Diets For Turbot Research Articles

Hydroxyproline supplementation on the performances of high plant protein source based diets in turbot (Scophthalmus maximus L.)

Abstract Hydroxyproline (hyp) is one of the bioactive molecules rich in fishmeal but low in plant protein sources. With increased utilization of plant proteins in aquafeeds, a better understanding is warranted for the necessity of hyp supplementation in high plant protein based diets. In the present study, isonitrogenous and isoenergetic turbot diets were formulated with 40%, 50% and 60% fishmeal substituted by plant proteins, with (or without) addition of 0.6% hyp. After an 8-week feeding trial in juvenile turbot, hyp supplementation significantly improved specific growth rate (SGR) and feed efficiency ratio (FER) in fish fed diets with 50% or higher fishmeal replaced, but not in the group with 40% fishmeal replaced by plant proteins. Hyp levels in plasma and tissues were reduced after plant protein substitutions and replenished by dietary supplementation. Dietary hyp significantly increased muscle hardness, springiness and chewiness of fish ( P

Evaluation of nutritional values of selected commercial fish meal sources in turbot (Psetta maxima) diets

This study was conducted to evaluate nutritional values of selected commercial fish meals (FM) with two experiments in diets of turbot. In experiment I, five diets based on two Peruvian anchovy meals (one is a flame-dried FM: Peru-1 and the other steam-dried FM: Peru-2), a Danish FM (Danish LT), a domestic anchovy LT meal (Domestic LT) and an Alaskan white FM (WFM) as major protein source were formulated to contain 56% protein. The diets were fed to fish with an initial average weight of 119.4 ± 0.1 g for 9 weeks. Growth rate, feed utilization, whole body and visceral compositions, nitrogen, lipid and energy balances did not significantly change in Experiment 1 among the treatments. In Experiment 2, four diets based on three FMs (Domestic LT, Danish LT and Peru-1) and their mixture (Mix FM) were formulated to contain 50% protein and fed to triplicated groups of fish with an average initial weight of 51.4 ± 0.1 g for 6 weeks. Once again, there were no significant differences in growth rate and feed consumption among the treatments. However, fish on Mix FM diet had significantly better FCR and PER than the others. The results of two experiment indicated that Danish LT and Domestic LT were better in terms of phosphorus (P) retention and losses than two Peruvian FMs and WFM, suggesting that although different sources of FMs were comparable in terms of growth and feed utilization, they could lead to substantial differences in environmental impacts.

Blue mussel meal as feed attractant in rapeseed protein-based diets for turbot (Psetta maximaL.)

Antinutritional factors in rapeseed products have been identified to reduce feed palatability and growth performance of turbot. Therefore, we evaluated the potential of blue mussel (Mytilus edulis L.) meal as feed attractant in rapeseed protein-based diets for turbot. Triplicate fish groups received isonitrogenous and isocaloric diets with fish meal (FM) protein replacements of 50% or 75% by rapeseed protein concentrate (RPC 50, RPC 75). These diets were supplemented with 0%, 2%, 4% or 8% of blue mussel meal. In contrast with RPC 50 diets, fish fed with RPC 75/0 showed significantly reduced daily feed intake (DFI) and specific growth rate (SGR). With increasing mussel meal inclusion, RPC 75 diets resulted in increased DFI and SGR, suggesting mussel meal as attractant in rapeseed proteinbased diets for turbot. Feed conversion was unaffected by any treatment. Protein productive value and apparent digestibility coefficients were unaffected by either RPC or mussel meal inclusion. With regard to the whole body composition, no differences in crude protein, crude lipid and ash content could be determined. Haematological characteristics were unaffected among the treatments indicating good nourished and unstressed fish. In conclusion, we demonstrated that the utilization of blue mussel meal improved the palatability of rapeseed protein-based diets for turbot.

The Use of Farmed Salmon Oil to Replace Anchovy Oil in Diet of Turbot, Psetta maxima, Reared in Brackish Water

This study was conducted to determine the effects of the use of farmed salmon oil (FSO) as a substitute for anchovy oil (AO) on growth and nutrient utilization performance, and proximate and fatty acid compositions of turbot, Psetta maxima. Two fish oil sources, AO and FSO, were incorporated into the diet at a level of 6.77% and fed to turbot with an initial average weight of 266.25 ± 0.53 g in brackish water for 9 wks. Each diet was tested in four replicates and fed to apparent satiation twice a day. At the end of the experiment, data of growth and nutrient utilization performances (feed conversion ratio, nitrogen, lipid and energy intakes, gains, and retentions), and organo‐somatic indices were similar between the dietary oil sources. Likewise, there were no significant differences in final whole body proximate compositions between two treatments. However, AO and FSO diets significantly affected whole body fatty acids and fatty acids classes. Briefly, FSO fish was characterized with higher n‐6 poly unsaturated fatty acids (PUFA) mainly 18:2n‐6 whereas AO fish with higher n‐3 PUFA and highly unsaturated fatty acids mainly 22:6n‐3. The whole body fatty acid profile reflected that of the diets. It is concluded that incorporation of FSO instead of AO in turbot diets supports similar growth and nutrient utilization performances but change whole body fatty acid profile.

Effects of dietary taurine supplementation to a casein-based diet on growth performance and taurine distribution in two sizes of juvenile turbot (Scophthalmus maximus L.)

Feeding trials were conducted to investigate the effects of dietary taurine on feeding, growth, feed utilization and taurine distribution in tissues of juvenile turbot (Scophthalmus maximus L.) with initial average weight of 6.3±0.01g (Trial 1) and 165.9±5.01g (Trial 2). The basal diet was supplemented with 0.0% (control), 0.5%, 1.0% and 1.5% taurine to formulate four isonitrogenous and isolipidic diets (Diet 1 (0.0%), Diet 2 (0.5%), Diet 3 (1.0%) and Diet 4 (1.5%)). The analyzed taurine concentrations were 0.16%, 0.64%, 1.15%, 1.66%, respectively. Each diet was randomly assigned to triplicate groups of 30 fish (6.3g) in 200L tank and 15 fish (165.9g) in 500L tank. Fish were fed twice daily (06:30 and 18:30) to apparent satiation for 10weeks. With the increase of dietary taurine, growth, feed efficiency ratio (FER) in fish with initial body weight of 6.3g first increased (0.0% to 1.0%) (P=0.000, P=0.000) and thereafter reached a plateau, while growth in fish with initial body weight of 165.9g first increased (0.0% to 0.5%) (P=0.006) and then gradually decreased. Feed intake (FI) in fish with both body weights (6.3g; 165.9g) increased with increasing dietary taurine (P=0.000; P=0.001) and thereafter gradually declined. With increasing dietary taurine, crude protein contents in fish of both body weights increased (P=0.049; P=0.000) and then reached a plateau, while the crude lipid content in fish with 165.9g weight increased with increasing dietary taurine (P=0.000). The contents of taurine in body, muscle, eye, liver and brain of turbot were correlated with consumed taurine, and the correlated coefficients in fish with 6.3g body weight were separately 0.955 (P=0.000), 0.945 (P=0.000), 0.881 (P=0.001), 0.947 (P=0.000) and 0.924 (P=0.002) while those fish with 165.9g body weight were 0.967 (P=0.000), 0.964 (P=0.000), 0.977 (P=0.000), 0.946 (P=0.000) and 0.997 (P=0.000). This result suggested that 1.0% taurine in diet of turbot with 6.3±0.01g weight and 0.5% taurine in diet of turbot with 165.9±5.01g weight are probably optimal.

Nutritional evaluation of rapeseed protein isolate as fish meal substitute for juvenile turbot (Psetta maxima L.) — Impact on growth performance, body composition, nutrient digestibility and blood physiology

The potential of a highly concentrated rapeseed protein isolate (RPI) as partial or total fish meal (FM) alternative in diets for turbot (Psetta maxima L.) was evaluated. In a feeding trial 12 experimental tanks of a saltwater recirculation system were stocked with 15 fish each. Fish were organized in triplicate groups and received isonitrogenous and isoenergetic experimental diets with 0, 33, 66, or 100% (designated as control, RPI 33, RPI 66, RPI 100) of FM protein replaced with RPI. Fish were fed over a period of 56days until apparent satiation.Feed intake, feed conversion ratio and growth performance did not significantly vary between fish fed the RPI 33 (129g RPIkg−1 diet) and the control diet. The RPI 66 (258g RPIkg−1 diet) and the RPI 100 (391g RPIkg−1 diet) diets caused reduced feed ingestion and feed efficiencies, resulting in lower growth performance. Apparent digestibility coefficient (ADC) of dry matter and protein calculated on the basis of stripped feces revealed significantly reduced values for fish fed with RPI 66 diet compared to control diet, whereas ADC in the RPI 100 group recovered to control value. Protein retention decreased with increasing FM substitution levels. Body composition of fish showed a significant reduction in dry matter and crude protein values of the RPI 66 and RPI 100 group compared to control group. Gross energy content varied between the RPI 33 and RPI 100 group, while crude lipid and ash content were unaffected among the treatment groups, suggesting no limitations in dietary mineral or phosphorus availability. Blood parameters including hematocrit, glucose, triglycerides and cortisol were similar between the treatment groups. Histopathology of liver tissue revealed a slight hypertrophy of hepatocytes in the control group and a severe hypertrophy in fish fed with RPI 33 diet. In line with a reduced condition factor and hepatosomatic index a slight hypotrophy of hepatocytes was observed in fish fed with the RPI 100 diet. Neither inflammatory nor degenerative changes of the mid gut were observed among dietary treatments.In conclusion, 66% (314gkg−1) of dietary FM could be replaced by RPI (258gkg−1) without affecting physiological parameters of turbot in terms of animal welfare, but growth performance decreased using FM protein replacement levels above 33% (corresponding to 157gkg−1).

Incorporation of a mixture of plant feedstuffs as substitute for fish meal in diets of juvenile turbot ( Psetta maxima)

A study was designed to evaluate the maximum level of substitution of fish meal in diets for turbot when a mixture of feedstuffs of plant origin was used and when the amino acid profile was adjusted to reflect amino acid profile of a reference fish meal based diet. Five diets were formulated: a reference diet (FM40) containing 40% fish meal and four other diets (FM30, FM20, FM10 and FM0) in which protein from fish meal was substituted by protein from lupin, corn gluten and wheat gluten meal. Amino acids profile of each diet was balanced by addition of crystalline amino acids. Turbot, initially weighing 26 g were fed these diets for 12 weeks and growth parameters were recorded. Protein (96%), energy (83%) and dry matter (73%) digestibility were very high in all diets tested. Feed intake was significantly decreased by the incorporation of plant protein in diets (from 10.2 g/kg ABW/day to 8.2 g/kg ABW/day in fish fed diets FM40 and FM0, respectively), growth rate was only affected in fish fed diets FM10 and FM0 (respectively, 2.2 and 1.9%/day against an average of 2.4%/day for the other treatments) and no effect on feed utilisation was observed. The whole body composition of fish and the nitrogen retention were significantly negatively affected when dietary fish meal incorporation was equal or less than 20% diet. Activities of alanine amino transferase (ALAT) were significantly increased by the dietary incorporation of plant protein. These results suggest that a sizeable amount of fish meal can be replaced by plant feedstuffs in diets of turbot when an adequate mixture of plant feedstuffs along with amino acid supplementation are used.

The effect of dietary vitamin E and C level on market-size turbot (Scophthalmus maximus ) fillet quality

Fish fillet quality has been shown to be influenced by the level of antioxidants in preslaughter diet. Thus, an experiment was conducted to study the effect of different levels of vitamin E and C on the fillet quality of market-size reared turbot (Scophthalmus maximus). Turbot of a mean initial weight of 347 ± 20 g were divided into four groups and fed commercial turbot diets (60% protein, 12% fat), supplemented with α-tocopheryl acetate (mg kg−1) and ascorbyl-2 monophosphate (mg kg−1) at the following dietary levels: 500/100, 1000/100, 100/1000, 100/100 respectively. Over a dietary supplementation period of 15 weeks, fish were fed to satiation and reached a final mean weight of 916 ± 29 g. α-Tocopherol levels increased significantly (P < 0.001) in tissue (i.e. muscle, liver, heart and kidney) of fish fed diets containing elevated levels of α-tocopheryl acetate. In ice storage, fillets of these fish exhibited significantly lower (P < 0.001) levels of lipid oxidation, and showed significantly less (P < 0.001) colour deterioration (higher hue angle and lower chroma). Elevated dietary α-tocopheryl acetate levels had a negative effect (P ≤ 0.001) on the concentration of ascorbic acid in muscle tissue. An increase in dietary vitamin C did not have any detectable effect on fillet quality. Prolonged feeding times had a negative effect on lipid oxidation (P < 0.001) and colour deterioration (P < 0.01). These results suggest that increased dietary α-tocopheryl acetate could prevent colour deterioration and lipid oxidation of turbot fillets in retail storage on ice.

Potential of plant-protein sources as fish meal substitutes in diets for turbot ( Psetta maxima): growth, nutrient utilisation and thyroid status

An experiment was conducted in order to assess the incorporation in diets for juvenile turbot of extruded lupin ( Lupinus albus) and heat-treated (RM1) or untreated (RM2) rapeseed meals ( Brassica napus) (26 and 40 μmol glucosinolate/g DM, respectively). The level of incorporation of 30% for each plant-protein, as well as 46% for RM1 and 50% for lupin was tested and compared with a fish meal based control diet. Triplicate groups of turbot (initial body weight of 66 g) were fed by hand with isonitrogenous and isoenergetic experimental diets, twice daily and to visual satiety, during 63 days. Extruded lupin can be incorporated in diets of turbot up to a level of 50% without adverse effects on growth performance and body composition. Rapeseed meal can only be incorporated at levels up to 30%, but a preliminary heat treatment of RM is necessary in order to improve its nutritional quality. In turbot-fed the RM-based diets, plasma T 4 levels were reduced with low dietary content in glucosinolate breakdown products (3.6 μmol/g), but no decrease in plasma T 3 levels was observed with the higher level of toxic compounds (4.4 μmol/g). A significant deiodinase type II compensatory effect, leading to an increase of the conversion of T 4 to T 3, was observed in vitro in the liver of turbot fed RM1-based diets. The intake of lupin-based diets also had an effect on thyroid status with an increase of plasma T 3 levels and of deiodinase type I activity in liver and kidney, suggesting an increase in the degradation of rT 3 and in the conversion of T 4 to T 3.

Partial or total replacement of fish meal by corn gluten meal in diet for turbot ( Psetta maxima)

The effect of corn gluten meal (CGM) as a partial or total replacement of fish meal was studied in turbot ( Psetta maxima). Five experimental diets containing a gradient of CGM were fed to triplicate groups of turbot (initial body weight of 65 g) over 9 weeks at 17°C. Turbot fed a diet containing 20% of CGM had comparable growth performances as these fed a fishmeal based diet. Total replacement of fish meal adversely affected growth. Digestibility of nutrients and energy of the diets decreased with the increase in levels of dietary corn gluten meal. Supplementation of arginine and lysine in diets containing CGM induced an improvement of the availability of these two amino acids. The incorporation of CGM in diets significantly affected plasma cholesterol and triglyceride concentrations while no effect was observed on plasma levels of thyroid hormones. These results suggest that protein from CGM can replace one third of fish meal protein in the diets for turbot.

Contents and organ distribution of pantothenic acid in maturing turbot (Psetta maxima )

Contents and organ distribution of pantothenic acid in maturing turbot (<i>Psetta maxima</i> )

Metabolizable energy from dietary carbohydrates in turbot, Scophthalmus maximus (L.)

Abstract. In a feeding experiment, the metabolizability of dietary carbohydrates in diets for turbot, Scophthalmus maximus (L.), was estimated and expressed as percentage of the metabolizability of dietary lipids. Four isoenergetic and isonitrogenous dietary treatments were applied with varying percentages of non-protein energy presented as starch. In order to obtain results allowing quantitative interpretation, an experimental design was used in which effects are reflected in varying body fat depositions only. Two methods were used simultaneously to overcome practical problems associated with differences in energy density between carbohydrates and lipids. The conventional method was based on equal feeding rates combined with the inclusion of inert filler in the diets, whereas the alternative method applied different dietary nutrient percentages in combination with different feeding rates. Although similar results were obtained, the alternative method was more convenient to use than the conventional method. Because of the experimental strategy applied, no significant effects on growth and protein utilization were obtained, but lipid deposition rates were significantly reduced at increased percentages of non-protein energy presented as starch. The metabolizable fraction of the gross dietary carbohydrate energy was estimated as 67% of that of dietary lipids. This reduction does not indicate that turbot have any systematic deficiency in metabolizing dietary carbohydrates.

Use of Synthetic Diets and Biochemical Criteria in the Assessment of Nutrient Requirements of Fish

Dietary allowances of nutrients have been formulated mainly from growth–response curves. The use of other criteria, especially those which exploit the biochemical role of nutrients, is discussed by reference to three different nutrients, namely thiamin, magnesium, and essential fatty acids.It is shown that erythrocyte transketolase activity provides a nutritional index of thiamin status in turbot (Scophthalmus maximus). The enzyme is saturated with coenzyme (thiamin pyrophosphate) at a dietary thiamin level of 2.6 mg/kg.Assessment of mineral requirements is shown to present special problems because complex interrelationships exist between some dietary minerals. It is shown that dietary magnesium deficiency (4 mg magnesium/100 g diet) leads to renal calcification in rainbow trout (Salmo gairdneri) at dietary calcium levels of 2.7 g/100 g (Ca: P ratio 1: 1). Elevation of dietary magnesium to 100 mg/100 g under these conditions gave freedom from pathology and enhanced growth.Ratios of certain fatty acids in the tissue phospholipids of rainbow trout are known to provide a useful index of essential fatty acid status. These ratios cannot be applied to turbot as this species does not chain elongate and desaturate 18-carbon acids at appreciable rates. Long chain polyunsaturated fatty acids of the ω3 series must be supplied preformed in the diet of turbot.