Dietary methionine requirement of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to determine the optimum dietary methionine (Met) requirement of juvenile Pseudobagrus ussuriensis with an initial average weight of 0.60 g reared in indoor flow‐through and aerated aquaria. Six isonitrogenous (430 g kg^?1 protein) and isolipidic (50 g kg^?1 lipid) test diets were formulated to contain graded levels of crystalline L‐methionine (4.9, 9.0, 11.8, 14.2, 18.1 and 20.8 g kg^?1 dry diets, respectively) at a constant dietary cystine level of 2.5 g kg^?1 dry diets. Equal amino acid nitrogen was maintained by replacing methionine with non‐essential amino acid mixture. Fish were randomly allotted to 18 aquaria (1.0 × 0.5 × 0.8 m) with 50 fish to each glass aquarium. Fish were fed twice daily (08:00 and 16:00) to apparent satiation. No significant difference was observed in survival of fish (84.67–91.33%). Specific growth rate (SGR), weight gain (WG), feed conversion ratio (FCR), protein productive value (PPV) and protein efficiency ratio (PER) were significantly affected by different dietary methionine levels (P < 0.05). WG, SGR PPV and PER increased, while FCR decreased with increasing dietary methionine level from 4.9 to 11.8 g kg^?1 (P < 0.05). However, with further increase from 11.8 to 20.8 g kg^?1, WG, SGR PPV and PER significantly decreased, FCR increased (P < 0.05). The whole body and muscle composition were affected by different dietary methionine levels (P < 0.05). Condition factor (CF) increased with increasing dietary methionine levels up to 11.8 g kg^?1 (P < 0.05) and after 11.8 g kg^?1 methionine diet, but not significant, declines were observed (P > 0.05). Hepatosomatic index (HSI) of the 4.9, 9.0, 11.8 and 14.2 g kg^?1 Met diets was significantly higher than that of fish fed diets 18.1 and 20.8 g kg^?1 Met diets (P < 0.05). Viscerosomatic index (VSI) of the 4.9, 9.0 and 11.8 g kg^?1 Met diets was significantly higher than that of fish fed diets 14.2, 18.1 and 20.8 g kg^?1 Met diets (P < 0.05). Quadratic regression analysis of WG and PER against dietary methionine levels indicated that the optimal dietary methionine requirement for maximum growth and feed utilization of juvenile Pseudobagrus ussuriensis was 14.3 and 14.1 g kg^?1 dry diet (35.3 and 34.8 g kg^?1 dietary protein), respectively, in the presence of 2.5 g kg^?1 dry diets cystine.     

Dietary lysine requirement of juvenile Protonibea diacanthus

An 8‐week experiment was conducted to determine the optimal dietary lysine requirement for juvenile Protonibea diacanthus. Six isonitrogenous and isolipidic diets were formulated to contain levels of 10.8 (L10.8), 18.2 (L18.2), 26.1 (L26.1), 33.9 (L33.9), 40.7 (L40.7) and 48.6 g/kg (L48.6) of diets and were fed to the juvenile Protonibea diacanthus, respectively. The results indicated that weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and final weight (FW) increased as the dietary lysine level increased from 10.8 to 26.1 g/kg and then decreased as the dietary lysine levels further increased (p < .05). The lowest feed conversion ratio (FCR) was found when dietary lysine level was 26.1 g/kg. Analysis of specific growth rate by two slope broken‐line model indicated that the estimated optimal dietary levels of lysine for juvenile Protonibea diacanthus was 23.06 g/kg (51.24 g/kg dietary protein).     

Effects of dietary protein and lipid levels on growth,feed utilization and body composition in Pseudobagrus ussuriensis fingerlings

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.     

Apparent digestibility coefficients of animal and plant feed ingredients for juvenile Pseudobagrus ussuriensis

A study was conducted to determine apparent digestibility coefficients (ADCs) of dry matter (DM), crude protein (CP), lipid, gross energy, phosphorus and amino acids (AAs) from Peruvian fish meal (PFM), native fish meal (NFM), meat bone meal (MBM), dried daphnia meal (DDM), soybean meal (SBM), full‐fat soybean (FSBM), cottonseed meals (CSM), rapeseed meal (RSM) and corn gluten meal (CGM) for Pseudobagrus ussuriensis (7.8 ± 0.06 g). Test diets were formulated to contain a 70:30 mixture of reference diet to test ingredient with chromic oxide (5 g kg^–1) serving as the inert marker. ADCs of DM ranged from 49.94% (CGM) to 87.11% (PFM), the highest ADCs of DM were observed in PFM and the lowest was found in CGM. ADCs of CP in the test ingredients ranged from 74.92% (CGM) to 93.41% (SBM). ADCs of crude lipid ranged from 51.80% (CGM) to 94.07% (PFM) for fish. ADCs of energy ranged from 56.42% (CGM) to 90.09% (PFM). ADCs of phosphorus ranged from 21.81% (CSM) to 65.70% (PFM). AA availability for the test ingredients followed a similar pattern to ADCs of CP, in which values for PFM, NFM and MBM were generally higher (p < .05) than those of other protein ingredients. Among all plant meals, the AA availability values in SBM were higher (p < .05) than those in CGM, CSM and RSM. The availability of most AAs in CGM was the lowest (p < .05) among all tested ingredients. In conclusion, PFM and NFM are good sources of available protein and AAs. When fishmeal supply is limited, MBM and DDM are substitutes for fishmeal reduction in P. ussuriensis diets; at the same time, SBM and FSBM are also very acceptable protein feedstuffs. However, CSM, RSM and CGM could not be used at high levels in P. ussuriensis diets because of their inferior digestibilities.     

Effect of replacing fish meal with soybean meal on growth,feed utilization and nitrogen and phosphorus excretion of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to evaluate the effects of replacing fish meal with soybean meal (SBM) on growth, feed utilization, and nitrogen (N) and phosphorus (P) excretion of juvenile Pseudobagrus ussuriensis (initial average weight 0.50 ± 0.00 g). Seven isonitrogenous and isolipidic diets were formulated to contain SBM to replace fish meal protein at 0% (S0), 10% (S10), 20% (S20), 30% (S30), 40% (S40), 50% (S50) and 60% (S60) respectively. To investigate the effects of supplementation with crystalline amino acid to balance diet S60, one diet was formulated to add 0.30% methionine (SM60). The results showed that there was no significant difference in weight gain among fish fed S0, S10, S20, S30 and S40 diets, however, a significant reduction in this variable occurred when 50% and 60% of fish meal protein was replaced by SBM (P < 0.05). Apparent digestibility coefficients of dry matter, crude protein and phosphorus of diets were affected by dietary SBM levels. N and P excretion indicate that fish meal replacement by SBM led to an increase in N excretion, but led to a reduction in P excretion. No differences were detected in growth, feed utilization and N and P excretion between fish feed diets S60 and SM60. The results of this study show that 40% of fish meal protein could be replaced by SBM in diets of juvenile P. ussuriensis without having a significant negative effect on growth or feed efficiency, but that higher dietary SBM levels reduce fish performance.     

A study on dietary l‐lysine requirement of juvenile yellow catfish Pelteobagrus fulvidraco

An 8‐week feeding trial was conducted to determine lysine requirement of juvenile yellow catfish (Pelteobagrus fulvidraco) by feeding formulated diets containing crystalline l ‐lysine. Six isonitrogenous and isoenergetic diets (405 g kg^?1 protein, 18 kJ g^?1 gloss energy) containing fish meal together with soybean protein concentrate as protein sources and fish oil together with soybean oil as lipid sources were formulated. Crystalline l ‐lysine was added into the six diets to acquire lysine concentrations of 17.3, 21.8, 26.0, 31.3, 35.5 and 41.9 g kg^?1 dry diets, respectively. Mixture of crystalline amino acid was supplemented to simulate the amino acid profile in muscle of yellow catfish. The results indicated that final body weight (FBW), weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency (PE) increased with the increase in dietary lysine level from 17.3 to 31.3 g kg^?1 of diet and then decreased as the dietary lysine levels further increased. No significant difference in survival rate was found among all the dietary treatments. One‐slope, quadratic broken‐line analysis on the basis of SGR showed that the dietary l ‐lysine requirement of juvenile yellow catfish was 33.1 g kg^?1 of dry diet (83.2 g kg^?1 of dietary protein).     

Partial fishmeal replacement by mussel meal or meat and bone meal in low‐fishmeal diets for juvenile Ussuri catfish (Pseudobagrus ussuriensis): Growth,digestibility, antioxidant capacity and IGF‐I gene expression

This study evaluated the effects of replacing fishmeal with mussel meal or meat and bone meal in low‐FM diet on growth performance, body composition, digestibility, antioxidant capacity and IGF‐I gene expression in juvenile Ussuri catfish (Pseudobagrus ussuriensis). The results showed that no significant changes in SGR, FE and PER were observed between MM₄₀ and LFM groups, but significantly reduced result was found in MBM₄₀ group. MM₄₀ group showed the higher ADC of lipid (93.30%) and lipase activity (95.00 U/gprot) than LFM group (90.97%; 70.18 U/gprot). MM₄₀ or MBM₄₀ diets led to significant reduction of SOD and CAT activities. MM₄₀ group showed significantly higher MDA level (5.84 nmol/mg) than LFM group (4.73 nmol/mg). The activities of LZM decreased significantly in MM₄₀ and MBM₄₀ groups compared with LFM group. MM₄₀ and MBM₄₀ groups showed no significant difference in hepatic IGF‐I gene expression levels compared with LFM group. The findings demonstrated that MM could substitute 400 g/kg of FM in low‐FM diet for Ussuri catfish without influencing the growth, but to some extent, spontaneous oxidative stress and immune damage could occur; when 400 g/kg of FM was replaced by MBM, significantly negative effects were observed on growth, antioxidant capacity and non‐specific immune response of Ussuri catfish.     

Optimal dietary methionine requirement of juvenile Chinese sucker,Myxocyprinus asiaticus

A total of 630 juvenile Chinese sucker, with an average initial weight of 1.72 ± 0.05 g, were fed seven diets for 56 days to study the effect of dietary methionine levels on growth, feed utilization, body composition and haematological parameters on juvenile Chinese sucker. Diet 1 using fish meal as the sole protein source and diets 2–7 using fish meal and fermented soybean meal as intact protein sources supplemented with crystalline amino acids contained six levels of l ‐methionine ranging from 6.4 to 18.9 g kg^?1 of dry diet at a constant dietary cystine level of 3.7 g kg^?1. Each diet was randomly assigned to three aquaria. Results indicated that the highest weight gain, specific growth rate (SGR), feed efficiency ratio, protein efficiency ratio and protein productive value occurred at 13.9 g methionine kg^?1 diet among the methionine supplemented dietary groups, beyond which they showed declining tendency. The whole body and muscle protein contents of juvenile Chinese sucker were positively correlated with dietary methionine level, while muscle lipid content was negatively correlated with it. The total essential amino acids content of muscle was increased significantly with increasing dietary methionine level from 6.4 to 13.9 g kg^?1 (P < 0.05). Apparent digestibility coefficients of dietary protein were significantly affected by dietary treatments. Serum protein, cholesterol and triacylglycerol increased with increasing dietary methionine levels, but showed a relatively lower value for fish fed the 18.9 g methionine kg^?1 diet. Quadratic regression analysis of SGR against dietary methionine level indicated that optimal dietary methionine requirement for juvenile Chinese sucker was 14.1 g kg^?1 of the diet in the presence of 3.7 g kg^?1 cystine (corresponding to 32.0 g kg^?1 of dietary protein on a dry‐weight basis).     

Dietary l‐lysine requirement of juvenile Chinese sucker,Myxocyprinus asiaticus

An 8‐week feeding trial was conducted to quantify the dietary l ‐lysine requirement of juvenile Chinese sucker with an initial weight of 1.81 ± 0.04 g reared in indoor flow‐through and aerated tanks. Six isonitrogenous and isoenergetic practical diets were formulated to contain graded levels of lysine (1.23%, 1.80%, 2.39%, 2.98%, 3.56% and 4.18% dry matter) at 0.6% increments from dietary ingredients and crystalline l ‐lysine. Each diet was randomly assigned to triplicate groups of 30 fish each and was fed to apparent satiation by hand three times a day (09:00, 13:00 and 17:00 hours) for 8 weeks. There were significant differences in growth performance and feed utilization among the treatments. Weight gain (WG), specific growth rate and protein efficiency ratio (PER) significantly increased with increasing lysine levels up to 2.39% of diet (P < 0.05) and remained nearly the same thereafter (P > 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (P < 0.05) and showed no significant differences when dietary lysine level increased from 2.39% to 4.18%. The N retention (% N intake) significantly increased with dietary lysine level but did not attain a plateau (P < 0.05). Survival could not be related to dietary treatments. Whole body protein increased (P < 0.05) and whole body lipid decreased (P < 0.05) with increasing dietary lysine level. The condition factor and hepatosomatic index were significantly affected by dietary lysine levels, however, viscersomatic index, whole body moisture and ash did not differ significantly among dietary treatments. Broken‐line analysis on the basis of WG and PER showed that dietary lysine requirements of juvenile Chinese sucker were 2.43% and 2.40% dry diet (5.52% and 5.45% dietary protein) respectively. Based on the ideal protein approach and the A/E ratios determined from muscle amino acid profile an estimation of the EAA requirements of Chinese sucker juveniles were calculated.     

Effects of replacing fish meal with corn gluten meal on growth,feed utilization,nitrogen and phosphorus excretion and IGF‐I gene expression of juvenile Pseudobagrus ussuriensis

Seven isonitrogenous and isolipidic diets containing fish meal (FM) protein replaced by corn gluten meal (CGM) protein at 0% (the control, C0), 10% (C10), 20% (C20), 30% (C30), 40% (C40), 50% (C50) and 60% (C60) were fed to juvenile Pseudobagrus ussuriensis for 8‐weeks to evaluate the effects of FM protein replaced by CGM protein on growth, feed utilization, nitrogen (N) and phosphorus (P) excretion and IGF‐I gene expression of juvenile P. ussuriensis. The results showed that the replacement level up to 40% did not affect the weight gain, specific growth rate (SGR), feed intake and protein efficiency ratio, whereas these parameters were depressed by further replacement level. Apparent digestibility coefficients (ADC) of dry matter, crude protein significantly decreased, but ADC of phosphorus significantly increased with increasing dietary CGM levels (p < .05). Fish fed diets with FM protein replaced by CGM protein led to an increase in nitrogen excretion, but led to a reduction in phosphorus excretion. No significant differences were observed in alpha‐amylase and lipase activities of intestine (p > .05). The lowest pepsin activity was found in C60 group. Fish fed diet C40, C50 and C60 had significantly lower serum lysozyme activity compared with fish fed diet C0 (p < .05). The lowest plasma alkaline phosphatase activity and the highest plasma alanine aminotransferase and aspartate aminotransferase activities were observed in C60 group. Fish fed diet C60 had significantly lower hepatic IGF‐I gene expression compared with fish fed diet C10 (p < .05). Broken‐line model analysis based on SGR against the CGM substitution level indicated that the appropriate replacement level was 37.7%.     

Effect of replacing fish meal with meat and bone meal on growth,feed utilization and nitrogen and phosphorus excretion for juvenile Pseudobagrus ussuriensis

The effect of replacing fish meal (FM) with meat and bone meal (MBM) in diets for juvenile Pseudobagrus ussuriensis was evaluated in a 90‐day feeding trial. Six isonitrogenous (crude protein, 430 g/kg) and isolipidic (crude lipid, 74 g/kg) diets were formulated to contain MBM to replace FM at 0 (S0), 200 (S20), 400 (S40), 600 (S60), 800 (S80) and 1000 g/kg (S100), respectively. The results showed that there was no significant difference in weight gain (WG) among fish fed S0, S20 and S40 diets. However, a significant reduction in WG occurred when 600, 800 and 1000 g/kg FM protein was replaced by MBM (p < .05). Similar trends were observed in specific growth rate and protein efficiency ratio. Apparent digestibility coefficients (ADC) of protein and dry matter of the diets S80 and S100 were significantly lower than those of the other diets. The ADC of phosphorus significantly reduced with the increase in dietary MBM level. Nitrogen and phosphorus excretion increased with the increasing dietary MBM level. Protease, lipase and amylase activities of the diets S80 and S100 were significantly lower than those of the other diets (p < .05). The results of this study showed that the optimum dietary MBM replacement level was 34.3% according to broken‐line model based on WG against dietary MBM replacement level.     

Induction of meiotic gynogenesis in bagrid catfish (Pseudobagrus ussuriensis) with homologous sperm and its confirmation for female homogamety

The bagrid catfish, Pseudobagrus ussuriensis, exhibits significant sexual dimorphism in growth rate and body size with males growing faster than females. Therefore, an all‐male culture can dramatically increase the output and profitability of fishery products. According to the monosex breeding route, super‐male individuals’ acquirement by XY male sex reversal and artificial gynogenesis is the key step. An effective protocol to induce meiotic gynogenesis using homologous sperms has been developed in this study. The most effective UV irradiation for sperm genetic inactivation was found to be at a distance of 20 cm with 66 μW/cm² light intensity for 25 min. Optimal treatment for cold shock was 5 min post‐fertilization at 0‐4°C for 30 min, which gave the best survival rate of 13.65 ± 2.87%. The sex ratio in the meiotic gynogens showed a significant female‐biased deviation (p < .05); thirty meiogynogens and their parents were further analysed using a male‐specific AFLP marker, of which only the male parent produced a male‐specific DNA band of 412 bp. These results indicated the female homogametic XX/XY sex determination system in P. ussuriensis. The optimization of a protocol for the successful induction of meiogynogenesis in the bagrid catfish lays the basis for all‐male production and is useful in ascertaining the genetic sex determination system in this promising aquaculture species.     

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%.     

Quantitative l‐lysine requirement of juvenile black sea bream (Sparus macrocephalus)

An 8‐week feeding experiment was conducted to determine the quantitative l ‐lysine requirement of juvenile black sea bream Sparus macrocephalus (initial mean weight: 9.13 ± 0.09 g, SD) in eighteen 300‐L indoors flow‐through circular fibreglass tanks provided with sand‐filtered aerated seawater. The experimental diets contained six levels of l ‐lysine ranging from 20.8 to 40.5 g kg^?1 dry diet at about 4 g kg^?1 increments. All the experiment diets were formulated to be isoenergetic and isonitrogenous. Each diet was assigned to triplicate groups of 20 fish in a completely randomized design. Weight gain and specific growth rate (SGR) increased with increasing levels of dietary lysine up to 32.5 g kg^?1 (P < 0.05) and both showed a declining tendency thereafter. Feed efficiency ratio and protein efficiency ratio was poorer for fish fed the lower lysine level diets (P < 0.05) and showed no significant differences among other treatments (P > 0.05). All groups showed high survival (above 90%) and no significant differences were observed. The whole body crude protein and crude lipid contents were significantly affected (P < 0.05) by dietary lysine level, while moisture and ash showed no significant differences. The composition of muscle and liver also presented similar change tendency. Total essential amino acid and lysine contents in muscle both obtained the highest value when fish fed 32.5 g kg^?1 lysine diet (P < 0.05). Serum protein, cholesterol and free lysine concentration were affected by different dietary treatments (P < 0.05), triacylglyceride and glucose contents were more variable and could not be related to dietary lysine levels. Dietary lysine level significantly affected condition factor and intraperitoneal fat ratio of juvenile black sea bream (P < 0.05) except for hepatosomatic index. There were no significant differences in white blood cell count and red blood cell count (P > 0.05), however, haemoglobin level was significantly influenced by different diets (P < 0.05). Analysis of dose (lysine level)‐response (SGR) with second order polynomial regression suggested the dietary lysine requirement of juvenile black sea bream to be 33.2 g kg^?1 dry diet or 86.4 g lysine kg^?1 protein.     

稚鳖赖氨酸营养的需要量

选择体重为(22.62±0.52)g稚鳖90只,平均分成6组,分别饲喂含赖氨酸为1.42、1.87、2.22、2.57、2.92和3.32%的等能等氮半合成饵料,试验期45d.结果表明,赖氨酸缺乏会降低鳖的生活力,导致其食欲下降、生长受阻、体蛋白沉积下降、肝生长受阻和赖氨酸-α-酮戊二酸还原酶活力下降(P＜0.01);赖氨酸对鳖的增重、饵料系数、体蛋白沉积量和净沉积率、体赖氨酸沉积量和净沉积率、肝重/体重和肝赖氨酸-α-酮戊二酸还原酶活力影响极显著(P＜0.01),并成极显著或显著二次回归关系(R2=0.7667-0.9594,P＜0.005～0.02).根据这些指标确定的赖氨酸需要量差异不明显,稚鳖赖氨酸需要量为2.40%或5.32g@(100gCP)-1.尽管赖氨酸对摄饵量和肝重也有极显著影响(P＜0.01),但是不呈显著二次回归关系(R2=0.3766-0.5990,P＞0.05).     

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

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

Dietary protein requirement of juvenile obscure puffer,Takifugu obscurus

A 10‐week feeding experiment was conducted to determine the optimum dietary protein requirement of juvenile obscure puffer (Takifugu obscurus). Six isoenergetic (20 MJ kg^?1 gross energy) diets were formulated to contain graded levels of 34%, 38%, 42%, 46%, 50% or 54% crude protein (as dry matter basis). The results showed final body weight, weight gain and specific growth rate (SGR) increased significantly with increasing protein levels up to 42% and then decreased thereafer. Second‐order polynomial regression analysis (y = ?0.0024x² + 0.1788x ? 1.3196, R² = 0.9032) indicated a maximum SGR at protein level of 37%. Feed conversion ratio (FCR) decreased with increasing levels of dietary protein up to 42% and increased thereafter. Second‐order polynomial regression analysis (y = 0.0054x² ? 0.4351x + 10.391, R² = 0.753) indicated a minimum FCR at protein level of 40%. Protein efficiency ratio (PER) of fish fed the 34%, 38% and 42% diets was significantly higher than that of fish fed the 46%, 50% and 54% diets, and broken‐line analysis indicated PER tended to decrease when dietary protein level was higher than 40%. Generally, whole body lipid content, total cholesterol, low‐density lipoprotein cholesterol and triacylglycerol decreased with increasing levels of dietary protein. Fish fed the 42% protein diet showed the highest essential amino acids (histidine, isoleucine, leucine, lysine and threonine) and non‐essential amino acids (aspartic acid and glutamic acid) in muscle. Based on the second‐degree polynomial regression analysis of SGR and FCR and broken‐line analysis of PER, the optimal dietary protein level of obscure puffer is estimated to be between 37% and 40% (% as dry matter basis).     

Dietary isoleucine requirement of juvenile blunt snout bream,Megalobrama amblycephala

A 9‐week feeding trial was conducted to estimate the dietary isoleucine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded isoleucine levels ranging from 5.3 to 20.1 g kg^?1 dry diet. At the end of the experiment, weight gain (WG), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) increased with increasing dietary isoleucine level up to 11.1 g kg^?1 dry diet, and dietary isoleucine level above 14.2 g kg^?1 dry diet declined these performances. Dietary isoleucine levels (14.2 and 17.3 g kg^?1 dry diet) significantly improved whole‐body protein content, but decreased whole‐body lipid, plasma triglyceride and cholesterol contents. Significantly lower visceral fat index (VFI) in fish fed with 14.2 g kg^?1 dietary isoleucine was observed compared to those fed with deficient or excessive isoleucine. Dietary isoleucine supplementation significantly increased plasma isoleucine concentration, while plasma valine and leucine concentrations showed a reversed trend. Dietary isoleucine levels regulated the target of rapamycin (TOR) gene expression and improved plasma superoxide dismutase (SOD) activity in juvenile blunt snout bream. Based on second‐order polynomial regression model analysis of SGR and FER, the optimum dietary isoleucine requirement was estimated to be 13.8 g kg^?1 dry diet (40.6 g kg^?1 dietary protein) and 14.0 g kg^?1 dry diet (41.2 g kg^?1 dietary protein), respectively.     

Quantitative l-lysine requirement of juvenile grouper Epinephelus coioides

An 8‐week feeding trial was conducted to determine the quantitative lysine requirement of juvenile grouper Epinephelus coioides (initial mean weight: 15.84 ± 0.23 g, mean ± SD) in eighteen 500‐L indoors flow‐through circular fibreglass tanks provided with sand‐filtered aerated seawater by feeding diets containing six levels of l ‐lysine ranging from 19.2 to 39.5 g kg^?1 dry diet in 4 g kg^?1 increments. The diets, in which 250 g crude protein kg^?1 diet came from fish meal and soybean protein concentrate, and 230 g kg^?1 from crystalline amino acids, were formulated to simulate the amino acid profile of 480 g kg^?1 whole chicken egg protein except for lysine. Each diet was assigned to three tanks in a completely randomized design. Grouper were fed to apparent satiation twice daily during the week and once daily on weekends. Weight gain and specific growth rate increased with increasing levels of dietary lysine up to 27.2 g kg^?1 (P < 0.05) and remained nearly the same thereafter (P > 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (P < 0.05) and showed no significant differences among other treatments (P > 0.05). Survival could not be related to dietary treatments. Body composition remained relatively constant except for lipid contents in muscle and liver. Total essential amino acid contents in liver increased with dietary lysine level although there was a slight decline for fish fed the highest lysine level of diet. Plasma protein content increased with increasing dietary lysine level (P < 0.05), but cholesterol, triacylglycerol and glucose contents were more variable and could not be related to dietary treatments. Dietary lysine level significantly influenced morphometrical parameters (condition factor, hepatosomatic index and intraperitoneal fat ratio) of juvenile grouper (P > 0.05). Broken‐line analysis of weight gain indicated the dietary lysine requirement of juvenile grouper to be 28.3 g kg^?1 diet or 55.6 g kg^?1 dietary protein.     

乌苏里拟鲿的染色体组型研究

采用体内注射PHA和秋水仙素,体内肾细胞短期培养,常规空气干燥法制备乌苏里拟鳞的染色体玻片标本.对100个中期分裂相记数统计,确定乌苏里拟鲿的染色体数为2n=52.由测得的核型参数和按Levan等提出的染色体划分标准得出:有12对中部着丝点染色体(m),9对亚中部着丝点染色体(sm),5对亚端部着丝点染色体(st).染色体臂数(NF)为94.乌苏里拟鳞组型公式为2 n=24m+18 s m+10st.