Digestive protease activities and free amino acids in white muscle as indicators for feed conversion efficiency and growth rate in Atlantic salmon (Salmo salar L.)

The aim of the present experiment was to screen several biochemical indices in fish and their interrelations in order to select variables for future studies of growth rate and feed conversion. Several parameters [trypsin activity, chymotrypsin activity, free amino acids (FAA) in plasma and white muscle, and RNA and RNA/protein ratio in the white muscle] were measured together with specific growth rate (SGR), feed intake and feed conversion efficiency (FCE) in four groups of diploid or triploid Atlantic salmon (Salmo salar L.) reared under different light regimes. SGR was measured on individually tagged fish, whereas feed intake and feed conversion was estimated on tank basis. A principal component analysis (PCA) explained 80.6% of the variance in the data, using all measured parameters, regardless of ploidy and light regime. Muscle free hydroxyproline showed the highest correlation, alone explaining 55% of SGR variability. The SGR also significantly correlated with trypsin activity (r=0.34), the activity ratio of trypsin to chymotrypsin (T/C) (r=0.39), plasma essential FAA (EAA) (r=0.39), plasma total FAA (TFAA) (r=0.37), the ratio of essential to non-essential FAA (EAA/NEAA) in the white muscle (r=–0.45), muscle RNA (r=–0.45) and RNA/protein ratio (r=–0.41). Tank FCE correlated positively (r=0.97) with SGR, T/C ratio and muscle free hydroxyproline, and negatively (r=–0.90) with muscle EAA/NEAA. The groups reared under continuous light (LL) regime showed significantly higher SGR than simulated natural photoperiod (SNP) groups, and with an apparently higher FCE. A higher growth rate was associated with either a higher consumption rate and/or a higher feed utilization. A negative correlation between muscle RNA concentration and SGR may indicate that increased growth rate under LL regime was not caused by an increased protein deposition rate.     

Evaluation of feed protein quality by measuring plasma free amino acids in Atlantic salmon (Salmo salar L.) after dorsal aorta cannulation

Two successive experiments were conducted in order to assess plasma free amino acid (FAA) profiles as a method for evaluating protein quality of fish feeds for Atlantic salmon, Salmo salar (L.). In experiment 1, the importance of meal size and inter‐fish variation was assessed by using dorsal aorta cannulated fish and diets that contained different sources of fishmeal (menhaden versus herring) which in the case of herring, had been dried at either 70 or 100 °C. In experiment 2, an attempt was made to mimic a production situation by comparing the FAA profiles in salmon fed diets containing two commercially available fishmeals that had been produced in accordance with industrial standards (Norse‐LT94® and NorSeaMink®; Norsildmel AL, Fyllingsdalen, Norway). FAA profiles in plasma 6 h after feeding were compared with feed true protein digestibility as determined in mink. Cannulated fish, held in individual tanks, were hand‐fed twice daily to pellet rejection (satiety) and daily records of the actual rations consumed were maintained. A total of 24 different amino acids and other amino‐containing compounds were detected using high‐pressure liquid chromatography. Morning and evening meal size showed significant correlations. Meal size had a significant effect on blood levels of the majority of essential free amino acids (EAA) as well as the total sum of FAA (TFAA). In experiment 1, a marked inter‐individual effect was found, possibly because of incipient sexual maturation. FAA profiles were therefore corrected for meal size by linear regression while repeated sampling via the permanently implanted cannula allowed paired comparisons of the different test diets, minimizing inter‐individual variation. Significant differences in plasma FAA profile, EAA and TFAA were detected between fish fed all diets in both experiments. The preceding parameters for fish ingesting each feed were directly related to their respective mink protein digestibility in experiment 1, but not in experiment 2. Our results show that dietary protein quality can be differentiated by the aforementioned protocol, and by using fish with a low metabolic rate feed qualities could be ranked correctly as in experiment 1.     

A novel konjac glucomannan–xanthan gum binder for aquaculture feeds: the effect of binder configuration on formulated feed stability,feed palatability and growth performance of the Japanese abalone,Haliotis discus hannai

As part of a programme to develop sustainable diets for macroalgivores, a 3‐month experiment was conducted to determine the effects of konjac glucomannan–xanthan gum (KX) binder configuration on formulated feed stability, feed palatability and growth performance of juvenile, hatchery‐reared, Haliotis discus hannai. This study was conducted in a recirculation facility in which four KX binder configurations were evaluated in a series of isonitrogenous experimental feeds and freshly harvested Laminaria digitata was included as a natural feed type. Dry matter leaching of the experimental feed treatments was assessed with no significant difference in the dry matter leaching between treatments observed. No differences (P > 0.05) were found in percentage survival, daily food consumption (DFC) and linear growth rate (LGR) between treatments. Food conversion efficiency (FCE), specific growth rate (SGR) and body weight/shell length (BW/SL) ratio were significantly higher when offered L. digitata. Trends showed that the best performing KX feed in terms of FCE, LGR, SGR and BW/SL ratio was produced with the 2% KX; 1 : 1 binder.     

Effect of fish meal replacement with Carinata Brassica carinata in low animal protein diets of rainbow trout Oncorhynchus mykiss (Walbaum) on trypsin activity,protein and amino acid digestibility and bioavailability

Replacement of >25% of fish meal (FM) with aerobically converted carinata meal (ACCM) in low (200g/kg) animal protein (reference = 200g/kg FM) diets of rainbow trout Oncorhynchus mykiss resulted in reduced growth, partly due to reduced feed consumption and protein utilization. In this study, we determined the effect of FM replacement with ACCM on trypsin activity, apparent digestibility coefficients (ADCs) of protein, and essential amino acid (EAA) or conditionally essential amino acid (CEAA) ADCs and bioavailability. Replacement of FM did not alter protein ADCs or trypsin activity. Replacement of >25% FM reduced all EAA and CEAA ADCs except for arginine and leucine which were only reduced by 75% FM replacement. Only serum free lysine and muscle free histidine were reduced by >25% FM replacement. Muscle free lysine was only reduced by 75% FM replacement. Replacement of FM reduced EAA peak concentrations and resulted in slower release of EAAs in serum. Cumulative total EAAs in serum and muscle decreased with FM replacement. Ratios of EAAs to lysine showed that tryptophan was the most limiting EAA. However, isoleucine, leucine, methionine and phenylalanine were also inadequate for muscle synthesis for the first 9–12 hr following force‐feeding. Optimal time for protein synthesis was ≥36 hr. Although any level of FM replacement did not reduce protein ADCs and trypsin activity, replacement of ≥25% FM reduced EAA ADCs and bioavailability of lysine and histidine, which partly contributed to the observed differences in growth.     

Effects of feeding frequency and dietary protein levels on juvenile allogynogenetic gibel carp (Carassius auratus gibelio) var. CAS III: growth,feed utilization and serum free essential amino acids dynamics

A 8 week growth trial of three feeding frequencies (2, 4 and 6 meals day^?1) and three dietary protein levels (30%, 34% and 38%) was conducted to investigate the influence of feeding frequency and dietary protein level on growth, feed utilization, serum free essential amino acids (EAA) dynamics and nitrogen (N), phosphorus (P), carbon (C) retention in juvenile allogynogenetic gibel carp (Carassius auratus gibelio) ‘CAS III’. The results showed that feeding frequency and dietary protein level increased feed intake (FI), specific growth rate (SGR) and feed efficiency (FE). SGR increased significantly with the increase in feeding frequency and dietary protein level. But, the increase in dietary protein level from 30% to 38% in group 6 meals day^?1 did not result in better growth. Compared with the group of 4 meals day^?1 × 38%, the fish fed the diet containing 30% crude protein at 6 meals day^?1 obtained similar SGR but showed lower FIp (protein intake). Compared with 2 meals day^?1, NREs (nitrogen retention efficiency) of 4 and 6 meals day^?1 were relatively higher. PRE (phosphorus retention efficiency) and CRE (carbon retention efficiency) increased significantly with feeding frequency while TNW (total nitrogen waste output), TPW (total phosphorus waste output) and TCW (total carbon waste output) decreased significantly. Feeding frequency and dietary protein level increased trypsin activity. Serum free EAA concentrations varied more synchronously at 6 meals day^?1 than 2 meals day^?1. It could be concluded that increasing feeding frequency could improve growth by increasing feed intake and feed efficiency for juvenile gibel carp. The increase in feeding frequency showed protein‐sparing effect.     

Lipostatic regulation of feed intake in Atlantic salmon Salmo salar L. defending adiposity at the expense of growth?

Production of Atlantic salmon Salmo salar L. utilizes feeds with high fat concentrations to give low feed:gain. However, increased dietary fat content inevitably leads to increased body fat deposition, and salmon with very high fat concentrations in the muscle (fillet) are regarded as being of inferior quality. Adiposity is thought to participate in the regulation of feed intake by means of negative feedback control. Thus, elevated adiposity is predicted to result in lower feed consumption, and thereby possibly impair growth. We tested the hypothesis that high body fat content in salmon would lead to reduced feed intake and growth. Salmon (740 g) were preconditioned with high‐ or low‐fat feed (38.8 and 27.8% dietary fat content) for 10 weeks to establish differences in body fat storage (build‐up phase). Thereafter, fat and lean fish (19.4% and 16.7% body fat content) were fed the high‐ and low‐fat feeds for an additional 7 weeks (Phase Two). During Phase Two, the fat fish consumed 30% less feed than lean fish, which resulted in corresponding differences in growth. The differences in adiposity seen at the end of the build‐up phase were still evident at trial end. Groups of fish, which were preconditioned with the same feed during the build‐up phase, had similar feed consumption and growth to each other during Phase Two, indicating that body fat was playing an important role in the regulation of feed intake.     

The optimum dietary essential: nonessential amino acid ratio for rainbow trout (Oncorhynchus mykiss), which maximizes nitrogen retention and minimizes nitrogen excretion

Although the ratio of essential to nonessential amino acids (EAA:NEAA ratio) in dietary protein has important effects on protein utilization by fish, there has thus far been little research aimed at quantifying these effects. In this study, we investigated the effect of dietary EAA:NEAA ratio on nitrogen (N) utilization and excretion of rainbow trout (Oncorhynchus mykiss). A 6-week dose-response experiment was conducted, with 6 levels of dietary EAA:NEAA ratio, ranging from 23:77 to 66:34. Protein content of all diets was 350 g kg^?1. Each experimental diet was fed to four replicate tanks of fish (35 fish per tank). Fish were fed a limited ration on the first two feedings of each day, and were fed to apparent satiation on the third feeding of each day. Response variables included feed intake, weight gain, lipid deposition, thermal-unit growth coefficient (TGC), feed efficiency ratio (FER), N retention, and N excretion (g kg^?1 gain). Mean feed intake, weight gain, TGC, FER and N retention all increased as EAA:NEAA ratio increased up to 57:43, and then decreased slightly as EAA:NEAA ratio increased further to 66:34. Maximum mean N retention of 46% and minimum mean N excretion of 29 g N kg^?1 gain was achieved by fish fed the diet containing an EAA:NEAA ratio of 57:43. Non-linear regression using a 2^nd order polynomial equation showed that 95% of the maximum N retention could be achieved with an EAA:NEAA ratio of 46:54, and 98% with an EAA:NEAA ratio ranging from 49:51 to 62:38.     

Weaning of juvenile pikeperch, Stizostedion lucioperca L., and perch, Perca fluviatilis L., to formulated feed

Weaning success of pond‐cultured pikeperch and wild‐caught perch (mean length 51 and 48 mm respectively) was evaluated using different weaning techniques and different formulated feeds. Juveniles that were fed formulated feed grew as well as or better than juveniles that were weaned successively using zooplankton or yolk. Four different formulated feeds (agglomerated marine larvae feed, marine larvae feed, trout feed and a semi‐moist feed) were evaluated regarding specific growth rate (SGR), condition factor and a subjective stomach fullness estimate. The agglomerated marine larvae feed gave significantly better weaning performance than the other feeds regarding all parameters (SGR = 7.3% day^?1 and 3.4% day^?1 for pikeperch and perch respectively).     

Digestive efficiency,free amino acid pools and quality of growth performance in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis> L.) affected by light regimes and vaccine types

This study comprised the results of three different seawater trials using unique combination of techniques to study protease digestive efficiency and growth performance quality to illustrate the effects of light regimes and vaccine types in Atlantic salmon (Salmo salar L.). Fish with higher growth had higher trypsin (T) and chymotrypsin (C) specific activities with higher T/C ratio or slope T/C ratio [calculated from the regression between trypsin (y) and chymotrypsin (x) specific activities] in the pyloric caeca. The T/C ratios indicated fish growth rates over a period of 1–2 months, while the slope T/C ratios indicated fish growth rates at sampling. Adaptation period for adjustment to the new environment of continuous light was 70 days, indicated by the differences in trypsin specific activities and the crossing of slope T/C ratio regressions following with the changes in growth rate directions between the control and the treated group. Vaccine types affected fish vertebral growth, and additional continuous light enhanced the impact of vaccines on fish growth during springtime, indicated by differences in slope T/C ratios. Continuous light stimulated fish growth during winter to spring, when the natural day length was short, without significantly changing white muscle and oocyte qualities in the fish of about 500 g, except for significantly increased white muscle RNA concentration. Continuous light also reduced fish growth rate later during summer, when the natural day length was long, by precedently decreasing the T/C ratio in late spring. Interestingly, plasma levels of free lysine related to tryptic digestion were correlated with trypsin specific activity levels. Continuous light caused higher levels of most free amino acids (FAA) involved in nitrogen metabolism, higher incorporation of essential FAA for protein synthesis, and higher protein turnover rate (free hydroxyproline levels) in both plasma and white muscle. However, continuous light did not affect higher protein content, intracellular buffering capacity and RNA levels in the white muscle of the fish of about 1 kg, probably due to limitation of FAA available for protein synthesis. It is therefore suggested that enhancing fish growth by continuous light stimulation should be accompanied by increasing availability or content of dietary protein (and probably minerals), which in turn would improve the quality of fish growth performance through increasing fillet protein concentration, strengthening vertebral growth, and delaying oocyte development.     

Protease activities, plasma free amino acids and insulin at different ages of Atlantic salmon (Salmo salar L.) with genetically different trypsin isozymes

We show significant relationships between digestion rate of dietary protein, absorption/transport rate of amino acids, and plasma insulin concentration. Digestion rate of dietary protein was indicated by protease activity ratio of trypsin to chymotrypsin in the pyloric caeca. Plasma total free amino acids and/or the ratio of essential to non-essential free amino acids indicated absorption/transport rate of amino acids. These relationships are associated with and likely to be primarily affected by genetic variation in the expression of different isozymes of trypsin, a key enzyme for feed utilization and growth, affecting digestion, absorption/transport rate of amino acids and plasma insulin levels in Atlantic salmon (Salmo salar L.).     

Is there lipostatic regulation of feed intake in Atlantic salmon Salmo salar L.?

High‐energy feeds, with increased fat concentrations, are often used in salmon farming to improve feed:gain ratio. However, fish are thought to regulate ingestion to meet their energy and nutrient intake requirements. Further, feeds with excessive fat content will lead to increased adiposity, which is thought to exert a negative feedback on feed intake via lipostatic regulation mechanisms. A test of the lipostatic model of feed intake regulation was carried out on juvenile Atlantic salmon Salmo salar L. (c. 165 g) in which body fat content (5.6% and 9.4% body fat) had been manipulated by feeding feeds with different fat concentrations. Thereafter, the fish were offered the high‐ and low‐fat feeds (15.6% and 26.5% dietary fat content) simultaneously, and our hypothesis was that feed preference and intake would reflect the state of fat storage. Thus, we predicted that, when given a choice of feeds, the lean fish would eat more, and that the body fat status of the groups would converge over time. The results indicated a general preference for the leaner feed irrespective of adiposity level, but leaner fish consumed more feed, grew faster and deposited more body fat than their fatter counterparts. Over time, body compositions converged among treatments, and differences in feed intake ablated. These findings seem to provide supportive evidence for a lipostatic regulation of feed intake in fish.     

Effects of supplementary feeds with different protein levels on growth and economic performances of Nile tilapia (Oreochromis niloticus) cultured in a rain-fed rice–fish ecosystem

This study investigated the effects of supplementary feeds with different crude protein (CP) levels on the growth and economic performances of sex-reversed Nile tilapia (Oreochromis niloticus) reared in a rain-fed rice–fish ecosystem for a period of 120 days. There were four treatments—namely, traditional feed (21% CP), formulated feed (26% CP), commercial feed (30% CP), and control (no feed was used)—with three replicates per treatment. Fish (30.04 g) were stocked in ditches at a rate of 0.5 fish m^?2 considering the total area and fed one of the tested feeds twice daily at the rate of 2%–5% of body weight. Water-quality parameters of the ditches were monitored fortnightly, and these parameters were found suitable for fish farming. Organic matter, total nitrogen, and available phosphorous in soil were increased significantly (P < 0.05) in the feed treatments after fish cultivation. Highly significant weight gain and SGR were observed with fish fed the commercial feed as compared with other treatments. The highest benefit-cost ratio (2.15) was found in the control, followed by formulated feed (1.90), but in the case of numerical net return, it was the opposite. However, commercial feed showed the lowest benefit-cost ratio (1.67) due to higher feed cost than other supplementary feeds. Therefore, this study suggests that fish fed with a formulated feed (26% CP) produced significantly higher net economic return in the rice–fish farming system.     

Evaluation of corn steep liquor as a supplementary feed for Labeo rohita (Ham.) fingerlings

The effects of corn steep liquor (CSL), a by-product of corn starch industry, in the fish diet at 25% (D1), 50% (D2) and 75% (D3) replacement of fish meal are investigated on the growth of Labeo rohita (rohu) fingerlings. Formulated feeds were iso-nitrogenous (39% crude protein) and iso-energetic (15.8?kJ/g). The CSL is found to be rich in protein (43.48%), lactic acid (20.79%) and minerals and is free from fibres, phytic acid and trypsin inhibitors. The sulphur amino acid content of CSL is found to be 2.43%, though it is deficient in lysine (0.73%). With diets D1 and D2, growth performance and feed efficiency in terms of weight gain, specific growth rate (SGR), feed intake, feed conversion ratio (FCR) and protein efficiency ratio (PER) as well as apparent digestibility (APD and ALD) were higher when compared to CD. With diet D3, they were similar to CD. Up to 50% level of CSL in the diets (D1 and D2), the protein and lipid contents of carcass were significantly higher (P?<?0.05) when compared to CD. The digestive enzyme activities are found to be similar in all the diet groups. The findings suggest that in the diet of rohu, fish meal can be replaced up to 75% level with CSL without hampering the growth of the fishes. The CSL appear to be a better plant protein source as partial replacement of fish meal.     

Marine microalgae from biorefinery as a potential feed protein source for Atlantic salmon,common carp and whiteleg shrimp

Two marine algal products MAP3 and MAP8 were examined for their suitability as fishmeal protein substitutes in feeds of three prominent farmed species, through short‐term feeding studies. Algal meals were tested at 5 and 10% protein replacement levels for Atlantic salmon and at 25 and 40% for common carp and whiteleg shrimp. At the end of the 12‐week period, the growth and feed performance of the two fish species did not reveal any significant difference between those fish offered the algae‐based feed and those offered the control feed. The whole body proximate compositions of Atlantic salmon fed the control and algae‐based feeds were not significantly different. In common carp, the lipid content in the fish fed higher level of MAP3 was significantly lower than that of the fish fed the control feed. In whiteleg shrimp, at the end of the 9‐week feeding period, growth performance and feed utilization did not differ between the treatment groups. Protein content in the shrimp fed the higher level of MAP8 was significantly lower than that of shrimp on the control feed. The three species could accept the algal meals in their feeds at the tested levels, though there were some noticeable effects on body composition at higher inclusion levels.     

Seasonally changing metabolism in Atlantic salmon (Salmo salar L.) I – Growth and feed conversion ratio

To determine seasonal variation in growth and feed conversion ratio (FCR), Atlantic salmon postsmolts (Salmo salar L.) were exposed to either simulated natural photoperiod (SNP) for 12 months or continuous light (LL) from January to June followed by SNP until December. Feed was given to excess and uneaten feed pellets were collected after every meal for estimation of feed intake and calculation of FCR. Body weight increased from 1086 ± 9 g (mean ± SEM) in January to 4970 ± 7 g (SNP) and 5190 ± 23 g (LL) in December. Specific growth rate (SGR), condition factor and feed intake displayed strong seasonal variation in both groups. Measurements of the thermal growth coefficient correlated highly with SGR (r = 0.98, P < 0.05), indicating that the seasonal variation in SGR was independent of temperature and fish size. Continuous light treatment resulted in increased growth from spring, while the fish exposed to simulated natural light had increased growth rate in late summer. Furthermore, LL improved FCR. Periods of high SGR were concurrent with periods of low FCR in both groups.     

Effects of fasting and feeding on plasma amino acid levels in brown trout

Plasma amino acid (AA) levels were analysed at various intervals during fasting and after feeding in juvenile brown trout, Salmo trutta. After 3 days of food deprivation, total plasma AAs decreased significantly (–26% vs. control) due to a fall in the most abundant essential AAs (EAA): branched-chain amino acid (BCAA) and Thr, and there was also a decrease in non-essential AA (NEAA) levels, especially Ala and Asn. After 15 days of fasting, BCAA increased, possibly related to muscle protein mobilization. After 50 days of food deprivation, a significant increase in Gln levels (40% vs. 15 days of fasting) and a decrease in BCAA (–25% vs. 15 days of fasting) was noted. Feeding a commercial trout pellet caused a clear and progressive increase in plasma AA levels. Both EAA and NEAA concentrations peaked at 11 h post-feeding (4068 ± 160 and 4261 ± 239 µM NEAA, respectively) with a greater increase in EAA (+62%) than NEAA (40%) with respect to control values. These data show that changes in the plasma AA pool clearly reflect the nutritional state of fish and help us to understand the complex AA metabolism.     

Maintenance ration, protein synthesis capacity, plasma insulin and growth of Atlantic salmon (Salmo salar L.) with genetically different trypsin isozymes

Growth was found to be associated with the changes of trypsin activity in the pyloric caecal tissues and the level of plasma insulin in Atlantic salmon (Salmo salar L.). A decrease in trypsin activity accompanied by an increase in plasma insulin was detected one month before an enhanced growth was observed. There were significant relationships between weight specific consumption rate, plasma insulin levels and fish growth. The correlation of weight specific consumption rate was higher with growth rate (R²=0.7, p<0.0001) than with plasma insulin concentration (R²=0.4, p<0.0001).When the comparison was made between Atlantic salmon carrying and lacking the trypsin variant TRP-2*92, the fish with the variant had lower maintenance ration (p<0.05), higher capacity for protein synthesis in the white muscle (p<0.02), and a greater ability to utilize the feed at a restricted ration than the fish without the variant. In Atlantic salmon lacking the variant, both plasma insulin concentrations and growth rates were significantly lower (p<0.05) in the fish fed 0.5% bw day^–1 than those fed 1% bw day^–1. Whilst the growth rates of TRP-2*92 salmon fed the different rations became similar one month after similar levels of plasma insulin were observed between them. The TRP-2*92 salmon may be defined as a high protein growth efficiency fish with low protein turnover rate.Genetic variation in trypsin isozyme pattern affects feed utilization, plasma insulin levels and growth in Atlantic salmon.     

Effects of replacing fish meal with soya protein concentrate on growth,feed efficiency and digestibility in diets for snakehead,Channa striata

Soya bean meal‐based formulated feeds have recently become available for snakehead culture in Vietnam. This study was conducted to determine the appropriate replacement of fish meal (FM) protein by another soya product, soya protein concentrate (SPC), in snakehead (Channa striata) diets. Five iso‐nitrogenous (45% crude protein) and iso‐caloric (19 KJ g^?1) practical diets were formulated to replace 0% (control), 40%, 60%, 80% and 100% of protein FM by protein SPC (100% FM, 40% SPC, 60% SPC, 80% SPC and 100% SPC respectively). A digestibility experiment was also conducted with the same formulated diets with addition of 1% chromic oxide. Fish fed 100% FM and 40% SPC diets had significantly better growth and survival compared with other treatments. Feed intake, feed conversion ratio, protein efficiency ratio and net protein utilization, trypsin and chymotrypsin activities of experimental fish fed 100% FM and 40% SPC diets were significantly higher than those fed other diets. The apparent digestibility coefficient (ADC) of the diet and diet components, ADC_diet, ADC_protein and ADC_lipid, of fish fed diet 40% SPC and 100% FM treatment were significantly higher than those of other treatments. The cost/kg fish produced in diets 100% FM and 40% SPC was much lower compared with other treatments. Dietary inclusion levels of SPC in diet above 40% significantly affected fish survival, growth, digestibility and trypsin and chymotrypsin activities, although fish chemical composition was not greatly affected.     

Performance of Different Types of Commercial Feeds on the Growth of Juvenile Silver Pomfret, Pampus argenteus, under Tank Culture Conditions

The present study was carried out using juveniles of silver pomfret, Pampus argenteus, produced in the hatchery by stripping eggs from spawners collected from the wild during 2004 and 2005 culture period. The experiments carried out during 2004 investigated the efficiency of using salmon feed mixed with cyclopeeze, salmon feed mixed with shrimp meat, salmon feed alone, and shrimp meat alone in the diet using 1 m³ capacity round fiberglass tanks in three replicates for each treatment with flow‐through seawater. The results showed that inclusion of shrimp meat in the diet either with salmon feed or alone give significantly high (P < 0.01) weight gain of up to 1.10 ± 0.06 g/fish/d and significantly lower (P < 0.001) feed conversion ratio compared to that of feeds without shrimp meat. The experiments carried out during 2005 investigated the use of commercially available feeds with feed additives. The results showed that feeding with “Gemma” feed with 54.0% crude protein and 19.0% crude fat or salmon feed with 41.4% crude protein and 23.9% crude fat give significantly high (P < 0.01) growth rates compared to that of pompano feed with 43.0% crude protein and 6.0% crude fat. The results of these investigations although show high growth rate of the fish compared to that of previous observations; there is yet an urgent need to formulate a suitable feed for this fish species for commercial ventures.     

鱼粉质量对中国对虾、真鲷、饲料转化率和蛋白质消化率的影响

IntroductionInherent to the practice of intensive aquaculture is the generation of wastes having immediate and verybroad effects on the aquatic environment.There is a growing consensus about the need to reduce waste pro-duction in aquaculture to minimize the negative impacts on the environment.Nitrogen(N) and phosphorus(P) wastes are major concerns for many aquaculture operations.In the past,formulation of diets in intensive aquaculture was often aimed at meeting requirements formaximum growt…