Dietary Threonine Requirement of Juvenile Red Drum Sciaenops ocellatus

Threonine is an indispensable amino acid required by all animals for normal growth and metabolic functions. An experiment was conducted in a brackish water (5 ± 1 ppt) recirculating system to quantify the minimum dietary threonine requirement of juvenile red drum Sciaenops ocellatus . The experimental diets contained 350/0 crude protein from red drum muscle and crystalline amino acids and 3.2 kcal available energy/g diet. Incremental levels of L-threonine were added to the diets and fed to juvenile red drum initially averaging 2.8 g/fish for 8 wk. Weight gain and feed efficiency of fish fed the various diets were significantly ( P < 0.05) affected and increased linearly as dietary threonine increased until plateauing around 0.8% of dry diet. Protein efficiency ratio and protein conversion efficiency values for fish fed the different diets also were significantly affected by threonine level and indicated requirement values of 0.8–0.9% of dry diet. Free threonine in plasma also significantly responded to increasing dietary threonine but indicated a slightly higher requirement value of approximately 1.0% of dry diet. Based on these data, the minimum threonine requirement of juvenile red drum was determined to be approximately 0.8% of dry diet (2.28% of dietary protein). This requirement level is similar to values reported for some other fish species. Based on this information diets may be formulated more precisely for aquacultural production of red drum.     

An Estimate of the Dietary Lysine Requirement of Juvenile Red Drum Sciaenops ocellatus

Quadruplicate groups of juvenile red drum (initial mean weight 2.7 g; 20 fish per replicate) were fed experimental diets containing 35% crude protein and graded levels of lysine for eight weeks. Lysine concentration in the basal diet was 1.2% and was supplied by a combination of peanut meal and shrimp-head meal. The basal diet was supplemented with lysine-HCI to provide 1.6, 2.0, and 2.4% lysine. Each of these diets contained an essential amino acid (EAA) premix. Two additional diets were formulated to contain 1.2 and 2.4% lysine without the EAA premix. Weight gain and feed efficiency (FE) data indicated between 1.2 and 1.6% dietary lysine was adequate. However, serum lysine concentrations indicated 1.6–2.0% lysine was required. Fish fed 1.2 or 2.4% lysine, without the EAA premix, exhibited reduced weight gain and feed efficiency. Results indicated that red drum were able to utilize crystalline amino acids when incorporated into diets containing intact protein and, when lysine was adequate, the proteins were deficient in at least one other essential amino acid. It is recommended that a dietary lysine level of 5.7% of the dietary protein be used in formulating red drum diets.     

An Estimate of the Dietary Lysine Requirement of Juvenile Red Drum Sciaenops ocellatus

Quadruplicate groups of juvenile red drum (initial mean weight 2.7 g; 20 fish per replicate) were fed experimental diets containing 35% crude protein and graded levels of lysine for eight weeks. Lysine concentration in the basal diet was 1.2% and was supplied by a combination of peanut meal and shrimp-head meal. The basal diet was supplemented with lysine-HCl to provide 1.6, 2.0, and 2.4% lysine. Each of these diets contained an essential amino acid (EAA) premix. Two additional diets were formulated to contain 1.2 and 2.4% lysine without the EAA premix. Weight gain and feed efficiency (FE) data indicated between 1.2 and 1.6% dietary lysine was adequate. However, serum lysine concentrations indicated 1.6-2.0% lysine was required. Fish fed 1.2 or 2.4% lysine, without the EAA premix, exhibited reduced weight gain and feed efficiency. Results indicated that red drum were able to utilize crystalline amino acids when incorporated into diets containing intact protein and, when lysine was adequate, the proteins were deficient in at least one other essential amino acid. It is recommended that a dietary lysine level of 5.7% of the dietary protein be used in formulating red drum diets.     

Dietary vitamin C requirement of red drum Sciaenops ocellatus

A feeding trial was conducted to determine the minimum dietary vitamin C requirement of juvenile red drum and characterize signs of vitamin C deficiency. Semipurified diets containing 400 g crude protein kg^–1 from lyophilized red drum muscle and crystalline amino acids were used in the feeding trial. The basal diet without supplemental vitamin C contained ≈ 6 mg vitamin C kg^–1 and was fed for a 1-week conditioning period. Red drum, initially averaging ≈ 3.6 g each, were fed diets supplemented with 0, 10, 20, 30, 45, 60, 75, or 150 mg vitamin C kg^–1 as ascorbate polyphosphate for a period of 10 weeks. Fish fed the basal diet began to exhibit overt signs of vitamin C deficiency, including reduced weight gain, lordosis, scoliosis and loss of equilibrium after 8 weeks. Total ascorbate was undetectable in liver of fish fed the basal diet while liver ascorbate levels in fish fed the other diets generally reflected dietary supplementation. Regression analysis of weight gain data using the broken-line model resulted in a minimum vitamin C requirement ( ± SE) of 15 ± 3 mg kg^–1 diet.     

Dietary vitamin E requirement of the red drum Sciaenops ocellatus

A 12-week feeding trial was conducted to establish the minimum dietary vitamin E requirement of juvenile red drum by broken-line regression analysis. The semi-purified basal diet was supplemented with 10, 20, 30, 40, 60 or 80 IU vitamin E kg⁻¹ as all-rac -α-tocopheryl acetate. Juvenile red drum were conditioned by feeding the basal diet for 8 weeks prior to the feeding trial to reduce whole-body vitamin E levels. Then, fish initially averaging 12.2 ± 0.4 g fish⁻¹ (mean ± SD) were fed the experimental diets at a rate approaching apparent satiation for 12 weeks. Weight gain and feed efficiency responses of fish fed diets were significantly ( P  < 0.01) altered by the level of vitamin E supplementation but not strictly in a dose-dependent manner. Vitamin E concentrations in liver and plasma also were significantly ( P  < 0.001) influenced by dietary vitamin E level. Plasma ascorbic acid in fish fed the basal diet tended ( P  = 0.066) to be lower than in fish fed diets containing the various levels of vitamin E. In addition, fish fed the basal diet showed edema in the heart, while fish fed all other diets were normal. Fish fed 60 or 80 IU all-rac -α-tocopheryl acetate kg⁻¹ diet had significantly higher respiratory burst of head kidney macrophages than fish fed all other diets, although dietary effects on hematocrit and neutrophil oxidative radical production were not significant. The minimum dietary vitamin E requirement of juvenile red drum was established based on broken-line regression of liver thiobarbituric acid reactive substances to be 31 mg all-rac -α-tocopheryl acetate kg⁻¹ diet.     

Reevaluation of the Dietary Protein Requirement of Japanese Flounder Paralichthys olivaceus

An experiment was conducted to determine the dietary protein requirement by different analysis methods and to study the effects of dietary protein levels on growth performance and body composition in Japanese flounder Paralichthys olivaceus fed white fish meal and casein-based diets for 8 wk. After a 1-wk conditioning period, one of six isocaloric diets containing 30, 36, 42, 48, 54, and 60% crude protein (CP) was fed to fish at approximately 4–5% of wet body weight on a dry matter basis to triplicate groups of 15 fish averaging 13.3 ± 0.06 g (mean ± SD). After 8 wk of the feeding trial, weight gain (WG) and feed efficiency (FE) from fish fed 48% CP diet were similar to those from fish fed 42% and 54% CP diets, and were significantly higher than those from fish fed 30, 36 and 60% CP diets ( P < 0.05). Fish fed 48 and 54% CP diets had a significant higher specific growth rate (SGR) than did fish fed 30 and 36% CP diets ( P 0.05). Protein efficiency ratio (PER) was inversely related to the dietary protein level. No significant differences existed in hematocrit (PCV) and survival rate among the dietary treatments. Broken-line model analysis indicated that the optimum dietary protein level could be 44.0 ± 3.0% for maximum WG in Japanese flounder. Polynomial regression analysis of the dose-response showed that maximum WG occurred at 50.2% ( R² = 0.94) based on WG, and the second-order polynomial regression analysis with 95% confidence limits revealed that the range of minimum protein requirement was between 38.9% and 40.3% based on WG. Therefore, these findings suggest that the optimum dietary protein requirement for maximum growth of Japanese flounder is greater than 40%, but less than 44% CP in the fish meal and casein-based diets containing 17.0 kJ/g of energy.     

Dietary lysine requirement of juvenile cobia (Rachycentron canadum)

An 8-week feeding trial was conducted to quantify the dietary lysine requirement of juvenile cobia with an initial average weight of 1.25 g reared in indoor flow-through and aerated aquaria. Six isonitrogenous and isoenergetic practical diets (44% CP and 16% lipid) containing six levels of dietary lysine ranging from 1.15 to 3.25% (dry weight) at about 0.4% increments, using fish meal and wheat gluten as sources of intact protein, supplemented with crystalline amino acids. Equal amino acid nitrogen was maintained by replacing lysine with nonessential amino acid mixture. Each diet was randomly assigned to three aquaria and was fed to apparent satiation by hand four times daily. The results indicated that there were significantly differences in growth performance and feed utilization among the treatments. Maximum weight gain, special growth rate and protein efficiency ratio occurred at 2.38% dietary lysine; but with the increase of dietary lysine from 2.38 to 3.25%, weight gain, special growth rate and protein efficiency ratio did not significantly increase. The hepatosomatic index, viscerosomatic index, condition factor, crude protein content in whole body and main composition in muscle were significantly affected by dietary lysine levels; however moisture, lipid and ash content in whole body were not significantly affected by the dietary lysine. There were significant differences in total serum protein, glucose and triacyglycerol concentrations in fish fed diets with different dietary lysine levels. Haematocrit and leukocyte count were significantly affected by dietary lysine level, but hemoglobin and red blood cell count were not significantly affected. Lysine concentration in serum was significantly increased with the increase of dietary lysine level from 1.15 to 2.38%. Broken-line analysis on the basis of special growth rate showed that the dietary lysine requirement of juvenile cobia was 2.33% of dry diet (5.30% dietary protein).     

Protein requirement of juvenile Manchurian trout Brachymystax lenok

SUMMARY: This study was conducted to determine the dietary protein requirement for the growth of juvenile Manchurian trout Brachymystax lenok . Three replicate groups of fish weighing 3.44 g were fed the five isocaloric diets containing various protein levels from 29% to 57% for 10 weeks. White fish meal was used as the sole protein source. Weight gain and feed efficiency of fish improved with increasing dietary protein level up to 43% and 49%, respectively, and reached a plateau above these levels. Dietary protein requirement using a broken-line model was estimated at 43.6% for weight gain of the fish. The protein efficiency ratio tended to decrease with increasing dietary protein level, but there was no significant difference among the diets containing 29%, 35% and 43% protein levels ( P > 0.05). The protein content of fish fed the 29% protein diet was significantly lower than that of fish fed the 57% protein diet ( P < 0.05). However, moisture, lipid and ash contents of fish were not significantly affected by dietary protein level ( P > 0.05). These findings indicate that 43–44% dietary protein level with 10% lipid and 19.2 MJ gross energy/kg diet could be recommended for the optimum growth and efficient protein utilization of juvenile Manchurian trout.     

Effects of dietary animal proteins on growth and body composition of the red drum (Sciaenops ocellatus)

Two experiments were conducted to determine the nutritional value of various dietary proteins for juvenile red drum. In the first 8-week feeding trial, diets containing similar quantities of lipid, carbohydrate, available energy and ash with 35% crude protein from either lyophilized whole-body croaker (Micropogon undulatus), striated beef muscle, red drum processing waste or commercially processed menhaden (Brevoortia tyrannus) fish meal were fed to juvenile red drum in brackish (6 ppt) water along with a control diet containing lyophilized muscle of red drum. The control diet produced significantly (P<0.05) greater weight gain (WG), feed efficiency (FE), and protein efficiency ratio (PER) values than all other diets; intermediate responses were observed for fish fed diets containing protein from red drum waste and whole-body croaker, while diets containing striated beef muscle and menhaden fish meal yielded the lowest values. Some differences in tissue indices and body composition of red drum including hepatosomatic index, whole-body ash and lipid, as well as liver lipid and glycogen were induced by the various diets. In the second 8-week feeding trial, the control diet containing red drum muscle was compared with similar diets containing protein from whole-body croaker and menhaden fish meal. Again the control diet produced the greatest WG, FE, and PER values followed by whole-body croaker and then menhaden fish meal. Effects of the dietary proteins on tissue indices and body composition were limited. The excellent protein quality and low-temperature processing of lyophilized red drum muscle resulted in superior performance of red drum relative to the other evaluated protein products, and lyophilized whole-body croaker provided better performance than commercially processed menhaden fish meal.     

Dietary protein requirement of juvenile shi drum,Umbrina cirrosa (L.)

This study was undertaken to determine the dietary protein requirement of shi drum (Umbrina cirrosa L.) with an initial weight of 86.3±0.4 g. The fish were fed five isoenergetic diets containing dietary protein levels ranging from 35% to 59% by 6% increments [the estimated digestible protein (DP) levels ranged between 29.6% and 52.8%], and the growth response over a 10‐week period was monitored. Each experimental diet was given to triplicate groups of fish. The final weight, weight gain and daily growth coefficient increased with the dietary protein level, reaching a plateau at the dietary level of 47% protein. The feed conversion ratio improved with increasing dietary protein level. The daily feed intake was significantly lower in fish fed 53% and 59% protein diets compared with those fed 35% protein diet. However, protein intake showed an increasing trend with increasing dietary protein and became significantly different between the 59% and the 35% protein diets. The protein efficiency ratio, protein retention and condition factor were not affected significantly by the dietary treatments. The final body composition was not influenced by the treatments. The recommended dietary protein percentage and DP/digestible energy (DE) ratio for juvenile shi drum diets are 51.4% (45.6% DP) and 28.5 g DP MJ DE^?1 respectively.     

Assessment of reference dietary amino acid pattern for juvenile red sea bream, <Emphasis Type="Italic">Pagrus major</Emphasis>

Four semi-purified diets, containing crystalline amino acids (CAAs), were fed to juvenile red sea bream, Pagrus major in order to ascertain the ideal dietary amino acid pattern for this species. A control diet containing 50% casein–gelatin as protein sources, but no CAAs were fed to the fish. The other diets contained 30% casein–gelatin and 20% CAAs. CAAs were added to diets to simulate with amino acid pattern of the red sea bream eggs protein (REP), red sea bream larvae whole body protein (RLP), red sea bream juvenile whole body protein (RJP), and brown fishmeal protein (BFP). The juveniles (average initial body weight, 1.58 ± 0.01 g) were maintained in triplicate tanks and fed twice daily for 30 days. The highest weight gain was observed in juveniles fed the RJP diet. No significant difference was observed in juveniles fed the RLP and BFP diet. Feed efficiency ratio, protein efficiency ratio and amino acid retention in the whole body were significantly (p < 0.05) affected by the simulated dietary amino acid patterns. The essential amino acid profile and A/E ratios of the whole body after the growth trial showed little difference among the dietary treatments. The results suggest that red sea bream juveniles are able to utilize high amounts of CAA in coated form. The amino acid pattern of RJP could be used as an appropriate of reference dietary amino acid for this species.     

Dietary Phosphorus Requirement of Juvenile Red Drum Sciaenops ocellatus

Eight isoenergetic and isonitrogenous diets containing graded levels of inorganic phosphorus were fed to juvenile red drum Sciaenops ocellatus for an 11 week period. Red drum were maintained in a brackish water (5–6 ppt) recirculating system. There were no significant differences in weight gain or feed conversion. However, survival was generally lower for fish fed deficient diets. Phosphorus supplements up to 0.86% increased bone calcium and scale ash, calcium, and phosphorus values. Bone ash and phosphorus were not significantly affected above 0.71% dietary phosphorus. It appears that approximately 0.86% dietary phosphorus is needed for maximum tissue mineralization of juvenile red drum.     

Effects of inorganic and organic dietary copper supplementation on growth performance and tissue composition for juvenile red drum (Sciaenops ocellatus L.)

A feeding trial was conducted to evaluate the dietary copper requirement of red drum (Sciaenops ocellatus) and compare the bioavailability of copper sulphate (CuSO₄) and copper‐ethanolamine. A basal diet was formulated using semi‐purified ingredients and analysed to contain 3 mg Cu/kg. Both copper sources were supplemented to the basal diet at either 5, 10 or 20 mg Cu/kg of dry diet. No significant differences were observed in growth performance of fish fed the various diets. However, red drum fed all copper‐supplemented diets retained more copper in liver and whole‐body tissues compared to fish fed the basal diet. Within both inorganic and organic copper treatments, the highest tissue copper concentrations were observed in fish fed diets supplemented with 10 mg Cu/kg. No significant differences were detected in net copper retention regardless of the nature of the copper source; hence, the bioavailability of copper sulphate and copper‐ethanolamine complex was not different in the diets for juvenile red drum. Furthermore, the minimum copper requirement for growth performance of juvenile red drum appeared to be satisfied when fish were fed the basal diet containing 3 mg Cu/kg diet, and no detrimental effects were observed in red drum fed diets supplemented with 20 mg Cu/kg.     

Effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco (Siluriformes, Bagridae, Pelteobagrus)

The present experiment was conducted to investigate the effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco . Nine diets were formulated to contain three protein levels (30%, 36% and 42%), each with three carbohydrate levels (24%, 30% and 36%). Each diet was randomly assigned to triplicate groups of 20 fish (initial mean body weight: 8.24±0.20 g) in indoor flow – through fibreglass tanks. The experiment continued for 8 weeks. Weight gain and specific growth rate were similar for the fish fed the 36% and 42% protein diets but higher than that fed the 30% protein diet. At the 36% protein level, carbohydrate contents varying from 24% to 36% ( P / E ratio of 24.0–28.2 mg protein kJ⁻¹) had no significant effects on growth performance and feed utilization ( P >0.05). Protein efficiency ratio tended to increase with dietary carbohydrate level at the same protein level. Dietary treatments significantly influenced body composition ( P <0.05), but not the condition factor, viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio ( P >0.05). Based on these observations, 36% protein and 24–36% carbohydrate with the P / E ratio of 24.0–28.2 mg protein kJ⁻¹ seemed suitable for optimal growth and feed utilization, and carbohydrate could cause protein-sparing effect in diets for juvenile yellow catfish.     

Quantitative dietary threonine requirement of juvenile Pacific white shrimp, Litopenaeus vannamei (Boone) reared in low-salinity water

An 8-week feeding trial was conducted to determine the threonine requirement of juvenile Pacific white shrimp Litopenaeus vannamei (Boone) in low-salinity water (0.50–1.50 g L⁻¹). Diets 1–6 were formulated to contain 360 g kg⁻¹ crude protein with fish meal, wheat gluten and pre-coated crystalline amino acids with six graded levels of l -threonine (9.9–19.0 g kg⁻¹ dry diet). Diet 7, which was served as a reference, contained only intact proteins (fish meal and wheat gluten). Each diet was randomly assigned to triplicate groups of 30 shrimps (0.48±0.01 g), each four times daily. Shrimps fed the reference diet had similar growth performance and feed utilization efficiency compared with shrimps fed the diets containing 13.3 g kg⁻¹ or higher threonine. Maximum specific growth rate (SGR) and protein efficiency ratio were obtained at 14.6 g kg⁻¹ dietary threonine, and increasing threonine beyond this level did not result in a better performance. Body compositions, triacyglycerol and total protein concentrations in haemolymph were significantly affected by the threonine level; however, the threonine contents in muscle, aspartate aminotransferase and alanine aminotransferase activities in haemolymph were not influenced by the dietary threonine levels. Broken-line regression analysis on SGR indicated that optimal dietary threonine requirement for L. vannamei was 13.6 g kg⁻¹ dry diet (37.8 g kg⁻¹ dietary protein).     

Predicting dietary essential amino acid requirements for hybrid striped bass

Three experiments were conducted that were designed to evaluate our ability to predict essential amino acid (EAA) needs of hybrid striped bass using the quantified lysine requirement and whole‐body amino acid concentrations. In the first experiment, six diets containing various amino acid profiles were fed to triplicate groups of fish initially weighing 7.7 g per fish. At the end of the 8‐week experiment, no significant differences were detected in growth rates or feed efficiencies (FE) between fish fed a practical diet containing 510 g kg^?1 herring fish meal (FM) and fish fed a purified diet containing the amino acid profile of herring fish meal (CAA‐FM). Growth responses of fish fed purified diets containing 100 (HSB), 110 (HSB110), 120 (HSB120) or 140 g 100 g^?1 (HSB140) of the amino acid profile of hybrid striped bass whole‐bodies were significantly lower than those of fish fed diet FM. In the second experiment, triplicate groups of fish (5.6 g per fish) were fed diets containing various energy : protein (E : P) ratios (34.8, 41.2, 47.5 and 53.9 kJ g^?1 protein) and one of two amino acid profiles (CAA‐FM and HSB120) in a 4 × 2 factorial design. Carbohydrate concentration was varied to achieve the desired energy concentrations. At the end of the 8‐week experiment, weight gain and FE were significantly higher in fish fed diets formulated to simulate the amino acid profile of herring fish meal (CAA‐FM) compared with fish fed diets formulated to contain 120 g 100 g^?1 of the amino acid profile of hybrid striped bass whole‐bodies (HSB120). Weight gain, FE and survival data indicated the optimum dietary E : P was 41.2 kJ g^?1 protein. Dietary treatments in the final experiment included three amino acid profiles and four levels of lipid in a 3 × 4 incomplete factorial design. Dietary amino acid treatments included the amino acid profile of herring fish meal (CAA‐FM) or 120 g 100 g^?1 of the predicted EAA requirement profile for hybrid striped bass (HSB120). The amino acid profile of the remaining dietary treatment (PRED+) was similar to that of the HSB120 treatment, but contained additional threonine, isoleucine and tryptophan. Diets CAA‐FM and HSB120 contained either 90, 130, 170 or 210 g kg^?1 lipid, whereas diet PRED+ contained 130 g kg^?1 lipid. Dietary treatments were fed for 10 weeks to triplicate groups of fish initially weighing 81.0 g per fish. Weight gain and FE were not significantly affected by dietary amino acid profile. Feed efficiency was significantly reduced in fish fed diets containing 210 g kg^?1 lipid compared with fish fed diets containing 90–170 g kg^?1 lipid. Intraperitoneal fat (IPF) ratio and hepatosomatic index (HSI) values generally increased as dietary lipid concentrations increased. Total liver lipid concentrations were significantly reduced in fish fed diets containing 210 g kg^?1 lipid compared with those of fish fed 90–130 g kg^?1 lipid. Results of this study indicate an appropriate dietary amino acid profile can be predicted for hybrid striped bass using the quantified lysine requirement and whole‐body amino acid concentrations. Further, the optimum E : P appears to be 40 kJ g^?1 protein.     

Total sulfur amino acid requirement of juvenile hybrid striped bass (Morone chrysops×M. saxatilis)

Two separate feeding trials were conducted to determine the total sulfur amino acid requirement of hybrid striped bass. Semipurified diets containing 35% crude protein from fish muscle and crystalline amino acids were supplemented with graded levels of methionine. Each diet was fed to juvenile fish in triplicate aquaria receiving freshwater for 8 weeks. Fish fed the basal diet which contained 0.38% methionine and 0.13% cystine experienced complete mortality within 1 week. Prior to death, some fish fed inadequate methionine were observed to have bilateral cataracts. Weight gain and feed efficiency of fish were significantly (P<0.01) affected by supplemental methionine. Regression analysis of weight gain data using the broken-line model indicated a total sulfur amino acid requirement (±s.e.) of 1.0% (±0.02%) of dry diet or 2.9% of dietary protein.     

Dietary protein requirement of giant mud crab Scylla serrata juveniles fed iso-energetic formulated diets having graded protein levels

The protein requirement of juvenile mud crab Scylla serrata (body weight=0.25±0.051 g, carapace width=9.3±0.04 mm) fed with different iso-energetic, iso-lipidic diets with graded protein levels (15–55% crude protein at 5% intervals) was determined. The feeding trial was conducted for a period of 63 days to determine the minimum and optimum protein requirement of juvenile S. serrata . The crabs fed with 15% and 20% dietary protein levels showed 100% and 12.5% of mortalities respectively. The mortalities observed in the above treatments were associated with the prolonged intermoult duration (46 and 32 days respectively). All other treatments recorded 100% survival. The best growth performance as well as the nutrient turn-over was recorded in crabs fed with 45% crude protein in the diet. Second-order polynomial regression of specific growth rate (SGR) as well as body protein gain vs. dietary protein levels suggested that 46.9–47.03% dietary protein is required for the best growth response and protein deposition in juvenile S. serrata . An extrapolation of 'SGR' and 'daily protein gain' upon the 'dietary protein level' axis ( Y =0) showed that 14.7–16.2% dietary protein is necessary for the minimum maintenance metabolism.     

Growth efficiency, body composition, survival and haematological changes in great sturgeon (Huso huso Linnaeus, 1758) juveniles fed diets supplemented with different levels of Ergosan

Growth performance, carcass quality, survival and haematological responses were determined when Huso huso juvenile (41.7±1.8 g) fed diets containing Ergosan (an algal product) at 0, 2.0, 4.0 and 6.0 g kg⁻¹ for 60 days. Each diet was fed to triplicate groups of fish at 10-day intervals (1–10, 20–30 and 40–50 with non-supplemented diets and 10–20, 30–40 and 50–60 with supplemented diets). Results showed that fish fed diets containing Ergosan had significantly higher growth than the control group ( P <0.05). Survival was not different among all dietary treatments ( P >0.05). Food conversion ratio in the fish fed a diet containing 4.0 and 6.0 g kg⁻¹ Ergosan was significantly better than the other treatments ( P <0.05), whereas protein efficiency ratio was not different between experimental diets. Lymphocyte count in the fish fed diets containing Ergosan was higher than the other treatments. Haematocrit, haemoglobin (Hb) concentration, number of erythrocytes, total leucocytes, monocyte, eosinophil, myelocyte, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration were not different between treatments. Neutrophil count in the control group was higher than the fish fed supplemented diets. Furthermore, whole body lipid, moisture and fibre were not different among dietary treatments ( P >0.05) but body protein in the fish fed a diet containing Ergosan at the level of 2.0 and 4.0 g kg⁻¹ was higher than the other treatments. Whole body ash content was higher in the control group. It was concluded that dietary administration of Ergosan can influence some growth and haematological parameters in great sturgeon, H. huso juveniles.     

Effects of Replacing Fish Meal with Soybean Meal in Diets for Red Drum Sciaenops ocellatus and Potential for Palatability Enhancement

Two 8-wk feeding trials were conducted with juvenile red drum to determine the maximum levels of soybean meal that may replace fish meal in diets containing 38% crude protein, without reducing weight gain. In the first experiment, fish fed diets containing up to 90% of the protein from soybean meal gained as much weight as fish fed a diet with 100% of protein from fish meal, but fish fed the diet with 100% of its protein from soybean meal gained significantly (P < 0.05) less. Supplementation of glycine and fish solubles individually at 2% (as-fed basis) in diets containing 90% of their protein from soybean meal tended to increase weight gain of fish compared to those fed a similar diet without supplementation. Similar results were obtained in the second experiment, as fish fed diets containing 90% of their protein from soybean meal gained as much weight as fish fed a diet with 100% of its protein from fish meal. Fish fed diets with 95% and 100% of their protein from soybean meal gained significantly less weight than those fed the diet with all of its protein from fish meal. Supplementation of glycine at 2% in the diet containing 95% of its protein from soybean meal significantly improved weight gain of fish relative to those fed a similar unsupplemented diet. Supplementation of fish solubles at 5% of diet on a dry-matter basis provided a nonsignificant increase in weight gain compared to that of fish fed a similar unsupplemented diet. In both experiments there was greater observed consumption of the soybean-meal-based diets than diets with all of their protein from fish meal. A minimum of 10% of protein from fish meal appears necessary in practical diets containing most of their protein from soybean meal to prevent impaired growth and feed efficiency of red drum.