Dietary pyridoxine requirement of fingerling Channa punctatus (Bloch) based on growth performance,liver pyridoxine concentration,and carcass composition

Seven casein gelatin-based diets containing 450 g/kg CP and 18.39 kJ/g GE with different levels of pyridoxine (0, 2, 4, 6, 8, 10, and 12 mg/kg diet) were fed to fingerling Channa punctatus (4.66 ± 0.46 g) for 12 weeks to determine pyridoxine requirement. Highest absolute weight gain (AWG; 25.81 g/fish, P < 0.05), protein retention (PRE; 23.69%, P < 0.05), energy retention efficiencies (ERE; 69.63%, P < 0.05), and minimum feed conversion ratio (FCR; 1.48) were noted at 8 mg pyridoxine/kg diet. However, liver pyridoxine content achieved the positive correlation as the dietary pyridoxine increased up to 10mg/kg. On the basis of broken-line analysis of AWG, PRE, FCR, and liver pyridoxine data, pyridoxine requirement is recommended between 7.6 and 10.4 mg/kg of dry diet.     

Dietary biotin requirement of fingerling Channa punctatus (Bloch)

ABSTRACT

Dietary biotin requirement of fingerling Channa punctatus (4.52 ± 0.46 g) was estimated by conducting a 16-week growth trial. Fish were fed casein gelatin-based purified diets (450 g/kg crude protein, 18.39 kJ/g gross energy) with seven levels of dietary biotin (0, 0.04, 0.09, 0.47, 1.02, 1.43, and 1.96 mg/kg diet) to triplicate groups near to satiation. Significantly higher absolute weight gain (P = 0.0018), specific growth rate (P = 0.0027), protein gain (P = 0.0016), protein deposition (P = 0.0038), and lower feed conversion ratio (P = 0.0003) were shown in fish fed diet containing 0.47 mg/kg biotin, whereas liver biotin concentration showed a significant improvement (P = 0.0021) with increasing levels of dietary biotin up to 1.02 mg/kg. Broken-line analysis of absolute weight gain, protein gain, and liver biotin concentrations indicated that fingerling C. punctatus require biotin at 0.46, 0.44, and 0.97 mg/kg diet. Based on protein gain, optimum pyridoxine requirement for fingerling C. punctatus is recommended at 0.44 mg/kg diet.     

Dietary pantothenic acid requirement of fingerling Channa punctatus (Bloch) based on growth,feed conversion,liver pantothenic acid concentration and carcass composition

A 16‐week feeding trial was conducted to determine the dietary pantothenic acid requirement of fingerling Channa punctatus. Six casein–gelatin‐based diets (450 g/kg CP; 18.39 kJ/g GE) with graded levels of pantothenic acid (0, 10, 20, 30, 40 and 50 mg/kg diet) were fed to triplicate groups of fish (6.2 ± 0.71 cm; 4.26 ± 0.37 g) near to apparent satiation. The growth evaluation in terms of absolute weight gain (AWG), feed conversion ratio (FCR) and protein retention efficiency (PRE) indicated the best performance (p < .05) in fish fed diet containing 30 mg/kg pantothenic acid. Highest haemoglobin, haematocrit and RBCs counts were also obtained in fish fed diet with 30 mg/kg pantothenic acid. Mean cell haemoglobin and mean cell volume were found to be lowest in fish fed pantothenic acid‐free diet indicating the anaemia in this group of fish. Superoxidase dismutase and catalase activities of liver tissue were found to improve (p < .05) with the increasing levels of dietary pantothenic acid from 0 to 30 mg/kg. However, liver pantothenic acid concentration responded positively with the increasing levels of pantothenic acid up to 40 mg/kg diet and then stagnation in liver pantothenic acid concentration with the further inclusion of pantothenic acid was recorded. Second‐degree polynomial regression analysis of AWG, FCR and PRE exhibited the pantothenic acid requirement at 36.4, 32.8 and 34.7 mg/kg diet, respectively. Data generated during this study would be useful in formulating pantothenic acid‐balanced commercial feeds for the intensive culture of this fish.     

Dietary copper requirement of fingerling Channa punctatus (Bloch) based on growth,feed conversion,blood parameters and whole body copper concentration

A 12‐week feeding trial was conducted to estimate the dietary copper requirement of fingerling Channa punctatus. Six casein?gelatin‐based test diets (450 g kg^?1 crude protein; 18.81 kJ g^?1 gross energy) with graded levels of copper as copper sulphate (3.7, 4.7, 5.7, 6.7, 7.7 and 8.7 mg copper equivalent kg^?1 diet) were formulated and fed to triplicate groups of fish (7.25 ± 0.81 cm; 5.21 ± 0.27 g) near to satiation. Fish fed diet with 6.7 mg kg^?1 copper had highest absolute weight gain (AWG; 51.63 g fish^?1), protein efficiency ratio (PER; 1.42 g fish^?1), protein gain (PG; 8.34 g fish^?1), haemoglobin (Hb; 9.68 g dL^?1), haematocrit (Hct; 31.18%) and RBCs (3.24 × 10⁶ × mm^?3). Feed conversion ratio (FCR) was found to be best (1.57) at above level of dietary copper. Whole body copper concentration was found to increase with the increasing levels of dietary copper. Hepatic thiobarbituric acid‐reactive substances concentration was found to decrease with increasing dietary concentrations of copper up to 6.7 mg kg^?1 beyond which a reverse trend in this parameter was noted. Broken‐line regression analysis of AWG, FCR and PG concentrations against varying levels of dietary copper yielded the requirement in the range of 6.66–6.78 mg kg^?1. Data generated during this study would be useful in formulating copper‐balanced commercial feeds for the intensive culture of this fish.     

Dietary thiamin requirement of fingerling Channa punctatus (Bloch) based on growth,protein gain,liver thiamin storage,RNA/DNA ratio and biochemical composition

Dietary thiamin requirement of fingerling Channa punctatus was quantified by feeding casein/gelatin‐based diets (450 g/kg CP; 18.39 kJ/g GE) with seven graded levels of thiamin (0, 0.5, 1, 1.5, 2, 2.5 and 5 mg/kg diet) to triplicate groups of fish (6.9 ± 0.93 cm; 4.91 ± 0.62 g) for 16 weeks. Fish fed diet with 2.5 mg/kg thiamin reflected highest absolute weight gain (AWG), protein gain (PG), RNA/DNA ratio and lowest feed conversion ratio. Similarly, highest liver thiamin concentration was also recorded in fish fed 2.5 mg/kg thiamin diet. Hepatic thiobarbituric acid reactive substance (TBARS) concentration responded negatively with increasing concentrations of dietary thiamin up to 2.5 mg/kg, whereas superoxide dismutase and catalase activities were found to improve with the increasing levels of dietary thiamin from 0 to 2.5 mg/kg. Transketolase activity also improved as the thiamin concentrations increased up to 2.5 mg/kg. Broken‐line regression analysis of AWG, PG, RNA/DNA ratio, liver thiamin concentrations, transketolase and TBARS activities exhibited the thiamin requirement in the range of 2.34–2.59 mg/kg diet. Data generated during this study would be useful in formulating thiamin‐balanced feeds for the intensive culture of this fish.     

Dietary riboflavin requirement of fingerling Channa punctatus (Bloch) based on growth,conversion efficiencies,protein retention,liver riboflavin storage,RNA/DNA ratio and carcass composition

A 16‐week experiment was conducted to determine the dietary riboflavin requirement of the fingerling Channa punctatus (6.7 ± 0.85 cm; 4.75 ± 0.72 g) by a feeding casein–gelatin‐based (450 g/kg crude protein; 18.39 kJ/g gross energy) purified diet containing graded levels of riboflavin (0, 2, 4, 6, 8, 10 and 12 mg/kg diet) to triplicate groups of fish near to satiation at 09:30 and 16:30 hr. Absolute weight gain (AWG), protein efficiency ratio (PER), specific growth rate (SGR, % per day), protein retention efficiency (PRE%) and RNA/DNA ratio were positively affected by increasing concentrations of dietary riboflavin to 6 mg riboflavin per kg diet. Feed conversion ratio (FCR) decreased up to 6 mg riboflavin per kg diet but did not decrease further with higher riboflavin supplementation. Hepatic thiobarbituric acid‐reactive substance (TBARS) concentration also supported the pattern of FCR, whereas superoxide dismutase and catalase activities increased with increasing concentrations of dietary riboflavin from 0 to 6 mg/kg. Liver riboflavin concentrations increased with increasing levels of riboflavin up to 8 mg/kg diet. Broken‐line regression analysis of AWG, PRE and liver riboflavin concentrations of fingerling C. punctatus with dietary riboflavin level indicated optimum growth and liver riboflavin saturation at 5.7, 6.1 and 7.7 mg riboflavin per kg diet, respectively.     

Effect of dietary isoleucine level on growth,protein retention efficiency,haematological parameter,lysozyme activity and serum antioxidant status of fingerling Channa punctatus (Bloch)

Isoleucine requirement of fingerling Channa punctatus (6.74 ± 0.09 g) was estimated by feeding seven trial diets (450 g/kg CP, 14.73 kJ/g DE) containing 3.8, 7.5, 11.3, 15.1, 19.3, 23.2 and 27.4 g/kg of isoleucine for 12 weeks. Growth and haematological parameters increased with the increasing concentrations of dietary isoleucine up to 16 g/kg. Carcass protein and fat increased significantly with the increasing concentrations of dietary isoleucine up to 16 g/kg and then stabilized. Moisture content showed reverse trend to that of carcass fat. Hepatosomatic index was found to be highest at 4 g/kg of dietary isoleucine. Viscerosomatic index and condition factor increased significantly with increasing levels of isoleucine up to 16 g/kg dry diet. Serum protein, lysozyme and superoxide dismutase activities were also found to increase significantly up to 16 g/kg dry diet. Significant reduction in alanine aminotransferase and aspartate aminotransferase activities was observed by increasing concentrations of dietary isoleucine up to 16 g/kg. Based on quadratic regression analysis of absolute weight gain, feed conversion ratio, protein retention and isoleucine retention efficiencies against varying concentrations of isoleucine, the optimum isoleucine requirement ranging between 17.95 and 18.39 g/kg dry diet, corresponding to 39.88–40.86 g/kg dietary protein, is recommended for maximizing growth of C. punctatus.     

Dietary protein requirement for fingerling Channa punctatus (Bloch), based on growth, feed conversion, protein retention and biochemical composition

An 8-week feeding trial was conducted in a flow-through system (1–1.5 L min⁻¹) at 27°C to determine dietary protein requirement for Channa punctatus fingerlings (4.58 ± 0.29 g) by feeding six isocaloric diets (18.39 kJ g⁻¹, gross energy). Diets containing graded levels of protein (300, 350, 400, 450, 500 and 550 g kg⁻¹) were fed to triplicate groups of fish to apparent satiation at 09:00 and 16:00 h. Maximum absolute weight gain (AWG; 8.11 g fish⁻¹), specific growth rate (SGR; 1.82%) and best feed conversion ratio (FCR; 1.48) were recorded in fish fed diet containing 450 g kg⁻¹ protein, whereas protein efficiency ratio (PER; 1.52), protein retention efficiency (PRE; 25%), energy retention efficiency (ERE; 78%) and RNA/DNA ratio (3.01) were maximum for the group fed dietary protein at 400 g kg⁻¹. Second-degree polynomial regression analysis of AWG, SGR and FCR data against varying levels of dietary protein yielded optimum dietary protein requirement of fingerling between 462.24 and 476.72 g kg⁻¹, whereas the regression analysis of PER, PRE, ERE and RNA/DNA ratio data showed a lower protein requirement of 438.28–444.43 g kg⁻¹ of the diet. Considering the PER, PRE, ERE and RNA/DNA ratio as more reliable indicators, this protein requirement is recommended for developing quality protein commercial feeds for C. punctatus fingerlings.     

Dietary threonine requirement of fingerling Indian major carp,Catla catla (Hamilton) estimated by growth,protein retention efficiency,threonine deposition,haematological parameters and carcass composition

A 12‐week feeding trial was conducted to determine the dietary threonine requirement of fingerling Indian major carp, Catla catla (3.35 ± 0.11 cm; 0.59 ± 0.06 g). Six casein‐gelatin based (33% crude protein; 3.23 kcal g^?1 digestible energy) amino acid test diets with graded levels of analysed threonine (0.74%, 0.96%, 1.21%, 1.48%, 1.72% and 1.93% dry diet) were fed to satiation to triplicate groups of fish. Absolute weight gain (g per fish), feed conversion ratio, protein retention efficiency, threonine deposition, RNA/DNA ratio and carcass protein significantly improved with the increase in dietary threonine and peaked at 1.48% of the dry diet. Haematological indices were also found to be best in fish fed at 1.48% threonine diet. Quadratic regression analysis of absolute weight gain, feed conversion ratio, protein retention efficiency, threonine deposition, RNA/DNA ratio, carcass protein, haemoglobin (g dL^?1), haematocrit (%) and RBCs (10⁶ × mm^?3) at 95% of maximum and minimum response exhibited the threonine requirement of fingerling C. catla between 1.35% and 1.48% dry diet, corresponding to 4.09–4.48% dietary protein. Present finding would be useful in formulating threonine‐balanced feeds for the intensive culture of C. catla.     

Effect of varying levels of dietary protein on the growth performance and feed conversion efficiency of snakehead Channa striata fry

Six isocaloric test diets, based on fishmeal-groundnut oil cake and containing 350–600 g kg^?1 protein at 50 g kg^?1 incremental levels were fed to snakehead, Channa Striata (Bloch), fry at a rate of 10% of body weight per day under laboratory conditions to determine the effect of varying level of dietary protein on the growth response. On the basis of percentage weight gain, daily weight gain, specific growth rate and daily tissue protein deposition, the dietary protein requirement of fry was found to be 550 g kg^?1 when fish meal was used as the major source of protein. There was a significant increase in carcass protein and a significant decrease in ash content with progressive dietary protein substitution. Fry fed with high protein diets tended to have lower carcass lipid contents and higher moisture contents.     

Dietary histidine requirement of fingerling Catla Catla (Hamilton) based on growth,protein gain,histidine gain,RNA/DNA ratio,haematological indices and carcass composition

To investigate the histidine requirement of fingerling Catla catla (3.65 ± 0.15 cm; 0.65 ± 0.36 g), six casein‐gelatin based diets (33% CP; 13.58 kJ g^?1 DE) containing graded levels of L‐histidine (0.25%, 0.39%, 0.53%, 0.67%, 0.83%, 0.96% of the dry diet) were fed near to satiation thrice a day for 12 weeks. Maximum absolute weight gain (AWG; 8.63 g fish^?1), protein gain (PG; 1.45 g fish^?1), histidine gain (HG, 48.19 mg fish^?1), RNA/DNA ratio (4.15), best feed conversion ratio (FCR; 1.31), highest haemoglobin (Hb, 9.61 g dL^?1), RBCs (2.84 × 10⁶ mm^?3) and haematocrit (Ht, 30.12%) were recorded in fish fed diet containing 0.67% histidine. However, broken‐line regression analysis of AWG, PG, HG, RNA/DNA ratio, FCR, Hb, Ht and RBCs against dietary histidine reflected the histidine requirement at 0.65%, 0.64%, 0.63%, 0.68%, 0.63%, 0.66%, 0.68% and 0.65% dry diet respectively. Carcass protein was found to improve significantly (P < 0.05) from 13.36% to 16.42% with the increase in dietary histidine from 0.25% to 0.67%. Based on regression analysis of AWG, PG, HG, RNA/DNA ratio, FCR, Hb, Ht and RBCs, it is recommended that the diet for fingerling catla should contain histidine in the range of 0.63–0.68% dry diet, equivalent to 1.91–2.06% of the dietary protein for optimum growth, feed utilization, blood profile and carcass composition.     

Effects of vitamin E supplementation on growth,lipid peroxidation and fatty acid composition of Dojo loach (Misgurnus anguillicaudatus Cantor) fingerlings

A high mortality of cultured loach during their early development has constrained loach aquaculture industry in China. The objective of this study was to evaluate the effects of dietary vitamin E (VE) supplementation on growth performance, lipid peroxidation and fatty acid composition of loach Misgurnus anguillicaudatus fingerlings. Six test diets supplemented with 0 (0E), 50 (50E), 100 (100E), 150 (150E), 200 (200E) and 500 mg kg^?1 (500E) of dl‐α‐tocopheryl acetate were fed loach fingerlings (mean initial weight 24.0 ± 0.2 mg) in triplicate for 40 days. Results showed that the fish fed diet 100E and 200E had significantly higher body weight gains and specific growth ratios and significantly lower feed conversion ratios compared with fish fed diet 0E. With the increase in dietary VE level, whole‐body VE content was significantly increased (except 500E) and thiobarbituric acid reactive substances value was significantly reduced. Increasing dietary VE level increased the percentages of 20:4n‐6 and 20:5n‐3 in neutral lipid fraction, but decreased the percentages of 20:4n‐6 and 20:5n‐3 in polar lipid fraction. In conclusion, VE requirement of loach fingerlings for optimum growth and functionally preventing lipid peroxidation was 136.1 mg kg^?1 of dry diet under the present experimental conditions.     

Dietary tryptophan requirement of fingerling Catla catla (Hamilton) based on growth,protein gain,RNA/DNA ratio,haematological parameters and carcass composition

A 12‐week feeding trial was conducted in eighteen 70 L indoor polyvinyl circular troughs provided with a water flow‐through system (1–1.5 L min^?1) at 28 ± 1 °C to evaluate the dietary tryptophan requirement of fingerling Catla catla (3.45 ± 0.24 cm; 0.60 ± 0.13 g). Six casein‐gelatin‐based amino acid test diets (330 g kg^?1 crude protein; 13.6 kJ g^?1 digestible energy) containing graded levels of L‐tryptophan (1.0, 1.4, 1.9, 2.3, 2.8, 3.4 g kg^?1 dry diet) were fed to triplicate groups of fish near to satiation at 08:00, 12:30 and 17:30 h. Absolute weight gain, feed conversion ratio, protein gain, RNA/DNA ratio, hepatosomatic index, viscerosomatic index, condition factor and haematological indices improved with the increasing levels of tryptophan from 1.0 to 2.3 g kg^?1 of dry diet. Significantly higher carcass protein was obtained at 2.3 g tryptophan per kilogram of the dry diet. Exponential analysis of absolute weight gain, feed conversion ratio, protein gain and RNA/DNA ratio against dietary tryptophan levels at 95% maximum and minimum responses displayed the tryptophan requirement at 2.5, 2.3, 2.5 and 2.1 g kg^?1 dry diet, respectively. Inclusion of dietary tryptophan in the range of 2.1–2.5 g kg^?1 dry diet, equivalent to 6.4–7.6 g kg^?1 dietary protein, is recommended in formulating tryptophan‐balanced feed for the culture of this fish species.     

Re-evaluation of vitamin E supplementation of practical diets for channel catfish, Ictalurus punctatus, production

A 10-month feeding trial was performed with channel catfish, Ictalurus punctatus , to re-evaluate the minimum level of dietary vitamin E supplementation required under conditions of commercial production. Four levels (0, 15, 30 and 60 mg kg⁻¹ diet) of supplemental vitamin E were added as DL -α-tocopherol acetate to a typical commercial catfish diet. Sixteen 0.04-ha ponds were stocked in July, at a rate of 25 000 fish ha⁻¹, with two size classes (averaging 18 and 265 g fish⁻¹) of fingerling channel catfish, and each diet was fed to fish in four replicate ponds once daily to satiation. After 10 months of feeding, a total harvest was performed to obtain final production data, and samples were obtained from fish in all ponds. Liver and plasma samples were obtained for α-tocopherol determination, and liver, heart and muscle samples were processed for histological evaluation.
No discernible differences occurred among fish fed the different diets with respect to weight gain or survival. Mean production rate was 9734 kg ha⁻¹, with a final average fish weight of 0.53 kg. A significant ( P < 0.05) effect of diet was noted in plasma and liver α-tocopherol levels, which increased with dietary supplementation. An effect of size also was apparent, with plasma and liver α-tocopherol levels being higher in larger fish compared with smaller fish within a dietary treatment. Histological evaluation revealed no differences among fish fed the different dietary treatments. Based on the lack of overt histological signs of deficiency, it appears that the current level of vitamin E supplementation of commercial catfish diets may be reduced considerably with no detriment to channel catfish health or production.     

Metabolism,interactions, requirements and functions of vitamin E in fish

Vitamin E is a generic term for a group of lipid‐soluble molecules, the tocopherols and tocotrienols, which have a function in the protection of organisms against lipid oxidation and which also may have other, more specific biological functions. In fish, as in other vertebrates, α‐tocopherol (TOH) is preferentially retained in the body compared to the other tocopherols, probably because of the presence of a tocopherol transfer protein (TTP) in the liver which binds the tocopherols with different affinities and returns them to the circulation. Tocopherols that bind weakly to TTP are to a greater extent excreted in the bile. α‐TOH interacts with other nutrients, and the requirement therefore varies with the dietary composition. High levels of polyunsaturated fatty acids, and low levels of vitamin C, selenium and astaxanthin increase the requirement. This is attributed to the dynamic nature of both lipid oxidation and the antioxidant defence, where oxidized vitamin E is recycled by other antioxidants. The interactions also determine the display of vitamin E deficiency signs, immune responses and effects on flesh quality. Within the mammalian nutrition research community, there is a controversy as to whether vitamin E is primarily an antioxidant or a specific modulator of cell signalling through regulation of enzyme activities and gene expression and some of the hypotheses are presented in this review.     

饲喂频率对黑鲷生长及体生化成分的影响

选取同一种饵料设置4个饲喂频率水平(分别为1次/d、2次/d、4次/d、6次/d),采用静水连续充气养殖系统,在盐度为26.0~27.0、温度为26.8~24.5℃的条件下对黑鲷成鱼和鱼种进行为期40d的生长实验。结果表明:(1)摄食率不受饲喂频率的显著影响,饲喂频率影响黑鲷的生长是由饲料转化率的改变引起的。(2)黑鲷成鱼和鱼种的水分含量随饲喂频率的增高而增加,黑鲷成鱼脂肪含量随饲喂频率的增高而下降,黑鲷鱼种脂肪含量随饲喂频率的增高而增加。(3)在本试验条件下,适宜饲喂频率随着黑鲷鱼体重的增加而提高,黑鲷鱼种的适宜饲喂频率为2次/d,黑鲷成鱼的适宜饲喂频率为4次/d。     

Dietary l‐lysine requirement of fingerling stinging catfish,Heteropneustes fossilis (Bloch) for optimizing growth,feed conversion,protein and lysine deposition

Dietary lysine requirement of fingerling Heteropneustes fossilis (6.96 ± 0.05 g) was quantified by conducting 12‐week feeding trial in a flow‐through system at 28°C. Casein–gelatin based isonitrogenous (38% CP) and isocaloric (14.7 kJ g^?1 DE) amino acid test diets with six levels of dietary lysine (1.5%, 1.75%, 2.0%, 2.25%, 2.5%, 3.0% dry diet) were fed to apparent satiation in triplicates. Broken‐line and second‐degree polynomial regression analyses at 95% plateau of absolute weight gain (AWG; g fish^?1), feed conversion ratio (FCR), protein deposition (PD; g fish^?1) and lysine deposition (LD; g fish^?1) exhibited lysine requirement between 2.0% to 2.3% of the dry diet, corresponding to 5.3–6.1% protein.     

Dietary vitamin E requirement of the red drum Sciaenops ocellatus

A 12-week feeding trial was conducted to establish the minimum dietary vitamin E requirement of juvenile red drum by broken-line regression analysis. The semi-purified basal diet was supplemented with 10, 20, 30, 40, 60 or 80 IU vitamin E kg⁻¹ as all-rac -α-tocopheryl acetate. Juvenile red drum were conditioned by feeding the basal diet for 8 weeks prior to the feeding trial to reduce whole-body vitamin E levels. Then, fish initially averaging 12.2 ± 0.4 g fish⁻¹ (mean ± SD) were fed the experimental diets at a rate approaching apparent satiation for 12 weeks. Weight gain and feed efficiency responses of fish fed diets were significantly ( P  < 0.01) altered by the level of vitamin E supplementation but not strictly in a dose-dependent manner. Vitamin E concentrations in liver and plasma also were significantly ( P  < 0.001) influenced by dietary vitamin E level. Plasma ascorbic acid in fish fed the basal diet tended ( P  = 0.066) to be lower than in fish fed diets containing the various levels of vitamin E. In addition, fish fed the basal diet showed edema in the heart, while fish fed all other diets were normal. Fish fed 60 or 80 IU all-rac -α-tocopheryl acetate kg⁻¹ diet had significantly higher respiratory burst of head kidney macrophages than fish fed all other diets, although dietary effects on hematocrit and neutrophil oxidative radical production were not significant. The minimum dietary vitamin E requirement of juvenile red drum was established based on broken-line regression of liver thiobarbituric acid reactive substances to be 31 mg all-rac -α-tocopheryl acetate kg⁻¹ diet.     

Effect of ration size on growth, conversion efficiency and body composition of fingerling mrigal, Cirrhinus mrigala (Hamilton)

Optimum ration size of Indian major carp, Cirrhinus mrigala fingerlings was determined by feeding purified diet (40% crude protein (CP); 3.61 kcal g^?1) at five ration sizes (2%, 4%, 6%, 8% and 10% of body weight per day) for 6 weeks. Feeding trial was conducted in triplicate. Fishes were randomly stocked at the rate of 20 fish per trough fitted with water flow‐through system. The best feed conversion ratio (FCR), specific growth rate (%) and protein efficiency ratio (PER) were evident at the ration size of 4–6% body weight. Second‐degree polynomial regression analysis of the FCR, PER, and protein and energy retention data indicated the breakpoints at ration size of 5.16%, 5.24%, 5.52% and 5.42% body weight per day. Carcass composition of fish fed different ration sizes varied significantly. Maximum carcass protein and minimum moisture content were noticed at 4% and 6% ration levels. A linear increase in fat content was evident with increasing ration levels up to 6% body weight. Ash content remained insignificantly different among various ration levels except at 2%, showing the significantly highest value. Water temperature, dissolved oxygen, free carbon dioxide, pH and total alkalinity were recorded regularly during the length of the experiment. No mortality was observed during the feeding trial. Based on the above results, it is recommended that feeding in the range of 5–5.5% body weight per day corresponding to 20 g protein and 181 kcal energy to 22 g protein and 199 kcal energy per kg of the diet per day is optimum for the growth and efficient feed utilization of C. mrigala.     

Influence of different sources and levels of dietary protein and lipid on the growth,feed efficiency,muscle composition and fatty acid profile of Snakehead Channa striatus (Bloch, 1793) fingerling

Nine isoenergetic (18.5 kJ g⁻¹) diets were formulated, in a 3 × 3 factorial design, by varying three levels of dietary protein (350, 400 and 450 g kg⁻¹) at each of three levels of dietary lipid (65, 90 and 115 g kg⁻¹) accordingly. Each diet was hand fed two times daily for 8 weeks to triplicate homogenous groups of eight fish (average weight 3.34 ± 0.02 g) per tank connected to a recirculation system. Results showed that the feed efficiency and growth performance significantly (P<0.05) increased with increasing protein level at the two lower lipid levels (65 and 90 g kg⁻¹), respectively, as indicated by indices such as %weight gain, specific growth rate, protein efficiency ratio, feed conversion ratio and feed intake, but did not at the highest lipid level (115 g kg⁻¹). The muscle polyunsaturated fatty acids (PUFA) content declined with increasing dietary protein level at the lipid levels producing the highest growth, suggesting that the utilization of PUFA influences growth. Whereas the muscle monounsaturated fatty acids level was generally lower than the dietary levels in all the treatments tested, indicating preferential catabolism for energy, the muscle saturated fatty acids level was comparatively higher than in the diets, indicating selective deposition. Docosa hexaenoic acid (22:6n3, DHA), which was very low in the diet and in the initial fish, was higher in the muscle of some of the treatments, indicating the ability of Channa striatus to desaturate and elongate short‐chain PUFA to long‐chain HUFA, due to the availability of dietary 18:3n3 and 20:5n3 (the precursors for DHA biosynthesis). It could be concluded, based on the results of this trial, that a diet formulated to contain 65 g kg⁻¹ lipid and 450 g kg⁻¹ protein, with a gross energy of 18.5 kJ g⁻¹ and a dietary n3/n6 PUFA ratio of about 0.1, is sufficient to promote good feed efficiency and growth performance in C. striatus fingerling.