Relative contribution of alternative proteins to the growth of Juvenile Cobia,Rachycentron canadum (Linnaeus)

Five isonitrogenous and isocaloric diets were fed to juvenile cobia, to assess the relative contribution of different proteins (fish meal, soybean meal, corn gluten and beer yeast) to the growth of cobia. The dietary effects on nitrogen and carbon turnover and on the isotopic diet‐consumer discrimination factors (Δ¹⁵N and Δ¹³C) were also assessed. Growth results showed that the final body weight, growth rate, feed conversion ratio and protein efficiency ratio of cobia fed diets with alternative protein were significantly lower (P < 0.05) than cobia fed diet formulated with 100% fish meal. The estimated half‐lives of nitrogen and carbon ranged between 9–11 days and 6–8 days, respectively, with significant differences among treatments (P < 0.05). Δ¹⁵N ranged between 0.0–1.2‰ and ?0.1–1.6‰ in whole fish and muscle and Δ¹³C ranged between 3.8–5.1‰ and 4.0–5.1‰ in whole fish and muscle respectively. Diets were formulated with low levels of dietary nitrogen (10%) supplied by alternative protein sources substituting fish meal. The relative contributions of the dietary nitrogen supplied from these sources to the growth of whole fish and muscle tissue ranged between 4.9–5.2% and 5.9–7.7% respectively. Results indicated that growth accounted for the majority of observed isotopic change in animals under all treatments. In whole animals and muscle tissue, isotopic change due to metabolism occurred faster for carbon stable isotopes than for nitrogen stable isotopes. Cobia fed diets formulated with alternative proteins showed reduced nitrogen turnover rate and increased Δ¹⁵N.     

Partial substitution of fish meal and full-fat soya bean meal with wheat gluten and influence of lysine supplementation in diets for rainbow trout, Oncorhynchus mykiss (Walbaum)

A 65-day study was undertaken to evaluate the utilization of lysine-supplemented wheat gluten meal as a protein source for rainbow trout, Oncorhynchus mykiss (Walbaum). The performance of the trout fed wheat gluten was compared to that of trout where protein was principally supplied using fish meal and full-fat soyabean meal. Six isonitrogenous diets (approximately 45% crude protein) were formulated. Thus, the reference diet (FS) was based on fish meal and full-fat soya bean meal while a further five diets were formulated with a mixture of wheat gluten and wheat middlings used to isonitrogenously replace approximately 75% and 57% of the full-fat soya and fish meal respectively. Crystalline l -lysine representing 0.00%, 0.29%, 0.58%, 0.87% and 1.16% of the complete diet was then added to the wheat-gluten-based diets. Optimal performance in terms of weight gain and apparent net protein utilization was achieved by the fish fed a wheat-gluten-based diet supplemented with lysine (0.58%) yielding a digestible lysine level of 1.9% of the complete feed. Within the range of supplements provided, lysine digestibility was high. However, at the highest levels of supplemental lysine the relationship between uptake and supplement level was not linear. Additionally, arginine digestibility was not affected by the level of lysine supplementation. However, amongst the wheat-gluten-based diets, optimal performance was associated with a lysine: arginine ratio of 1.1: 1. Despite a lysine: arginine ratio of approximately 1.1: 1, the overall performance of the fish fed the fish-meal-soya-based reference diet was poorer than expected. The results are discussed with respect to optimal patterns of gross and digestible amino acids, lysine-arginine antagonism and the possible relationship between antinutritional factors and the poor performance of the fish fed the fish-meal-soya-based reference diet.     

Replacement of Soybean Meal in Channel Catfish, Ictalurus punctatus, Diets with Cottonseed Meal and Distiller's Dried Grains with Solubles

Two pond experiments were conducted to evaluate cottonseed meal (CSM), distiller's dried grains with solubles (DDGS), and supplemental lysine as replacements for soybean meal (SBM) in channel catfish diets. In Experiment 1, fish fed diets in which SBM was totally replaced with CSM gained similar weight as fish fed control diet, but fish fed CSM diet in Experiment 2 had 9.5% lower weight gain than fish fed control diet. In both experiments, feed conversion increased significantly for fish fed CSM diet. There were no consistent trends in body composition of fish fed CSM diet versus control diet. Fish fed the DDGS + SMB diet had higher (Experiment 1) or similar (Experiment 2) weight gain than fish fed control diet. Feed conversion ratio was significantly lower in both experiments for fish fed SBM + DDGS diet than that of fish fed control diet. Body fat tended to be higher in fish fed SBM + DDGS diet compared to fish fed control diet. It appears that about 50% of SBM can be replaced with CSM + lysine in catfish diets without negatively affecting fish performance. Further, DDGS can be used up to at least 30% when the diet is supplemented with lysine.     

Replacement of fishmeal by soy protein concentrate with taurine supplementation in diets for golden pompano (Trachinotus ovatus)

Two 7‐week feeding trials were conducted to evaluate the capacity of golden pompano (Trachinotus ovatus) to use soy protein concentrate (SPC) as a dietary fish meal substitute. In trial I, fish were fed with a control diet (C) containing 400 g kg^?1 fish meal and other four diets in which the fish meal in diet C was replaced by SPC at 20 (R20), 40 (R40), 60 (R60) and 80% (R80). In trial II, a 3 × 2 design was used, and 40 and 80% of the fish meal in diet C were replaced by SPC, with or without 5 g kg^?1 taurine supplementation (six diets, C + T, R40 + T, R80 + T, C, R40 and R80, were formulated). In trial I, no significant difference was found in the feed intake between feeding treatments. The weight gain and nitrogen retention efficiency (NRE) decreased, whereas the feed conversion ratio (FCR) and phosphorus retention efficiency (PRE) increased, with decreasing dietary levels of fish meal. No significant differences were found in the weight gain, FCR and NRE between fish fed diets C and R20, whereas fish fed diets C and R20 had higher weight gain than those fed diets R40, R60 and R80. In trial II, no significant differences were found in the feed intake, weight gain, FCR, NRE and PRE between fish fed diets C + T and C. No significant differences were found in the feed intake, weight gain and NRE between fish fed diets R40 and R40 + T or between fish fed diets R80 and R80 + T. At the end of trial II, no significant differences were found in the condition factor, hepatosomatic index and body composition between fish fed diets C and C + T, or between fish diets R40 and R40 + T, or between fish fed diets R80 and R80 + T, except that fish fed diet R40 had lower body protein content than that of fish fed diet R40 + T. The present study reveals that taurine supplementation can elevate fish meal replacement level by SPC in the golden pompano diets. Fish meal can be reduced from 400 to 320 g kg^?1, if fish meal is substituted by SPC without taurine supplementation, and can be further reduced to 240 g kg^?1, if fish meal is substituted by SPC with 5 g kg^?1 taurine supplementation.     

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).     

A Comparative Study of the Dietary Lysine Requirement of Juvenile Striped bass Morone saxatilis and Sunshine bass M. chrysops x M. saxatilis

Previous reports have indicated there are significant differences in both the dietary lysine requirement and the metabolic rate of striped bass and its hybrids. However, there is very little directly comparative data to confirm these suggestions. A series of experiments was conducted to comparatively assess efficiency of protein and energy retention between striped bass Morone saxatilis and sunshine bass M. chrysops♀×M. saxatilis♂ grown under identical culture conditions. In experiment one, a dose response study was conducted using digestible energy (DE) levels of 3,200 kcal/kg and 3,600 kcal/kg. At each level of DE, six levels of dietary lysine were fed to striped bass and sunshine bass. Ten sunshine bass weighing 3.48 ± 0.08 g or six striped bass weighing 3.23 ± 0.14 g were stocked into 15-L tanks supplied with single-pass flow-through fresh water. After 12 wk on the experimental regime, feed conversion ratios (FCR), weight gain, and % nitrogen (N) retention were determined. Nonlinear regression analysis indicated that the dietary lysine requirement of both bass groups was similar. The dietary lysine requirement was determined to be 2.0 ± 0.08% of dry diet (or 6.0 ± 0.26 g lysine/1,000 kcal DE), and 1.7 ± 0.08% of dry diet (or 4.7 ± 0.22 g lysine/1,000 kcal DE), for the 3,200 and 3,600 kcal DE/kg diets, respectively. A second experiment comparatively assessed growth, metabolism, and energy partitioning between striped bass and sunshine bass. Two diets were formulated to be isonitrogenous and isocaloric with a calculated DE level of 3462 kcal/kg and contained lysine concentrations approximating the published dietary requirements of sunshine bass (low lysine = LL diet) and striped bass (high lysine = HL diet). The diets were fed at an average rate of 2% of body weight/d to 25 juvenile striped bass or hybrid bass held separately in eight 2000-L single-pass flow-through tanks supplied with freshwater. In general, growth performance of sunshine bass was superior to striped bass. Both bass groups performed better when fed the HL diet. Mean FCRs were 1.19 ± 0.12 and 1.94 ± 0.29, respectively, for hybrids and striped bass fed the LL diet (P= 0.066); and 1.17 ± 0.07, and 1-58 ± 0.08, respectively, for hybrids and striped bass fed the HL diet (P = 0.011). Mean % gain/d values were significantly higher (P= 0.001) for hybrids (2.77 ± 0.85) than for striped bass (1-30 ± 0.27) when fed the LL diet. When fed the HL diet, mean % gain/d was significantly higher (P = 0.003) for sunshine bass (2.72 ± 0.83) compared to striped bass (1.51 ± 0.25). Additionally, when fed the HL diet, sunshine bass had significantly higher percent nitrogen (P= 0.006) and energy retention (P= 0.014) when compared to striped bass. These results further document that sunshine bass are more efficient at protein and energy retention compared to striped bass in freshwater.     

Effects of shrimp waste meal on growth performance and chitinase activity in juvenile cobia (Rachycentron canadum)

The effects of replacing fish meal (FM) with shrimp waste meal (SWM) in diets fed to juvenile cobia (Rachycentron canadum) were investigated through a 6‐week trial. SWM was added to replace FM at fractions of 0%, 10%, 20% and 25% of the diet. The result showed the survival rates of the fish were higher than 86.7%. The weight gain and feed conversion rate showed an increasing trend as the SWM proportion in diet increased from 0% to 25%, but the protein efficiency ratio showed a decreasing trend in efficiency. In addition, the hepatosomatic index increased significantly when the SWM percentage was 20% and 25%. There were no significant differences in the protein and ash concentration of the muscle among all dietary groups. However, the muscle lipid content was low when fish fed in diets with high SWM level. Chitinase activity was extremely high in the pyloric caeca tissue of cobia, and increased specific activities of chitinase were only found in the foregut of cobia fed diets containing 10% SWM for a 6‐week period. A challenge test showed that SWM could not enhance cobia resistance to Photobacterium damselae ssp. piscicida infection. Our results suggest that the administration of a 10% SWM diet could potentially reduce the use of FM in the diet of cobia.     

The Effects of Substituting Selected Oilseed Protein Concentrates for Fish Meal in Rainbow Trout Oncorhynchus mykiss Diets

Three oilseed protein concentrates (soybean, canola, and sunflower) were evaluated to determine their potential, when supplemented with deficient essential amino acids, to partially or completely replace fish meal in diets fed to rainbow trout Oncorhynchus mykiss . Triplicate aquaria of juvenile trout (average weight of 12 g) were fed the experimental diets for 10 wk, at which time the average weight of the fish was approximately sixfold higher than the initial weight. Average fish weight gains on diets in which the protein component was 100% fish meal; 75% fish meal, 25% soybean protein concentrate; 50% fish meal, 50% soybean protein concentrate; and 75% fish meal, 25% sunflowerseed protein concentrate were not significantly different ( P < 0.05). The average weight of fish fed a commercial feed was significantly lower than that of fish fed the 100% fish meal diet, but not significantly different from fish fed the three other formulations mentioned above. Fish fed diets containing 50% fish meal, 50% canola protein concentrate; and 25% fish meal, 75% sunflowerseed protein concentrate had significantly lower average final weights than those of fish fed the other diets. Feed conversion ratio patterns among the dietary treatment groups reflected those of weight gain. Fish survival exceeded 95% on all diets. Apparent protein digestibility coefficients ranged from 79.5% (75% soybean protein concentrate, 25% canola protein concentrate) to 90.6% (100% soybean protein concentrate). The results of this study demonstrated that certain oilseed protein concentrates have good potential as protein sources in rainbow trout feeds when properly supplemented with essential amino acids.     

Nutritional requirements of cobia, Rachycentron canadum (Linnaeus): a review

Cobia culture has been rapidly gaining in popularity since the early 1990s; however, the relative success of modified commercial diets in aquaculture has delayed the need for specific research into the nutritional requirements of cobia. Recent work has determined optimum dietary protein and lipid levels in juvenile cobia at 45 and 5–15% dry weight respectively. Maximum growth and feed conversion ratios have been recorded at 27–29 °C in juvenile cobia with an optimum ration level determined at 9% initial body weight per day. There is limited information on amino acid and essential fatty acids (EFA) requirements in cobia. Several studies have explored alternate protein sources in juvenile cobia with relative success observed with meat meal, yeast-based protein and various plant based sources including soybean meal. There is no literature on the vitamin or mineral requirements of cobia or the nutritional requirements of larger fish. Therefore future research should focus on the amino acid, EFA, vitamin and mineral requirements of cobia while the protein, lipid and energy requirements of larger cobia should be addressed. Additional work on feed ingredients, choice and palatability would also aid in maximizing culture production while minimizing costs thereby producing a more sustainable product.     

Feeding of juvenile cobia,Rachycentron canadum: Evaluation of practical feeds,comparison of commercial fishmeal replacers,and estimation of essential amino acid requirements

Three studies were conducted with juvenile cobia, Rachycentron canadum: (Study 1) a 10‐week feeding trial within floating net cages to test the nutritional efficacy of different dietary feeding regimes (trash‐fish control diet, a semimoist diet, an in‐house dry formulated diet, and a commercial cobia feed); (Study 2) a 10‐week feeding trial within an indoor water‐recirculating tank‐based system to test the nutritional efficiency of different potential dietary fishmeal replacers (poultry byproduct meal, soy protein concentrate, feather meal), a diet without taurine supplementation, and a commercial cobia feed; and (Study 3) estimation of the essential amino acid (EAA) requirements of cobia based on EAA whole‐body composition in fast‐growing cobia fed a trash‐fish‐based diet. Fish performance in terms of growth and feed efficiency was the greatest within the outdoor net‐cage feeding trial, with fish fed the control trash‐fish‐based diet exhibiting the best performance. Although fish growth was poorer within the indoor feeding trials, fish performance was similar for most diets, with apparent crude protein digestibility coefficients of over 75% being obtained in all experimental diets in both feeding trials. The estimated EAA requirements of cobia obtained during this study were similar to those reported for other similar marine carnivorous fish species.     

The evaluation of practical diets on a basis of digestible crude protein,lysine and methionine for Litopenaeus vannamei

A feeding trial was conducted to evaluate the efficacy of replacing fish meal (FM) with blood meal (BM), poultry by‐product meal (PBM), meat and bone meal (MBM) and shrimp head meal (SHM), rapeseed meal (RM) and peanut meal (PM) on a digestible basis of crude protein and lysine and methionine in five practical diets for the Pacific white shrimp at the FM levels of 300, 250, 200, 150 and 100 g kg^?1 under laboratory conditions. Each of the five experimental diets was hand‐fed to four replicate tanks of shrimp with an average weight of 0.33 ± 0.03 g to satiation at each meal. The shrimp were fed three times a day over a six‐week period. The per cent weight gain of initial body weight (WG%) was significantly lower in shrimp fed 100 g kg^?1 FM diet, but the value for hepatosomatic index (HSI) and the level of blood urea nitrogen (BUN) tended to be higher in shrimp fed 100 g kg^?1 FM diet than those in shrimp fed other diets. The lowest value for feeding rate (FR) occurred for shrimp fed the basal diet and was significantly lower than that in shrimp fed the FM diets at 100–150 g kg^?1. Shrimp fed diets containing 200 g kg^?1 or lower FM had significantly lower feed utilization than those fed the 250 g kg^?1 FM diet and the basal diet. The protein efficiency ratio (PER) in the shrimp fed the basal diet was significantly higher than in the other FM diets. Decreasing the FM replacement level significantly reduced nutrient digestibility except in the cases of ash and gross energy, but it did not affect the survival, condition factor (CF), body composition, digestive enzyme activity or plasma transaminase activity. The results of the study indicate that feeding a diet formulated on a digestible basis and involving FM replacement with other protein sources at a greater replacement proportion will not produce a level of shrimp growth equal to that achieved by feeding the basal diet.     

Improvement of fish meal replacements by soybean meal and soy protein concentrate in golden pompano diet through γ‐ray irradiation

A 5‐week feeding trial was conducted to examine the effect of γ ‐ ray irradiation on the inclusion of soybean meal (SBM) and soy protein concentrate (SPC) in diets of juvenile golden pompano (Trachinotus ovatus). One diet containing 320 g kg^?1 fish meal served as a reference (C), and another four diets were formulated with 75% of the fish meal replaced by SBM (SM), SPC (SC), SBM irradiated with γ ‐ ray at 30 kGy (SM30) or SPC irradiated with γ ‐ ray at 30 kGy (SC30). The weight gain was higher in fish fed diets SM30 and SC30 than in fish fed diets SM and SC, respectively, whereas fish consumed more diet SM30 than diets SM, SC or SC30. No significant differences were found in feed conversion ratio, nitrogen retention efficiency (NRE), phosphorus retention efficiency (PRE), condition factor, hepatosomatic index (HSI), body composition, waste outputs of nitrogen (NWO) and phosphorus (PWO) either between fish fed diets SM and SM30 or between fish fed diets SC and SC30. The weight gain and PWO were higher, but the PRE and the body phosphorus content were lower in fish fed diet C than those in fish fed diets SM30 or SC30. No significant differences were found in the NRE, condition factor, HSI and body composition (i.e. moisture, crude protein, crude lipid and ash) between fish fed diets C and SM30 or between fish fed diets C and SC30. Macromolecular proteins in SBM and SPC were degraded, whereas the contents of peptides with molecular weight <6.5 kDa were increased by γ‐ray irradiation. This study reveals that γ ‐ ray irradiation can improve the performance of SBM and SPC as a fish meal substitute in the golden pompano diet.     

Comparison of the bioavailability of lysine in blood meals of various origins to that of l-lysine HCL for rainbow trout (Oncorhynchus mykiss)

The bioavailability of lysine in blood meals from various origins was examined in rainbow trout. Bioavailability of lysine of the blood meals was assessed in comparison to that of l-lysine HCL using a slope ratio assay experimental design. A corn gluten meal-based diet, deficient in lysine (1.5% diet), was used as the basal diet. Two levels of spray-dried poultry blood meal (SDBM), flash-dried bovine blood meal (FDBM), disc-dried poultry blood meal (DDBM), and lysine-HCL substituted corn gluten meal in the basal diet to produce experimental diets containing 1.8 or 2.2% lysine. These diets were pair-fed to rainbow trout (initial body weight = 25 g/fish) reared at 15 °C for 12 weeks. Weight gain, feed efficiency ratio (FER, gain: feed), retained nitrogen (RN), and recovered energy (RE) increased significantly (P < 0.05) with increasing lysine levels. Diets containing SDBM and FDBM recorded significantly greater weight gain, FER, RN and RE compared to DDBM (P < 0.05). At the 1.8% lysine level, the diet containing FDBM recorded significantly greater weight gain, and RN than the diet supplemented with l-lysine HCl. The weight gain, FER and RN of the fish fed diets containing SDBM was not significantly different from that of the fish fed the diets with l-lysine HCl, at both lysine levels. At the 2.2% lysine level, feeding diets containing FDBM and DDBM resulted in significantly lower weight gain than diet supplemented with l-lysine HCl, suggesting that other nutrients may have become more limiting than lysine at high levels (20%) of blood meal. Results suggest that the bioavailability of lysine in SDBM or FDBM is slightly greater than that of l-lysine HCL. Bioavailability of lysine in the DDBM used in this study appeared to be significantly lower than that of spray-dried or flash-dried blood meals.     

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.     

Evaluation of fish-meal free diets for rainbow trout, Oncorhynchus mykiss

Eight experimental diets were formulated for rainbow trout using agricultural byproducts as major ingredients. Each experimental diet contained varying amounts of corn grain, corn gluten meal, corn gluten feed and one of the following: 200 g kg^?1 peanut meal, 200 or 400 g kg^?1 soybean meal (SBM), 390 g kg^?1 low-allergen soy flour, 310 g kg^?1 soy protein concentrate, 300 g kg^?1 low-allergen soy protein concentrate or 200 g kg^?1 SBM + 110 g kg^?1 blood meal. One diet contained 200 g kg^?1 SBM and canola oil as the main lipid source. The remaining diets contained 95 g kg^?1 menhaden oil. Fish fed a commercial trout diet exhibited significantly greater weight gain (322%), and a lower feed conversion ratio (0.89) but significantly lower protein efficiency ratio (2.18) than fish fed the experimental diets. Within the experimental diets, fish fed the 400 g kg^?1 soy flour diet and the 400 g kg^?1 soybean meal diet had significantly higher weight gains (276% and 268%) and protein efficiency ratios (2.58 and 2.52), and lower feed conversion ratios (1.02 and 1.03) than fish fed other experimental diets. Fillet flavour varied between treatments. Most notable was the lower fishy flavour and higher chicken flavour of fish fed the diet that contained canola oil rather than menhaden oil. Microscopic evaluation of the liver and five sections of the gastrointestinal tract failed to demonstrate any differences between treatment groups. The ingredient costs of several experimental diets were lower than the estimated cost of a standard commercial trout diet. However, the superior feed conversion ratios of fish fed the control diet resulted in lower feed costs per unit of fish produced.     

Effect of Dietary Lipid Level and Feeding Frequency on the Growth,Feed Utilization,and Body Composition of Juvenile Spotted Seabass,Lateolabrax maculatus

A 6‐wk feeding trial was conducted to evaluate the effects of different dietary lipid levels and feeding frequencies on the growth performance, feed utilization, and body composition of juvenile spotted seabass, Lateolabrax maculatus. Two experimental diets were prepared with two different dietary lipid contents, low lipid (7%; LL) and high lipid (14%; HL). Each diet was fed to triplicate groups of fish (5.5 ± 0.01 g) to apparent satiation at three meals per day, two meals per day, one meal per day, and one meal every 2 d, respectively, for 6 wk. Fish growth performance in terms of weight gain (WG) and specific growth rate (SGR) was significantly affected by frequency of feeding, with increasing values as feeding frequency increased up to twice daily, regardless of dietary lipid content. In addition, fish fed the diet with the HL level (14%) showed significantly higher WG and SGR than those fed the LL diet (7%) at all the feeding frequencies tested. Feed efficiency (FE) and protein efficiency ratio (PER) were affected by both dietary lipid level and feeding frequency. FE and PER values were significantly higher in fish fed the HL diet and/or when fish were fed twice or thrice a day. However, daily feed intake and daily energy intake were significantly affected only by feeding frequency and were significantly reduced when the fish were fed only once every 2 d compared with those fed more frequently. Whole‐body moisture content of fish tended to decrease with increasing dietary lipid level and frequency of feeding. In contrast, whole‐body lipid content increased in fish as dietary lipid level and feeding frequency increased. Consequently, we can conclude that feeding spotted seabass twice daily to apparent satiation is acceptable and sufficient to achieve good growth and FE, as fish performance was not significantly enhanced when feeding was increased from two to three times daily.     

Growth, feed utilization and carcass composition of catfish Clarias batrachus (Linn.) fingerlings fed on dried fish and chicken viscera incorporated diets

A 30‐day feeding trial was conducted to evaluate dried fish and chicken viscera, and a combination of oil cakes as complete substitutes for fish meal in the diet of catfsh Clarias batrachus (Linn.) fingerlings. Triplicate groups of fingerlings with a mean initial body weight of 2.0 g were each fed four isonitrogenous diets at 4% of wet body weight. Performance of the diets was judged on the basis of feed acceptability, body weight gain, feed conversion ratio and protein efficiency ratio. A significant increase (P < 0.05) in body weight gain, protein efficiency ratio and a decreased feed conversion ratio (P < 0.05) was observed in fish fed on fish meal, followed by fish viscera, chicken viscera and only plant protein incorporated diets. Although inferior to fish meal and dried fish viscera, growth and feed utilization responses of fingerlings fed on dried chicken viscera and plant protein diets were similar. The fish accumulated a significantly greater (P < 0.05) amount of fat (18.3%) in the body carcass when fish viscera was incorporated in the diet. The study revealed that satisfactory growth and feed utilization responses could be achieved through replacement of fish meal by dried fish and chicken viscera in the diet of catfish fingerlings.     

Effects of dietary protein and lipid levels on growth performance and body composition of black sea bass Centropristis striata (Linnaeus 1758) during grow-out in a pilot-scale marine recirculating system

The influence of four formulated practical diets, with different protein and lipid levels, on the growth and body composition of black sea bass ( Centropristis striata L.) pre-adults was evaluated in a pilot-scale marine recirculating system. Four test diets were prepared with a combination of two protein levels (44% and 54%) and two lipid levels (10% and 15%). The diets were as follows: low protein and low lipid (LP:LL; 44:10), low protein and high lipid (LP:HL; 44:15), high protein and low lipid (HP:LL; 54:10) and high protein and high lipid (HP:HL; 54:15). Fish (mean weight=75.5 g) were fed the respective diets for 90 days. For fish fed LP:HL, body weight gain was significantly ( P <0.05) higher than fish fed LP:LL. Increasing the protein level from 44% to 54% did not produce a significant effect on weight gain at high lipid level. A significant ( P <0.01) interactive effect between dietary protein and lipid levels on the growth and feed utilization was observed. Total lipid content in the whole body, muscle and liver was significantly affected by the dietary lipid levels. The results suggested that a combination of 44% dietary protein and 15% lipid was optimal for the growth of black sea bass.     

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.     

Improvement of quality of sesame Seasamum indicum seed meal protein with supplemental amino acids in feeds for rohu Labeo rohita (Hamilton) fingerlings

An 8-week feeding trial was conducted in a static indoor rearing system to examine the effects of partial substitution of fish meal (FM) protein with sesame seed meal protein with and without supplemental amino acids in diets for rohu Labeo rohita fingerlings (average weight 3.82 ± 0.05 g). Before incorporation into diets, sesame Seasamum indicum seed meal was fermented with lactic acid bacteria Lactobacillus acidophilus in order to reduce/eliminate the antinutritional factors tannin and phytic acid present in it. Twelve experimental diets (diets D1 to D12) were formulated replacing the FM protein from a reference diet with sesame seed meal protein at different levels (four sets of diets, of which each set of three diets contained 30%, 40% and 50% replacement of FM protein by sesame seed meal protein respectively). Diets D1 to D3 were not supplemented with any amino acid. Lysine was supplemented to diets D4 to D6. Diets D7 to D9 were supplemented with methionine–cystine (together), and diets D10 to D12 contained lysine and methionine–cystine (together). Lysine and methionine–cystine were added to the diets at 5.7% and 3.1% of dietary protein respectively. The groups of fish fed diets without any supplemental amino acids had significantly lower percentage weight gain, specific growth rate (SGR) and higher feed : gain ratio (FGR) than the groups of fish fed on other experimental diets. The addition of lysine and methionine–cystine to the diet in which 50% of FM protein was replaced by sesame meal protein (diet D12) significantly improved fish weight gain and FGR. The percentage live weight gain and SGR values differed significantly (P < 0.01) from each other in the fish fed diets D10 to D12, which were supplemented with all three amino acids. The results of the present study suggest that rohu fingerlings can effectively utilize the supplemented amino acids and that sesame seed meal protein can replace up to 50% of FM protein in the diets for rohu if the sesame seed meal is properly processed (fermented) and supplemented with deficient amino acids.