Effects of varying protein and lipid levels and protein‐to‐energy ratios on growth,feed utilization and body composition in juvenile Nibea diacanthus

A two‐factor experiment was designed to determine the suitable dietary protein and lipid levels for juvenile Nibea diacanthus. Nine extruded pellet diets were formulated to contain three levels of protein (420, 470 and 520 g kg^?1) and three levels of lipid (70, 110 and 150 g kg^?1). Each diet was randomly fed to triplicate groups of 25 juvenile N. diacanthus (initial weight 12.12 ± 0.23 g) for 8 weeks in net cages. The results showed that weight gain rate (WGR), specific growth rate, final body weight and energy retention were significantly influenced by the dietary protein and lipid levels‐. The highest WGR (982.5g kg^?1.) of N. diacanthus was found in the group with dietary protein and lipid of 520 and 150 g kg^?1. Feed intake and feed efficiency were significantly impacted by the dietary protein levels. An interactive effect between dietary protein and lipid on the protein retention and protein efficiency ratio was observed. There were no significant differences in condition factor and survival among all treatments. Hepatosomatic index and viscerasomatic index of N. diacanthus were positively related with dietary lipid levels, but negatively with dietary protein levels. Crude protein, crude lipid, ash, moisture and energy contents of the whole body, muscle and liver were influenced by dietary protein and lipid levels. Moreover, total essential amino acid pattern of the muscle was correlated to those of dietary protein. Total protein concentration in the serum was affected by dietary protein and lipid levels. Meanwhile, both serum cholesterol and triglyceride concentrations increased with increasing dietary lipid levels. These results demonstrate that the diet containing 470 g kg^?1 protein and 110 g kg^?1 lipid is optimal for juvenile N. diacanthus and analysis of WGR by quadratic regression indicated that the estimated optimal protein‐to‐energy ratio for juvenile N. diacanthus was 24.53 mg protein kJ^?1.     

Effects of dietary protein and lipid levels on growth,feed utilization and body composition in red‐tailed catfish juveniles (Hemibagrus wyckioides,Chaux & Fang 1949)

A feeding trial was conducted in a recycling water system during 10 weeks to determine the optimal protein to lipid ratio in Asian red‐tailed catfish (Hemibagrus wyckioides). Six diets of two protein levels (390 and 440 g kg^?1) with three lipid levels (60, 90 and 120 g kg^?1) were formulated. Fish (1.96 g) were fed six diets with four replicates to apparent satiation at a stocking density of 50 fish per tank (500 L). Faeces were collected in cultured tanks at the end of the feeding trial for digestibility measurement. Significantly, improved growth performances (P < 0.01) and higher feed utilization (P < 0.001) were observed in fish fed with higher lipid diets. However, higher protein diets did not significantly improve fish growth but they reduced FCR (P < 0.001) and protein efficiency ratio (P < 0.01). Higher lipid diets also resulted in significantly increased adipose‐somatic index, carcass fat and reduced moisture of the fish. The study revealed the protein sparing effect of dietary lipid in the catfish and highest growth performance was found by fish fed 390 g kg^?1 protein and 120 g kg^?1 lipid diet with P/E ratio of 20.48 mg protein kJ^?1. DP/DE ratio for maximal growth rate in diets was 21.48 mg protein kJ^?1.     

Effects of different dietary carbohydrate‐to‐lipid ratios on growth,plasma biochemical indexes,digestive and immune enzymes activities of juvenile orange‐spotted grouper Epinephelus coioides

An 8‐week feeding trial was conducted to investigate the effects of dietary carbohydrate‐to‐lipid (CHO:L) ratios on growth, liver and muscle glycogen content, haematological indices, and liver and intestinal enzyme activity of juvenile grouper (Epinephelus coioides). Five isonitrogenous (496.0 g/kg protein) and isoenergetic (21.6 KJ/g gross energy) diets with varying CHO:L ratios of 0.65 (D1), 1.31 (D2), 2.33 (D3), 4.24 (D4) and 8.51 (D5), respectively, were fed to triplicate groups of 20 fish (average 10.02 ± 0.1 g) for 8 weeks. Results showed that the weight gain rate, specific growth rate and protein efficiency ratio (PER) of juvenile grouper increased first and then decreased with the increase in CHO:L ratio, reaching a maximum value in the D4 (CHO:L = 4.24) diet. The trend for the feed conversion ratio was opposite to the PER. Along with the diet CHO:L ratios, the apparent digestibility coefficients (ADC) of crude lipid and energy for the juvenile groupers decreased gradually, while the ADC of dry matter, liver and muscle glycogen level increased gradually. Total protein, triglycerides and cholesterol in serum were all maximized in the D4 diet and glucose in the D5 (CHO:L = 8.51) diet. Digestive enzyme activity in the intestine was significantly affected by dietary CHO:L ratio. Liver hexokinase, phosphofructokinase and glucose‐6‐phosphate dehydrogenase activity increased significantly as CHO:L ratio increased. Liver lysozyme and acid phosphatase activity in the groupers fed the D3 (CHO:L = 2.33) diet was significantly higher than that of other diets. Liver fructose‐1,6‐bisphosphatase and alkaline phosphatase activity reached a maximum value in the D4 diet and was significantly higher than that in the D1 diet. Taking the above results together, it can be concluded that an optimal dietary CHO:L ratio of 2.33 is suitable for grouper culture concerning growth performance and health.     

Determination of optimal temperature(s) in juvenile red‐spotted grouper Epinephelus akaara (Temminck & Schlegel) based on growth performance and stress responses

This study sought to determine the optimal temperature(s) for aquaculture of juvenile red‐spotted grouper Epinephelus akaara (Temminck & Schlegel) (mean initial BW: 3.1 g). Growth performance, insulin‐like growth factor 1 (IGF‐1) expression and thermal stress responses (plasma cortisol, glucose, and hepatic heat shock protein 60 expression) were evaluated at three constant temperatures (24°C, 26°C and 28°C) in a 2‐week trial. At the end of the trial, final BW was significantly higher at 26°C and 28°C than at 24°C (p < 0.05); a quadratic regression analysis of final BW showed the optimum temperature for growth was 27.5°C (p < 0.05, R² = 0.806). The highest hepatic IGF‐1 expression was observed at 26°C (p < 0.05). On the other hand, hepatic heat shock protein 60 expression was highest at 28°C (p < 0.05), suggesting thermal stress. In conclusion, temperature optima, which support excellent growth but induce minimal thermal stress, was 26°C. This fine information within a narrow temperature range is expected to give empirical information for red‐spotted grouper farmers to sustain maximal production efficiency with avoiding thermal stress and to determine the future location of production, especially in consideration of arising seawater temperatures.     

Effects of the dietary protein to energy ratio on growth,feed utilization and body composition in Macrobrachium nipponense

Oriental river prawn (Macrobrachium nipponense) has been widely cultured in Asian countries. However, its nutritional studies are very limited. In the present 8‐week study, we investigated the effects of dietary protein to energy ratio (P/E ratio) on the growth, feed utilization and body composition in juvenile M. nipponense (initial weight 0.302 ±0.03 g). Two‐factor experiment was designed and nine semi‐purified diets were formulated to contain three lipid levels (20, 80 and 140 g kg^?1) and three protein levels (330, 380 and 430 g kg^?1), producing P/E ratios from 16.5 to 23.4 mg KJ^?1 protein. The results indicated that the growth, survival rate and protein efficiency were dose dependently improved by the increased dietary lipid, but not dietary protein content. Increased dietary lipid content and/or protein content increased lipid accumulation in whole body, hepatopancreas and muscle, but did not change the feed intake and hepatopancreas weight. In conclusion, our present study indicated that M. nipponense is a species with relatively high‐energy requirement. It could utilize dietary lipid content up to 140 g kg^?1, while the dietary protein with more than 330 g kg^?1 would not promote growth and protein efficiency. Taken together, 330 g kg^?1 dietary protein and 140 g kg^?1 dietary lipid level with P/E ratio 16.49 could be optimum for M. nipponense.     

Effects of dietary protein and lipid levels on growth, feed conversion and body composition in rohu, Labeo rohita (Hamilton), fingerlings

Twelve experimental diets (D‐1 to D‐12) in a 4 × 3 factorial design (four protein levels: 250, 350, 400 and 450 g kg^?1 and three lipid levels: 50, 100 and 150 g kg^?1) were formulated. Carbohydrate level was constant at 250 g kg^?1. Rohu fingerlings (average wt. 4.3 ± 0.02 g) were fed the experimental diets for 60 days in three replicates at 2% BW  day^?1. Weight gain (%), specific growth rate (% day^?1) and feed gain ratio (FGR) indicated that diets containing 450 g kg^?1 protein and 100 or 150 g kg^?1 lipid (diets D‐11 and D‐12) resulted in best performance, although results were not significantly different from those of diet D‐9 (400 g kg^?1 protein and 150 g kg^?1 lipid). Protein efficiency ratio was highest with diets D‐6 (350 g kg^?1 protein and 150 g kg^?1 lipid) and D‐9 (400 g kg^?1 protein and 150 g kg^?1 lipid) (P > 0.05) and declined with higher and lower protein diets at all levels of lipid tested. Elevated lipid level (50, 100 or 150 g kg^?1) did not produce better FGR in diets containing 400 and 450 g kg^?1 dietary protein (P > 0.05). The combined effects of protein and lipid were evident up to 400 g kg^?1 protein. Growth and FGR showed consistent improvement with increased lipid levels from 50 to 150 g kg^?1 at each protein level tested except with diets containing 450 g kg^?1 protein. Apparent nutrient digestibility (for protein, lipid and energy) did not show significant variation among different dietary groups (P > 0.05). Whole body protein and lipid contents increased significantly (P > 0.05) with dietary protein level. The results of this study indicate that rohu fingerlings are adapted to utilize high protein in diets with varying efficiency. The fish could utilize lipid to spare protein but there is no significant advantage from this beyond the dietary protein level of 350–400 g kg^?1 in terms of growth and body composition.     

Dietary protein requirement of juvenile kelp grouper (Epinephelus moara)

Dietary protein requirement of juvenile kelp grouper Epinephelus moara was investigated through a feeding trial. Experimental diets with graded crude protein (CP) levels (33.01%, 38.54%, 45.21%, 50.71%, 56.10% and 63.09% of dry matter respectively) were formulated. Six triplicate groups of fish (20 individuals per replicate with initial mean weight 6.00 g) were fed with each diet for 8 weeks. Best growth performance of fish was detected in 56.10% CP diet. The specific growth rate (SGR) significantly elevated with increasing dietary CP level to 50.71%, but there was no significant difference thereafter (p < .05). The feed conversion ratio (FCR) decreased significantly with dietary CP levels from 33.01% to 56.10% (p < .05). Glucose (GLU) and total protein (TP) concentrations in plasma had an increasing trend with dietary protein increasing. In the 33.01% CP group, plasma triglyceride (TG) content was significantly higher (1.67 mmol/L) than that in other dietary treatments (0.65–1.14 mmol/L). The lowest alanine transaminase (ALT) activity was observed in the 56.10% CP group (163.16 U/L). Crude lipid content in the muscle and liver was significantly elevated with increasing dietary protein levels (p < .05). The glycogen content in the liver decreased significantly as CP levels increased (p < .05). The fish fed diet with higher CP level (56.10% and 63.09%) had significantly higher energy retention (ER) and lipid retention (LR) than other treatments. Based on the broken‐line regression analysis of SGR and FCR, the optimal dietary protein requirement for juvenile kelp grouper is 54.61%–56.22%.     

Effects of dietary protein to energy ratios on growth,body composition and digestive enzyme activities in Chinese mitten‐handed crab,Eriocheir sinensis

This study aimed to determine the optimal protein to energy ratio (P/E ratio) and evaluate the effect of dietary protein and lipid levels on growth performance, body composition and digestive enzymes activities in Chinese mitten‐handed crab, Eriocheir sinensis. Nine practical diets containing three levels both for protein (DP 30%, 35% and 40%) and lipid (DL 2%, 7% and 12%) with P/E ratios ranging from 13.69 to 19.79 mg KJ^?1 were fed to four replicates of crabs (3.39 ± 0.10 g) for 10 weeks. Weight gain increased significantly with the increase in DP level at each DL level. Moreover, weight gain increased in crabs fed with diets containing DL level from 2% to 12% and DP level from 30% to 35%. However, the diet containing 40% DP and 12% DL levels significantly decreased the growth performance and protein efficiency of the crabs. The whole crab and hepatopancreas lipid contents also increased as dietary lipid increased, but not dietary protein. The total protease activity increased significantly with the increase in dietary protein at each lipid level. The lipase activity was statistically comparable among different DL levels at each DP level. Taken together, the crab fed the diet containing 35% protein and 12% lipid levels with P/E 15.77 mg KJ^?1 revealed optimal growth, feed utilization efficiency and digestive enzymes activities. Moreover, our study indicated that the higher dietary lipid level at a relatively lower dietary protein level could provide protein sparing effect in Eriocheir sinensis.     

Effects of varying dietary protein to lipid ratios on growth performance and body composition of juvenile pike perch (Sander lucioperca)

The present study investigated the effect of varying dietary protein‐to‐lipid ratios (P/L) on growth performance and body composition of pike perch (Sander lucioperca) fingerlings with an initial body weight of 1.35–1.40 g. Triplicate groups were reared during 56 days in recirculation systems and fed six experimental diets containing three dietary levels of lipid (90, 130, 170 g kg^?1 of dry matter, d.m.) combined with two levels of dietary protein (470, 540 g kg^?1 d.m.). During the experimental period the fixed feeding rates decreased from 10% to 5% of the total fish biomass per day. In contrast to previous results obtained with this species, the present study clearly demonstrated the occurrence of protein sparing effect. The best results for feed conversation ratio and specific growth rates were obtained in the treatments containing highest lipid level: diet 3 (P/L 47/17) and diet 6 (P/L 53/17). The d.m. and crude lipid contents of pike perch whole body increased in direct proportion of the dietary lipid levels. No difference was observed on crude protein and ash content among the treatments. Increasing hepatosomatic index at highest dietary lipid level suggested a limited lipid utilization of percids.     

Induced maturation and fertilized egg production of the red‐spotted grouper,Epinephelus akaara,using adaptive physiology of photoperiod and water temperature

As a preliminary investigation into the effects of environmental factors on gonadal development using adaptive physiological characteristics, we examined the involvement of photoperiod and water temperature in the ovarian development of the red‐spotted grouper, Epinephelus akaara. During October 2014 (non‐breeding season), the photoperiod and water temperature were adjusted to 12L:12D and 18°C respectively. Every 3 weeks, daylight was increased as follows a 13L:11D and 14L:10D in the photo‐thermal treatment group, and the control group was maintained under natural conditions. After 9 weeks, water temperature was increased to 23°C in the photo‐thermal treatment group. In photo‐thermal treatment group, GSI increased significantly after 9 weeks (1.36 ± 0.19) and 12 weeks (3.31 ± 0.20) compared with the control group. At 12 weeks after photo‐thermal treatment, all fishes matured into ovaries containing late vitellogenic oocytes. The expression of FSHβ and LHβ mRNAs also increased significantly. However, in the control group, the ovarian development was maintained at an immature stage. Based on these results, we demonstrate that exposure to long photoperiod and high water temperature can induce the sexual maturation of immature red‐spotted grouper during the non‐breeding season.     

不同蛋白质水平下添加小肽对石斑鱼生长、消化酶、血清生化和抗氧化能力的影响

设计6组实验,测定在3种不同饲料蛋白质水平（44%,48%,52%）下添加2种水平的小肽（0.05%,0.1%）对赤点石斑鱼（Epinephelus akaara）生长、消化酶、血清生化和抗氧化能力的影响。饲料分别为D1（44%,0.05%）,D2（44%,0.1%）,D3（48%,0.05%）,D4（48%,0.1%）,D5（52%,0.05%）,D6（52%,0.1%）。每组饲料3个平行,每个玻璃钢纤维桶（500 L）放15尾石斑鱼[初始体质量（42.16±0.23）g],实验进行8周。结果显示,各组石斑鱼增重、特定生长率、肌肉粗蛋白、脂肪和灰分无显著差异,随着蛋白质和小肽水平的增加,肌肉粗脂肪、血清胆固醇和甘油三酯质量浓度降低（P<0.05）;胃蛋白酶活性在d2组最高,小肽对肠道淀粉酶、胰蛋白酶和脂肪酶活性不存在显著影响,在d1组活性较高（p>0.05）;各组石斑鱼肝脏丙二醛和过氧化物酶差异不显著（P>0.05）。由上述结果可以看出在不同蛋白质水平下添加小肽可以降低石斑鱼的蛋白需求,促进脂肪代谢,增加消化酶活性。 

     

饲料蛋白质和脂肪水平对赤眼鳟生长和鱼体营养成分的影响

采用3×3因子试验设计,配制9种试验饲料,研究饲料不同蛋白质水平(31%、37%和43%)和脂肪水平(3.5%、5.5%、7.5%)对平均体重为5.49 g赤眼鳟(Squaliobarbus curriculus)鱼种生长和鱼体组成的影响。实验选取赤眼鳟鱼种810尾,随机分成9组,每组2个重复,饲养期6周。结果显示:饲料蛋白质和脂肪的交互作用对赤眼鳟的特定生长率有显著影响(P<0.05),饲料蛋白质水平对饲料系数影响显著(P<0.05),当饲料蛋白质水平为37%、脂肪水平为3.5%时赤眼鳟特定生长率最大,饲料系数最低。随着特定生长率的升高,赤眼鳟的肥满度和肌肉蛋白质的含量升高;赤眼鳟肌肉和肝脏脂肪含量均随着饲料中可消化能的增加而增加。     

Growth,feed utilization and body composition of juvenile Manchurian trout,Brachymystax lenok (Pallas) fed different dietary protein and lipid levels

A 10‐week feeding trial with four dietary protein levels (400, 450, 500 and 550 g kg^?1 crude protein) and two dietary lipid levels (80 and 160 g kg^?1 crude lipid) was conducted to assess optimum dietary protein and lipid levels for the growth, feed utilization and body composition of juvenile Manchurian trout (initial weight 11.80 ± 0.15 g). Fish were fed twice daily (08:30 and 16:30 h) to apparent satiation. The results showed that fish fed the diet with 500 g kg^?1 protein and 80 g kg^?1 lipid had the highest growth and feed efficiency. However, fish fed the diet with 450 g kg^?1 protein and 160 g kg^?1 lipid showed comparable growth to that of the fish fed diet 5 (500/80) and had higher protein efficiency ratio (PER), nitrogen retention (NR) and energy retention (ER) than other groups (P < 0.05). Growth, PER, NR and ER of fish fed the 160 g kg^?1 lipid diet was significantly higher (P < 0.05) than that of fish fed the 80 g kg^?1 lipid diet at 400 and 450 g kg^?1 protein diet, whereas these values showed an opposite trend at 500 and 550 g kg^?1 protein diet, and the lowest PER, NR and ER was found by fish fed the 400 g kg^?1 protein diet with 80 g kg^?1 lipid. Fish fed diets with 400 g kg^?1 protein had lower feed intake (FI) than that of other groups. Feed intake of fish fed 80 g kg^?1 lipid level was significantly lower than that of fish fed 160 g kg^?1 lipid diet at 400 g kg^?1 protein (P < 0.05), while no significant differences were observed at 450, 500 and 550 g kg^?1 protein‐based diets. Contrary to moisture content, lipid content of whole body and muscle increased significantly (P < 0.05) with increasing lipid levels. The results of this study indicated that the diet containing 450 g kg^?1 protein and 160 g kg^?1 lipid, with a P/E ratio of 23.68 g protein MJ^?1 would be suitable for better growth and feed utilization of juvenile Manchurian trout under the experimental conditions and design level used in this study.     

Growth,precocity, enzyme activity and chemical composition of juvenile Chinese mitten crab,Eriocheir sinensis,fed different dietary protein‐to‐energy ratio diets

A growth experiment was conducted to determine the optimum dietary protein‐to‐energy (P/E) ratio of juvenile Chinese mitten crab Eriocheir sinensis. Six practical diets were formulated with P/E ratios ranging from 15.94 to 21.25 g protein MJ^?1 gross energy (g MJ^?1). Results showed that specific growth rates related with molting were significantly affected by dietary P/E ratio (P < 0.05). The specific growth rates both in body weight (SGRw) and carapace width (SGRcw) for the entire experimental period were not significantly affected by dietary P/E ratio (P > 0.05). Molting frequency, survival rate and crab body composition were also significantly affected by dietary P/E ratio (P < 0.05). Rate of precocity displayed negative trends with growth rate, and the trend with SGRcw was significant (P < 0.01). The activities of alkaline phosphatase, trypsinase and steapsin were significantly affected by dietary P/E ratio (P < 0.05). Molting frequency (P < 0.001), SGRw1‐2 (P < 0.05) and SGRw0‐2 (P < 0.05) were positively and significantly related to alkaline phosphatase activity. We recommend 18.13–19.20 g MJ^?1 as the optimum dietary P/E ratio for juvenile E. sinensis, based on growth performance, rate of precocity and digestive enzyme activities.     

Effects of dietary protein and lipid levels on growth,body composition and flesh quality of juvenile topmouth culter,Culter alburnus Basilewsky

Nine experimental diets at three protein (35%, 40% and 45% crude protein) and lipid (5%, 8% and 11% crude lipid) levels with variable digestible protein to digestible energy (DP/DE) ratios ranged from 21.9 to 27.8 g protein MJ^?1 were fed to topmouth culter (Culter alburnus Basilewsky) fingerlings (initial weight 6.5 ± 0.9 g) in triplicated groups (30 fish per replicated) for a period of 10 week to assess the optimum dietary DP/DE ratio and the protein sparing effect by utilizing dietary lipid. 27 cages of 1.5 m³ capacity placed in a lake located in Wuhan were used for rearing the fish. At the end of the experiment, maximum weight gain and thermal‐unit growth coefficient was found in fish fed diet D4 with 45% protein, 8% lipid and P/E ratio of 26.2 g protein MJ^?1, but without a significant difference compared to fish fed diet D5 with 40% protein, 8% lipid and DP/DE ratio of 25.3 g protein MJ^?1. The best flesh quality evaluated by muscle collagen content was found in fish fed D5. High fat accumulation with increasing dietary lipid levels was observed in whole body but not in muscle tissue. Hence, it may be concluded that the optimum formulation for maximum growth and quality of topmouth culter is a diet containing 40% protein and 8% lipid with a resultant DP/DE ratio of 25.3 g protein MJ^?1. In addition, the protein sparing effect by inclusion lipid was observed but limited.     

Effects of dietary protein to energy ratios on growth and body composition of juvenile Chinese sucker,Myxocyprinus asiaticus

A growth experiment was conducted to investigate effect of dietary protein to energy ratios on growth and body composition of juvenile Myxocyprinus asiaticus (initial mean weight: 10.04 ± 0.53 g, mean ± SD). Nine practical diets were formulated to contain three protein levels (340, 390 and 440 g kg^?1), each with three lipid levels (60, 100 and 140 g kg^?1), in order to produce a range of P/E ratios (from 22.4 to 32.8 mg protein kJ^?1). Each diet was randomly assigned to triplicate groups of 20 fish in 400‐L indoors flow‐through circular fibre glass tanks provided with sand‐filtered aerated freshwater. The results showed that the growth was significantly affected by dietary P/E ratio (P < 0.05). Fish fed the diets with 440 g kg^?1 protein (100 and 140 g kg^?1 lipid, P/E ratio of 31.43 and 29.22 mg protein kJ^?1) had the highest specific growth rates (SGR) (2.16 and 2.27% day^?1, respectively). However, fish fed the diet with 390 g kg^?1 protein and 140 g kg^?1 lipid showed comparable growth (2.01% day^?1), and had higher protein efficiency ratio (PER), protein productive value (PPV) and energy retention (ER) than other groups (P < 0.05). No significant differences in survival were found among dietary treatments. Carcass lipid content was positively correlated with dietary lipid level, but irrespective of protein level and inversely correlated with carcass moisture content. Carcass protein contents increased with increasing dietary lipid at each protein level. The white muscle and liver composition showed that lipid increased with increasing dietary lipid level (P < 0.05). Dietary protein concentrations had significant effect on condition factor (CF), hepatosomatic index (HSI) and viscerosomatic index (VSI) (P < 0.05). However, dietary lipid concentrations had no significant effect on CF, HSI (P > 0.05). Based on these observations, 440 g kg^?1 protein with lipid from 100 to 140 g kg^?1 (P/E ratio of 29.22 to 31.43 mg protein kJ^?1) seemed to meet minimum requirement for optimal growth and feed utilization, and lipid could cause protein‐sparing effect in diets for juvenile Chinese sucker.     

Effect of dietary lipid and protein levels with different protein to energy ratios on growth performance,feed utilization and body composition of Rutilus frisii kutum (Kamenskii, 1901) fingerlings

A 3 × 5 factorial design including three lipid levels (100, 130 and 180 g kg^?1 diet, based on dry matter) and five dietary protein levels (370, 420, 470, 520 and 570 g kg^?1 diet, based on dry matter) was conducted to investigate the optimum dietary lipid and protein requirements for Rutilus frisii kutum fingerlings. Triplicate groups of 80 kutum (500 ± 60 mg initial weight) were stocked in 250‐l tanks and fed to apparent satiation thrice daily for 8 weeks. The results showed that the growth performance and feed utilization were significantly (P < 0.05) affected by dietary protein and lipid levels. Weight gain, specific growth rate and feed conversion ratio of kutum improved significantly with increasing protein level from 370 to 470 g protein kg^?1 diet, but there was a significant decrease in growth parameters with increasing protein level from 470 to 570 g protein kg^?1 diet. Also, the higher values of weight gain, specific growth rate and better feed conversion ratio were observed for fish fed diets containing 130 g kg^?1 lipid diet. The results of this study showed that diet containing 420 g kg^?1 protein and 130 g kg^?1 lipid with a P:E ratio of 19.22 mg protein kJ^?1 of gross energy is optimal for kutum fingerlings.     

Effects of dietary choline on growth performance,lipid deposition and hepatic lipid transport of grouper (Epinephelus coioides)

The number of 360 individuals with an average initial weight of 87.8 ± 0.04 g was fed six diets containing graded levels of choline at 8.1 (control group), 602.5, 1119.0, 1511.5, 1970.0 and 4029.0 mg choline kg^?1 diet, respectively, to investigate the effects of dietary choline on growth performance, lipid deposition and hepatic lipid transport for grouper, Epinephelus coioides. Dietary methionine was estimated to be 10.02 g kg^?1, less than the requirement (13.10 g kg^?1). The results of 10‐week study period indicated that the best values of specific growth rate (SGR), feed conversion rate (FCR) and protein efficiency rate (PER) all occurred in 1119.0 mg choline kg^?1 diet (P < 0.05). The survival range increased from 8.1 to 1511.5 mg choline kg^?1 diet and then plateaued. Dietary choline supplementation significantly decreased the liver lipid content of grouper (P < 0.05), but the lipid content of the muscle tended to be increased firstly and then decreased (P < 0.05). Liver choline concentration reached a plateau in 1511.5 mg choline kg^?1 diet and then levelled off (P < 0.05). Serum high density lipoprotein‐cholesterol (HDL‐C) and total cholesterol (TCHO) levels were firstly decreased and then increased with dietary choline supplementation. A reversed tendency, however, was found in triglyceride. Broken‐line regression analysis of SGR and liver choline content indicated that choline requirement of grouper was 1093.7 and 1579.7 mg kg^?1 diet, respectively.     

Growth and body composition of juvenile white shrimp,Litopenaeus vannamei,fed different ratios of dietary protein to energy

A 10‐week feeding experiment was conducted to evaluate the effect of different protein to energy ratios on growth and body composition of juvenile Litopenaeus vannamei (initial average weight of 0.09 ± 0.002 g, mean ± SE). Twelve practical test diets were formulated to contain four protein levels (300, 340, 380 and 420 g kg^?1) and three lipid levels (50, 75 and 100 g kg^?1). Each diet was randomly fed to triplicate groups of 30 shrimps per tank (260 L). The water temperature was 28.5 ± 2 °C and the salinity was 28 ± 1 g L^?1 during the experimental period. The results showed that the growth was significantly (P < 0.05) affected by dietary treatments. Shrimps fed the diets containing 300 g kg^?1 protein showed the poorest growth. However, shrimp fed the 75 g kg^?1 lipid diets had only slightly higher growth than that fed 50 g kg^?1 lipid diets at the same dietary protein level, and even a little decline in growth with the further increase of dietary lipid to 100 g kg^?1. Shrimp fed the diet with 420 g kg^?1protein and 75 g kg^?1 lipid had the highest specific growth rate. However, shrimp fed the diet with 340 g kg^?1 protein and 75 g kg^?1 lipid showed comparable growth, and had the highest protein efficiency ratio, energy retention and feed efficiency ratio among dietary treatments. Triglycerides and total cholesterol in the serum of shrimp increased with increasing dietary lipid level at the same dietary protein level. Body lipid and energy increased with increasing dietary lipid level irrespective of dietary protein. Results of the present study showed that the diet containing 340 g kg^?1 protein and 75 g kg^?1 lipid with digestible protein/digestible energy of 21.1 mg kJ^?1 is optimum for L. vannamei, and the increase of dietary lipid level has not efficient protein‐sparing effect.