Effects of soluble dietary cellulose on specific growth rate,survival and digestive enzyme activities in three freshwater crayfish (Cherax) species

The current study evaluated the effect of soluble dietary cellulose on growth, survival and digestive enzyme activity in three endemic, Australian freshwater crayfish species (redclaw: Cherax quadricarinatus, marron: C. tenuimanus, yabby: C. destructor). Separate individual feeding trials were conducted for late‐stage juveniles from each species in an automated recirculating freshwater, culture system. Animals were fed either a test diet (TD) that contained 20% soluble cellulose or a reference diet (RD) substituted with the same amount of corn starch, over a 12‐week period. Redclaw fed with RD showed significantly higher (P < 0.05) specific growth rates (SGR) compared with animals fed the TD, while SGR of marron and yabby fed the two diets were not significantly different. Expressed cellulase activity levels in redclaw were not significantly different between diets. Marron and yabby showed significantly higher cellulase activity when fed the RD (P < 0.05). Amylase and protease activity in all three species were significantly higher in the animals fed with RD (P < 0.05). These results indicate that test animals of all three species appear to utilize starch more efficiently than soluble dietary cellulose in their diet. The inclusion of 20% soluble cellulose in diets did not appear, however, to have a significant negative effect on growth rates.     

The use of diatom Skeletonema costatum on aquaculture‐produced purple sea urchin (Paracentrotus lividus) larvae and post‐larvae diet

The quality of the microalgae provided on Paracentrotus lividus larvae rearing is a primordial factor having a direct (nutritional properties) and indirect (water quality) impact on growth, competence and survival. Skeletonema costatum is a diatom commonly used in the bivalve cultivation. However, the use of this diatom in P. lividus larval cultivations is poorly known. The Rhodomonas spp. is a microalgae commonly used in sea urchin larvae culture. Three different diets were tested on P. lividus larvae and post‐larvae cultivation (D1—Rhodomonas marina, D2—S. costatum, D3—mixture of both algae). Larvae fed with the D2 diet (55.8%) and D3 (39.9%) had a survival at 15 DAH higher than D1 (5.5%). The low survival in D1 could be due to the higher microbiological load on microalgae (Vibrio alginolyticus and V. pectenicide). Larvae fed with S. costatum (D2) showed a lower development than other diets. The competency index was lower for larvae fed with the D2. These results show that microalgae diversified diets contribute to a better development of P. lividus larvae. During the settlement and post‐settlement phase, there was also a lower growth of the sea urchin fed with the D2 and a higher survival for D3.     

Effect of diets supplemented with feed additives on growth,feed utilization,survival, body composition and intestinal bacterial load of early weaning European seabass, <Emphasis Type="Italic">Dicentrarchus labrax</Emphasis> post-larvae

The present study was carried out to evaluate the effect of supplementation of Garlen®, Diamond V XPC®, and Bactozyme® and their combination in the diets of European sea bass, Dicentrarchus labrax larvae development in hatcheries on feed intake, growth performance, feed efficiency, intestinal bacterial, survival rate, and economics analysis. Dicentrarchus labrax juveniles (1.4 ± 0.5 mg) were distributed into eight experimental groups with a density of 2.5 larvae per liter. Eight iso-nitrogenous (55% crude protein) and iso-caloric (19.2 ± 0.2 MJ/kg, DM) weaning diets were formulated to contain the control diet (no feed additives), individually or mixed alternatively with three feed additives (Garlen®; Diamond V XPC®, and Bactozyme®). Each experimental diet was allocated to three tanks of fish and fed for 12 weeks. Growth and survival rate (S %) were improved for larvae fed the diets supplied with either (Diamond V XPC® + Bactozyme®) or (Garlen® + Diamond V XPC® + Bactozyme®), respectively compared to the control larvae group. The best FCR value was recorded for larvae fed a diet supply with (Garlen® + Diamond V XPC® + Bactozyme®), while the control larvae group recorded the worst FCR. The optimum significant (P ≤ 0.05) nutrient utilization values, larvae body crude protein content, activity test (ATV%), and profit index (PI) values were observed for larvae fed a diet containing Diamond V XPC® + Bactozyme® or Garlen® + Diamond V XPC + Bactozyme® compared to other treatments. The opposite trend was observed for total bacterial (TBC) and Vibrio sp. counts. No significant (P ≥ 0.01) difference was recorded in Aeromonas sp. count values in all experimental treatments. The results from this study show that (Garlen®; Diamond V XPC®, and Bactozyme®) individually or mixed alternately as growth promoters and immune stimulants in early weaning larval diets of European sea bass under hatchery conditions led to improve growth performance, feed utilization, survival, lowest intestinal bacterial load, and highest profit index (LE).     

Effect of dietary <Emphasis Type="SmallCaps">l</Emphasis>-tryptophan on cannibalism,survival and growth in pikeperch <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L.) post-larvae

The effect of supplemented commercial diets with crystalline l-tryptophan (TRP—5, 10 and 20 g TRP kg^?1) on cannibalism, survival and growth parameters of pikeperch post-larvae (Sander lucioperca) was evaluated. Fifteen-day-old pikeperch larvae (mean weight—6.8 mg) were reared during the next 28 days (20.5 °C, 16L:8D) in glass aquaria in a recirculating aquaculture system. The enzyme-linked immunosorbent assay showed that TRP-supplemented diets were effective in increasing the levels of serotonin (5-HT) in the body tissue of pikeperch. TRP supplementation resulted in a slight decrease in both types of cannibalism, although the reduction in cannibalism impact did not amount to more than a few percent. TRP treatment had no significant influence on the final survival of pikeperch post-larvae (ranged from 20.1 ± 12.4 to 29.0 ± 12.9 %). However, contrary to the earlier studies conducted on other fish species, no significant difference in the growth rates and feeding behavior of pikeperch between TRP-fed and control group were found. The final body weight and growth rate ranged from 0.211 ± 0.014 to 0.243 ± 0.016 and from 12.19 ± 0.38 to 12.76 ± 0.35 % day^?1, respectively. To our knowledge, this is the first study reporting the effects of TRP supplementation on the cannibalism–survival–growth relations in fish in the post-larval stage.     

Effects of culture conditions on larval growth and survival of stalked barnacles (Pollicipes pollicipes)

Pollicipes pollicipes (Crustacea: Scalpelliformes) is a highly prized food in Portugal and Spain and consequently a species of considerable interest to aquaculture. Surprisingly, however, larval culture conditions for this barnacle have not been optimized. This study investigated the effects of temperature, diet, photoperiod and salinity on the growth and survival of P. pollicipes larvae. Temperature had a significant effect on specific growth rate (2.6–5.9% total width per day, from 11 to 24°C), reducing mean development time to the cyprid from 25 days at 11 °C to 10 days at 24°C, although this was accompanied by a significant increase in mortality to over 90% above 22°C. Mid‐range temperatures (15–20°C) maximized total survival (19–31% respectively). Algal diets of Tetraselmis suecica, T. suecica/Skeletonema marinoi and S. marinoi/Isochrysis galbana did not affect specific growth rate significantly, but survival (on average 39% in 15 days) and the proportion of high‐quality healthy cyprids was significantly higher on the latter two diets (11–15% of initial number of larvae). Photoperiod did not significantly affect the survival, although specific growth rate was significantly higher at 24:0 and 16:8 L:D. Salinity (20–40 g L^?1 range) did not affect growth and survival significantly. The best growth and survival were accomplished using rearing temperatures of 15–20°C, daily feeding with T. suecica/S. marinoi or I. galbana/S. marinoi and a photoperiod of 24:0 L:D.     

Metamorphosis of larvae of Crassostrea virginica fed microencapsulated diets

This paper reports the results of two feeding experiments in which oyster larvae (Crassostrea virginica) were grown to metamorphosis on microencapsulated diets, and provides the first successful case of culturing oyster larvae to metamorphosis on an artificial diet. Five to 25% of the larvae fed microencapsulated diets grew to the “eyed” stage in 22–25 days. About 2–20% of these “eyed” larvae metamorphosed and settled and 25–40% of these settled larvae produced spat (> 0.05 mm). Two concentrations of two microencapsulated diets were tested; results indicated that diet concentration affects larval growth and development.Microcapsules with capsule walls made of a lipid mixture containing ethyl cellulose and stearic acid improved the retention of water-soluble components. Capsules were more stable at low temperature (5°C) than at higher temperatures (22 and 28°C). Inclusion of lipid algal extract in gelatin-acacia capsules promoted better growth of larvae than those not containing the algal extract. This suggests that attractants or phagostimulants could play an important role in microencapsulated diets.     

Effect of dietary taurine levels on growth performance and taurine content of Nibea albiflora larvae

The effect of taurine supplementation to a microencapsulated diet at 0 % (T-0 %), 1 % (T-1 %) and 2 % (T-2 %) level on growth performance and taurine content of Nibea albiflora larvae was evaluated. The microencapsulated diet was prepared using wet granulation and fluidized bed coating process. Scanning electron microscopy microphotography of the microencapsulated diet showed the appearance with a dense film around the core. More than 50 % of diet particles were between 250 and 590 μm. A 30-day feeding experiment was conducted with larvae at 15 days after hatching (DAH), in which larvae were weaned at 20 DAH from copepods to the experimental diets or fed copepods throughout the experimental period. The survival and total length of larvae were significantly higher in T-1 % group compared with T-0 % group (P < 0.05). The survival, total length and wet weight of larvae were significantly higher in T-2 % group compared with T-0 % group (P < 0.05). Fish larvae fed copepods had the best growth performance in survival, total length and wet weight, which were significantly higher than those in other treatments (P < 0.05). The taurine content of larvae fed with supplemental taurine (T-2 %, T-1 %) was significantly higher than that of larvae fed without supplemental taurine (T-0 %) (P < 0.05). These results confirmed that taurine is an essential nutrient for N. albiflora larvae.     

Complete replacement of fish meal by other animal protein sources on growth performance of <Emphasis Type="Italic">Clarias gariepinus</Emphasis> fingerlings

To completely replace the fish meal by a mixture of earthworm and maggot meals, experimental diets were tested during 42 days on Clarias gariepinus fingerlings. Five isoproteic and isoenergetic diets (40 % crude protein and 17.9 ± 0.3 kJ g^?1) including the control diet (D1) based on fish meal, were formulated. All these diets satisfied the essential amino acids requirements of C. gariepinus fingerlings. These diets were tested on triplicate groups of 50 fishes (initial body weight: 3 ± 0.1 g) bred in tank (0.5 m³). The approximate ratios 2:5; 1:4; 1:12 and 0:1 between the earthworm meal and the maggot meal were used, respectively, to formulate four diets D2, D3, D4 and D5 without fish meal. After the feeding period, significant differences (P < 0.05) were observed on growth, feed utilization between control diet (D1) and test diets (D2–D5). Fish fed earthworm- and maggot-based diets were grown better than those fed the control diet. Survival and feed utilization were not significantly affected by the ratio between earthworm meal and maggot meal in the test diets. Lipid content was higher in carcass and fillet of fishes fed earthworm- and maggot meals-based diets than that of those fed fish meal-based diet. This study indicates that when the ratio 2:5 between the earthworm meal and the maggot meal is used to entirely replace fish meal and the ratio lysine/arginine of the diet is inferior to 1, the growth performances and feed utilization of Clarias gariepinus fingerlings are improved.     

Evaluation of Cuphea Meal as an Ingredient Replacement in Channel Catfish,Ictalurus punctatus,Diets

ABSTRACT

Cuphea meal is a new, alternative feedstuff that has potential as a sustainable, economical replacement for wheat, rice, and corn ingredients in channel catfish, Ictalurus punctatus, diets. Channel catfish fingerlings were fed a control diet containing wheat or two experimental diets containing 7.5% cuphea meal, or 12.5% cuphea meal for eight weeks to determine if cuphea meal could replace wheat products in catfish diets. Mean (±SE) weight gains were 317.8 ± 28.8 g, 407.0 ± 36.9 g, and 372.8 ± 29.8 g for fish fed the control diet, the 7.5% cuphea meal diet, and the 15% cuphea meal diet, respectively, and there were no significant differences (P < 0.05) among treatments. Mean (±SE) whole-body protein of fish fed the cuphea diets (13.3 ± 0.66 and 14.5 ± 0.21%) was significantly (P < 0.05) higher than that of fish fed the wheat diet (12.7 ± 0.44%). Cuphea meal enhanced body composition of juvenile channel catfish without affecting growth or survival. Therefore, cuphea meal is a promising candidate for replacement of wheat bran at the levels tested.     

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.     

Effects of dietary l-tryptophan on the agonistic behavior,growth, and survival of freshwater crayfish Astacus leptodactylus Eschscholtz

In this study, the effects of dietary tryptophan (a precursor of 5-hydroxytryptamine, 5-HT, serotonin) on the agonistic behavior, growth, and survival of freshwater crayfish were investigated. For this aim, a control diet (D1) and three experimental diets (D2, D3, and D4) were prepared. D1 contained no additional tryptophan (TRP), but D2, D3, and D4 diets were supplemented with TRP at 0.50, 0.75, and 1.00 % in dry diet, respectively. The control contained 0.33 % TRP. Results revealed that higher supplemental dietary TRP levels caused a significant decrease in the aggressive behavior (P < 0.05), but an increase in the calmness of crayfish. In addition, the results showed that 5-HT levels in the hemolymph before the fight (after 15 days of feeding; resting) were significantly different (P < 0.05) between D1 and D4. There was a significant difference (P < 0.05) in the 5-HT level of hemolymph between the crayfish fed control and D4 after 15 days of feeding. However, after the fight, 5-HT concentration was significantly higher (P < 0.05) in TRP-supplemented A. leptodactylus as compared with the control. The findings of this study showed that supplemental dietary TRP caused a significant increase (P < 0.05) in the growth and survival rate of A. leptodactylus. The crayfish fed D4 had the best survival rate at the end of the experiment (91.60 % in August). The findings of this study also showed that difference in survival rate between the crayfish fed control and D2 in June, July, and August was not significant (P > 0.05). In addition to these, supplemental dietary TRP gave rise to significantly higher specific growth rate (SGR) values in June and July (P < 0.05). For example, in June, it was 0.38 for the crayfish fed D4, 0.28 for the crayfish fed D3, 0.18 for the crayfish fed D2, and 0.13 for the crayfish fed control. However, in August, the highest SGR (0.56) was obtained from the crayfish fed control. The results also showed that the SGRs of females were lower than the males in June, July, and August (P < 0.05). In conclusion, this research shows that the aggressive behavior of A. leptodactylus can be suppressed, and rearing efficiency (i.e., increased growth and high survival rate) of this species can be improved by increasing TRP levels to 1.00 % in its diet.     

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.     

Evaluation of dietary protein and lipid requirements of two-banded seabream (Diplodus vulgaris) cultured in a recirculating aquaculture system

The objective of this study is to investigate the effects of dietary protein and lipid levels on the growth performance and bioeconomic benefits of two-banded seabream (Diplodus vulgaris) juveniles, a candidate species for aquaculture sector. Eight experimental diets were formulated with four protein (50, 45, 40 and 35 %) levels for each of the two lipid levels (15 and 10 %). Triplicate groups of juvenile fish with an average initial body weight of ~3.64 g were reared in a recirculating aquaculture system and hand fed twice a day until satiation for a period of 60 days. In the experiment, no difference in survival rate was found between the different groups. Relative growth rate (RGR), specific growth rate (SGR), feed conversion ratio (FCR) and daily feed intake were not significantly affected by increasing protein and/or lipid treatments in this present study. However, the RGR, SGR and FCR values showed slightly better efficiency in the experimental group (35/15) fed with lower protein content (35 %) and higher lipid level (15 %) compared with those fed other diets. According to bioeconomic analyses results, the diet with the 35 % protein and 15 % lipid generated the best profit. The results suggest that two-banded seabream can be accepted as a promising alternative species for the aquaculture industry and optimum growth of two-banded seabream fingerlings can be obtained when they are fed a diet containing 35 % crude protein and 15 % crude lipid.     

Dry whey meal as a protein source in practical diets for Nile tilapia,Oreochromis niloticus fingerlings

ABSTRACT

This study was conducted as a trial of using dry whey meal (DWM) as a substitute for fish meal (FM) in practical diets for Nile tilapia, Oreochromis niloticus. Triplicate fish groups were fed on five isonitrogenous (30.2%) and isolipidic (6.9%) diets. The control diet (D1) used FM as the sole protein source. In the other four diets (D2–D5), FM protein was substituted by 25, 50, 75, or 100% DWM. Fish (3.5 ± 0.1 g) were stocked at a rate of 20 fish per 100-L aquarium and fed one of the tested diets up to satiation twice daily for 12 weeks. Fish growth, feed utilization, protein efficiency ratio, apparent protein utilization, and energy utilization for fish fed DWM diets up to 75% FM (D2–D4) tended to be higher but were not statistically different than the control diet. No significant effect of diet was found in whole-body moisture, crude protein, and total ash contents. Whole-body lipid content in fish fed the 100% DWM (D5) diet was significantly higher than that for fish fed the control diet. The optimal replacement level of FM by DWM was estimated by second-order polynomial regression to be 62.5%.     

Effects of the supplementation of vitamin D<Subscript>3</Subscript> on the growth and vitamin D metabolites in juvenile Siberian sturgeon (<Emphasis Type="Italic">Acipenser baerii</Emphasis>)

The objective of this study was to evaluate the effects of the supplementation of vitamin D₃ on the growth, vitamin D metabolites, and osteocalcin secretion in juvenile Siberian sturgeon (Acipenser baerii). A 90-day growth trial was conducted with juvenile Siberian sturgeon (initial body weight 3.47 ± 0.14 g) fed seven isonitrogenous and isoenergetic practical diets (45% CP and 13% lipid) containing 60 (basal diet), 240, 450, 880, 1670, 3300, or 1.0 × 10⁵ IU/kg feed (D60~D 1.0 × 10⁵) vitamin D₃. The results showed that weight gain and specific growth rate increased as the dietary vitamin D₃ levels increased from 450 to 3300 IU/kg (P < 0.05). The fish fed with D1670 and D3300 diets had higher crude lipid and ash levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, or D3300 diets had higher 25-OH-D₃ and 1,25-(OH)₂-D₃ levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, D3300, or D1.0 × 10⁵ diets had higher osteocalcin levels than the fish fed the D60 diet (P < 0.05). Based on the broken line method analysis of weight gain and osteocalcin, the dietary vitamin D₃ requirement of juvenile Siberian sturgeon was estimated to be 1683.30 and 1403.27 IU/kg per diet, respectively.     

Effects of dietary lipid levels on growth,feed utilization,body composition,fatty acid profiles and antioxidant parameters of juvenile chu’s croaker <Emphasis Type="Italic">Nibea coibor</Emphasis>

The present study aimed at determining the growth performance, feed utilization, body composition and antioxidant status of chu’s croaker (Nibea coibor) juveniles fed with increasing levels of dietary lipid: 6 % (D6), 9 % (D9), 12 % (D12) and 15 % (D15). Each diet was assigned to triplicate groups of fish in a total of 12 floating pens (300 fish, 25 fish per pen). After a 49-day growth trial, survival rate was not affected. D12 and D15 led to significantly higher specific growth rate (SGR). Fish fed D12 showed the highest protein efficiency ratio (PER), protein and lipid retention efficiencies (PER and LRE, respectively). The hepatosomatic and viscerosomatic indexes (HIS and VSI, respectively) increased, while feed conversion ratio (FCR) and feed intake (FI) decreased. Body protein, ash and muscle lipid contents were not significantly affected, but significantly higher body and liver lipid were noticed in fish fed with D15. Monounsaturated fatty acid (MUFA) was found to decrease compared to the experimental diets in muscle, while high unsaturated fatty acid (HUFA) was selectively accumulated in all treatments. Serum alanine transaminase (ALT, 14.13–22.53 U/L), aspartate transaminase (AST, 34.31–51.25 U/L), cholesterol (CHO, 2.02–3.03 mmol/L) and triglyceride (TG, 5.61–8.50 mmol/L) were correlated with increasing dietary lipids. Liver malate dehydrogenase (MDA, 3.32–6.67 mmol/L) and superoxide dismutase (SOD, 42.69–52.86 U/mg prot) increased with dietary lipids, while total antioxidant capacity (t-AOC, 1.08–3.50 U/mg prot) decreased. Polynomial regression analyses between SGR and dietary lipid levels showed that the optimal dietary lipid requirement of chu’s croaker is 12.9 % of dry matter.     

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。     

Feeding and digestion in the caridean shrimp larva of Palaemon elegans Rathke and Macrobrachium rosenbergii (De Man) (Crustacea: Palaemonidae) on live and artificial diets

Larvae of two caridean shrimp species, Macrobrachium rosenbergii (De Man) and Palaemon elegans Rathke, were fed live and artificial diets. P. elegans larvae fed exclusively live Artemia salina (15 nauplii mL^?1) developed into first postlarval stage (PL1) within 12 days at a temperature of 25°C and salinity 32.5 g L^?1. Their survival and mean total length at this stage were 88.5% and 6.7 mm respectively. M. rosenbergii larvae fed on 15 Artemia mL^?1 started to metamorphose into PLl within 24 days at 29–30°C and 12 g L^?1. Attempts to completely replace live Artemia for rearing P. elegans during early stages failed, and only a partial replacement was achieved for the larvae of both species. P. elegans larvae survived (49%) solely on a microgranulated diet (Frippak PL diet) from stage zoea (Z) 4–5 to PL1. Similarly, a microencapsulated diet (Frippak CD3) also sustained M. rosenbergii larvae from Z5–6 to PL1 with a 28% survival. Development of the larvae of both species was retarded by 2–3 days and their survivals were lower than those fed on the live diet. The inability of the early larvae of these caridean species to survive on artificial diets is attributed to their undeveloped guts and limited enzymatic capabilities. Trypsin activity in the larvae was determined for all larval stages. It was found that the highest trypsin activity, at stage Z4–5 in P. elegans and at stage Z5–6 in M. rosenbergii, coincides with a rapid increase in the volume of the hepatopancreas and the formation of the filter apparatus. These morphological changes in the gut structure appear to enable the larvae to utilize artificial diets after stage Z5–6. Low larval trypsin activities may be compensated by the easily digestible content of their live prey during early larval stages (Z1–Z4/5) and by longer gastroevacuation time (GET) and almost fully developed guts during later stages.     

Phototrophic Bacteria as Feed Supplement for Rearing Penaeus monodon Larvae

Larvae of the giant tiger prawn Penaeus monodon were reared from the naupliar to pos-tlarval stage, based on a diet of waste-grown phototrophic bacterium Rhodovulum sulfido-philum , the marine diatom Skeletonema costatum , and brine shrimp Artemia The experimental design consisted of feeding the protozoea with diatoms and varying proportions of bacterial biomass as diet D0 (0%), D1 (1%), D2 (2%), D3 (3%), and D5 (5%), while mysis and postlarvae were fed the above diet supplemented with Artemia nauplii. Controls were not fed with bacteria biomass (diet D0). The addition of R. sulfidophilum biomass in the diet had significant effects on the growth and survival of P. monodon larvae. In the first experiment, the larvae fed with diet D1 ( Skeletonema + 1% R. sulfidophilum ) reached the first postlarval stage (PL1) on the ninth day of feeding and had a mean total length (TL) of 6.13 ± 0.05 mm, which was significantly higher ( P < 0.001) than TL of larvae fed with the other three diets. In another experiment, prawn larvae fed with diet D2 had the highest overall survival of 46% and a significantly larger mean TL of 6.88 ± 0.18 mm at PL1 compared to larvae fed with diet D0 and D3 ( P > 0.05). However, in both experiments prawn larvae fed with the various diets showed significant differences in their length-at-stage ( P > 0.05), and the lowest growth and survival were obtained from diets comprising 3% and 5% bacterial biomass, which also gave the highest levels of ammonia-nitrogen in the culture water. Addition of more than 2% R. sulfidophilum biomass apparently deteriorates the quality of the culture water.     

Development of a Squid-hydrolysate-based Larval Diet and its Feeding Performance on Summer Flounder, Paralichthys dentatus, Larvae

Locally generated squid‐processing byproduct was processed into concentrated hydrolysate (22% solids, 17.3% protein, and 3.0% lipid, primarily phospholipids—11.6% eicosapentaenoic acid/24.5% docosahexaenoic acid on a lipid weight basis). Two microparticulate diets (65% protein, 19% lipid, 7.5% carbohydrate, and 19.12 MJ/kg energy, on a dry weight basis) were prepared using squid hydrolysate (SH) and squid‐herring hydrolysate as sole protein sources (73.3 and 78.65% of the whole diet, respectively). A 22‐d feeding trial with summer flounder, Paralichthys dentatus, larvae of 17 d after hatch showed that the survival rate (92%) of larvae fed SH was significantly (P < 0.05) higher than those of larvae fed live Artemia nauplii (81%) and a commercial diet, Proton (65%), while specific growth rates (SGR) were comparable (2.23% /d for SH and 2.86% /d for Artemia) with the lowest for Proton (1.39% /d). After switching from commercial and Artemia diets to a SH diet for 17 d following the 22‐d feeding, significant improvements were seen in survival rates of postweaning larvae fed previously commercial (65.28–76.57%) and Artemia diets (81.25–89.07%).