Optimum Dietary Protein Level Research Articles

미꾸리(Misgurnus anguillicaudatus) 치어 성장을 위한 사료의 적정 단백질 및 지질 함량

A feeding trial was conducted to determine the optimum dietary protein and lipid levels for the growth of juvenile muddy loach Misgurnus anguillicaudatus. Eight experimental diets (designated as P20L7, P20L14, P30L7, P30L14, P40L7, P40L14, P50L7 and P50L14) were formulated to contain 20%, 30%, 40% and 50% protein with 7% and 14% lipid. Three replicate groups of muddy loach (1.5 g/fish) were fed one of the experimental diets ad libitum for 8 weeks. Survival of fish fed the P20L14 diet was lower than in other groups (P<0.05). Specific growth rate (SGR) and feed efficiency (FE) of fish were affected by dietary protein (P<0.05) and lipid (P<0.005) levels. SGR and FE of fish tended to decrease with increasing dietary lipid level at the same protein level. There were no significant differences in SGR and FE among fish fed diets containing different protein levels ranging from 30% to 50% with the same lipid level. Whole body moisture and lipid contents were affected by dietary protein and lipid levels. Crude lipid content of fish fed the 14% lipid diets was higher than that of fish fed 7% lipid diets at each protein level. The results of this study indicate that a diet containing 30% protein with 7% lipid would be suitable for the optimum growth and effective feed utilization of juvenile muddy loach.

배합사료의 단백질 및 지질 함량이 종어(Leiocassis longirostris Gunther) 치어의 성장과 체성분에 미치는 효과

We ran a feeding trial to determine optimal dietary protein and lipid levels for growth of juvenile long snout bullhead Leiocassis longirostris Gunther. Eight experimental diets (P20L7, P20L14, P30L7, P30L14, P40L7, P40L14, P50L7 and P50L14) were formulated to contain 20%, 30%, 40% or 50% protein combined with either 7% or 14% lipid. Three replicate groups of fish (mean mass: 3.9 g/fish) were fed one of the experimental diets ad libitum for 8 weeks. Survival of fish fed the P20L14 diet was lower than that of fish fed the P40L14, P50L7 and P50L14 diets. Growth of fish fed diets containing 7% lipid increased with increasing protein level (up to 50% protein); growth of fish fed diets containing 14% lipid increased with increasing protein level (up to 30% protein). The feed efficiency of fish fed a diet with 50% protein and 7% lipid was higher than that of other groups. Whole body moisture and lipid contents were affected by dietary lipid level but not by dietary protein level. The crude lipid contents of fish fed 14% lipid diets were higher than those fed 7% lipid diets across all protein levels (other than the 50% level). Thus, under our experimental conditions, an increase in dietary protein level improved growth and feed efficiency of fish; a diet containing 50% protein with 7% lipid was optimal for growth and effective feed utilization in juvenile long snout bullhead.

Comparative Histological Changes in the Greenlip AbaloneHaliotis laevigataGastrointestinal Tract in Response to Water Temperature, Different Dietary Protein Levels, and Animal Age

The land-based culture of greenlip abalone Haliotis laevigata in southeastern Australia is carried out using seawater that is prone to seasonal temperature fluctuations and is done almost exclusively using artificial feeds. Although some nutrition research has been done to identify the optimum dietary protein level, typically farms use only 1 diet for grow-out after the juveniles are weaned. Little consideration has been given to the effects of fluctuating water temperatures and dietary protein levels on the morphology of the gastrointestinal tract (GIT) of abalone. Because these factors are known to impact growth in other aquatic species, it is important that they are investigated further to improve growth in abalone species. In this study, the histological changes of the GIT of greenlip abalone in response to 2 water temperatures and 4 dietary levels of crude protein (juvenile, 27% and 36%; subadult, 24% and 33%) for juveniles (1.75 g) and subadults (22.93 g) were investigated. The epithelial thickness of the stomach and crop; intestinal villus height, width, and area; lamina propria height; and stomach, crop, and intestinal neutral and acidic goblet cell numbers were measured. The stomach epithelium was significantly thicker at 14°C than 22°C in both juveniles and subadults, whereas the crop epithelium was significantly thicker at 22°C than 14°C in juveniles. The crop epithelial thickness of subadults was reduced by increasing dietary protein; however, juveniles did not show the same response. Juvenile abalone were more sensitive to temperature fluctuations than subadults, whereas significant effects of dietary protein levels were only observed in subadults. The alterations in the morphology of the GIT did not appear to be detrimental to the health and growth of the abalone. Further research is required to investigate the interactive effects of water temperature and dietary ingredients, particularly in regard to antinutritional factors, on the morphology and function of the GIT to improve our understanding of abalone physiology.

Evaluation of the optimum dietary protein level for the maximum growth of juvenile beluga (Huso husoL.1758)

A 10-week feeding trial was carried out to evaluate the optimum dietary protein level for the maximum growth of juvenile beluga, Huso huso. Fish averaging 1.34 0.07 g (mean SD) was randomly distributed into 18 circular fibreglass tanks of 500 L capacity (20 fish per tank). Six iso-caloric diets were formulated to contain 30 (CP30), 35 (CP35), 40 (CP40), 45 (CP45), 50 (CP50) and 55% (CP55) crude protein (CP). Fish were fed each of the six experimental diets in triplicate groups. At the end of feeding trial, weight gain (WG) and specific growth rate (SGR) in fish fed CP40 and CP45 diets were significantly higher than those of fish fed CP30 ,C P35 ,C P50 and CP55 diets (P < 0.05). Lipid retention increased significantly from 24.7% to 31.6%, but protein retention decreased from 54.6% to 35.6% with increasing protein levels from 30% to 50%. Muscle total essential and non-essential amino acid (EAA & NEAA) concentrations increased with the dietary protein level up to CP45 diets. Muscle total EAA concentrations (%) of fish fed CP45 were significantly higher than those of fish fed CP30 ,C P 35 ,C P 50 and CP55, but there was no significantly different between those of fish fed CP40 and CP45. Muscle total NEAA concentration (%) of fish fed CP45 were significantly higher than those of fish fed CP30 and CP35 diets. Broken-line analysis of WG suggested that the optimum dietary protein level could be 38.9% for maximum growth performance in juvenile beluga (1.3–77 g).

Effects of Protein and Lipid Levels in Practical Diets on Growth and Body Composition of Tongue Sole, Cynoglossus semilaevis Gunther

AbstractA 9‐wk feeding experiment was conducted to estimate the optimal dietary protein and lipid levels for tongue sole, Cynoglossus semilaevis Gunther (initial average weight of 43.8 ± 0.18 g). Six practical test diets were formulated to contain three protein levels (45, 50, and 55%, respectively) at two lipid levels (12 and 16%, respectively) with P/E ratios ranging from 87.1 to 110.5 mg protein/kcal. Each diet was randomly fed to triplicate groups of 20 fish per tank (1000 L). The results showed that fish fed the diet with 55% protein and 12% lipid (P/E ratio of 110.5 mg protein/kcal) had the highest thermal‐unit growth coefficient (TGC), feed efficiency ratio, protein productive value, and energy retention. TGC was significantly increased with increasing dietary protein levels irrespective of dietary lipid levels (P &lt; 0.05). However, fish fed the diet with 16% lipid showed significant lower growth than fish fed the diet with 12% lipid. These results suggest that the diet containing 55% protein and 12% lipid with P/E of 110.5 mg protein/kcal is optimal for tongue sole and the increase of dietary lipid level has no effective protein‐sparing effect.

Effects of dietary protein and lipid levels on growth, feed utilization and body composition inPseudobagrus ussuriensisfingerlings

An 8-week feeding trial was conducted to investigate the optimum dietary protein and lipid levels for growth, feed utilization and body composition of Pseudobagrus ussuriensis fingerlings (initial weight: 3.40 ± 0.01 g). Twelve diets containing four protein levels (350, 400, 450 and 500 g kg−1 crude protein) and three lipid levels (50, 100 and 150 g kg−1 crude lipid) were formulated. Fish were randomly allotted to 36 aquaria (1.0 × 0.5 × 0.8 m) with 25 fish to each glass aquarium. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. The results showed that weight gain and specific growth rate (SGR) decreased with increasing dietary lipid level from 50 to 150 g kg−1 at the same dietary protein level. Fish fed the diets containing 150 g kg−1 lipid exhibited higher feed conversion ratio (P < 0.05), lower protein efficiency ratio (PER) and nitrogen retention efficiency (NRE) relative to fish fed the diet containing 50 and 100 g kg−1 lipid. Weight gain and SGR significantly increased with increasing dietary protein from 350 to 450 g kg−1 at the same dietary lipid level, and even a little decline in growth with the further increase in dietary protein to 500 g kg−1. Daily feed intake, NRE and PER were significantly affected by both dietary protein and lipid levels (P < 0.05) and tended to decrease with increasing dietary protein and lipid levels. Whole-body protein content increased as protein levels increased and lipid levels decreased. Whole-body lipid and muscle lipid content increased with increasing dietary lipid level, and decreased with increasing dietary protein at each lipid level. There was no significant difference in condition factor and viscerosomatic index among fish fed the diets. Hepatosomatic index was affected by dietary lipid level (P < 0.05), and increased with increasing dietary lipid level at the same protein level. These results suggest that the diet containing 450 g kg−1 protein and 50 g kg−1 lipid with a P/E ratio of 29.1 mg protein kJ−1 is optimal for growth and feed utilization of P. ussuriensis fingerlings under the experimental conditions used in the study.

Effects of dietary protein level on growth performance, nitrogen and energy budget of juvenile hybrid sturgeon, Acipenser baerii ♀ × A. gueldenstaedtii ♂

An 8-week growth trial was conducted to estimate the optimal dietary protein level for juvenile hybrid sturgeon, Acipenser baerii ♀×A. gueldenstaedtii♂ (initial body weight, 25.1±0.12g). Effects of protein levels on nitrogen and energy budget of the fish were studied. Seven isoenergetic diets were formulated to contain seven levels of crude protein (250, 300, 350, 400, 450, 500 and 550gkg−1) and each diet was fed to triplicate groups of fifty fish at 21.4±0.6°C in twenty one 1m3 concrete tanks.The results showed that specific growth rate (SGR) increased when dietary protein levels increased from 250 to 400gkg−1 and then decreased significantly. Feed intake (FI) decreased steadily with increasing dietary protein levels. Fish fed 250gkg−1 protein diets showed the lowest feed efficiency (FE), and those fed 500 and 550gkg−1 protein diets showed significantly higher values than the other diets except 450gkg−1. Protein retention efficiency (PRE) was highest in 250–300gkg−1 groups, followed by 350–500gkg−1 groups and was significantly lower in 550gkg−1 group. Proportions of nitrogen intake (CN) allocated to excretory nitrogen (UN) were lowest in 250–300gkg−1 protein diets, followed by 350–500gkg−1 protein diets and highest in 550gkg−1 protein diet, whereas recovered (growth) nitrogen (RN) followed the inverse pattern with UN. Percentages of gross energy intake (IE) used for excretory energy (UE) increased steadily when dietary protein levels increased. Fish fed 400–550gkg−1 protein diets showed significantly higher proportion of metabolizable energy (ME) than those fed 250–350gkg−1 protein diets. The lowest and highest percentages of recovered (growth) (RE) were observed in 250 and 550gkg−1 groups. Nitrogen and energy budget equation of the fish fed 350gkg−1 protein diet was 100CN=11.72FN+58.78UN+29.50RN and 100IE=35.08FE+4.53UE+34.16ME+26.23RE.Five-parameter saturation kinetic model and second-order polynomial regression analysis indicated that the optimal dietary protein level for maximal growth of the fish was 340 and 370gkg−1. Diets with excessive protein contents not only resulted in inferior growth performance but also high proportions of protein and energy used for excretion.

Effect of Dietary Protein and Lipid Levels on Growth and Nutrient Utilization of Freshwater Angelfish Pterophyllum scalare

Nine semi-purified diets containing three levels of protein (300, 350, 400 g/kg) and three levels of lipid (60, 80, 100 g/kg) were fed ad libitum to juvenile freshwater angelfish Pterophyllum scalare (1.64±0.01 g) to determine the optimum dietary protein and lipid levels. Fish were stocked in 27 flow-through fiber-reinforced plastic tanks with 100 l water (10 fish/replicate) and fed 60 days. Fish were batch-weighed every 15 days to determine growth. The dietary protein level had a significant effect on protein efficiency rate (PER) but not on weight gain, feed conversion ratio (FCR), or specific growth rate (SGR). In contrast, the dietary lipid level had a significant effect on weight gain, FCR, and SGR but not on PER. The interaction of dietary protein and lipid had a significant effect on weight gain, FCR, SGR, and PER. No protein-sparing effect of the lipid was observed. Fish fed the diet containing 300 g protein and 60 g lipid per kg diet had a significantly better weight gain, SGR, PER, and FCR.

Effect of dietary protein and lipid levels on growth, nutrient utilization and whole‐body composition of blue gourami, Trichogaster trichopterus fingerlings

Nine semi-purified diets were prepared with three levels each of protein (300, 350 and 400 g/kg) and lipid (60, 80 and 100 g/kg) and fed ad libitum to Trichogaster trichopterus fingerlings (0.61 ± 0.03 g) in triplicate groups (10 fish/replicate) for 90 days to determine optimum dietary protein and lipid levels. Twenty-seven flow-through fibre-reinforced plastic tanks (200 l capacity each with 100 l of water) were used for rearing the fish. The dietary protein, lipid and their interactions had significant effects (p < 0.05) on weight gain, feed conversion ratio, specific growth rate, nutrient retention and digestibility, but not on hepato- and viscerosomatic indexes (p > 0.05). Dietary protein and the interaction of protein with lipid had significant effect (p < 0.05) on whole-body dry matter, lipid and energy contents, but not on protein and ash contents (p > 0.05). But, the dietary lipid had significant (p < 0.05) effect on whole-body dry matter, protein, lipid and energy contents except the ash contents (p > 0.05). For each level of dietary protein, the increase in dietary lipid resulted significant increase (p < 0.05) in whole-body lipid contents without affecting the protein and ash contents (p > 0.05). Based on better growth and dietary performances, the optimum dietary protein and lipid levels of blue gourami fingerling are 350 and 80 g/kg diet respectively.

The eco-nutrition requirements for dietary protein and its rhomb characteristics in juvenile turbot (Scophthalmus maximus L.)

We evaluated the dietary protein requirements of juvenile turbot (Scophthalmus maximus L.) and their effects on aquatic quality. Five experimental diets were formulated containing 450, 480, 500, 520, and 540 g/kg. Each diet was randomly assigned to triplicate groups of juvenile turbot (mean initial body weight 34.5 +/- 5.5 g) for 88 d. Both the weight gain ratio and feed efficiency increased with increasing dietary protein up to 500 g/kg, but no further improvement was detected when dietary protein levels were > 500 g/kg. Protein intake and digestion increased with protein levels, while fecal nitrogen and nitrogen content in seawater increased only when dietary protein exceeded 500 g/kg. Protein digestibility was highest at intermediate dietary protein levels. Chemical oxygen demand, nitrite-nitrogen (NO (2) (-) -N) and phosphatic-phosphor (PO (4) (3-) -P) levels increased in the rearing water as dietary protein levels increased. The optimum eco-nutrition level of dietary protein for juvenile turbot was 500 g/kg under the current experimental conditions. The diets containing 540 and 500 g/kg protein had similar growth rates and feed conversion ratios, but levels of ammonia (NH (4) (+) ) and nitrogen were considerably higher in the water and feces, respectively, at the higher level of dietary protein. The difference in the pattern of change between body weight gain and ammonia concentration in water with increasing dietary protein is described by rhomb characteristics.

Optimal dietary protein levels for juvenile Pacific threadfin (Polydactylus sexfilis) fed diets with two levels of lipid

This study was designed to estimate the optimal dietary protein level for juvenile Pacific threadfin fed two levels of dietary lipid. Ten semi-purified diets were formulated to contain five levels of dietary protein (25, 30, 35, 40 and 45%) at either 10 or 14% dietary lipid. A commercial diet containing 14% lipid and 50% protein was fed as a reference treatment. Juvenile threadfin (initial body weight, 3.4 g) were hand fed these diets at 7% body weight/day for 8 weeks with 3 replications per dietary treatment. Fish were cultured in an indoor flow-through system with 31‰ seawater at 26 °C. There were 20 fish per replicate. The dietary lipid levels did not cause significant changes in growth performance or body composition (P > 0.05). In contrast, the diet with 25% protein resulted in significantly (P < 0.05) lower weight gain and higher feed conversion ratios (FCR) than the diets with 30–45% protein. The lowest FCR occurred in fish fed diets containing 35% protein and 10% lipid or 30% protein and 14% lipid. Increased dietary protein level resulted in decreased protein efficiency ratio, hepatosomatic index, and lipid level in carcass or whole fish. Protein and energy retentions in carcass or whole fish were negatively correlated to dietary protein levels. Estimation using a polynomial model, 41% protein supported maximum growth of Pacific threadfin under these experimental conditions. Fish fed the test diets containing 35% protein, however, had similar growth performance but better protein utilization than fish fed either the commercial feed or the diet with 40% protein. These results demonstrate the possibility of reducing protein content in commercial feeds and thus lowing feed costs needed for Pacific threadfin culture.

Optimum dietary protein and lipid levels for growth of juvenile sea cucumber Apostichopus japonicus

A feeding trial of three protein (200, 300 and 400 g kg−1) and two lipid levels (20 and 100 g kg−1) was conducted to determine the proper dietary protein and lipid levels for growth of juvenile sea cucumber Apostichopus japonicus. Dietary protein and lipid levels were adjusted by adding with different levels of soybean meal, squid liver oil and soybean oil, respectively. Three replicate groups of sea cucumbers (average weight of 1.3 g) were fed the experimental diets for 12 weeks. At the end of the feeding trial, survival was not affected by dietary protein and lipid levels (P > 0.05). Weight gain (WG) and specific growth rate (SGR) of sea cucumbers were significantly affected by dietary protein (P < 0.006) and lipid levels (P < 0.001). The highest WG and SGR were observed in sea cucumbers fed the 200 and 400 g kg−1 protein diet with 20 g kg−1 lipid (P < 0.05). WG and SGR of sea cucumbers fed the diet containing 20 g kg−1 lipid were higher than those of sea cucumbers fed the 100 g kg−1 lipid diets (P < 0.05) at each dietary protein level. Apparent digestibility coefficients of dry matter, crude protein, carbohydrate and gross energy of sea cucumbers fed the 20 g kg−1 lipid diets were significantly higher than those of the 100 g kg−1 lipid diets at 200 and 400 g kg−1 protein (P < 0.05). Moisture, crude protein, crude lipid and ash contents were not significantly different among the groups. The results of this study indicate that the diet containing 200 g kg−1 protein (170 g kg−1 digestible protein) with 20 g kg−1 lipid (13 g kg−1 digestible lipid) may be sufficient for optimum growth of juvenile sea cucumber.

Optimum Dietary Protein Level for Juvenile Silver Pomfret, Pampus argenteus (Euphrasen)

A feeding trial was conducted in a flow-through system in 1 m3 tanks using seawater to determine the optimum dietary protein requirement of juvenile silver pomfret, Pampus argenteus (Euphrasen). Fish were stocked a density of 12 juveniles per tank. Five semi-purified iso-energetic diets were formulated with fish meal to contain graded levels of 35, 40, 45, 50, and 55% crude protein. Each diet was fed to triplicate groups of fish to apparent satiation twice daily. The growth of fish fed 50% protein diet was not significantly different (P > 0.05) from that of fish fed 45 or 55% diet, but significantly higher than that of fish fed 35 or 40% diet. Feed conversion ratio (FCR) ranged between 1.7 and 2.5%, and 35% protein diet had significantly higher FCR than those of 45, 50 and 55% diets. Protein efficiency ratio of fish fed 55% protein diet was significantly lower than rest of the diets. Fish fed 50% dietary protein showed significantly best apparent net protein utilization. There were no significant differences between the survivals of fish which ranged between 80.6 and 88.9%. Based on the polynomial regression analysis of %weight gain, the optimal dietary protein level for silver pomfret was estimated to be 49%.

Effect of Genotype and Dietary Protein Level on Growth Performance and Carcass Characteristics of Fattening Pigs in Central Vietnam

This study aimed to determine the optimum dietary crude protein level in a typical diet for fattening pigs fed ad libitum under normal climate conditions in Central Vietnam. One hundred and ninety two gilts of Mong Cai local breed (MC), F1 Large White×Mong Cai and F2 crossbreds of (Landrace×Mong Cai)×Large White were used. At the start of the experiment, Mong Cai pigs weighed 12 kg at 11 weeks of age, F1 pigs 12.1 kg at 8 weeks of age and F2 pigs 12.2 kg at 8 weeks of age. Four diets differing in crude protein (CP) content (10.1, 13.1, 16.1 and 18.9% in DM) were formulated from rice bran, corn meal, cassava meal and fish meal. Calculated digestible energy content of the diets ranged from 13.5 to 13.8 MJ per kg DM. Pigs were housed individually in pens of 2.5 m 2 each and had ad libitum access to feed in a trough as well as water in bowls. The final weights after a growing period of 150 days were 66, 86 and 96 kg for MC, F1 and F2, respectively. Feed intake of MC pigs was highest at 13.1% CP while F1 and F2 had the highest feed intake at 16.1% CP. The results showed that for MC the maximum gain was obtained at levels between 13 to 16% CP. For the F1 the maximum gain was at dietary protein levels of 16-17%. For F2 the max gain was obtained at CP levels of 16 to 18%. Feed conversion was highest in MC pigs (~4.0) followed by F1 (~3.3) and F2 (~3.1), and within genotypes was lowest at the optimum CP level (p<0.05). Back fat thickness in MC (33.1 mm), F1 (23.0 mm) and F2 (20.5 mm) pigs was different and within genotypes was the lowest at intermediate CP levels. In conclusion, increasing the dietary crude protein contents in practical diets for pigs in Vietnam can increase production on small holder farms. Optimal performance for MC, F1 and F2 pigs is achieved at different dietary crude protein contents.

Optimal Dietary Protein and Lipid Levels for Growth of Long-nosed Barbel, Hemibarbus longirostris

A 10-week feeding trial with four dietary protein levels (22%, 32%, 42% and 52%) and two dietary lipid levels (8% and 17%) was conducted to investigate the optimum dietary protein and lipid levels for growth of long-nosed barbel fingerlings. Survival rate of fish was not affected by either the dietary protein or the dietary lipid level. Weight gain and feed efficiency were affected by the dietary protein level (P<0.01), but not by the lipid level, and increased with the dietary protein level at the both lipid levels. Weight gain and feed efficiency of fish fed the 52% protein diets with 8-17% dietary lipids were not significantly different from those of fish fed the 42% protein diets with 8-17% dietary lipids and 32% protein diet with 17% dietary lipid. Daily feed intake of fish was not affected by either dietary protein or dietary lipid level. Protein efficiency ratio and protein retention rate of fish fed the 32% protein diet with 17% dietary lipid were significantly higher than those of fish fed the 52% protein diets with 8-17% dietary lipids. Moisture content of fish fed the diets containing 8% lipid were higher than those of fish fed the diets containing 17% dietary lipid at each protein level. Crude lipid content of fish fed the diets containing 17% dietary lipid were higher than that of fish the fed the diet containing 8% dietary lipid at each protein level. The results of this study indicated that 32% protein and 17% lipid could be the optimum dietary level for growth of juvenile long-nosed barbel.

Dietary Protein Source and Level Affects Growth in Neon Tetras

AbstractNutritional studies for aquarium fishes like the neon tetra Paracheirodon innesi are sparse in comparison with those for food fish. To determine the optimum dietary protein level and source for growth of neon tetras, diets were formulated to contain 25, 35, 45, and 55% dietary protein from either marine animal protein or plant protein sources in a 4 × 2 factorial treatment design. Neon tetras (initial weight, approximately 0.12 g) were reared in 5‐L fiberglass tanks (25 fish/tank, 3 tanks/diet) in a freshwater recirculating system. Fish were hand‐fed the experimental diets three times per day for 12 weeks. Average weight gain of neon tetras fed diets with marine protein sources was significantly higher than that for fish fed diets based on plant proteins. Fish fed diets containing 45% or 55% crude protein had significantly greater weight gain than did fish fed 25% crude protein from either protein source. Fish fed 25% crude protein from either source had a significantly higher feed conversion ratio than did those fed 45% or 55% crude protein. Survival ranged from 71% to 84% and was not significantly altered by dietary protein source or level. No significant interactions between dietary protein source and level were found for any of the response variables. As the price of fish meal continues to increase, the formulations of feeds for food fish will probably contain lower amounts of fish meal and higher amounts of plant protein products. If a similar trend occurs for ornamental fish diets, further refinement of nutritional requirements and assessment of palatability of feed ingredients for neon tetras and other aquarium species will be required.

DIETARY PROTEIN REQUIREMENT FOR JUVENILE SPINIBARBUS SINENSIS

The objective of this study was to investigate the dietary protein requirement of the juvenile Spinibarbus sinensis and determine effects of dietary protein levels on feed intake,growth and nutrition utilization. White fish meal was used as the dietary protein source,and six isocaloric experimental diets were formulated to contain different protein levels of 20.49%,26.48%,34.20%,41.02%,49.94% and 55.86% (referred to as D1,D2,D3,D4,D5 and D6 respectively). Each treatment had four replicates and 12 fish (initial weight of (10.36±1.40)g (mean±S.D.)) of each replicate were reared in a circulated filtered system for 10 weeks at (27.5±0.5) ℃ in a circulated filtered rearing system. Fish were hand fed to satiation once daily at 18:00. Feces were collected from the second week by siphoning and washed immediately everyday. A sample of 9 fish at the start of feeding experiment and 4 fish per group at the end of experiment were sampled and stored frozen at-26℃ for proximate composition analysis. Fish were weighted individually after 48h starvation at the end of the experiment.The results showed that as dietary protein increased,the feeding rate of dry matter (FRdm) decreased gradually from D1 to D4 firstly,and then leveled off. However,a positive correlation between the feeding rate of protein (FRp) and dietary protein levels was found (r= 0.982,p0.01). Apparent digestibility of diet dry matter significantly decreased from (73.12±1.07) to (55.02±0.95)% from D1 to D6 (p0.05),whereas,there was no significant difference in the apparent digestibility of dietary protein among all treatments. Specific growth rates of weight (SGRw),specific growth rates of energy (SGRe) and feed efficiency (FE) were significantly increased from D1 up to D4 (p0.05),and D4 group obtained the highest values of these three indices. Then SGRw,SGRe and FE reached a plateau and did not differ significantly among D4,D5 and D6. Protein efficiency ratio (PER) decreased from 178.23 to 116.60% as dietary protein level increased from D1 to D6. Values of protein productive values (PPV) had a similar trend like PER,which decreased from 23.92 to 18.62% as dietary protein levels increased from D1 to D6. Energy productive values (EPV) significantly increased from (20.05±0.39) to (28.87±0.81)% as dietary protein increased from D1 to D4,then decreased to (23.49±2.00)% for D6. Based on the broken line models between SGRw,SGRe,FE and dietary protein levels,the optimal dietary protein requirement for juvenile S. sinensis was estimated to be 39.6%— 42.2% when white fish meal was the sole protein source and the dietary energy value was 15.71 MJ/kg. This optimum dietary protein level for juvenile S. sinensis is higher than some other omnivorous fishes. It suggested that the food habit of juvenile S. sinensis preferring animal plankton and zooplankton make it need more dietary protein for growth. Simultaneously,the growth rate of juvenile S. sinensis is slower than those of some other fish species,which could be due to its small diet intake ratio and low apparent digestibility of dietary protein.

The effect of protein levels on growth, postprandial excretion and tryptic activity of juvenile mulletMugil platanus(Günther)

The objective of the present work was to determine the optimum dietary protein level for juvenile mul- lets. Five isocaloric diets were formulated to contain increasing levels (300, 350, 400, 450 and 500 g kg � 1 ) of crude protein (CP) corresponding to 18.7 MJ meta- bolizable energy kg � 1 . All diets were tested in tripli- cate. Each experimental unit was composed of a 50 L tank with 50 juveniles (meanSE initial weight and length equal to 1.17 � 0.02 g and 4.34 � 0.03 cm respectively). Diets were oiered ¢ve times a day until apparent satiation for 35 days. No signi¢cant diier- ence (P40.05) was observed in survival rate, feed e⁄ciency and body composition between treatments. However, weight gain, feed consumption and speci¢c growth rate were higher in ¢sh fed the 350 g kg � 1 CP level than those fed the highest protein content diet (500 g kg � 1 CP). The amount of postprandial ammo- nia excreted by mullet was linearly related to protein intake. Intestinal tryptic activity was inversely pro- portional to the percentage of dietary CP. It is likely that diets containingo350 g kg � 1 CP will be needed for on-growing mullet, especially when reared in ponds with abundant natural food.

Effect of dietary protein levels on growth performance and whole body composition of summerling and winterling spotted barbel (Hemibarbus maculates Bleeker)

Six test diets with protein levels varying from 250 to 500 g kg−1 were fed to six triplicate groups of summerling (initial weight: 1.56 g) and seven test diets with protein levels varying from 200 to 500 g kg−1 were fed to seven triplicate groups of winterling (initial weight: 9.49 g) for 8 weeks. Weight gain (WG) and feed efficiency (FE) of summerling significantly increased with increasing dietary protein levels from 250 to 350 g kg−1 and slightly declined, but without statistical significance at a dietary protein level of 400 g kg−1, then further significantly decreased with increasing protein levels to 450 and 500 g kg−1; WG of winterling increased significantly with increasing dietary protein levels from 200 to 300 g kg−1 (P < 0.05), and above this level, WG had a tendency to decrease with increasing dietary protein levels. Winterling fed diets with 300 and 400 g kg−1 of dietary protein had significantly higher FE than those fed other diets. WG data analysis by quadratic regressions showed that the optimum dietary protein levels required for the maximum growth of summerling and winterling were 374 and 355 g kg−1 of dry diet respectively. Protein efficiency ratio of both summerling and winterling negatively correlated with levels of dietary protein. The whole body moisture, protein, lipid and ash of summerling after being fed various test diets for 8 weeks were significantly different among treatments (P < 0.05). The whole body moisture and fat of winterling were also significantly affected by dietary protein levels (P < 0.05), while the whole body protein and ash of winterling were not (P > 0.05).

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.