Changes in amino acid composition in the tissues of African catfish (Clarias gariepinus) as a consequence of dietary L-carnitine supplements

A study was undertaken to examine the effect of different amounts of dietary lysine (13 and 21 g kg^?1 diet), lipid (80 and 160 g kg^?1 diet) and L ‐carnitine (0.2 and 1.0 g kg^?1 diet) on growth performance, proximate composition and amino acid metabolism of the African catfish (Clarias gariepinus). Juvenile African catfish (23 ± 1.5 g/fish) were stocked into 70‐L aquaria (16 aquaria, 28 fish/aquarium) connected to a recirculation system during a maximum period of 74 days. All groups were fed at a level of 24 g kg^?0.8 day^?1 in an experiment run at pair feeding. Animals receiving 1.0 g carnitine accumulated up to six times more carnitine in their tissues than animals receiving 0.2 g (P < 0.05). Acyl‐carnitine and free L ‐carnitine levels increased in the whole body and in tissues. Dietary L ‐carnitine supplements increased protein‐to‐fat ratios in the body, but did not affect growth rate. Protein‐to‐fat ratios were only affected when the biosynthesis capacity of L ‐carnitine was restricted due to low lysine levels and when there was a shortage of dietary fat. When lysine was offered at 21 g kg^?1 feed, dietary L ‐carnitine supplements did not affect the amino acid concentrations of body tissues. Dietary L ‐carnitine supplements raised the concentration of glutamic acid > aspartic acid > glycine > alanine > arginine > serine > threonine in skeletal muscle tissue (P < 0.05). Total amino acid concentration in muscle and liver tissues (dry‐matter basis) increased from 506 to 564 and from 138 to 166 mg g^?1, respectively, when diets were offered with high L ‐carnitine, low lysine and low fat levels. These data suggest that dietary L ‐carnitine supplementation may increase fatty acid oxidation and possibly decrease amino acid combustion for energy.     

Tryptophan requirement of juvenile Asian sea bass Lates calcarifer

The dietary requirement of tryptophan for juvenile Asian sea bass (Lates calcarifer Bloch) was studied. The juveniles (mean initial weight, 5.30 ± 0.06 g) were given semi‐purified test diets containing fish meal, gelatin, squid meal, and crystalline amino acids, for 12 weeks. Each set of isonitrogenous and isocaloric test diets contained graded levels of tryptophan. Fish (15 per tank) were reared in 250‐L fiberglass tanks provided with continuous flow‐through sea water at 26°C and salinity of 28 p.p.t. Fish were fed twice daily at a feeding rate of 8% of the body weight day^?1 for the first 4 weeks and at 3.5–2.5% of the body weight day^?1 from 5 to 12 weeks. The experiment was in a completely randomized design with two replicates per treatment. Mean percentage weight gains and feed efficiency ratios were significantly different in fish fed varying tryptophan levels. Survival was 100% in all treatments. On the basis of break‐point analysis of the growth response, the dietary tryptophan requirement of juvenile Asian sea bass is 0.41% of the dietary protein. This information will be useful in further refinement of practical feed formulations for the Asian sea bass.     

Sulphur amino acid requirement of juvenile Asian sea bass Lates calcarifer

The dietary requirement of juvenile Asian sea bass Lates calcarifer Bloch for total sulphur amino acids was studied. Fish (average initial weight of 2.59 ± 0.08 g) were reared in twelve 500 L fibreglass tanks provided with flow-through seawater at 26°C and salinity of 31 p.p.t. for 12 weeks. They were fed semi-purified test diets containing 6.2, 7.2, 8.1, 9.0, 10.8, or 12.6 g methionine kg⁻¹ dry diet and a basal level of 3.1 g cystine kg⁻¹ dry diet. The mean crude protein of the diets (containing defatted Peruvian fishmeal, squid meal, soybean meal, and free amino acid mixture to simulate the pattern of hydrolysed sea bass protein) was 46.02%. The crude fat content of the diets was 10.51% from a 1 : 1 mixture of cod liver oil and soybean oil. Survival was 100% in all treatments. On the basis of the growth response, the total sulphur amino acid requirement of juvenile Asian sea bass was estimated to be 13.4 g kg⁻¹ dry diet (2.9% of protein). Fish fed low levels of l -methionine had significantly lower weight gains and feed efficiency ratios as well as slightly higher hepatosomatic indices. No nutritional deficiency signs were observed other than growth depression in fish fed on diets that were low in methionine. This information is valuable in further refinement of formulations of practical diets for the Asian sea bass.     

Effects of dietary l‐carnitine supplements on growth and body composition in beluga sturgeon (Huso huso) juveniles

The effects of dietary l ‐carnitine on growth performance, whole body composition and feed utilization were studied in beluga, Huso huso. Fish were randomly allocated in 15 tanks (30 fish per tank) and triplicate groups were fed to satiety during 84 days one of five isonitrogenous (41% CP) and isoenergetic (20 MJ kg^?1) diets, each differing in l ‐carnitine content [0 (control), 300, 600, 900 and 1200 mg kg^?1 diet]. At the end of the trial, fish grew from 19‐ to 23‐fold in weight, from 8.4 g to a maximum of 191 g. Fish fed 300–600 mg l ‐carnitine had the highest specific growth rate (SGR, 3.69 and 3.72% day^?1) and protein efficiency ratio (PER, 0.95 and 0.99), and the lowest feed conversion ratio (FCR, 1.4 and 1.3) than the other groups (P < 0.0001). SGR, PER and FCR were the poorest for fish fed 1200 mg l ‐carnitine, while fish fed the unsupplemented and 900 mg l ‐carnitine supplemented diet showed intermediate performance. Body lipid concentration decreased significantly from 5.8 to 5.1% (P < 0.0001) with dietary l ‐carnitine supplementation increasing from 0 to 300 mg. Energy content was significantly lower in fish fed the 900 and 1200 mg l ‐carnitine diet (5.8 MJ kg^?1), when compared with the other treatment groups (6.4–6.6 MJ kg^?1). The results indicated that feeding sturgeon on diets supplemented with 300 mg l ‐carnitine kg^?1 diet improved growth performance, and stimulated protein‐sparing effects from lipids.     

Nutritional evaluation of various plant protein sources in diets for Asian sea bass Lates calcarifer

A biological assay was conducted to evaluate the suitability of various leguminous seed meals and leaf meals as dietary protein sources for Asian sea bass, Lates calcarifer. In the growth experiment, fish (initial mean weight ± standard error (SE) of 3.8 ± 0.5 g) were fed isonitrogenous and isocaloric diets containing test ingredients to replace 13–18% of the diet. The same diet formulations were used in a digestibility experiment, except that 1% Cr₂O₃ was added as an external indicator. The growth of the control fish was comparable to fish fed leguminous seed meal-based diets, and better than those given leaf meal-based diets. The control diet had the highest apparent protein digestibility (APD) value. No significant differences were observed between the APD of white cowpea ( Vigna unguiculata ), green mungbean ( V. radiata ) and papaya ( Carica papaya ) leaf meal-based diets. However, the cassava ( Manihot esculenta ) leaf meal-based diet had the lowest APD value. The present findings suggest that white cowpea and green mungbean meals can be used as protein sources in practical diets to replace 18% of the sea bass diet without affecting their growth.     

Dietary arginine requirement of fingerling Indian major carp,Labeo rohita (Hamilton) based on growth,nutrient retention efficiencies,RNA/DNA ratio and body composition

To quantify the optimum dietary arginine requirement of fingerling Indian major carp, Labeo rohita (4.10 ± 0.04 cm; 0.62 ± 0.02 g), an 8‐week growth trial was conducted in eighteen 70‐L indoor circular aqua‐coloured troughs provided with a flow‐through system at 28 ± 1°C. Isonitrogenous (40 g 100 g^?1 crude protein) and isocaloric (4.28 kcal g^?1 gross energy) amino acid test diets containing casein and gelatin as intact protein sources with graded levels of arginine (0.5, 0.75, 1.0, 1.25, 1.50 and 1.75 g 100 g^?1 dry diet) were fed to triplicate groups of fish to apparent satiation at 07:00, 12:00 and 17:30 hours. Growth performance of fish fed the above diets was evaluated on the basis of absolute weight gain (AWG), specific growth rate (SGR), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE) and energy retention efficiency (ERE). Maximum AWG (2.61), SGR (2.80), best FCR (1.35), highest PER (1.85), PRE (37%) and ERE (76%) were recorded at 1.25 g 100 g^?1 dietary arginine. Maximum body protein (18.88 g 100 g^?1) and RNA/DNA ratio (5.20) were also obtained in a 1.25 g 100 g^?1 arginine dry diet. Except for the reduced growth performance in fish fed arginine‐deficient diets, no other deficiency signs were apparent. Based on the broken‐line and second‐degree polynomial regression analysis of the AWG, SGR, FCR, PER, PRE and ERE data, the optimum arginine requirement for fingerling Labeo rohita was found to be in the range of 1.22–1.39 g 100 g^?1 of the dry diet, corresponding to 3.05–3.47 g 100 g^?1 of dietary protein.     

Effects of dietary l-tryptophan and lighting conditions on growth performance of European sea bass (Dicentrarchus labrax) juveniles reared in a recirculating water system

The aim of the present study was to investigate possible stressful effects on European sea bass Dicentrarchus labrax reared under constant darkness (0L‐24D) and to examine the possible anti‐stressful effect of dietary tryptophan (TRP) supplementation. Juvenile European sea bass (initial body weight 4.23 ± 0.032 g) were reared for 10 weeks under 0L‐24D and 12L‐12D and fed either a commercial diet (0.47% TRP) or the same diet supplemented with L‐TRP (2.47% TRP). Results showed that lighting conditions had no significant effect on fish growth, while a depressive effect by the TRP supplementation was obvious. All fish populations reared under 0L‐24D exhibited reduced body protein, lipid and ash content and increased food consumption. Reduced body lipids, food consumption and nutrient utilization were observed in TRP‐supplemented fed fish, along with lower liver lipids. Dietary TRP enrichment significantly lowered liver saturated and monounsaturated acids and increased poly‐ and highly‐unsaturated fatty acids, especially in combination with 0L‐24D. These changes were also considerably reflected in carcass fatty acid composition.     

Growth rate of tank-reared Mediterranean amberjack, Seriola dumerili (Risso 1810) fed on three different diets

Mediterranean amberjack Seriola dumerili (Risso 1810) has aquaculture potential. The growth rate and food conversion ratio of S. dumerili on three different types of food (A: 100% frozen sardines; B: 50% frozen sardines and 50% pellet; C: 100% pellet) were measured, and analysed with respect to temperature, condition index and chemical composition of the fish fillet. Wild S. dumerili, average body weight 248 g and average total length 26.9 cm were caught in August and September 1994 in the South Adriatic Sea near Dubrovnik, Croatia and kept in three tanks (n=15 in each tank; duration of experiment, 226 days). The fish that were fed on diet A [initial weight, 252 ± 71 g; total length (TL), 24.3 ± 2.6 cm] started feeding immediately; however, fish assigned to diet C began to feed entirely on the pelleted diet 1 month after the start of the experiment. The mortality of fish fed on diet A was negligible, the registered growth rate was 313 ± 74 g (124.2%), specific growth rate was 0.32% day^?1 and the food conversion rate was 6.7. The fish fed on diet B (initial weight, 246 ± 74 g; TL, 28.2 ± 2.5 cm) started to feed on day 3 and achieved a total growth rate of about 98% (final weight gain, 241 ± 69 g) and specific growth rate of 0.24% day^?1 (feed conversion rate of 9.00 and mortality 13%). The fish fed on diet C (initial weight, 246 ± 74 g; TL, 28.2 ± 2.5 cm) started to feed on the pellets after 1 month and had a growth rate of 87% (weight gain 214 ± 85 g), a specific growth rate of 0.24% day^?1 and a food conversion rate of 10.6 with considerable mortality (27%). In all three diet groups the fish grew with considerable variation in food consumption and growth rate, depending on seasonal temperature variations of the ambient sea water supplied to the rearing tanks. Chemical analysis showed that the protein level (amount) in the fish meat exceeded 20% in all three fish fillet samples.     

Survival and changes in growth of juvenile tench (Tinca tinca L.) fed defined diets commonly used to culture non-cyprinid species

The study is an attempt to evaluate the feasibility of intensive tench culture using non‐specific diets as a preliminary step to check the acclimatization of the species under intensive rearing systems. Five‐month‐old juvenile tench were reared in recirculating systems at mean water temperatures of 22°C for 75 days. Fish fed with four different commercial diets (trout starter, trout first feeding, sea‐bass and eel), showed significantly higher final weights than the fish fed either eel or sea‐bass diets. Initial weight for all treatments was 2.3 ± 0.53 g. Final weight for the commercial diet groups was 3.56 ± 0.4 g, compared with the remaining groups that reached 2.09 ± 0.47 g (P < 0.05). Significantly higher survival rates were observed in the eel and sea‐bass groups (84.7 and 51.5%, respectively) than in either of the trout diet groups (38%). Specific growth rates (1.26 vs –0.18) and condition factor (1.26 vs 0.93) were also higher than those fed with salmonid diets (P < 0.05). Results obtained in this study indicate that regardless of the species’ slow growth, when compared with other cyprinids, final growth rates and survival of tench fed exclusively on sea‐bass or eel diets can be considered satisfactory. It must be pointed out that these promising results were obtained at lower temperatures than previous studies of tench in culture systems. The use of belt feeders did not show improvement in growth compared with manually fed fish when trout diets were used.     

Rearing temperature enhances hepatic glucokinase but not glucose-6-phosphatase activities in European sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) juveniles fed with the same level of glucose

The aim of this work was to elucidate if the previous results observed in hepatic glucokinase (GK) and glucose-6-phosphatase (G6Pase) activities in European sea bass and gilthead sea bream are due to temperature per se or to differences in feed intake at different water temperatures. For that purpose triplicate groups of fish (30 g initial body weight) were kept at 18 degrees C or 25 degrees C during two weeks and fed a fixed daily ration of a glucose-free or 20% glucose diet. At the end of the experimental period, plasma glucose levels in both species were not influenced by water temperature but were higher in fish fed the glucose diet. Higher hepatic GK activity was observed in the two fish species fed the glucose diet than the glucose-free diet. In the glucose fed groups, GK activity was higher at 25 degrees C than at 18 degrees C. Glucose-6-phosphatase activities in both species were not influenced by water temperature. In European sea bass and in contrast to gilthead sea bream it was observed an effect of dietary composition on G6Pase activities with surprising higher activities recorded in fish fed the glucose diet than in fish fed the glucose-free diet. Overall, our data strongly suggest that European sea bass and gilthead sea bream are apparently capable to strongly regulate glucose uptake by the liver but not glucose synthesis, which is even enhanced by dietary glucose in European sea bass. Within limits, increasing water temperature enhances liver GK but not G6Pase activities, suggesting that both species are more able to use dietary carbohydrates at higher rearing temperatures.     

Trypsin activity and physiological aspects in larval rearing of European sea bass (Dicentrarchus labrax) using live prey and compound diets

The aim of this study was to evaluate the potential of a compound diet as a live prey substitute for feeding European sea bass larvae ( Dicentrarchus labrax L.). The effect of a commercial diet (Nippai ML feed) and live prey ( Artemia nauplii) on tryptic enzyme activity, protein content, growth (standard length) and survival rates of sea bass larvae were tested during a 27-day rearing experiment. Sea bass larvae were divided into two groups. The live food group (control group) was fed exclusively on newly hatched Artemia nauplii (Inve AF grade), the test group was fed exclusively with the compound diet from day 15 onwards. As trypsin has been demonstrated to be a useful indicator for evaluating digestibility of food and the nutritional condition of fish larvae, individual tryptic enzyme activity was determined in both feeding groups. Larvae older than 14 days after hatching and fed on live food showed a significantly higher tryptic enzyme activity than larvae fed the compound diet. A similar relationship between tryptic activity and standard length in both test groups was detected only in small larvae (standard length < 7 mm). The usefulness of proteolytic enzyme activity measurements in larval fish research, as well as its use in aquaculture nutrition research, was confirmed. Protein content, increase in length and survival rates of the sea bass larvae were additionally determined in order to evaluate an influence on the diet. The protein content of larvae fed the Artemia nauplii was higher and the growth of larvae fed the compound diet was reduced. Larval mortality was not affected by the diet given.     

Enhanced intestinal epithelial barrier health status on European sea bass (Dicentrarchus labrax) fed mannan oligosaccharides

The study assesses the effects of dietary mannan oligosaccharides (MOS) in European sea bass (Dicentrarchus labrax) posterior intestinal lipid class composition and its possible relation to the potential prostaglandins production and Gut Associated Lymphoid Tissue (GALT) stimulation.Fish were fed 4 g kg^?1 MOS (Bio-Mos^® Aquagrade, Alltech, Inc., USA) for eight weeks. Fish fed MOS presented higher (P ≤ 0.05) weight gain, total length, and specific and relative growth rates than fish fed the control diet. Stimulated posterior gut of fish fed MOS showed higher (P ≤ 0.05) prostaglandins production than fish fed the control diet. Lipid class analyses of posterior gut revealed a reduction (P ≤ 0.05) in the neutral lipid fraction in fish fed MOS compared to fish fed the control diet, particularly due to a reduction (P ≤ 0.05) in triacylglycerols content. The polar lipid fraction increased (P ≤ 0.05) in fish fed MOS compared to fish fed the control diet, mainly due to an increase (P ≤ 0.05) in phosphatidylethanolamine and phosphatidylcoline contents.Light microscopy of posterior gut revealed increased number or goblet cells as well as higher level of infiltrated eosinophilic granulocytes for fish fed MOS. Transmission electron microscopy qualitative observations revealed a better preserved cytoarchitecture of the intestinal epithelial barrier in the posterior gut of fish fed MOS. Posterior gut of fish fed MOS presented more densely packed non-damaged enterocytes, better preserved tight junctions structure, healthier and more organized microvilli, and a higher presence of infiltrated lymphocytes and granulocytes compared fish fed the control diet.The present study indicates that dietary MOS enhances European sea bass posterior gut epithelial defense by increasing membrane polar lipids content in relation to a stimulation of the eicosanoid cascade and GALT, promoting posterior gut health status.     

Partial replacement of dietary fish oil with blends of vegetable oils (rapeseed, linseed and palm oils) in diets for European sea bass (Dicentrarchus labrax L.) over a long term growth study: effects on muscle and liver fatty acid composition and effectiveness of a fish oil finishing diet

Triplicate groups of European sea bass (Dicentrarchus labrax L.), of initial mass 5 g, were fed one of three practical type diets for 64 weeks. The three diets differed only in the added oil and were 100% fish oil (FO; diet A), 40% FO/60% vegetable oil blend (VO; diet B) where the VO blend was rapeseed oil, linseed oil and palm oil in the ratio 10/35/15 by weight and 40% FO/60% VO blend (diet C) where the ratio was 24/24/12 by weight. After final sample collection the remaining fish were switched to a 100% FO finishing diet for a further 20 weeks. After 64 weeks fish fed 60% VO diet B had significantly lower live mass and liver mass than fish fed diets A and C although SGR, FCR and length were not different between groups. There were no differences in any of the above parameters after either 14 or 20 weeks on the FO finishing diet. Fatty acid compositions of flesh were correlated to dietary fatty acids although there was selective retention of docosahexaenoic acid (22:6n-3; DHA) regardless of dietary input. Inclusion of dietary VO resulted in significantly reduced flesh levels of DHA and eicosapentaenoic acid (20:5n-3; EPA) while 18:1n-9, 18:2n-6 and 18:3n-3 were all significantly increased in fish fed the 60% VO diets. Fatty acid compositions of liver showed broadly similar changes, as a result of dietary fatty acid composition, as was seen in flesh. However, the response of flesh and liver to feeding a FO finishing diet was different. In flesh, DHA and EPA values were not restored after 14 or 20 weeks of feeding a FO finishing diet with the values in fish fed the two 60% VO diets being around 70% of the values seen in fish fed FO throughout. Conversely, and despite liver DHA and EPA levels being reduced to only 40% of the value seen in fish fed 100% FO after 64 weeks, the levels of liver DHA and EPA were not significantly different between treatments after feeding the FO finishing diet for 14 weeks. However, a 200 g portion of sea bass flesh, after feeding the experimental diets for 64 weeks followed by a FO diet for 14 weeks, contained 1.22 and 0.95 g of EPA + DHA for fish fed FO or 60% VO, respectively. Therefore, sea bass grown for most of the production cycle using diets containing 60% VO can still contribute a significant quantity of healthy n-3 HUFA to the human consumer.     

Rapid metabolic adaptation in European sea bass (Dicentrarchus labrax) juveniles fed different carbohydrate sources after heat shock stress

A study was conducted to evaluate the effect of two dietary carbohydrate sources (waxy maize starch and glucose) on the metabolic adaptation of sea bass juveniles (initial weight: 24 g) to a heat shock treatment (temperature rise from 18 degrees C to 25 degrees C within 24 h). Two isonitrogenous and isolipidic diets were formulated to contain 20% waxy maize starch (WS diet) or 20% glucose (GLU diet). Triplicate groups of fish were fed to near satiation for 4 weeks at both temperatures (18 degrees C and 25 degrees C). Then, fish previously maintained at 18 degrees C were submitted to a heat shock (18 degrees C to 25 degrees C) and continued to be fed with the same diets during 1 more week. The higher water temperature significantly improved growth performance, feed efficiency, as well as protein efficiency ratio, independently of diet. At 25 degrees C, but not at 18 degrees C, growth of fish fed the WS diet was higher than that of fish fed the GLU diet. Plasma glucose levels were higher in sea bass fed the GLU diet and not influenced by water temperature. Fish fed a glucose diet or reared at high temperatures (25 degrees C) showed enhanced liver glycolytic, lipogenic and gluconeogenic capacities compared to fish fed a starch diet or reared at low temperatures (18 degrees C). For the majority of the enzymes studied, 1 week seemed to be enough time for metabolic adaptation in sea bass submitted to an acute heat shock. Irrespective of carbohydrate source, HSP70 gene expression was similar in both cold water (18 degrees C) and warm water (25 degrees C) acclimated sea bass. A weak down regulation was observed after heat shock only in fish fed the GLU diet. This suggests that HSP70 gene expression is not affected by the rearing temperature per se.     

Effect of diet composition and lysine supply on growth and body composition in juvenile turbot (Psetta maxima)

A 10-week feeding trial was conducted to study the effect of feeding level and dietary lysine concentration on growth, protein and lysine retention, and body composition in juvenile turbot. Maintenance requirement for lysine and the efficiency of lysine utilisation were determined as well. Two experimental diets were formulated based on fishmeal or wheat gluten as main protein sources, containing 6.4 g (Diet A, control) and 4.5 g lysine per 100 g CP (Diet B), respectively. Diets were fed once daily at six feeding levels (per day 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% of body weight [BW] and ad libitum) to a total of 432 fish of 48 g initial BW. No differences in the growth parameters were observed between diets at the same feeding level, except a lower feed to gain ratio (p < 0.05) at the highest feeding level at Diet B. Whole-body composition was not affected by diet, whereas muscle protein concentration was significantly lower for fish fed Diet B. Amino acid concentration in whole-body protein was affected by dietary treatment and fish fed Diet B showed lower concentrations of all essential amino acids. In fish muscle protein, lysine, methionine, leucine, isoleucine, and valine concentrations were significantly lower in Diet B. Efficiency of lysine utilisation for growth (k_lys) was determined by linear regression analysis and amounted for 0.69 for Diet B. The maintenance lysine requirement defined at zero lysine retention was 6.5 mg · kg^?0.8 · d^?1. Lysine intakes at zero protein retention were 13.0 mg and 12.9 mg · kg^?0.8 · d^?1 for Diet A and B, respectively. Growth and nutrient retention were similar for both diets and, therefore, a lysine deficiency in Diet B did not occur. In conclusion, a proportion of 330 g wheat gluten per kg feed did not influence growth performance and maintenance requirement for lysine in juvenile turbot. However, the effect of diet composition on the amino acid profile of body protein might be relevant for the derivation of the amino acid requirement from protein retention.     

Effects of exogenous enzymes (phytase, non-starch polysaccharide enzyme) in diets on growth, feed utilization, nitrogen and phosphorus excretion of Japanese seabass, Lateolabrax japonicus

A feeding experiment was conducted to investigate the effects of exogenous enzymes (phytase, non-starch polysaccharide enzymes: WX and VP, supplied by DSM) on growth performance and excretion of Japanese seabass (Lateolabrax japonicus) (initial mass 6.26+/-0.10 g). A basal diet was used as a control that contained a mixed protein source, and lysine, methionine and valine were supplemented to simulate the essential amino acid pattern of fish meal. Four other diets were supplemented with 200 mg phytase (500 IU), 400 mg VP, 800 mg WX, or a combination of 800 mg WX and 400 mg VP per kg diet, respectively. Each diet was assigned to triplicate groups of fish in floating sea cages, and each cage was stocked with 60 fish. The results showed specific growth rate (SGR) and feed efficiency ratio (FER) were not significantly improved by the phytase supplementation. However, supplementations with WX and VP significantly enhanced the SGR and FER (P<0.05). Phosphorus retention was significantly increased by the supplementation with phytase, whereas nitrogen retention was also enhanced by supplementations of non-starch polysaccharide enzymes (P<0.05). The excretion experiment showed that the soluble phosphorus and ammonia nitrogen in starved fish were constant, irrespective of dietary treatments. The total phosphorus effluent in fish fed the diet with phytase supplementation was significantly lower compared with the control group after feeding to satiation (P<0.05), but soluble phosphorus excretion was still independent of dietary treatments. The ammonia excretion in satiated fish significantly decreased with supplementations of non-starch polysaccharide enzymes.     

Experimental treatments with diflubenzuron and deltamethrin of sea bass, Dicentrarchus labrax L., infected with the isopod, Ceratothoa oestroides

Sea bass with approximate average weights of 5 and 20 g were treated against Ceratothoa oestroides infection with: (i) medicated pellets of diflubenzuron PC90 at a dosage of 3 mg kg^?1 body weight (BW) per day for 14 days. Lice were counted at the beginning of treatment and 19 days after treatment. The drug cleared all lice in the treated group; in the control group, infection remained high 30 days after beginning the experiment. It was concluded that medicated pellets containing 3 mg kg^?1 BW diflubenzuron effectively cleared pre‐adult and adult stages of the isopod parasite over a 14‐day period. No adverse effects were recorded in treated sea bass during the trials and no reinfection occurred 15 days after end of the treatment. (ii) Deltamethrin by means of bath treatments in infected sea bass kept in experimental tanks at 20°C. Before treatment, toxicity on healthy fish was preliminarily assessed by testing five fish from each size group at concentrations of 30, 10, 5, 3, 1, 0.1, 0.05 and 0.01 mg L^?1 for 30 min. The therapeutic concentrations tested were: 10, 5, 3, 0.15, 0.1, and 0.05 μg L^?1 and assessed at 1, 24 and 48 h. Best results were achieved with the 10 μg L^?1 (0.01 mg L^?1) dose, where prevalence was reduced from 100 to 0% over 24 h in both large and small fish. No parasite recovery was observed at 48 h. The dose of 5 μg L^?1 reduced prevalence from 100 to 11.7% and to 0% for small and large fish, respectively. Finally, with the 3 μg L^?1 dose, prevalence was reduced from 100 to 37.5% (small fish) and to 13.3% (large fish). Lower doses were ineffective on the parasites at either 24 or 48 h.     

Effects of dietary protein and lipid levels on growth and feed utilization of wild‐caught striped sea bream,Lithognathus mormyrus

A feeding trial was carried out to determine the effects of dietary protein and lipid levels on the growth performance and feed utilization of wild‐caught striped sea bream (Lithognathus mormyrus). The experimental fish were collected from a local lagoon (Çardak Lagoon, Çanakkale, Turkey), transferred to the Marine Net Cage Unit and fed by hand to apparent satiation with a commercial sea bream feed (Biomar; 42% crude protein, 16% crude lipid). Approximately 4 weeks were needed to acclimate the fish to farming conditions. No pathological signs were observed and no fish losses occurred during the adaptation period. For the test trials four test diets with different levels of protein and lipid were formulated [low protein and low lipid (LP:LL), low protein and high lipid (LP:HL), high protein and low lipid (HP:LL), and high protein and high lipid (HP:HL)] and fed to L. mormyrus (mean weight 85.0 ± 4.6 g SEM) in the net cages (Ø 2 m, depth 2.5 m) for 60 days. During the experiment water temperature varied between 21.1 and 26.4°C; dissolved oxygen 8.4–9.6 mg L^?1; pH 7.2–8.6; and salinity 23.3–25.6‰. Growth performances of fish fed high protein diets were higher compared to fish fed low protein diets, irrespective of the dietary lipid level (P < 0.05). Feed conversion ratio (FCR) and protein efficiency ratio (PER) were not influenced by dietary protein or lipid levels (P > 0.05). Preliminary results indicate that striped sea bream can be easily adapted to farming conditions in net cages, and that a diet containing 50% crude protein and 15% crude lipid (HP:LL) levels with 23.0 g protein MJ^?1 gross energy of protein/energy ratio would be suitable for striped sea bream growth.     

Amino acid supplementation of methanol-grown dried microbial cells in diets for young chicks

Growth rates and efficiency of food conversion of young chicks fed on diets marginally limiting in total nitrogen and containing 150 g/kg diet of flash-dried microbial cells (MC) with and without amino acid supplements, were measured in three experiments. Performance of these animals was compared with that of groups fed on a methioninefortified soya bean meal (SBM) control diet. In all experiments, chicks fed on the SBM control diet grew faster and were more efficient than chicks fed on the basal unsupplemented MC diet. In Experiment 1, arginine supplementation markedly enhanced weight gain and efficiency of food utilisation of chicks offered the basal MC diet; methionine had no effect. The second experiment demonstrated that a supplement containing methionine, arginine and tryptophan was more effective in augmenting the nutritional value of MC than either methionine with arginine or tryptophan with arginine. In the final experiment, weight gain and food intake of chicks fed on MC with supplements of arginine, methionine and tryptophan were increased markedly by additions of lysine and glutamic acid but not by addition of lysine alone. In all experiments, performance of animals in MC supplemented groups was lower than that of animals fed on the SBM control diet.     

Effect of feeding frequency as a rearing system on biological performance,survival, body chemical composition and economic efficiency of Asian seabass Lates calcarifer (Bloch, 1790) reared under controlled environmental conditions

A 70-day rearing trial was done to determine the optimal frequency of feeding on growth performance (GP), feed conversion rate (FCR), cannibalism, survival rate (SR), body chemical composition and economic efficiency of the Asian sea bass. This study tested four different treatments of feeding frequencies (FF), once (T1), twice (T2), three times (T3), and four times (T4) per day. An average initial weight of Asian sea bass fry was 0.2 g (SD = ±0.12) were stocked 10 individuals per m³ (9.14 m × 1.82 m × 1.22 m, L × W × H; water depth 0.61 m) with two replicates per treatment (4 × 2 = 8). Fry were fed a mixture of larval commercial feed and shrimp with a pellet diet containing (46% CP). Initially, the feeding rate of 8% biomass per day was further adjusted according to fish biomass on a weekly basis. Results showed that, the FF significantly affected (p < 0.05) on growth indictors and survival rate (SR). Specifically fry fed three times a day (T3) had the best FBW, FL, SGR, ADWG and FCR followed by T4 and T2 while fry fed one time a day was the lowest in these parameters. Also, VSI, HSI and CF (k) significantly differed among the treatments. The fish whole body content of protein, moisture and ash did not significantly (p < 0.05) be affected by feeding frequency, but lipid content differed and both T3, T4 were the highest. It could be concluded that, increasing FF up to three times a day had a positive effect on weight gain, survival rate and feed utilization of Lates calcarifer. The second degree polynomial regression indicates that fed three times a day is optimum for best growth performance and survival for Asian sea bass.