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The present study evaluated the effects of feeding frequency (FF) and dietary protein/carbohydrate (P/CH) ratios on intestinal histomorphology, microbiota profile, and digestive and oxidative stress-related enzyme activities of gilthead seabream (Sparus aurata). To this purpose, two practical diets were formulated: one with 50% P and 10% CH (P50/CH10) and other with 40% P and 20% CH (P40/CH20). Triplicate groups of fish with9.1±0.01 gwere fed these diets for 60 days until visual satiation at a FF of 1, 2, or 3 meals per day. Distal intestine histomorphology was not affected by diet composition or FF. However, the pyloric caeca (PC) of fish fed 1 meal per day presented more gut fold height alterations than the other groups, except in fish fed diet P50/CH10 3 meals per day, where no changes was observed. Fish fed diet P40/CH20 3 meals per day also presented higher PC submucosa cellularity than the other groups. Fish fed diet P40/CH20 presented a higher number of operational taxonomic units, microbial richness, and diversity indices than fish fed diet P50/CH10. Amylase was the only measured digestive enzyme affected by the experimental conditions, presenting higher activity in fish fed diet P50/CH10 once per day. Glucose-6-phosphate dehydrogenase activity was lower in fish fed 2 meals per day than only 1. While catalase activity was lower in fish fed 2 than 3 meals per day. Glutathione reductase activity was the only measured parameter affected both by dietary P/CH ratio and FF, being inferior in fish fed once per day the P50/CH10 diet than the P40/CH20 diet and, also in the P50/CH10 diet, to fish fed 1 than those fed 3 meals per day. Overall, no major interactions was observed between dietary P/CH ratio and FF; however, a P40/CH20 diet fed 2 meals per day might be recommended for gilthead seabream juveniles.

The effect of partially replacing fishmeal (FM) by black soldier fly larvae meal (Hermetia meal--HM) in meagre (Argyrosomus regius) diet was evaluated for nutrient digestibility and digestive enzyme activity. For that purpose, triplicate groups of fish (18.0 ± 0.02 g) were fed during 48 days either a control diet (CTR), without HM, or one of three diets including 100, 200 and 300 g/kg of HM, replacing 17, 35 and 52% of FM, respectively. Apparent digestibility coefficients (ADCs) of dry matter, energy, protein, lysine, isoleucine, leucine, phenylalanine, alanine, glutamate, glycine and serine presented a decreasing response with increased HM inclusion. Chitin ADC was null, independent of dietary HM inclusion. Total alkaline protease activity increased while trypsin activity decreased with dietary HM inclusion. No intestinal chitinolytic activity was detected. Intestinal alkaline protease zymogram revealed nine bands with proteolytic activity against casein, with molecular weights ranging between 15 and 75 kDa. Anti-protease activity in the intestine was not affected by dietary inclusion of HM compared to the CTR diet. Overall, it is concluded that replacement of up to 17% FM with HM (100 g/kg HM inclusion level) in meagre diets has no major adverse effects in diet digestibility and digestive enzyme activity.

Made available in DSpace on 2020-12-12T02:21:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Proper inclusion of carbohydrates in aquafeeds can increase protein and lipid retention preventing the catabolism of these nutrients for energy purposes. This research aimed to evaluate performance, metabolic and enzymatic indicators in pacu (Piaractus mesopotamicus) juveniles fed diets with 350 or 400 g/kg starch (S) and 190 or 210 g/kg digestible protein (P) (diets S35P19, S35P21, S40P19 and S40P21 respectively). Overall, the best growth performance was achieved with diet S35P21. Dietary protein and starch levels had no effect on feed intake, feed conversion ratio and protein efficiency ratio. The lowest whole-body protein content was recorded in fish fed the S35P19 diet, while fish fed diet S40P21 presented the highest whole-body lipid content. Regardless of dietary protein level, S40 diets led to higher plasma glucose and triglycerides levels, and higher liver glycogen content. No differences were observed on hepatosomatic index or muscle lipids content. Increasing dietary starch level led to an increase in mesenteric fat index and in liver glucokinase activity, while higher dietary protein promoted a decrease in liver lipid content. Fish fed diet S40P21 showed higher liver glucose-6-phosphate dehydrogenase activity than fish fed the S35P21 and S40P19 diets. Dietary protein and starch levels had no effect on pyruvate kinase and fructose-1,6-bisphosphatase activity. Overall, dietary starch enhanced glycolytic and lipogenic pathways but did not depress gluconeogenic pathway. The results of this study indicate that a diet with 350 g/kg starch and 210 g/kg digestible protein was the most adequate for pacu in terms of growth performance and feed utilization. Universidade Estadual Paulista (Unesp) Centro de Aquicultura da Unesp (Caunesp) Universidade Estadual Paulista (Unesp) Faculdade de Ciências Agrárias e Tecnologia (FCAT-Unesp) Universidade do Porto CIMAR/CIIMAR - Centro Interdisciplinar de Investigação Marinha e Ambiental Universidade do Porto Faculdade de Ciências Departamento de Biologia Universidade Estadual Paulista (Unesp) Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista (Unesp) Centro de Aquicultura da Unesp (Caunesp) Universidade Estadual Paulista (Unesp) Faculdade de Ciências Agrárias e Tecnologia (FCAT-Unesp) Universidade Estadual Paulista (Unesp) Faculdade de Ciências Agrárias e Veterinárias

Nannochloropsis gaditana was tested as functional ingredient in low fishmeal diets for gilthead seabream juveniles, and its short‐term effects were evaluated in terms of intestinal morphology, digestive function, intestinal immunological and oxidative status, and intestinal microbiota. A diet with 850 g/kg of the protein provided by plant feedstuffs and 150 g/kg provided by fishmeal was used as control, and three other diets identical to the control were supplemented with 5, 7.5 and 15 g/kg N. gaditana meal and fed to 56.6 g fish for 37 days. At the end of this period, intestinal mucosa integrity and digestive capacity (luminal enzyme activity and absorption) were not altered by dietary microalgae supplementation. Intestinal transcript levels of key markers of inflammation (IL‐1β and TNF‐α) and of key enzymes involved in redox homeostasis (CuZnSOD, MnSOD and catalase) were also similar across experimental groups. However, microbiota richness increased with dietary supplementation of microalgae, and such modulation requires further investigation, particularly regarding its potential effects on disease resistance at short and long term.

This study aimed at evaluating the effects of short-chain fructooligosaccharides (scFOS), xylooligosaccharides (XOS) and galactooligosaccharides (GOS) on growth performance, hepatic metabolism, gut microbiota and digestive enzymes activities of white sea bream juveniles. Four diets were formulated: a control diet with fish meal (FM) and plant feedstuffs (PF) (30FM:70PF) and three test diets similar to control but supplemented with 10 g of scFOS, XOS or GOS per kilo diet, which were fed to fish during 12 weeks. Prebiotics had no effect on growth, feed efficiency or gut microbiota. Plasmatic triglycerides were lower in fish fed XOS than FOS and GOS diets. Malic enzyme activity was lower in fish fed XOS than FOS diet. Fish fed XOS diet had lower fatty acid synthetase (FAS), a key lipogenic enzyme and higher alanine aminotransferase activities. Fifteen days after the start of the trial, an enhancement of total alkaline protease, trypsin and lipase activities was observed in fish fed prebiotics, but such effect disappeared at 12 weeks. In conclusion, scFOS, XOS or GOS seem to have limited applicability in white sea bream feed.

The gut microbiomes of fish play important roles in host development, digestion and health. Evidence suggests that abiotic factors, such as diet and rearing temperature, could affect fish gut microbiota. In this study, the effect of dietary short-chain fructooligosaccharides (scFOS) on turbot intestinal health, microbiota and digestive enzymes was investigated at two rearing temperatures: 15 and 20 °C. Four practical diets were supplemented with scFOS at 0, 5, 10 and 20 g kg−1. scFOS did not affect fish performance. PCR-DGGE did not show differences in bacterial profiles between dietary treatments; however, the number of operational taxonomic units, richness and diversity were higher at 20 °C. Enzyme activities in the foregut were not affected by rearing temperature, while in the hindgut, enzyme activities were higher at 15 °C. Total alkaline protease, α-amylase and lipase activities in the foregut were higher in fish fed 20 g kg−1 scFOS. Prebiotic supplementation had no effect on hindgut α-amylase activity, while lipase activity of fish reared at 20 °C was higher in fish fed diet with 5 g kg−1 scFOS. No differences were observed in intestinal morphology. This was the first study to simultaneously evaluate the effect of dietary prebiotic level and rearing temperature on fish intestinal microbiota and health.

To assess the effect of feeding frequency on the utilization of dietary starch by white sea bream juveniles, triplicate groups of fish were fed an experimental diet (400 g kg−1 protein, 140 g kg−1 lipids and 350 g kg−1 pregelatinized maize starch) to apparent visual satiation 2, 3 or 4 times a day for 63 days. Growth performance, feed utilization efficiency, glycaemia, cholesterolaemia, plasma triacylglycerides, liver lipids and glycogen content were unaffected by feeding frequency. α-Amylase activity increased from the pyloric caeca to the posterior intestine and was higher in fish fed twice a day than in fish fed 3 or 4 times a day. Hepatic glucokinase (GK) activity decreased with the increase in feeding frequencies, whereas fructose-1,6-bisphosphatase (FBPase) activity increased. Hepatic glucose-6-phosphate dehydrogenase and glutamate dehydrogenase activities were unaffected by feeding frequency. Overall, feeding frequency did not improve white sea bream dietary starch utilization. α-Amylase, GK and FBPase activities responded to dietary starch consumed at each meal, denoting a good metabolic adaptation of the fish to the feeding conditions.

This study was the first to investigate the effect of soy antinutrients, saponins and phytosterols, in on-growing sea bass. Seven diets were formulated: a control diet (fishmeal and fish oil based) and six diets containing 1 or 2 g kg−1 levels of soya saponins, 5 or 10 g kg−1 levels of phytosterols or a combination of 1 g kg−1 saponins + 5 g kg−1 phytosterols or 2 g kg−1 saponins + 10 g kg−1 phytosterols. After a 59 days feeding trial fish were weighed, faeces collected for digestibility studies and plasma sampled for cholesterol quantification. At day 15 and 59, distal intestine (DI) samples were collected for histological evaluation and quantification of maltase (Malt), alkaline phosphatase (AlP) and leucine aminopeptidase (LAP) activities. At day 59, DI was collected for gene expression of AlP, Malt and immune related genes. Antinutrients had no effect on fish performance, digestibility, plasma cholesterol levels and digestive enzymes activities and gene expression. Only mild morphological changes were present in groups fed high levels of saponins + phytosterols. Expression of immune related genes showed no differences between groups. Overall, on-growing sea bass showed high tolerance to dietary antinutrients up to the levels tested.

A 14 weeks growth trial was performed to estimate the protein requirement for growth and maintenance of zebra sea bream (Diplodus cervinus) juveniles. For that purpose, nine isolipidic diets were formulated to contain increasing protein levels (from 50 to 550 g kg−1) at the expense of carbohydrate. Each diet was assigned to duplicate groups of 20 fish, with an average body weight of 7.7 g. Feed efficiency improved with dietary protein up to 400 g kg−1, no further differences being noticed at higher protein levels. Fish fed the 50 g kg−1 protein diet lost weight during the trial. In the other groups, weight gain improved as dietary protein increased up to 350–400 g kg−1. Fish fed diets with 250 g kg−1 protein or lower had lower whole-body protein content than the other groups. A curvilinear-plateau model was used to adjust weight gain and protein gain (g kg ABW−1 day−1) to dietary protein levels. Based on that model, the optimum dietary protein requirement for maximum weight gain was estimated to be 437.6 g kg−1 and for maximum protein gain 461.9 g kg−1, corresponding to a protein intake of 7.63 g kg ABW−1 day−1. Protein requirement for maintenance was estimated to be 1.01 g kg ABW−1 day−1.

Summary This work aims to establish normal reference intervals for selected hemato-biochemical parameters, based on their potential clinical relevance, and which may contribute to evaluating the health, nutritional and welfare status of Senegalese sole (Solea senegalensis Kaup, 1858) juveniles. Thirty-one healthy Senegalese sole juveniles grown under intensive aquaculture conditions were used in the study. Based on the robust method with Box–Cox transformation data the established reference intervals for hematological parameters were: hematocrit 12–26%, hemoglobin 2.8–6 g dl−1, erythrocytes 90–97.0% total, leucocytes 4–10% total; erythrocyte indices and differential leucocytes counts were also evaluated. Reference intervals for biochemical parameters were (g dl−1) glucose 19–86 mg dl−1, total protein 2.6–6.3, albumin 1–2.34, globulins 1.8–4.1, lipids 0.7–1.3, triglycerides 0.3–1.8, total cholesterol 0.1–0.9 g dl−1, HDL-cholesterol 4–65 mg dl−1, LDL-cholesterol 7–532 mg dl−1, sodium 124–202 mmol L−1), potassium 1.1–4.6 mmol L−1, calcium 7.6–13.2 mg L−1, magnesium 1.8–4.8 mg L−1, inorganic phosphorus 3.4–9.5 mg L−1, alkaline phosphatase 93–598 U L−1, aspartate aminotransferase 118–605 U L−1, lactate dehydrogenase 8.7–782 U L−1, and creatine phosphokinase 31.5–552 U L−1. This data is expected to provide a valuable tool to monitor the stress, health and nutritional conditions of Senegalese sole juveniles under aquaculture production.

The effect of short-chain fructooligosaccharides (scFOS) incorporation on growth, feed utilization, body composition, plasmatic metabolites and selected liver enzyme activities of turbot juveniles reared at winter (15 °C) and summer (20 °C) temperatures was studied. Four comparable diets were formulated to contain circa 50 : 50 fish meal and plant ingredients as protein sources. Experimental diets included increasing levels of scFOS (0, 5, 10 and 20 g kg−1). Final weight was higher at 20 °C, but thermal growth unit, feed efficiency, nitrogen and energy retention were better at 15 °C. scFOS supplementation did not affect fish growth performance. Fish reared at 15 °C had higher liver glycogen, visceral and hepatosomatic indices. Liver lipids, plasma triglycerides, total lipids, cholesterol HDL and LDL were higher in turbot reared at 20 °C. Malic enzyme, fatty acid synthetase, alanine aminotransferase and glutamate dehydrogenase activities were higher in fish reared at 15 °C. Malic enzyme was lower in turbot fed with 20 g kg−1 scFOS compared to control diet; however, fatty acid synthetase presented an increasing trend as dietary scFOS increased up to 10 g kg−1. Glutamate dehydrogenase activity was higher in fish fed the control diet. Results seem to indicate no benefits of scFOS incorporation to diets on growth performance of turbot.

This study aimed to elucidate the effects of two soy antinutrients, saponins and phytosterols, on growth, intestinal health and function of European sea bass juveniles. Seven fishmeal-based diets were formulated: a control diet without antinutrients and six experimental diets containing low or high levels of soyasaponins (SapL and SapH, respectively), low or high levels of phytosterols (PhytL and PhytH, respectively) and low or high levels of soyasaponins + phytosterols (SapPhytL and SapPhytH, respectively). A feeding trial was conducted for 59 days after which blood was collected for plasmatic cholesterol quantification and intestinal samples were collected for histology, digestive enzymes activity and gene expression analysis. Histology was also performed at day 15. PhytL resulted in high distal intestine (DI) relative weight and decreased plasma cholesterol, while PhytH caused inflammatory changes in the DI. SapH depressed maltase and alkaline phosphatase activity in DI and the histological evaluation indicated some inflammatory changes. The SapPhytH resulted in decreased maltase activity in the DI and indications of inflammatory changes that were supported by the results on gene expression profiles. The antinutrients tested did not compromise growth, however, caused some gastrointestinal disturbance that may affect fish in the long term.

The objective of this study was to evaluate the potential of free amino acids to replace protein-bound amino acids in diets for Solea senegalensis juveniles. For this purpose, fish with 4.26 g mean initial weight were fed during 55 days with diets containing 500 g kg−1 protein and 100 g kg−1 lipid, based on fish meal and fish oil as main protein and lipid sources (control diet), or diets where 20%, 35% and 50% of fish meal were replaced by crystalline amino acids, using L-lysine HCl as lysine source. To access the efficiency of the crystalline lysine source, another diet was formulated with 35% fish meal replacement but using L-lysine sulphate instead of L-lysine HCl as lysine source. Overall, growth performance, feed utilization, nutrient retention, whole-body and amino acid composition did not show significant differences among groups. In conclusion, up to 50% protein-bound amino acids can be replaced by crystalline amino acids in diets for Senegalese sole juveniles without negative effects in fish performance. Additionally, it was shown that L-lysine sulphate and L-lysine-HCl may be used interchangeably by Senegalese sole juveniles, with the potential economic benefits involved.

Summary The aim of this study was to assess plasma biochemistry parameters with the potential of being used as indicators of the nutritional status for healthy gilthead seabream juveniles. Triplicate groups of 18 seabream (body weight of 58 g) were kept unfed for 24 h, 7 or 14 days. Nine fish per treatment were then sampled randomly for blood collection and the following parameters analyzed in the plasma using standard clinical methods: glucose; protein; triglycerides; cholesterol; calcium; magnesium; inorganic phosphorus; alkaline phosphatase (ALP); aspartate aminotransferase (AST); lactate dehydrogenase (LDH); gamma-glutamyl transferase (GGT); creatine phosphokinase (CPK); and lipase. Biochemical parameters showed lower variability among individuals than did enzymatic parameters. Plasma glucose, protein, cholesterol, calcium and inorganic phosphorus levels were inversely related to the duration of starvation. On the contrary, plasma triglycerides decreased significantly during the first week of starvation and remained stable in the second week. Plasma ALP, AST and LDH decreased significantly after 1 week of starvation and then remained constant. In healthy seabream juveniles, plasma glucose, protein, cholesterol, calcium and inorganic phosphorus are responsive to starvation and may be useful indicators of the nutritional status of the animals. Indicative baseline reference values for gilthead seabream juveniles starved for 24 h and held at optimum temperature are: protein, 3.7–4.9 g dl−1; cholesterol, 341–407 mg dl−1; calcium, 13.1–8.0 mg dl−1; and inorganic phosphorus, 10–14.2 mg dl−1. Plasma triglycerides, along with plasma enzyme activities, may be useful as indicators of short term starvation. For these parameters baseline values after 1 week of starvation were: triglycerides: 138–230 mg dl−1; ALP: 58–125 U L−1; AST: 15–127 U L−1; and LDH 61–677 U L−1. Plasma glucose is only responsive to longer starvation periods, remaining relatively stable during the first week of starvation, and ranging from 59 to 196 mg dl−1.

The effect of dietary protein reduction balanced by an increase in carbohydrate (starch) level on growth performance, feed utilization and intermediary metabolism of Senegalese sole juveniles was evaluated at two temperatures, 12 and 18°C. For that purpose two isolipidic (16% lipids) diets were formulated to contain 550gkg−1 protein and 90gkg−1 starch (diet HP:LC), and 450gkg−1 protein and 200gkg−1 starch (diet LP:HC). Each experimental diet was fed to triplicate groups of 20 fish (initial body weight: 15.9g) within each temperature. Diets had no effect on growth and feed utilization. Temperature affected growth but not feed efficiency, with fish growing more at 18°C. Fatty acid synthetase and glutamate dehydrogenase activities were higher at 12°C than at 18°C while activity of the other measured enzymes was not affected by water temperature. Glucokinase and malic enzyme activities were lower while fructose 1,6-bisphosphatase activity was higher in fish fed the HP:LC diet. Our data suggest that protein can be reduced from 550 gkg−1 to 450 gkg−1 by increasing starch level in high lipid diets for Senegalese sole juveniles without affecting overall performance. A reduction in protein content through an increase in dietary starch decreases hepatic gluconeogenesis. Increasing temperature from 12°C to 18°C improves fish growth but does not affect feed efficiency.

A 74-day trial was undertaken to evaluate the effects of temperature (16 and 22 °C) and dietary protein/lipid ratio on the performance of juvenile Senegalese sole (mean body weight: 6.4 g). Four experimental diets were formulated to contain two protein levels (550 g kg−1 and 450 g kg−1) combined with two lipid levels (80 g kg−1 and 160 g kg−1). Growth was higher at 22 °C and within each temperature in fish fed diets 55P8L and 45P16L. Feed efficiency, N retention (% NI) and energy retention (% EI) were higher at 22 and at both temperatures in fish fed diet 55P8L. Temperature affected whole-body composition, with dry matter, protein, lipid and energy being higher and ash lower in fish kept at higher temperature. Independently of temperature, whole-body lipid, energy and ash were higher and protein was lower in fish fed the high-lipid diets. Visceral and hepatosomatic indices were not affected by diet composition but were higher in fish kept at 16 °C. Liver glycogen and lipid contents and activities of glutamate dehydrogenase, alanine and aspartate aminotransferases were not affected by diet or water temperature. Malic enzyme (ME) and glucose 6-phosphate dehydrogenase activities were higher in fish fed the low-lipid diets. ME activity was higher at lower temperature. In conclusion, increasing water temperature from 16 to 22 °C improves growth and feed efficiency of Senegalese sole juveniles; regardless of water temperature, the diet with 550 g kg−1 protein and 80 g kg−1 lipid promoted the best growth and feed efficiency.

The effects of various dietary protein levels on growth performance, whole body composition and nutrient utilization were studied in two-banded sea bream (Diplodus vulgaris), a candidate species for aquaculture. Fish (initial weight 6.1 g) were fed to satiety six iso-energetic diets, containing 5%, 12.5%, 25%, 35%, 45% or 55% of crude protein during 72 days. Fish fed 35% and 45% protein attained better growth and feed utilization than the other groups (P < 0.05). Daily growth index and feed conversion ratio were the poorest for fish fed 5% and 12.5% protein (P < 0.001), while the 25% and 55% protein groups had intermediate performance. Lipid retention increased significantly from 13.7% to 30.1% (P < 0.0001) and protein retention decreased from 35.5% to 21.3% (P < 0.01) with increasing protein levels from 12.5% to 45%. Muscle protein, lipid and energy concentrations were not significantly affected by dietary protein level. The estimated protein requirement for maintenance and maximum growth of two-banded seabream growing from 6 to 20 g were 7.5% and 35.7%, respectively. Protein requirements as calculated from body protein gain were 2.3 and 6.5 g of protein intake per kilogram body weight per day.

A trial was undertaken to estimate the protein requirement of white sea bream (Diplodus sargus). Five fish meal-based diets were formulated to contain graded levels of protein (from 60 to 490 g kg⁻¹). Each diet was assigned to triplicate groups of 25 fish with a mean individual body weight of 22 g. Fish fed the 60 g kg⁻¹ protein diet lost weight during the trial, while growth improved in the other groups as dietary protein level increased up to 270-370 g kg⁻¹. Feed efficiency improved as dietary protein level increased. Maximum protein efficiency ratio (PER) was observed with the 17% protein diet. N retention (NR) (% N intake) was not different among groups fed diets with 17% protein and above. Ammonia excretion (g kg⁻¹ABW day⁻¹) increased as dietary protein level increased, while no differences in urea excretion were noted. An exponential model was used to adjust specific growth rate and NR (g kg⁻¹ day⁻¹) to dietary protein level. Based on that model, dietary protein required for maximum retention was 330 g kg⁻¹, while for maximum growth it was 270 g kg⁻¹. On a wet weight basis, there were no differences in whole body composition of fish-fed diets with 170 g kg⁻¹ protein and above, except for the protein content, which was lower in group fed the 170 g kg⁻¹ protein diet than the 490 g kg⁻¹ protein diet. Specific activities of hepatic amino acid catabolism enzymes (glutamate dehydrogenase, alanine aminotransferase and aspartate aminotransferase) increased as dietary protein levels increased. There were no differences among groups in fatty acid synthetase and malyc enzyme but 6-phosphate dehydrogenase (G6PDH) was significantly lower in fish fed the 60 g kg⁻¹ protein diet than the 170 and 490 g kg⁻¹ protein diets.

An experiment was performed to evaluate the growth performance and feed utilization of white sea bream juveniles (initial weight, 14 g) fed diets of cornstarch of diierent origins (normal and waxy). Four experimental diets were formulated to be isolipidic and to contain normal and waxy starch (26% or 42%) at two protein (36% and 48%) levels. The growth trial lasted 15 weeks and, at the end of the trial, there were no diierences in the growth rate among groups. At the highest dietary starch level ^ but not at the lowest level ^ the feed e⁄ciency ratio and PER were signi¢cantly lower in ¢sh fed the waxy starch diet. Protein e⁄ciency ratio and N retention (% N intake) were not aiected by starch source but were signi¢cantly higher in the diets with a lower protein content. No diierences in energy retention (% energy intake) were observed among groups. Except for the protein content, which was signi¢cantly higher in ¢sh fed diets with a high protein level, no other diierences were observed among groups in whole-body composition. Hepatosomatic Index (HSI) was signi¢cantly higher in ¢sh fed highstarch diets, but there were no diierences in visceral indices among groups. The apparent digestibility coe⁄cients of protein and energy were not aiected by the dietary starch level, but were signi¢cantly lower in diets including waxy starch. Glutamate dehydrogenase activity was higher in ¢sh fed highprotein diets, but it was not aiected by dietary starch source. Alanine aminotransferase and aspartate aminotransferase activities were not diierent among groups. Glucose 6-phosphate dehydrogenase, malic enzyme and fatty acid synthetase activities were not aiected by the dietary starch level, but were signi¢cantly lower in ¢sh fed waxy starch. The results of this study indicate that diets for white sea bream juveniles may include up to 42% starch without negative eiects on ¢sh performance. Moreover, normal starch appears to be more e⁄ciently used as an energy source than waxy starch.

An 83-day feeding trial was carried out to determine the eiect of diierent dietary protein and lipid levels on the growth performances and carcass composition of white seabream. Juveniles (10.7 � 0.2 g) were fed to satiation on four diets, varying in protein (15% and 28%) and lipid (12% and 16%) levels. The best growth performance was observed in ¢sh fed on diets with higher protein level. Dietary lipids did not aiect growth performance. Voluntary feed intake decreased with a increasing dietary protein level at both dietary lipid levels. Feed conversion ratio improved with the increase in dietary protein and lipid levels. Carcass composition remained unaltered by dietary protein levels (P40.05). Carcass protein content tended to decrease, while lipid content tended to increase in groups fed on 16% lipid, compared with the 12% lipid groups. Additionally, protein retention was higher in ¢sh fed on low-protein and low-lipid levels, compared with the high-protein and high-lipid group (29% vs.19%). Lipid retention increased significantly with dietary protein level (Po0.001). Energy retention improved with dietary protein, but was not aiected by dietary lipid levels. On the basis of our results, feeding white seabream on 15% dietary protein had a negative eiect on growth and feed utilization. Dietary lipid did not induce a protein-sparing action in Diplodus sargus juveniles.

A 12-week growth trial was performed to evaluate the effect of lupin seed meal as a protein source in diets for gilthead sea bream (Sparus aurata) juveniles. Six experimental diets were formulated to be isonitrogenous and isoenergetic and to contain 10%, 20% and 30% of raw lupin (Lupinus angustifolius) seed meal protein or 20% and 30% lupin (L. angustifolius) seed meal processed by infrared radiation (micronized) in place of fish meal protein, the only protein source of the control diet. Fish accepted all diets well and no significant differences in feed utilization among groups were noticed during the trial. Final weight of fish fed the experimental diets was identical or higher than the control group. Final weight of fish fed diets including 20% micronized lupin protein was even significantly higher than that of fish fed the fish meal-based control diet. Moreover, at the same dietary lupin seed meal protein inclusion levels, final weight of fish fed diets including micronized lupin was significantly higher than with raw lupin. A trend was also noticed for a decrease of final weight with the increase in lupin seed meal in the diets. At the end of the trial no significant differences in proximate whole-body composition, hepatosomatic and visceral indices were observed among groups. It is concluded that lupin seed meal can replace up to 30% fish meal protein in diets for gilthead sea bream juveniles with no negative effects on growth performance. Furthermore, micronization of lupin seeds improves its dietary value for gilthead sea bream juveniles. At the same dietary lupin inclusion levels, diets including micronized lupin seeds promote significantly higher growth rates than raw lupin seeds.

A growth trial was conducted to estimate the phosphorus requirement of European sea bass juveniles. Six experimental isonitrogenous and isoenergetic semi-purified diets (casein based) were formulated to contain 0.48%, 0.65%, 0.77%, 0.86%, 1.05% and 1.25% phosphorus (diets D1, D2, D3, D4, D5 and D6 respectively). Dicalcium phosphate was used as dietary phosphorus source. Twelve groups of 25 fish of 10 g initial body weight were allocated to 55-L tanks in a thermoregulated water recirculating system. Each experimental diet was assigned to duplicate groups of these fish. The trial lasted for 10 weeks and fish were fed two times a day, 6 days a week, to apparent visual satiation. At the end of the trial, final weight of fish fed diet D1 was significantly lower than that of the other groups, except of fish fed diet D4. Mortality of fish fed diet D1 was significantly higher than that of fish fed the other diets, except for diet D6. Feed efficiency and protein efficiency ratios were significantly lower with diet D1 than with the other diets. Nitrogen retention (% nitrogen intake) of fish fed diet D1 was significantly lower than in the other groups, except that of fish fed diet D4. Energy retention (% energy intake) was not significantly different among groups. At the end of the trial there were no differences in whole body composition among groups. Whole body phosphorus content averaged 0.72% (on a fresh weight basis) and was not significantly affected by dietary phosphorus content. Phosphorus retention averaged 6.1 g kg−1 weight gain and was not significantly different among groups. Phosphorus retention (% phosphorus intake) was significantly higher in fish fed diets D2 and D3 than in fish fed higher dietary phosphorus levels. Expressed per unit body weight per day, phosphorus retention was not significantly different among groups fed diets D2 to D6, while phosphorus losses linearly increased with dietary phosphorus intake. Results of this trial indicate that the phosphorus requirement of sea bass juveniles was satisfied with a diet containing 0.65% of phosphorus.

A 12-week growth trial was conducted to evaluate corn gluten meal as an alternative protein source to fish meal in diets for gilthead sea bream juveniles. The experimental diets were formulated to be isonitrogenous and isoenergetic and to have 20%, 40%, 60% and 80% of fish meal protein, the only protein source in the control diet, replaced by corn gluten meal. At the end of the growth trial only the group fed the diet with 80% corn gluten protein exhibited significantly reduced growth and feed efficiency compared with the fish meal-based diet. This was most likely due to a dietary amino acid deficiency in that diet. A trend was noticed for feed efficiency to improve with the replacement of fish meal protein in the diets up to 60%. There were no significant differences among groups in protein and energy retention (as percentage of intake). At the end of the trial whole body water content of the experimental groups was significantly lower and the lipid content of groups including 60% and 80% corn gluten protein was significantly higher than that in the control. No other differences were observed in whole body composition among groups. Apparent digestibility coefficients (ADC) of the diets were evaluated in a separate trial. The ADC of dry matter of the experimental diets was significantly higher than in the control diet; there were no significant differences among diets in the ADC of energy and protein, except for the ADC of protein of diet with 80% corn gluten protein, which was significantly lower than the control. The results of this study indicate that corn gluten meal can replace up to 60% fish meal protein in diets for gilthead sea bream juveniles with no negative effects on fish performance.

Juvenile gilthead sea bream with a mean initial body weight of 5 g were fed for 12 weeks with experimental diets containing 10% and 20% fishmeal protein (sole protein source in the control diet) replaced by processed pea seed meals. The processed pea seed meals were dehulled, defibred, extruded and microground pea seed meal (PSM1) or whole pea treated by infrared radiation and ground (PSM2). Apparent digestibility coefficients of the experimental diets were determined in a separate trial. At the end of the growth trial there were no significant differences in growth performance, feed utilization or whole-body composition among experimental groups. There were no differences in apparent protein digestibility among experimental groups (except for fish fed PSM1 at the lowest inclusion level). Both dry matter and energy digestibility of the diets, including PSM2 and with the highest inclusion level of PSM1, were significantly lower than those of the control diet. The results of this study suggest that pea seed meal may replace up to 20% fishmeal protein in diets for gilthead sea bream juveniles without affecting fish performance. Further studies should focus on technological treatments to increase utilization of pea seed meal carbohydrate, as both apparent dry matter and energy digestibility were affected by dietary inclusion level and by pea seed meal processing method.

The aim of this trial was to compare the performance of rainbow trout fed diets including local or imported fish meal as the main protein sources, and to test the effect of reducing the fish meal content or including a fish protein hydrolysate in the diets. Two experimental diets were formulated to include 35% (diet 2) or 20% (diet 3) of a local processed whole fish meal; two other diets were formulated similar to diets 2 and 3 but with 5% fish protein hydrolysate replacing the same amount of fish meal (diets 4 and 5 respectively); a diet similar to diet 2, but including Norwegian fish meal, was used as a control (diet 1). The growth trial lasted 14 weeks and was carried out in floating net cages (325-L capacity), with duplicate groups of 20 rainbow trout of an initial average weight of 58 g. The apparent digestibility coefficients (ADC) of the diets were evaluated in a separate laboratory trial. At the end of the growth trial, there were no significant differences in growth rate and protein efficiency ratio among groups. Feed conversion ratios were significantly better in groups fed diets 3, 4 and 5 than in the other groups. Nitrogen retention (% of N intake) was significantly higher in fish fed diets 4 and 5 than in those fed diet 2. There were no significant differences in energy retention (% of energy intake) among groups. At the end of the trial, there were no significant differences among groups in proximate composition of whole fish. The ADC of protein, energy and phosphorus of diets 1 and 2 were significantly lower than those of diets 3 and 5. It was concluded that, under the experimental conditions tested, performance of rainbow trout fed practical diets including good quality local processed fish meal is similar to that of fish fed diets including Norwegian fish meal. A reduction in the fish meal from 35% to 20% of the diet or the inclusion of a fish protein hydrolysate had no negative effects on growth performance and improved feed utilization.

Two trials were performed to study the effect of periodic feed deprivation (trial 1) or feed restriction, followed by satiation feeding (trial 2) on the growth performance of turbot juveniles under commercial rearing conditions. In trial 1, duplicate groups of 350 fish with an initial weight of 62 g were fed a commercial diet to apparent visual satiation for 7, 6, 5 or 4 days a week for 83 days. At the end of the trial, fish weight was directly related to the number of feeding days but feed efficiency and protein efficiency ratio were not affected by treatments. At the end of the trial, there were no differences in whole-body composition among groups. In trial 2, duplicate groups of 500 fish with an initial weight of 33 g were fed a commercial diet to satiation (100%) or feed restricted to 90%, 80% and 70% of satiation for 90 days. Thereafter, all groups were fed to satiation for 34 days. During the feed restriction period, growth was directly related to feed intake, while during the satiation feeding period, it was inversely related to the previous feeding level. At the end of the trial, the final weight was not different among groups. At the end of the feed restriction period, whole-body lipid content showed a trend to decrease with an increase in the feed restriction level. The results of this study indicate that under practical conditions, turbot juveniles should be fed daily as even cycles of short periods of feed deprivation negatively affect growth, while not improving feed efficiency. On the contrary, even after a relatively long feed restriction period, fish shows compensatory growth, and this may be used as a feed management strategy for controlling fish production in commercial farms.