protein retention was observed in fish fed the 45% crude‐protein diet. Protein and dry matter digestibilities did not differ (P > 0.05) for diets containing 40, 45, or 50% crude protein. Therefore, based on weight gain and at a dietary energy concentration of 4600 kcal/kg, the estimated protein requirement for juvenile cachara between 16 and 85 g is 49.25% crude protein. This is equivalent to 44.79% digestible protein and a gross energy to digestible protein ratio of 10.27 kcal/g.     

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.     

Effects of dietary highly unsaturated fatty acids and astaxanthin on the fecundity and lipid content of pond-reared Penaeus monodon (Fabricius) broodstock

Five diets that contained fresh squid meat as the basic constituent and were supplemented with different amounts of highly unsaturated fatty acids (HUFA) and astaxanthin were fed to pond‐reared Penaeus monodon broodstock. Diet A was sole squid meat. Diets B and C were supplemented with astaxanthin 50 and 100 mg kg^?1 respectively. Diets D and E were supplemented with HUFA 5 and 10 g kg^?1 and astaxanthin 50 mg kg^?1 respectively. The result showed that the group fed diet E had the best reproductive performance in all experimental groups. It had a higher proportion of spawns (71.5%), spawning rate (0.047), a shorter latency period (7.7±0.3 d), higher absolute fecundity (× 10³) (361.6±5.5) and egg production/female (× 10³) (597.0±18.0) than all the other experimental groups. The fatty acid composition in broodstock diets strongly affected the tissue and fecundity of broodstock. Good correlations between the content of 20:4n‐6 in eggs and the fecundity (r²=0.6109) and egg production (r²=0.9876) of broodstock were found. On the other hand, 22:6n‐3 and DHA/EPA ratio was negatively correlated with the fecundity of broodstock (r²=0.5362, 0.8702 respectively). The result also showed that the balance between n‐3 and n‐6 fatty acid families, total polyunsaturated fatty acids and total saturated fatty acid and 20:5n‐3 (EPA) and 22:6n‐3 (DHA) may play vital roles in maturation and reproductive performance of P. monodon broodstock.     

Dietary threonine requirement of fingerling Indian major carp, Cirrhinus mrigala (Hamilton)

Indian major carp fingerling, Cirrhinus mrigala (3.85±0.75 cm, 0.52±0.21 g), were fed isonitrogenous and isocaloric diets (40% crude protein, 4.28 kcal g^?1, gross energy) containing casein, gelatin and crystalline amino acids with graded levels of l ‐threonine (1.00, 1.25, 1.50, 1.75, 2.00 and 2.25 g 100 g^?1, dry diet) to determine the dietary threonine requirement. The feeding trial was conducted in triplicate for 8 weeks. Diets were fed twice a day at 08:00 and 16:00 hours at 5% body weight day^?1. The ration size and feeding schedule were worked out before the start of the feeding trial. Highest weight gain (304%) and best feed conversion ratio (1.43) were evident in fish fed diet containing 1.75% dietary threonine. Second‐degree polynomial regression analysis of weight gain, feed conversion ratio and protein efficiency ratio data indicated the dietary threonine requirement to be at 1.84%, 1.81% and 1.78%, respectively, corresponding to 4.60%, 4.52% and 4.45% of dietary protein. Minimum carcass moisture, fat and maximum carcass protein were evident in fish fed 1.75% threonine level. However, ash content did not affect body composition, except the 1.00% threonine level, which showed a significantly higher ash content value. Based on the above results, it is recommended that the diet for C. mrigala should contain threonine at 1.80 g 100 g^?1 dry diet, corresponding to 4.50 g 100 g^?1 dietary protein for optimum growth and efficient feed utilization.     

Effects of protein and lipid concentrations in broodstock diets on growth, spawning performance and egg quality of yellowfin sea bream (Acanthopagrus latus)

A study was conducted to determine the effects of dietary protein and lipid concentrations on growth, spawning performance and egg quality of yellowfin sea bream, Acanthopagrus latus. Nine diets representing a combination of three protein concentrations (40, 50 and 60%) and three lipid concentrations (15, 20 and 25%) were tested with three replicates. Each replicate was stocked with 10 fish with a sex ratio of 1:1 and the average weights were 415 g and 236 g for females and males, respectively. Fish were fed to satiation twice daily. The weight gain of A. latus broodstock was not significantly (P > 0.05) different among fish fed diets with the various protein and lipid concentrations. Except for relative fecundity and survival rate of 3-day-post-hatch (3DPH) larvae, spawning performance of A. latus was not significantly affected by different concentrations of dietary protein or lipid. Relative fecundity was found to be significantly elevated by dietary lipid at 20% concentration. However, survival rate of 3DPH larvae was highest from broodstock fed diets with 40% protein and 25% lipid, 50% protein and 15% lipid and 60% protein and 15% lipid concentrations. Egg diameter generally increased with increasing dietary protein from 40 to 60% at each lipid concentration. Total length of hatchlings followed an inverse relationship with dietary protein regardless of the lipid concentration. The oil globule diameter (OGD) of hatchlings significantly increased with decreasing dietary protein from 60 to 40%. Yolk sac length (YSL) and OGD of hatchlings was generally greatest at 15% dietary lipid concentration irrespective of protein concentrations. Total length of 3DPH larvae was greatest from broodstock fed diets with 50% protein and 20% lipid, respectively. Body protein content of broodstock was not significantly affected by dietary protein and lipid concentrations. However, increasing dietary lipid generally resulted in increasing body lipid content regardless of the dietary protein concentration. Protein and lipid contents of eggs, hatchlings and 3DPH larvae were significantly affected by dietary protein and lipid concentrations of the broodstock diets. The present study revealed that the best reproductive performance of A. latus broodstock was achieved at 40% dietary protein and 20% dietary lipid concentrations based on relative fecundity, fertilization rate, hatchability and survival of 3DPH larvae.     

Evaluation of pea protein isolate as alternative protein source in diets for juvenile tilapia (Oreochromis niloticus)

To evaluate isolated pea protein as feed ingredient for tilapia (Oreochromis niloticus) juveniles, triplicate groups were fed with four isonitrogenous [crude protein: 421.1–427.5 g kg⁻¹ in dry matter (d.m.)] and isoenergetic (gross energy: 20.46–21.06 MJ kg⁻¹ d.m.) diets with varying protein sources for 8 weeks. Fish meal-based protein content of diets was substituted with 0% (diet 100/0=control group), 30% (diet 70/30), 45% (diet 55/45) and 60% (diet 40/60) isolated pea protein. Tilapia juveniles with an initial body weight of 2.23–2.27 g were fed in average at a level of 5% of their body weight per day. Highest individual weight gain (WG: 21.39 g) and specific growth rate (SGR: 4.21% day⁻¹) and best feed conversion ratio (FCR: 0.90) were observed in tilapia fed diet 100/0, followed by fish-fed diet 70/30 (WG: 19.09 g; SGR: 4.03% day⁻¹; FCR: 0.98), diet 55/45 (WG: 16.69 g; SGR: 3.80% day⁻¹; FCR: 1.06) and diet 40/60 (WG: 16.18 g; SGR: 3.74% day⁻¹; FCR: 1.06). Although fish fed diet 100/0 showed the best performance, inclusion of 30% protein derived from pea protein isolate resulted in a growth performance (in terms of WG and SGR) that did not differ significantly from diet 100/0 in contrast to fish fed diet 55/45 and 40/60. Crude ash content in the final body composition of the experimental fish decreased with increasing dietary pea protein content, while crude protein and lipid content remained equal between the groups. Significant decreasing growth performance and body ash incorporation of tilapia at higher inclusion levels seem to be mainly related to the dietary amino acid profile and phytic acid contents.     

Effect of Varying Protein‐to‐Energy Ratios on Growth,Nutrient Retention,Somatic Indices,and Digestive Enzyme Activities of Singhi,Heteropneustes fossilis (Bloch)

Effects of varying protein‐to‐energy (P/E) ratios on growth performance, nutrient retention, body composition, and digestive enzyme activities of Singhi, Heteropneustes fossilis (7.90 ± 0.40 g; 9.40 ± 0.20 cm) were evaluated. Six experimental diets (350_Low, 350_High, 400_Low, 400_High, 450_Low, and 450_High) in a 3 × 2 factorial design were formulated to contain three protein levels (350, 400, and 450 g/kg crude protein) and two energy levels (4.07 and 4.54 kcal/g gross energy [GE]) to provide six different dietary P/E ratios (86.1, 77, 98.3, 88, 110.6, and 99 mg protein/kcal GE). The diets were hand‐fed to triplicate groups of fish for 84 d to apparent satiation at two feeding frequencies. Live weight gain, feed conversion ratio, protein retention efficiency, energy retention efficiency, somatic indices, and digestive enzyme activities were maximized by the groups fed on 400 g/kg protein with 4.07 kcal/g GE in diet 400_Low with a P/E ratio of 98.3 mg/kcal energy. The results indicate that 400 g/kg of dietary protein and 4.07 kcal/g of dietary GE with a P/E ratio of 98.3 mg protein/kcal energy is optimum for achieving efficient growth, feed conversion, and nutrient retention in H. fossilis.     

Effect of totally or partially replacing fish meal by alternative protein sources on growth of African catfish Clarias gariepinus (Burchell, 1822) reared in concrete tanks

A 12‐week feeding trial was carried out in concrete tanks to examine complete and partial replacement (75%) of fish meal (FM) with poultry by‐product meal (PBM), meat and bone meal (MBM) and soybean meal (SBM) in practical feeds for African catfish Clarias gariepinus. Triplicate groups of fish (initial body weight ranged from 90.33 to 93.93 g fish⁻¹) were fed seven isonitrogenous and isocaloric diets of 20% digestible protein and 300 kcal 100 g⁻¹ of digestible energy. The control contained 25% herring meal, whereas in the other six diets, PBM, MBM and SBM replaced 75% or 100% of the FM. Final body weight (FBW) and specific growth rate (SGR) of the fish fed diets containing PBM (75% and 100%), SBM (75% and 100%) and MBM (75%) were all higher, but not significantly different than those for fish fed the control diet. Replacing 100% of the FM by MBM significantly lowered FBW and SGR. Concerning whole body composition, there were no significant differences in ash and gross energy content of whole‐body among fish; fish fed diets containing PBM‐100% recorded significantly lower protein content compared with the control diet, while fish fed diet SBM‐100% recorded significantly lower moisture content compared with the control diet. Also fish fed diets SBM‐100% and PBM‐75% recorded higher lipid and gross energy contents compared with the control diet. The study revealed that satisfactory growth and feed utilization responses could be achieved through the replacement of FM by PBM, SBM and MBM in the diet of African catfish.     

Evaluation of juvenile silver perch Bidyanus bidyanus (Mitchell) nutritional needs using high- and low-protein diets at two feeding levels

Juvenile silver perch Bidyanus bidyanus (Mitchell) of 3.2 g average weight were reared under controlled conditions on diets containing 23.4% and 40.6% protein. Diets were administered at 3% or 6% of the fish biomass per day. Both the protein concentrations and the feeding level of the diet influenced growth and proximate composition of the fish at the end of the 100-day growth trial. The energy requirement for these fish for maintenance was found to be 81.9 kcal × BW^–0.8 and, for each unit of energy retained per metabolic body weight, 7.05 needed to be supplied, whereas for each gram of protein retained per metabolic body weight, 5.79 g were required. The results indicate that it is possible to obtain the same weight increment when feeding a 23.4% protein diet at a level of 6% body mass day^–1 compared with only 3% body mass day^–1 of a 40.6% protein diet. This study provides the first estimation of nutrient requirements for juvenile silver perch, and these estimations require further refinement.     

Optimal protein replacement of fish meal by mackerel condensate in diet for giant freshwater prawn (Macrobrachium rosenbergii)

The optimal protein replacement of fish meal (FM) by mackerel condensate (MC) was investigated in giant freshwater prawn, Macrobrachium rosenbergii (0.90 ± 0.01 g initial weight) over a 12‐week trial. The experimental diets replaced the FM partially in a baseline FM‐based diet (0MC), by substituting MC for 10% (10MC), 20% (20MC), 30% (30MC), 40% (40MC), 50% (50MC) and 60% (60MC) of the FM, and a commercial diet (CD) was included for comparison. The prawn fed with 40MC had superior growth performance and feed utilization. Significant increases in amylase and cellulase‐specific activities indicated improved carbohydrate utilization in this dietary group (P < 0.05). The proteolytic activity was maintained through the key gastrointestinal enzymes (pepsin, trypsin and chymotrypsin). A slight improvement in carcass compositions was also observed in the prawns fed 40MC, and the total haemocyte count was significantly increased by this diet, without negative effects on the hepatopancreatic histology. These findings indicate that a 40% protein replacement of FM by MC is optimal for giant freshwater prawn, and similar use of it in the aquafeed of other species appears worth further studies.