Digestibility of dietary components and amino acids in plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings

The apparent digestibility (AD) of dietary components, energy and essential amino acids (EAA) of selected locally available plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings was studied. The AD of the test ingredients (ADi) differed (P < 0.05) and ranged from 66.2 to 89.6% for ADi_DM, from 63.6 to 91.3% for ADi_CP, from 65.4 to 85.3% for ADi_OM and from 69.8 to 89.3% for ADi_GE. The highest ADi_DM, ADi_OM and ADi_GE in the test ingredients was obtained for broken rice, maize meal and soybean meal, while the lowest values were obtained for duckweed meal. Soybean meal and duckweed meal had the highest ADi_CP, while there were no differences (P > 0.05) between the other test ingredients. The AD of total and individual EAA was higher in soybean meal, duckweed meal and broken rice than in the other test feed ingredients (P < 0.05). The lowest AD of individual EAA was found in maize meal, followed by cassava leaf meal and sweet potato leaf meal (P < 0.05). The low AD of individual plant feed ingredients may limit their potential to be used as replacement for fish meal in the feed.     

Digestibility of dietary components and amino acids in animal and plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings

The apparent digestibility (AD) of dietary components, energy and essential amino acids (EAA) of selected locally available animal and plant protein feed ingredients in striped catfish (Pangasianodon hypophthalmus) fingerlings was studied. The AD of the test ingredients (ADi) differed (P < 0.05) and ranged from 81.1% to 90.8%, for ADi_DM, from 84.0% to 95.0% for ADi_CP, from 78.4% to 86.9% for ADi_OM and from 79.0% to 87.8% for ADi_GE. The highest ADi_DM, ADi_CP and ADi_OM in the test ingredients were found for shrimp head meal, catfish by‐product meal, golden apple snail and groundnut cake, while the lowest values were obtained for earthworm meal and rice bran. The highest ADi_GE was found in rice bran, followed by golden apple snail and catfish by‐product meal, while there were no differences (P < 0.05) between the other test ingredients, except for earthworm meal. The AD of total and individual EAA was high in catfish by‐product meal and shrimp head meal, followed by decreasing AD in golden apple snail, groundnut cake, rice bran and earthworm meal ingredients (P < 0.05). The low AD of earthworm meal may limit its potential to be used as replacement for fish meal in the feed.     

Effect of ingredient particle sizes and dietary viscosity on digestion and faecal waste of striped catfish (Pangasianodon hypophthalmus)

The ingredients’ particle size and dietary viscosity may alter digestion, performance and faecal waste management of fish. This study aimed to assess the effect of grinding screen sizes of feed ingredients and dietary viscosity on digestibility, faecal waste and performance of striped catfish (Pangasianodon hypophthalmus, Sauvage, 1878). The experiment had a 2 × 3 factorial‐design: two feed mesh particle sizes, by grinding ingredient mixtures at two screen sizes (0.8 versus 1.0 mm); and three dietary viscosity levels, created by exchanging carboxymethylcellulose by guar gum (GG) (0, 3 and 6 g of GG/kg of diet). Six diets were assigned to 18 tanks, each connected to three faecal settling tanks. All aquaria were stocked with 20 fish (82 g per fish). After 52 experimental days, dietary viscosity negatively affected both feed digestibility and performance of striped catfish; as a result, the amount of organic matter in the culture system through faeces had increased significantly. The coarse diets significantly increased the digestibility of dry matter and carbohydrate but worsened feed conversion ratio. Increasing dietary viscosity tended to increase the viscosity and moisture content of the faeces, but significantly accelerated the faecal disintegration through the reduction of both faecal recovery and the amount of recovered faeces.     

Effect of dietary Yucca schidigera extract on growth,total ammonia–nitrogen excretion and haematological parameters of juvenile striped catfish Pangasianodon hypophthalmus

A feeding trial with striped catfish, Pangasianodon hypophthalmus was performed to determine the effect of Yucca schidigera in practical diet on the growth, feed utilization, body composition, total ammonia–nitrogen (TAN) excretion and haematological parameters. A diet with fish meal as the main protein source without yucca extract was used as the control diet (Diet 1). Four diets were formulated with 0.075 (Diet 2), 0.1 (Diet 3) and 0.15 (Diet 4)% of yucca extract respectively. Fifteen fish per tank (initial mean weight 1.78 ± 0.05 g) were randomly allocated to 15 fibreglass tanks (80‐L) connected to a freshwater closed recirculation system (temperature 29.7 ± 1.0°C). The experimental diets were tested in triplicates for 12 weeks. The specific growth rate of fish fed Diet 4 was significantly higher when compared with fish fed Diet 1. The growth of fish fed diets Diet 2 and Diet 3 were not significantly different compared with fish fed the Diet 1. Striped catfish fed Diet 4 had significantly lower feed conversion ratio compared with fish fed Diet 1 and Diet 2 (P < 0.05).The incorporation of high level Yucca schidigera extract in the diets reduced TAN compared with Diet 1. Dietary inclusion of Yucca extract levels did not significantly affect the biometric parameters or whole body proximate composition of the striped catfish (P > 0.05). The PCV (%) in fish significantly increased with high levels of Yucca inclusion (Diet 4) compared with control diet. Fish fed Diet 4 showed significantly higher haemoglobin levels than Diet 1 (P < 0.05). The results indicate that dietary inclusion of Yucca schidigera extract is promising as a feed additive that could improve growth performance and some haematological parameters and the best Yucca schidigera level was 0.15%.     

Doses response of dietary viscosity on digestibility and faecal characteristics of striped catfish (Pangasionodon hypophthalmus)

The study analysed the dose–response relationship between dietary viscosity and nutrient digestibility, faecal waste characteristics in striped catfish and the long‐term impacts of viscosity on performance of striped catfish. This was done in two experiments: Exp.1 lasted 29 days, in which six dietary viscosity levels were created by including different amount of guar gum (GG; 0, 0.25, 0.5, 1.0, 2.0 or 3.0 g/kg) and Exp.2 lasted 60 days and assessed the long‐term effects of three dietary GG levels (0, 0.5 and 3.0 g/kg) were checked. In Exp.1, digestibility of nutrients (except crude fat) decreased linearly with dietary viscosity. With increasing viscosity, removal efficiency of faeces from the water reduced linearly, whereas the total amount of faeces produced and the fraction of big‐sized faecal particles (>2 mm). increased linearly. In Exp.1, viscosity did not affect performance. However, in Exp.2, the GG inclusion level of 3.0 g/kg (1.72 cP for the viscosity) affected fish performance. In conclusion, the best strategy for faecal waste management in striped catfish by dietary viscosity is to keep it as low as possible in the diet.     

Effect of dietary carbohydrate sources on growth performance and utilization for gibel carp (Carassius auratus gibelio) and Chinese longsnout catfish (Leiocassis longirostris Günther)

The nutritional function of monosaccharides, disaccharides and polysaccharides for omnivorous gibel carp and carnivorous Chinese longsnout catfish were investigated and the ability of these two species to utilize carbohydrates was compared. For each species, triplicate groups of fish were assigned to each of five groups of isoenergetic and isonitrogenous experimental diets with different carbohydrate sources: glucose, sucrose, dextrin, soluble starch (acid‐modified starch) and α‐cellulose. The carbohydrates were included at 60 g kg^?1 in Chinese longsnout catfish diets and at 200 g kg^?1 in gibel carp diets. A growth trial was carried out in a recirculation system at 27.8 ± 1.9 °C for 8 weeks. The results showed that fish with different food habits showed difference in the utilization of carbohydrate sources. For gibel carp, better specific growth rate (SGR) and feed efficiency (FE) were observed in fish fed diets containing soluble starch and cellulose, but for Chinese longsnout catfish, better SGR and FE were observed in fish fed diets containing dextrin and sucrose. Apparent digestibility coefficient of dry matter (ADC_d) and apparent digestibility coefficient of energy (ADC_e) were significantly affected by dietary carbohydrate sources in gibel carp. ADC_d and ADC_e significantly decreased as dietary carbohydrate complexity increased in Chinese longsnout catfish except that glucose diet had medium ADC_d and ADC_e. In both species, no significant difference of apparent digestibility coefficient of protein was observed between different carbohydrate sources. Dietary carbohydrate sources significantly affected body composition, and liver phosphoenolpyruvate carboxykinase (PEPCK), pyruvate kinase (PK), glucose 6‐phosphate dehydrogenase (G6PD) and malic enzyme (ME) activities also varied according to dietary carbohydrate complexity. Fish with different food habits showed different abilities to synthesize liver glycogen, and the liver glycogen content in gibel carp was significantly higher than in Chinese longsnout catfish. The influence of carbohydrate source on gluconeogenesis and lipogenesis was also different in the two fish species.     

Oral administration of Escherichia coli lipopolysaccharide enhances the immune system of striped catfish,Pangasianodon hypophthalmus (Sauvage)

Lipopolysaccharide (LPS), a component of Gram negative bacteria, was reported as important immunostimulant for fish. In this study, striped catfish were fed diets containing different Escherichia coli LPS concentrations (0%, 0.01% and 0.05%) for 2 weeks and then fed control feed (0% LPS) for 4 weeks. Plasma cortisol and glucose were rather low and did not differ significantly among treatments (P > 0.05). The respiratory burst activity, lysozyme, complement, total of antibody as well as mortality in fish challenged with Edwardsiella ictaluri were recorded every 2 weeks (W2, W4 and W6). The lysozyme activity significantly increased in fish treated with LPS (P < 0.05) in W2, W4 and W6. The highest values of respiratory burst activity were observed at week 4 in fish fed 0.01% LPS. There were significant differences in total of antibody between fish fed LPS (0.01%) and control in W2, W4. The challenge test with Edwardsiella ictaluri showed that fish fed 0.01% LPS had lower cumulative mortality (40%, 33% and 42%) compared with the fish fed 0.05% LPS (50%, 40% and 47%) and control fish (40%, 57% and 53%) in the three difference sampling times respectively. These results suggest that feed supplemented with 0.01% LPS could enhance immunity of striped catfish after 2 weeks of oral administration and fish could be protected against bacterial infection during the following 4 weeks.     

Effect of cryoprotectants, extenders and freezing rates on the fertilization rate of frozen striped catfish, Pangasius hypophthalmus (Sauvage), sperm

The effects of four cryoprotectants (methanol, MeOH; dimethyl sulphoxide, DMSO; dimethyl acetamide, DMA; and ethylene glycol, EG), three extenders (calcium‐free Hanks' balanced salt solution, C‐F HBSS, Hanks' balanced salt solution, HBSS and sodium chloride, NaCl) and two different freezing procedures (one‐ and two‐step) on the cryopreservation of striped catfish (Pangasius hypophthalmus (Sauvage)) sperm were investigated. Sperm were frozen using a controlled‐rate freezer in 250 μL straws and stored for 2 weeks in a liquid nitrogen (LN₂) container. They were then airthawed at room temperature, and fertilization, motility and viability were assessed. The highest fertilization rate of 41% (81% of control) was achieved with the combination of 12% DMSO and 0.9% NaCl using a one‐step freezing procedure (10°C min^?1). Also, DMA resulted in a higher fertilization rate (30% or 51% of the control) than MeOH (18% or 38% of the control) or EG (8% or 12% of the control). In addition, the three extenders used did not affect fertilization rates after cryopreservation with each cryoprotectant. There were no significant differences among the three cryoprotectant concentrations and between the one‐ and two‐step freezing procedures. However, fertilization rates of cryopreserved sperm were significantly lower than the controls (P<0.05). The results of this study indicate that high fertilization rates of striped catfish eggs can be achieved using cryopreserved sperm when frozen at 10°C min^?1 in DMSO or DMA with either 0.9% NaCl or C‐F HBSS.     

Effect of dietary calcium on growth and survival of silver catfish fingerlings, Rhamdia quelen (Heptapteridae), exposed to different water pH

The purpose of this study was to verify the effect of dietary Ca²⁺ on the growth and survival of silver catfish fingerlings (Rhamdia quelen) exposed to different water pH (5.5, 7.5 and 9.0). Silver catfish fingerlings were randomly placed in a thermoregulated water re‐use system with twelve 250 L‐tanks, two 1000 L‐biofilters and a 2000 L‐reservoir with a medium flow of 3.84 L min^?1 tank. Stocking density was 0.16 fingerlings L^?1. To prepare the treatment diets, the control diet (0.8 g kg^?1 Ca²⁺) was supplemented with CaCO₃ to yield experimental diets with 6.4, 9.5 and 23.9 g kg^?1 Ca²⁺. There were three replicates/treatments. Survival was more than 93.9% in all treatments. Exposure of silver catfish fingerlings to alkaline or acid water reduced growth, and this effect was not ameliorated by dietary Ca²⁺ supplementation. Moreover, when fingerlings were maintained in water with pH 7.5, the best dietary Ca²⁺ range for silver catfish fingerling growth was 0.8–6.4 g kg^?1.     

Evaluation of feed utilization and growth performance of juvenile striped catfish Pangasianodon hypophthalmus fed diets with varying inclusion levels of corn gluten meal

A nutrition trial with striped catfish (Pangasianodon hypophthalmus) juveniles was undertaken to evaluate the effect of replacing dietary fishmeal (FM) protein with corn gluten meal (CGM). A diet with FM as the main protein source was used as the control diet (FM). Five experimental diets (approximately 320 g kg^?1 crude protein) were formulated to progressively replace 20% (CGM20), 40% (CGM40), 60% (CGM60), 80% (CGM80) and 100% (CGM100) of FM protein. Fifteen fish per tank (initial weight 11.2 ± 0.6 g) were randomly distributed into 18 80‐litre fibreglass tanks connected to a closed recirculation system (temperature 30.3 ± 1.0 °C). The diets were tested in triplicate for 12 weeks. The final weight and specific growth rate (SGR) of fish fed diets CGM20, CGM40 and CGM60 were not significantly different compared to fish fed the FM diet. Feed intake (FI) tended to decrease with increasing dietary CGM level. Striped catfish fed FM, CGM20 and CGM40 had significantly lower feed conversion ratio (FCR) compared with fish fed CGM80 and CGM100 (P < 0.05). The protein efficiency ratio (PER) of fish fed the CGM80 and CGM100 diets was significantly lower than those of all other treatments (P < 0.05). Total ammonia‐nitrogen (TAN) excretion increased with elevated dietary CGM inclusion. The viscerosomatic index (VSI) of fish fed the CGM80 and CGM100 diets were significantly higher (P < 0.05) than those of fish fed the other treatments. The crude lipid content in the final body composition of the striped catfish was elevated significantly with increasing dietary CGM levels. Fish fed the CGM80 and CGM100 diets displayed haematocrit levels significantly lower (P < 0.05) than those fed the other diets. The haemoglobin content in fish was significantly higher in fish fed CGM20 and lower at CGM100 compared to fish fed the FM diet. The results of the present trial indicated that the optimum level of FM protein replacement with CGM determined by quadratic regression analysis was 25.1% on the basis of maximum SGR.     

Effect of dietary essential fatty acids on level of oestradiol‐17β and vitellogenin,reproductive performance and larval quality of striped catfish (Pangasianodon hypophthalmus) in out‐of‐spawning season

A study was conducted to determine the effect of essential fatty acid in striped catfish (Pangasianodon hypophthalmus) broodstock diets on a level of oestradiol‐17β and vitellogenin, reproductive performance and larval quality in out‐of‐spawning season. Five female and five male broodstock were stocked into a net cage (3 × 5 × 1.5 m³) and fed with pelleted diets containing 1.5% fish oil and different amounts of corn oil (CO) in diet formulation, that is 0%, 1%, 2% and 3% respectively. Gonadal development, oestradiol‐17ß and vitellogenin concentrations were examined every 2 weeks. Oestradiol‐17ß and vitellogenin concentrations showed an increase during the maturation process. The significantly highest percentage of female mature, fecundity, hatching rate, larval production and larval survival rate were obtained from fish fed with 2% corn oil in the diet. This result revealed that the administration of 2% corn oil in the diet as a source of n‐6 (linoleic acid) and 1.5% fish oil as a source of n‐3 (linolenic acid) can improve the reproductive performance of striped catfish broodstock in out‐of‐spawning season.     

Effect of dietary protein, lipid and carbohydrate ratio on growth, feed efficiency and body composition of pikeperch Sander lucioperca fingerlings

Pikeperch Sander lucioperca fingerlings were fed nine practical diets containing three levels of protein (P=34%, 43% and 50%), lipid (L=10%, 16% and 22%) and carbohydrate (C=10%, 15% and 20%) for 10 weeks in a recirculating water system at 23°C. Dietary treatments were distributed by orthogonal design with dietary energy content ranging from 15.5 to 23.1 MJ kg^?1 diet. Significant differences (P<0.05) in weight gain (%) and feed efficiency (FE) were observed after feeding trial. Relatively low growth and FE were found in fish fed diets containing 34% dietary protein level compared with that of fish fed diets with 43–50% protein levels, suggesting that 34% dietary protein probably is below the protein requirements of pikeperch fingerlings. Fish fed diets containing P43L10C15, P43L22C20 and P50L16C20 had significantly (P<0.05) higher weight gain and FE than fish fed the diets containing other dietary P/L/C ratios. There was no significant difference in weight gain and FE between fish fed diets of P43L10C15, P43L22C20 and P50L16C20. These results may indicate that pikeperch require at least 43% of dietary protein for adequate growth and FE, and considering the fish growth and feed ingredient cost P43L10C15 diet is more cost‐effective formulation for pikeperch fingerling. However, protein efficiency was not significantly affected by dietary P/L/C ratio.     

Effects of dietary Nutrafito Plus on growth,haemotological parameters and total ammonia‐nitrogen excretion of juvenile striped catfish Pangasianodon hypophthalmus

A feeding trial was performed to determine the effect of a commercial source of Yucca schidigera and Quillaja saponaria extracts (Nutrafito Plus^®), in practical diets, on striped catfish Pangasianodon hypophthalmus growth, feed utilization, body composition, total ammonia‐nitrogen (TAN) excretion and haematological parameters. Four experimental diets were supplemented with Nutrafito Plus^® at 0%, 0.01%, 0.02% and 0.03% (diets: control, N01, N02 and N03 respectively). Three replicate groups of striped catfish, with initial mean weight of 1.78 ± 0.05 g, were fed one of the four diets for 12 weeks. The specific growth rate (SGR) and final weight of fish fed diet N03 was significantly higher (P < 0.05) than fish fed the other dietary treatments. The growth performance of fish fed diets N01 and N02 were not significantly different compared to fish fed the control diet. Striped catfish fed diet N03 had improved feed conversion ratio (FCR), net protein utilization (NPU) and protein efficiency ratio (PER) than the control (P < 0.05). The inclusion of the high dietary level of Yucca schidigera and Quillaja saponaria, diet N03, reduced TAN compared to all groups. Dietary inclusion of Yucca schidigera and Quillaja saponaria at all levels investigated did not affect the whole body proximate composition of the striped catfish (P > 0.05). The packed cell volume (PCV) and haemoglobin level in fish fed diet N03 was significantly higher than in the fish fed the control diet. The present study demonstrates that dietary inclusion of Yucca schidigera and Quillaja saponaria induced positive effects on growth performance and haematological parameters and decreased TAN excretion in striped catfish.     

Comparison on growth performance,body coloration changes and stress response of juvenile river catfish,Pangasius hypophthalmus reared in different tank background colour

The effects of different tank background colours (green, black and white) on the growth performance and body coloration of juvenile river cafish, Pangasius hypophthalmus, were examined in this study. The experimental fish with an initial body weight (BW) 0.13 ± 0.05 g and total length (TL) 2.54 ± 0.37 cm were used, and groups of 15 fish per tank were randomly distributed. The experiment was conducted for 20 days as a triplicate for each treatment. Survival, growth in BW, body weight gain (BWG), total length (TL), total length gain (TLG), specific growth rate (SGR), condition factor, feed conversion ratio (FCR), swimming speed, body coloration and stress response were evaluated. River catfish reared in white and green tanks attained significantly higher BW, BWG, TL, TLG and SGR compared to the black tank. The white tank attained significantly better FCR compared to the black tank. River catfish showed the most active swimming behaviour in the green tank (5.49 ± 1.32 cm/s) while the least in the white tank (3.37 ± 0.93 cm/s). Body coloration of river catfish in the black tank showed almost pure black body coloration (75.59 ± 9.08), followed by the green tank (126.23 ± 17.46) and the white tank (148.19 ± 10.51). However, there was no significant difference in the stress level of river catfish reared in white and black tanks and insignificant to those reared in the green tank. The findings in this study showed that the white and green background colour tanks can be used for promoting growth of river catfish culture while the black background colour tank can enhance body coloration that is suitable as ornamental fish.     

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

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

Production performance of sutchi catfish Pangasianodon hypophthalmus S. in restricted feeding regime: effects on gut,liver and meat quality

The experiment was carried out to evaluate the production performance of sutchi catfish, Pangasianodon hypophthalmus in restricted feeding regimes and their effects on gut and liver indices and body composition. Four feeding regimes were evaluated: fed to satiation twice per day (treatment daily feeding); 1‐day food deprivation and 1‐day feeding (treatment 1D‐1F), 2‐day deprivation and 2‐day feeding (treatment 2D‐2F) and 5‐day deprivation and 5‐day feeding (treatment 5D‐5F). Fingerlings (mean weight 37 ± 3 g, mean total length 18 ± 2 cm) were stocked in replicated earthen ponds at a density of 25 000 ha^?1 and cultured for 18 weeks during which commercial diet (33% crude protein) were delivered to apparent satiation on the feeding day according to the treatment. Results showed that the daily feeding and 1D‐1F treatments resulted in similar individual weight gain (515–536 g) and net fish production (10 954–11 387 kg ha^?1) as compared with treatment 2D‐2F (weight gain 309 g; net production 6700 kg ha^?1) or treatment 5D‐5F (weight gain 251 g; net production 5651 kg ha^?1). While fish body protein levels were not affected by food deprivation, lipid contents were lowest in treatments 2D‐2F and 5D‐5F. The study concluded that sutchi catfish could be cultured in alternate‐day feeding regime without any negative effects on production and meat quality of fish resulting in a net profit of USD 2750 ha^?1 pond.     

饲料糖水平对眼斑双锯鱼幼鱼生长性能和体成分的影响

为确定眼斑双锯鱼(Amphiprion ocellaris)幼鱼人工配合饲料的适宜糖水平,研究了糖水平为4.4%、8.4%、12.2%、16.1%、20.5%、24.5%和28.4%的人工饲料对眼斑双锯鱼幼鱼生长、饲料转化率和体成分的影响。结果显示,随着糖水平的升高,幼鱼增重率(WG)和特定生长率(SGR)呈先增加后降低趋势。回归分析表明,糖水平16.49%时WG最大;糖水平16.73%时SGR最大。饲料系数(FCR)随糖水平增加呈现先下降后上升的趋势,而蛋白质效率(PER)、蛋白质沉积率(PRR)和脂肪沉积率(LRR)的变化则相反。回归分析显示,糖水平9.20%时FCR最小;糖水平8.57%时PER最大;糖水平10.97%时PRR最大;糖水平14.12%时LRR最大。全鱼粗脂肪质量分数随糖水平升高而增加,糖水平20.5%时达到最高水平后略有下降。综合生长参数与糖水平的回归分析结果,眼斑双锯鱼生长最快的糖添加量为16.49%~16.73%;综合饲料效率参数与糖水平的回归分析结果,饲料效率最高的糖添加量为8.57%~14.12%。     

Effect of dietary cadmium level on the growth,body composition and several hepatic enzymatic activities of juvenile yellow catfish,Pelteobagrus fulvidraco

The present study was conducted to investigate the effect of dietary cadmium (Cd) level on the growth, body composition and several enzymatic activities of juvenile yellow catfish, Pelteobagrus fulvidraco. The experimental diets were formulated with CdCl₂·2.5H₂O at levels of 0, 0.01, 0.1 and 1.0 g kg^?1 diet, resulting in four dietary Cd levels of 0.25 (control), 4.92, 48.57 and 474.7 mg Cd kg^?1 diet respectively. They were fed to juvenile yellow catfish (mean initial weight: 3.26±0.07 g, mean±SD) for 4 weeks. Weight gain, specific growth rate, feed intake and protein efficiency ratio tended to decline with increasing dietary Cd levels (P<0.05). In contrast, the feed conversion ratio was the lowest when the dietary Cd level was 0.25 mg Cd kg^?1 diet. Dietary Cd levels significantly influenced body composition and Cd accumulation. Whole body and vertebrae Cd content generally increased as the dietary Cd levels increased (P<0.05). However, muscle Cd content was detected only in fish fed the diets containing the highest Cd level of the diet (P>0.05). Hepatic alkaline phosphatase, glutathione peroxidase and lactate dehydrogenase activities increased (P<0.05) with increasing dietary Cd level. Succinate dehydrogenase was very variant and not related to dietary treatments. Malic dehydrogenase activity showed no significant differences among the treatments (P>0.05). The present study provided for the first time the toxic assessment of dietborne Cd in yellow catfish, based on growth performance and the changes in hepatic enzymatic activities for the fish species.     

Effect of dietary protein levels on growth,feed utilization and carcass composition of endangered bagrid catfish Horabagrus brachysoma (Gunther 1864) fingerlings

An 84‐day feeding trial was conducted to study the effect of different levels of dietary protein, 250 (P25), 300 (P30), 350 (P35), 400 (P40) and 450 g (P45) kg^?1 dry matter (DM) on growth, feed intake, feed utilization and carcass composition of bagrid catfish Horabagrus brachysoma fingerlings. Triplicate groups of fingerlings with mean initial body weight of 2.2 g were fed the experimental diets twice daily, till satiation, in 150‐L tanks supplied with flow‐through freshwater. Daily dry matter intake by the fingerlings decreased significantly (P < 0.05) when fed P25 diet, containing 250 g protein kg^?1. The highest body weight gain, specific growth rate (SGR) and protein efficiency ratio (PER), and the lowest feed conversion ratio (FCR) were observed in fish fed 350 g protein kg^?1 diet. The fish fed with P45 diet had the lowest (P < 0.05) carcass lipid content. The polynomial regression analysis indicates that H. brachysoma fingerlings require 391 g dietary crude protein kg^?1 diet.