Utilization of different raw and pre-gelatinized starch sources by juvenile yellowfin seabream Sparus latus

Raw corn starch (RCS), raw tapioca starch (RTS), raw potato starch (RPS), pre‐gelatinized corn starch (PCS), pre‐gelatinized tapioca starch (PTS) and pre‐gelatinized potato starch (PPS) were evaluated as starch sources in diets for yellowfin seabream Sparus latus in a 56‐day growth trial. Seven isonitrogenous semi‐purified diets comprising a non‐starch cellulose control diet and the six different starch sources holding 200 g kg⁻¹ starch each were prepared and fed to triplicate groups of juvenile yellowfin seabream S. latus. Fish were fed for 8 weeks. Weight gain (WG) and specific growth rate (SGR) for fish fed RCS, RTS and RPS diets were equal, as well as for fish fed PCS, PTS and PPS diets, but values in groups fed the raw starch sources were significantly higher compared with fish fed the pre‐gelatinized starches. Feed efficiency and protein efficiency ratio in fish fed different starch source diets showed no significant differences but were significantly higher than those fed a non‐starch control diet. Protein productive value was improved by starch incorporation to diets. PCS, PTS or PPS groups showed lower feed intake compared with RCS, RTS or RPS groups, and the differences were significant between PCS, PPS and RCS, RPS groups. Whole‐body protein and ash contents and muscle compositions were not affected by different starch sources. Whole‐body and liver lipid contents, liver moisture and glycogen contents were significantly affected by starch source. Values of hepatosomatic index, intraperitoneal fat ratio, viscerosomatic index and condition factor did not vary between experimental treatments. Plasma total protein concentration for RCS, RTS or RPS fed fish was significantly higher than that for PCS, PTS or PPS fed fish, but significantly lower than that for non‐starch fed fish. Plasma cholesterol and triacylglycerol concentrations were unaffected by starch source, but were significantly higher in fish fed the non‐starch control diets. Plasma glucose concentrations in all dietary groups were relatively stable. In conclusion, raw corn, tapioca and potato starches at a 200 g kg⁻¹ inclusion level were well utilized as energy sources by yellowfin seabream, which was evidenced by better WG and SGR. Pre‐gelatinization of the starches had no positive effect on starch utilization.     

Effects of raw corn starch levels on growth, feed utilization, plasma chemical indices and enzyme activities in juvenile yellowfin seabream Sparus latus Houttuyn

A 10‐week growth trial was conducted to evaluate the effect of raw corn starch levels on the growth, feed utilization, plasma chemical indices and metabolic enzyme activities of juvenile yellowfin seabream Sparus latus. Four semi‐purified experimental diets with different raw corn starch levels (5%, 10%, 20% and 26%) and a high‐protein control diet were prepared before the experiment and hand‐fed to triplicate groups of juvenile yellowfin seabream Sparus latus. Weight gain and specific growth rate for fish fed the diet containing 26% raw corn starch were significantly lower than those for fish fed 10% or 20% corn starch diets or the high‐protein control diet. Fish fed 10% or 20% corn starch diets had a slightly better growth performance than those fed the 5% corn starch diet. Feed efficiency ratio and protein efficiency ratio (PER) for 20% raw corn starch fed fish were the highest among all groups, although no statistically significant differences were found among the experimental groups. The high‐protein control group had a significantly lower PER value than other groups. Protein productive values for fish fed the 5% raw corn starch diet and the high‐protein control diet were significantly lower than those of fish fed the 20% raw corn starch diet, but not significantly different from the values of any other group. The values of intraperitoneal fat ratio, viscerosomatic index and condition factor, as well as body and muscle compositions, were unaffected by corn starch levels. The hepatosomatic index and liver glycogen level for fish fed 5%, 10%, 20% raw corn starch and the high‐protein control diets were equal but significantly lower compared with that of fish fed the 26% raw corn starch diet. Plasma values of the fish were not affected by various dietary treatments, except that a significantly higher plasma glucose concentration was measured in the high‐protein control group compared with the values in the other groups. There were variations in the activities of hepatic hexokinase and pyruvate kinase of the yellowfin seabream after they had been fed different dietary raw corn starch levels for 10 weeks. The overall results showed that a 20% inclusion level of raw corn starch in the diet was better utilized by juvenile yellowfin seabream than 5%, 10% or 26% levels and had a protein‐sparing effect.     

黄鳍鲷幼鱼对几种不同糖源的利用

本研究用来评价黄鳍鲷幼鱼对饲料中葡萄糖、麦芽糖、糊精、玉米淀粉和预糊化玉米淀粉的利用。本试验饲料为6种等氮(粗蛋白:45%,干重)等脂(粗脂肪:9%,干重)的半纯化饲料,其中对照组糖源为纤维素。每种饲料设3个平行。试验鱼初始体重为(3.57±0.13)g(平均值±均差)。试验鱼饲养在含18个水族箱的循环系统中。水温保持在(27±1)℃。试验周期为8周。本试验用来评价黄鳍鲷幼鱼对饲料中不同糖源利用的指标为生长指标、饲料效率、蛋白质效率和肝脏的6-磷酸葡萄糖脱氢酶、苹果酸脱氢酶、异柠檬酸脱氢酶和葡萄糖-6-磷酸脱氢酶。试验结果表明,黄鳍鲷幼鱼体增重、特定生长率、肝体比、肠系膜脂肪体比、饲料效率、蛋白质效率、肝脂肪合成有关酶活性和全鱼、肌肉、肝脏组成均受到饲料中不同糖源的显著影响。预糊化玉米淀粉和麦芽糖组比其它糖源组显著具有更好的体增重和特定生长率,但与对照组没有显著性差异。黄鳍鲷幼鱼生长和体增重与饲料中糖源的复杂性没有相关性。饲喂预糊化淀粉和对照饲料鱼的饲料效率和蛋白质效率显著比其它组高。饲料中糖的添加增加了黄鳍鲷幼鱼的肝体比,但对照组肝体比与糊精组,玉米淀粉组没有显著性差异。预糊化玉米淀粉组肠系膜脂肪体比比其它饲料组要高。结论:基于体增重和特定生长率为指标,饲料中添加25%预糊化玉米淀粉和麦芽糖可以提高黄鳍鲷幼鱼的生长。另外,玉米淀粉预糊化显著提高了黄鳍鲷对玉米淀粉的利用。     

Optimal dietary carbohydrate to lipid ratio for juvenile yellowfin seabream (Sparus latus)

A growth experiment was conducted to determine the optimal carbohydrate‐to‐lipid (CHO: L) ratio for juvenile yellowfin seabream cultured in 340‐L indoor recirculating tanks. Seven isonitrogenous (450 g kg⁻¹ dietary protein) and isoenergetic (14.1 MJ kg⁻¹) diets with increasing CHO: L ratios (0.03–5.09 g: g) were fed to triplicate groups of 30 fish with an initial weight of 4.91 g for 56 days. Fish were fed to satiation twice a day and the water temperature ranged between 28 and 31.7 °C during the experimental period. Survival was high in all the groups and was not affected by dietary treatments. Best weight gain (WG) and specific growth rate (SGR) were observed in fish fed diets with CHO: L ratios of 0.29 and 0.72, which were not significantly different from that of 0.03, 1.26 and 1.92, but apparently higher than that of 3.22 and 5.09. Feed efficiency (FE), protein efficiency ratio (PER) and protein production value (PPV) followed the same general pattern as WG and SGR. Highest level of energy production value (EPV) was found in fish fed diets with CHO: L ratio of 0.72. Proximate compositions of fish whole body and tissues were markedly affected by dietary CHO: L ratios. Whole body, muscle and liver lipid increased as CHO: L ratios decreased, whereas moisture contents were reduced. Dietary CHO: L ratios had no significant effect on protein content in whole body and muscle. Plasma total cholesterol levels of fish fed diets with CHO: L ratios less than 0.72 were significantly higher than those of the other groups. Triacylglyceride levels decreased linearly as dietary CHO: L ratios increased. Viscerosomatic index (VSI) significantly increased as dietary CHO: L ratios decreased. Intraperitoneal fat ratio (IPF) of fish fed diets with CHO: L ratios less than 1.92 were significantly higher than those fed CHO: L ratios of 3.22 and 5.09. Hepatosomatic index (HSI) did not vary between the test diets. Based on second‐order polynomial regression analysis of WG against dietary carbohydrate and lipid levels, 84.1 g kg⁻¹ of carbohydrate and 136.3 g kg⁻¹ of lipid, corresponding to a CHO: L ratio of 0.62, in a diet holding 450 g kg⁻¹ of crude protein and 14 KJ g⁻¹ of metabolizable energy, proved to be optimal for juvenile yellowfin seabream.     

Effect of dietary chromium picolinate on growth performance and blood parameters in grass carp fingerling, <Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>

An experiment was conducted to investigate the effect of dietary chromium picolinate supplement on growth and haematology parameters of grass carp, Ctenopharyngodon idellus. Six diets with increasing dietary chromium picolinate levels 0, 0.2, 0.4, 0.8, 1.6 and 3.2 mg kg⁻¹ were fed to triplicate groups of 20 fish (initial weight of 12.78 ± 1.16 g, mean ± SD) in a flow water system for 10 weeks. Fish fed the diet supplemented with 0.8 mg Cr kg⁻¹ had significantly improved weight gain (WG), feed efficiency ratio (FER), protein efficiency ratio (PER) and protein retention (PR). Fish fed high-chromium diets exhibited lower whole-body crude lipid contents than fish fed low-chromium diets. Liver glycogen concentrations for fish fed the diet with 0.2 mg Cr kg⁻¹ was the highest (77.67 mg g⁻¹). Fish fed the diet supplemented with 1.6 and 3.2 mg Cr kg⁻¹ had significantly lower liver glycogen concentrations than other groups (P < 0.05). The highest serum insulin concentrations were observed in fish fed the diet supplemented with 0.8 mg Cr kg⁻¹, but serum insulin concentrations decreased (P < 0.05) when dietary supplementation of chromium was higher than 0.8 mg Cr kg⁻¹. Cholesterol concentrations decreased in direct proportion to dietary chromium level and achieved the lowest level when the fish were fed the 0.8 mg Cr kg⁻¹ diet, but increased when the fish were fed the diet with more than 0.8 mg Cr kg⁻¹ (P < 0.05). Fish fed the diet supplemented with 0.8 mg Cr kg⁻¹ had higher triglyceride and high-density lipoprotein cholesterol (HDL-C) concentrations compared to other treatments. The results of the present study suggested that chromium picolinate could modify serum carbohydrate and lipid metabolism profile, and that the optimal dietary chromium level was 0.8 mg kg⁻¹ for grass carp according to growth.     

The growth performance of southern catfish fed diets with raw, precooked cornstarch and glucose at two levels

The ability of juvenile carnivorous southern catfish (Silurus meridionalis Chen) to use different levels, kinds and physic state (glucose, raw cornstarch and precooked cornstarch) of dietary carbohydrate was evaluated in term of growth performance. All diets contained 100 g kg^?1 lipid and 16 kJ metabolizable energy. Three isonitrogeneus (400 g kg^?1) diets were formulated to contain 150 g kg^?1 raw cornstarch, precooked cornstarch and glucose. Another three isonitrogeneus (300 g kg^?1) diets were formulated to contain 300 g kg^?1 raw cornstarch, precooked cornstarch and glucose. A control diet was formulated with no carbohydrate containing 500 g kg^?1 protein. Each experimental diet was fed to four tanks of 10 fish (28.3 ± 0.5 g) for 8 weeks at 27.5 °C. Specific growth rate (SGR) of 300 g kg^?1 glucose diet was significantly lower than those of other diets (P < 0.05). Feeding rates (FR) of 300 g kg^?1 glucose and control diets were significantly lower than those of the other diets (P < 0.05). Feed efficiency (FE) was significantly decreased with increased dietary carbohydrate level (P < 0.05). Feed efficiency of the 300 g kg^?1 glucose diet was significantly lower than those of the 300 g kg^?1 raw and precooked cornstarch diets (P < 0.05). The protein efficiency ratio (PER) was significantly increased with dietary carbohydrate level except that of the 300 g kg^?1 glucose diet, which was lowest among all diets (P < 0.05). The results suggested that both dietary starch and glucose were utilized for energy in southern catfish and had a protein‐sparing effect. At 150 g kg^?1 inclusion level, the utilization of raw and precooked cornstarch and glucose did not vary significantly, but a higher dietary glucose level (300 g kg^?1) had a markedly detrimental effect on growth in southern catfish.     

Effects of dietary phosphorus and starch levels on growth performance,body composition and nutrient utilization of grass carp (Ctenopharyngodon idella Val.)

Six iso‐nitrogenous (410 g kg^?1) diets with three levels of total phosphorus (P4, P10 and P18 g kg^?1) and two levels of starch (S200 and S350 g kg^?1) were fed to triplicate groups of 30 fish to evaluate whether the high level of dietary phosphorus could improve the utilization of starch. Over 8‐week‐growth trial, best weight gain (WG) and specific growth rate (SGR) (P < 0.05) were observed in fish fed the P10/S200 and P18/S200 diets. WG and SGR significantly decreased as starch levels increased whereas for P4, while lipid contents of liver and whole body, hepatosomatic index and intraperitoneal fat ratio (IPF) significantly increased. These results suggested that high dietary starch will depress the growth performance and cause lipid accumulation. Within both starch levels, fish fed diet with P4 tended to produce lower (P < 0.05) WG and SGR, and had higher (P < 0.05) values of IPF. The whole body lipid, ash, calcium, phosphorus and iron contents were significantly affected by dietary phosphorus levels. Supplied phosphorus could improve the growth and decrease the whole body lipid, but there is no more effect after the phosphorus requirement was met at 10 g kg^?1.     

Comparative evaluation of dietary protein levels and plant–animal protein ratios in Macrobrachium rosenbergii (de Man)

The effects of varying dietary protein level (200, 250, 300 and 350 g protein kg^?1 diet) and plant : animal protein ratio (1 : 2, 1 : 1, 1 : 1.5 and 2 : 1) on growth of juvenile Macrobrachium rosenbergii (de Man) with approximately 0.27 g initial body weight were evaluated in two separate 30‐days study using practical diets. Significantly lower survival rate was recorded in prawns fed a diet containing 200 g kg^?1 dietary protein (66.67%) whilst 300 and 350 g kg^?1 protein gave the highest survival (96.67%). Significant differences (P < 0.05) in feed conversion ratio and protein efficiency ratio were recorded among different dietary protein levels. The results of the study showed that highest growth rate and maximum utilization of protein were recorded in prawns fed 300 g kg^?1 dietary protein and further increase in the dietary protein does not have any added advantage. There existed no statistically significant difference (P > 0.05) in the specific growth rate, protein efficiency ratio, weight gain and survival rate among the juveniles of M. rosenbergii fed varying plant–animal protein ratios at 300 g kg^?1 protein. Better‐feed conversion ratio was recorded in diets having a plant to animal protein ratio of 1 : 1 (2.62) followed by 1 : 1.5 (2.66), however there was no significant difference between them (P > 0.05). Based on the present study, it would be possible to replace animal protein by low‐cost plant protein in prawn feed. Better growth performance in juveniles of M. rosenbergii can be achieved by the incorporation of equal proportions of plant and animal protein (A : P = 1) in the diet.     

The specific dynamic action of southern catfish, <Emphasis Type="Italic">Silurus meridonalis</Emphasis> Chen,fed diets containing either raw or precooked corn starch or glucose

The growth performance of carnivorous southern catfish (Silurus meridionalis) was lower when fed a diet containing glucose as a carbohydrate source than when fed one containing starch. To test whether this decreased growth performance was partly due to higher metabolic costs induced by the fast assimilation of dietary glucose, the postprandial metabolic responses of southern catfish juvenile (36.7 ± 1.9 g) fed diets containing either raw or pre-cooked corn starch and glucose were investigated at 27.5°C. The peak metabolic rate of fish fed a raw corn starch diet was significantly higher than that of fish fed precooked corn starch and glucose diets (P < 0.05). The specific dynamic action (SDA) coefficients (energy expended on SDA as a percentage of energy content of the meal) of fish fed raw or precooked corn starch diets were significantly higher than that of fish fed a glucose diet (P < 0.05). The postprandial metabolic rate of fish fed a raw starch diet displayed a classic response – increased metabolic rate immediately after feeding, followed by a decreased metabolic rate several hours after feeding – as has been documented earlier in this species. However, the postprandial metabolic rate of fish fed a glucose diet had two alternating cycles of increasing and decreasing metabolic rate, which has not been reported previously. This bimodal pattern of the SDA curve was also found in a subsequent experiment in which purified d-glucose (0.1 g dry mass) was packed into sections of grass carp (Ctenopharyngodon idellus) intestine (0.05 g dry mass). The results suggest that the digestibility and absorption speed of the dietary carbohydrate has a significant effect on postprandial metabolic response in juvenile southern catfish. The results of this study may provide useful data in terms of the utilization of dietary carbohydrates by carnivorous fishes.     

Effect of dietary carbohydrate‐to‐lipid ratios on growth performance,body composition,nutrient utilization and hepatic enzymes activities of herbivorous grass carp (Ctenopharyngodon idella)

Six isonitrogenous (390 g kg^?1) and isoenergetic (16.2 kJ g^?1) diets with varying carbohydrate : lipid (CHO : L) ratios (202.5–1.74), were fed to triplicate groups of 25 fish in indoor recirculation system. Over 8‐week‐growth trial, best weight gain (WG), specific growth rate, feed conversion ratio, protein efficiency ratio and protein production value (P < 0.05) were observed in fish‐fed diets with CHO : L ratio of 7.5. Fish fed either the lowest (1.7) or highest (202.5) CHO : L ratio tended to produce lower (P < 0.05) growth and feed conversion efficiencies. The values of viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio increased as dietary CHO : L ratios decreased. There were no significant differences in whole body and liver crude protein among dietary treatments. Whole body and liver lipid increased as CHO : L ratios decreased. Plasma cholesterol and triacylglyceride levels increased linearly as dietary CHO : L ratios decreased. Activities of glucokinase and pyruvate kinase were stimulated by elevated levels of dietary carbohydrate; however, activities of lipase (LPS) and alkaline phosphatase were stimulated by elevated levels of dietary lipid. Based on a second‐order polynomial regression analysis of WG against dietary carbohydrate and lipid levels, 275 g kg^?1 of carbohydrate and 59 g kg^?1 of lipid, corresponding to a CHO : L ratio of 4.7, in a diet holding 390 g kg^?1 of crude protein and 16.3 kJ g^?1 of gross energy, proved to be optimal for grass carp. These results indicated that utilization of dietary lipid and carbohydrate was moderate in grass carp, but the fish were a little more capable of utilizing lipid compared with carbohydrate.     

Effects of different dietary protein and lipid levels on growth, feed utilization and body composition of red porgy (Pagrus pagrus) fingerlings

Two feeding trials were conducted to determine the minimum dietary protein level producing maximum growth, and the optimum protein to energy ratio in diets for red porgy (Pagrus pagrus) fingerlings, respectively. In the first trial, six isoenergetic diets were formulated with protein levels ranging from 400 to 650 g kg^?1 in increments of 50 g kg^?1, and fed for 11 weeks to 2.8 g average initial weight fish. Weight gain, specific growth rate and feed efficiency were significantly higher with diets containing higher protein levels, when compared with dietary levels below 500 g kg^?1. The highest protein efficiency ratios were obtained in fish fed 500 g kg^?1 dietary protein. The minimum dietary protein level producing maximum fish growth was found to be 500 g kg^?1. In the second trial, 15 g average initial weight fish were fed for 12 weeks, six diets containing three different lipid levels (100, 150 and 200 g kg^?1) combined with two protein levels (450 and 500 g kg^?1). Weight gain values increased when dietary lipids increased from 100 to 150 g kg^?1, with a further decrease for 200 g kg^?1 lipids in diets; the lowest fish growth being supported by 200 g kg^?1 dietary lipids. Fish growth was significantly higher when dietary protein increased from 450 to 500 g kg^?1. There was no evidence of a protein‐sparing effect of dietary lipids. Liver protein and lipid contents were low when compared with other fish species. All diet assayed produced high liver glycogen accumulation. The recommended protein and lipid levels in diets for red porgy fingerlings were 500 and 150 g kg^?1, respectively.     

Evaluation of dietary inclusion of housefly maggot (Musca domestica) meal on growth,fillet composition and physiological responses for barramundi,Lates calcarifer

The study was to evaluate the effects of dietary fish meal (FM) partially replaced by housefly maggot meal (HMM) on growth, fillet composition and physiological responses of juvenile barramundi, Lates calcarifera. HMM at 100, 150, 200 and 300 g kg^?1 was supplemented in the basal diet to replace dietary FM protein. Basal diet without HMM supplementation was used as control. Total of five experimental diets were fed to triplicate groups of juvenile barramundi (initial weight: 9.66 ± 0.22 g) in a flow‐through rearing system for 8 weeks. Fish fed all experimental diets showed no effects (P > 0.05) on weight gain and whole body protein, lipid and moisture content. Fish fed control diet and 100 g kg^?1 HMM diet had the highest (P < 0.05) hepatic superoxide dismutase (SOD) activity, followed by 150 g kg^?1 HMM group, the lowest in 200 and 200 g kg^?1 HMM groups. Hepatic thiobarbituric acid reactive substance (TBARS) value was the highest in fish fed 150–300 g kg^?1 HMM diets, followed by 100 g kg^?1 HMM group and the lowest in fish fed the control diet. Fish fed the 300 g kg^?1 HMM diet had lower plasma lysozyme activity than fish fed other diets. The results indicated that up to 300 g kg^?1 HMM can be used to substitute dietary FM protein without negative effect on growth. Although physiological responses were also considered, up to 100 g kg^?1 HMM in barramundi diet was recommended.     

Growth performance,oxidative stress indices and hepatic carbohydrate metabolic enzymes activities of juvenile Nile tilapia,Oreochromis niloticus L., in response to dietary starch to protein ratios

The effect of various dietary starch to proteins ratios (STA/P) on growth performance, oxidative status and liver enzyme activities involved in intermediary metabolism in juvenile Nile tilapia was evaluated. Four isocaloric‐practical diets (12.73 MJ kg^?1 digestible energy) with increasing STA/CP ratios were formulated. These were designated D₀ (344 g crude protein (CP) and 163.5 g starch (STA) kg^?1), D₁ (310 g CP and 243 g STA kg^?1), D₂ (258 g CP and 322 g STA kg^?1) and D₃ (214 g CP and 401 g STA kg^?1). Each diet was fed to triplicate groups of 60 fish (2.7 g) for 45 days. Compared with the control diet (D₀), significantly (P < 0.05) depressed growth and feed efficiency were observed only in the groups fed on diet D₃. The activities of hepatic enzymes involved in glycolysis and lipogenesis pathways were significantly enhanced in groups fed on diet D₃ compared with other diets. A significant (P < 0.05) increase in catalase activity was detected only in groups fed on diet D₃. Similarly, a significant (P < 0.05) enhancement in superoxyde dismutase, glutathione S‐transferases and glutathione peroxidise was observed in groups fed on diets D₂ and D₃ compared with other diets. Results demonstrate the ability of juvenile Nile tilapia to spare protein by dietary carbohydrate.     

Effectiveness of l‐ascorbyl‐2‐polyphosphate as an ascorbic acid source for sea cucumber,Apostichopus japonicus

A feeding trial was conducted to determine the adequate dietary ascorbic acid (AsA) levels and the effects on growth, meat quality and antioxidant status of sea cucumber (10.04 ± 0.06 g), Apostichopus japonicus. l ‐ascorbyl‐2‐polyphosphate (35% AsA equivalent) was supplemented separately to the basal diet to obtain five AsA levels, 0, 598, 1473, 4676 and 14340 mg kg^?1 diet respectively. After 60‐day feeding trial, the sea cucumbers fed diets containing 598 and 1473 mg AsA kg^?1 showed significantly higher (P < 0.05) body weight gain and specific growth rate values than the sea cucumbers fed control diets. The sea cucumbers fed diets containing 1473 and 4676 mg AsA kg^?1 showed significantly higher (P < 0.05) hydroxyproline contents than those of the sea cucumbers fed diets containing 0 and 598 mg AsA kg^?1. Antioxidant enzymes such as total antioxidant capacity, superoxide dismutase and glutathione peroxidase showed increasing trends with the increasing dietary AsA levels, but no significant differences (P > 0.05) were observed when the sea cucumbers fed diets with high dietary AsA levels. The content of malondialdehyde had the opposite trend of antioxidant enzymes. In conclusion, the adequate dietary AsA level focusing on growth performance of sea cucumber is between 598 and 1473 mg kg^?1 diet. Furthermore, high level of dietary AsA (between 598 and 4676 mg kg^?1 diet) improved meat quality and antioxidant status.     

Effects of two dietary protein levels on energy balance and digestive capacity of <Emphasis Type="Italic">Octopus maya</Emphasis>

Octopus maya is a carnivorous species and protein is the main energy source. During the present study, two different dietary protein levels (40 and 60% CP) were offered to octopuses as specifically designed artificial diets, to determine protein needs and the effects on metabolism. Frozen crab (Callinectes spp.) was used as control. Results obtained demonstrated that crab remains as one of the best diets for O. maya. The artificial diet with 60% CP produced a low but positive growth rate, and at times, a physiological response similar to that observed in octopuses fed crabs. The present results show the capacity of O. maya juveniles to adjust their digestive enzymes to different types of food and protein level, and this appears to be well correlated with octopus growth. General proteases and trypsin from the pancreas were well correlated with growth rates. A low activity was observed in octopuses fed 40% PC diet (negative growth rate), while a high activity was present in octopuses fed 60% CP diet and crabs (low and high growth rate, respectively). In contrast, these same enzymes were inducted in the salivary glands of octopuses fed with the diet that promoted weight loss (40% CP diet), while a reduced activity was observed in octopuses fed crabs. Energy budget indicates that the animals ingested more than 1,000 kJ week⁻¹ kg⁻¹; with such energy, octopuses should satisfy their physiological demands such as was observed when animals were fed crab (I = 1,300 kJ week⁻¹ kg⁻¹; P = 834 kJ week⁻¹ kg⁻¹). However, a very low digested energy was observed in octopuses the fed artificial diets, indicating that these could have a factor that limits digestibility.     

The effect of dietary methionine on growth,antioxidant capacity,innate immune response and disease resistance of juvenile yellow catfish (Pelteobagrus fulvidraco)

An 11‐week feeding trial was conducted to evaluate the effect of dietary methionine on the growth, antioxidant status, innate immune response and disease resistance to Aeromonas hydrophila of juvenile yellow catfish. Six isonitrogenous and isolipidic practical diets were formulated to contain different graded methionine levels ranging from 6.1 to 16.4 g kg^?1 of dry weight. The results indicated that growth performance and feed utilization were significantly influenced by the dietary methionine levels; fish fed the diet containing 6.1 g kg^?1 methionine level had lower specific growth rate, percentage weight gain (PWG), feed efficiency and protein efficiency ratio than those fed the other diets (P < 0.05). Fish fed the diet containing 16.4 g kg^?1 methionine level had lowest protein contents in whole body and muscle among all treatments. Triacylglycerols, cholesterol, aspartate aminotransferase, alanine aminotransferase and haemoglobin (Hb) in plasma or whole blood were significantly affected by dietary methionine levels. Fish fed the diet containing 6.1 g kg^?1 methionine level had higher superoxide dismutase, glutathione peroxidase activities and malondialdehyde values than those fed other diets. Fish fed diets containing 9.7 and 11.8 g kg^?1 methionine levels had higher lysozyme activity, total immune globulin, phagocytic activity and respiratory burst than those fed other diets. The lowest survival after A. hydrophila challenge was observed in fish fed a diet containing 6.1 g kg^?1 methionine. Quadratic regression analysis of PWG against dietary methionine levels indicated that the optimal dietary methionine requirement for the maximum growth of juvenile yellow catfish was estimated to be 11.5 g kg^?1 of the diet in the presence of 4.0 g kg^?1 cystine (corresponding to 23.5 g kg^?1 of dietary protein on a dry weight basis).     

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.     

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

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

Use of vitamin C as an immunostimulant. Effect on growth,nutritional quality,and immune response of <Emphasis Type="Italic">Labeo rohita</Emphasis> (Ham.)

Teleost fish lack the enzyme for endogenous synthesis of ascorbic acid (AA), an essential micronutrient for fish. The aim of this study was to examine the effect of higher levels of dietary vitamin C on growth, nutritional quality, and immunomodulation in the Indian major carp, rohu (Labeo rohita). Four groups of L. rohita were fed experimental diets containing either no vitamin C (control) or supplemented with vitamin C at 500 mg kg⁻¹ (Exp-1), 1000 mg kg⁻¹ (Exp-2), or 1500 mg kg⁻¹ (Exp-3) for 60 days. Growth parameters (NWG, ADG, and SGR), serological parameters (TSP, TSA, TSG, and A:G), haematological parameters (TLC, TEC, Hct, MCV, and MCH), and different non-specific immunological parameters (PR, PI, respiratory burst activity, and bactericidal activity) were evaluated during the experimental trial. Fish fed a vitamin C-supplemented diet showed higher specific growth rate (SGR) up to 1000 mg kg⁻¹ compared with control fish. Different haematological and serological parameters along with non-specific immune parameters were influenced by vitamin C supplementation. Among the non-specific immune parameters phagocytic activity (PR and PI) and respiratory burst activity (NBT cells) were significantly (P ≤ 0.05) enhanced by increasing doses of vitamin C supplementation. Higher levels of dietary vitamin C significantly (P ≤ 0.05) enhanced protection against Aeromonas hydrophila (AH1) infection compared with controls. Results from this study help to establish the beneficial effect of vitamin C on growth and immunmodulation in rohu (L. rohita).     

Influence of lupin and rapeseed meals on the integrity of digestive tract and organs in gilthead seabream (Sparus aurata L.) and goldfish (Carassius auratus L.) juveniles

Two rearing trials were conducted to evaluate the effects of dietary lupin (LM) and rapeseed (RM) meals in gilthead seabream (Sparus aurata L.) and goldfish (Carassius auratus L.) juveniles. Each plant meal was incorporated at the rate of 200 g kg^?1 in two distinct diets, which were compared with a fishmeal‐based diet as control. After 1 month, the two plant diets did not influence the whole body growth, but the digestive systems were affected. The splenosomatic index was reduced with two plant meals in goldfish and with RM in seabream. The hepatosomatic index was only reduced in LM‐fed seabream. Cellular characteristics were also affected. The largest liver cells were observed in RM‐fed goldfish suggesting changes in metabolic function. The LM and RM diets stimulated in seabream, especially the reaction in haematopoietic tissues with the proliferation of melano‐macrophages centres, and a tendency for elongated villus height in the anterior intestine thus that possibly compensated for a reduction in digestive function. Such adaptive structural modifications and the absence of degenerative signs allowed concluding that the integrity of the digestive system was maintained in fish fed plant meals.