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Effect of dietary lipid levels on performance, body composition and fatty acid profile of juvenile white seabass, Atractoscion nobilis
Aquaculture 289 (2009) 101–105
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Aquaculture j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a q u a - o n l i n e
Effect of dietary lipid levels on performance, body composition and fatty acid profile of juvenile white seabass, Atractoscion nobilis Lus M. López a,⁎, Eduardo Durazo a, María Teresa Viana b, Mark Drawbridge c, Dominique P. Bureau d a
Facultad de Ciencias Marinas, Universidad Autónoma de Baja California (UABC), PO Box 453, Ensenada BC 22860, Mexico Instituto de Investigaciones Oceanológicas, UABC, PO Box 453, Ensenada BC 22860, Mexico Hubbs-SeaWorld Research Institute, 2595 Ingraham St., San Diego, CA 92109, USA d Fish Nutrition Research Laboratory, Dept. of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada N1G 2W1 b c
a r t i c l e
i n f o
Article history: Received 24 September 2008 Received in revised form 31 December 2008 Accepted 4 January 2009 Keywords: White seabass Formulated diet Dietary lipids Growth Fatty acids
a b s t r a c t The objective of this study was to determine the optimum dietary lipid level of white seabass, Atractoscion nobilis, which is one of the most important species in California and Baja California for sport and commercial fisheries. Triplicate groups of fish were fed for 50 days with isonitrogenous experimental diets formulated with increasing lipid levels (2.6, 7.4, 11.6, 15.3 and 19.4% lipid) using menhaden oil as the lipid source. A commercial diet (CD, 49.9% crude protein, 14.7% lipid) was also fed to triplicate groups of fish. Survival throughout the growth trial ranged from 89 to 100% but the survival of fish fed the 2.6% lipid and the commercial diet was significantly less than the rest of the diets. Final mean body weight, feed conversion ratio (FCR), and nitrogen retention efficiency (NRE: N gain/N intake) were significantly greater for diets 15.3 L and 19.4 L compared to the rest of the treatments. Daily feed intake (DFI) was variable (3.5 ± 0.08 to 8.6 ± 0.03) and significantly affected by dietary treatment. Lipid content of whole body, muscle and liver increased with increasing dietary lipid levels. Muscle and liver fatty acid (FA) composition reflected dietary FA profiles. Tissue n−3 and n−6 highly unsaturated fatty acids (HUFAs) content increased in direct proportion to dietary lipid levels. Published by Elsevier B.V.
1. Introduction White seabass, Atractoscion nobilis, is an important recreational and commercial species found in waters off the coasts of southern California, USA and northern Baja California, Mexico (Donohoe, 1999; Vojkovich and Crooke, 2001). Due to their large size, quality flesh and high market value this species had been over-exploited and in a condition of severe depletion in California until a program for stock enhancement started in the early 1980s (Drawbridge et al., 1999). Efforts have been focused on the culture of this fish species to support stock replenishment but there is also great interest in evaluating the feasibility of farming this species under commercial conditions. Although some information has been published concerning the nutrient requirement for white seabass (Kent et al., 2001; López et al., 2004, 2006), basic studies concerning its nutritional requirements are still lacking. It is well known that marine carnivorous fish preferentially utilize protein as an energy source but lipids are a source of dietary energy and essential fatty acids (EFA) and can spare protein in the diet of many fish species (Wang et al., 2005; Martins et al., 2007; Schuchardt et al., 2008). Within certain limits, increasing the dietary lipid level ⁎ Corresponding author. Tel.: +52 646 1744570; fax: +52 646 1744103. E-mail address: [email protected] (L.M. López). 0044-8486/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.aquaculture.2009.01.003
has been shown to improve the feed efficiency of marine fish species (Cho et al., 2005; Du et al., 2005). Studies conducted in our laboratory have indicated that diets with high lipid inclusion (over 22%, provided by fish oil) produce poorer performance in white seabass than diets with lower lipid levels (15 to 18%, López et al., 2006). Many studies have analyzed the effects of dietary lipid level on growth performance and body composition in marine fish, like European sea bass (Peres and Oliva-Teles, 1999), red sea bream and Japanese yellowtail (Oku and Yogata, 2000), haddock (Nanton et al., 2001), grouper (Luo et al., 2005), cobia (Wang et al., 2005) and Atlantic halibut (Martins et al., 2007). Although the dietary FA profile is generally reflected in fish tissue, the influence of dietary lipid level on white seabass FA profiles has not been studied. Thus, the aim of the present study was to evaluate the effects of varied levels of dietary lipid on growth performance, body composition, and FA profile of whole body, muscle and liver of white seabass fingerlings. 2. Materials and methods 2.1. Diet formulation Five isonitrogenous experimental diets (67.06 ± 0.33%, CP) were formulated to contain five lipid levels (2.6, 7.4, 11.6, 15.3 and 19.4% of dry matter). Ingredients, proximate composition and gross energy of
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Table 1 Ingredient and chemical composition of the experimental and a commercial diets (CD) on a dry weight basis Ingredient (g/100 g) Fish meala Krill mealb Corn starch Fish oilc Gelatin Minerals mixtured Vitamin mixturee Sodium benzoate Antioxidantf
Diets 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
60.0 13.0 12.9 0.0 8.0 4.0 2.0 0.1 0.01
60.0 13.0 11.2 1.7 8.0 4.0 2.0 0.1 0.02
58.5 14.5 7.2 5.7 8.0 4.0 2.0 0.1 0.02
59.0 13.0 4.3 9.6 8.0 4.0 2.0 0.1 0.03
58.0 14.3 0.0 13.6 8.0 4.0 2.0 0.1 0.03
67.0 11.6 7.6 13.8 22.1 30.2
66.4 15.3 7.6 10.7 23.0 29.0
66.4 19.4 6.5 7.7 23.7 28.1
Proximate composition (% of dry matter basis) Crude protein 68.2 67.3 Crude lipid 2.6 7.4 Ash 8.3 8.1 NFE + crude fiberg 20.9 17.2 19.8 21.2 Gross energy (kJ g− 1) −1 h GP:GE ratio (mg kJ ) 34.3 31.9
CD
49.9 14.7 10.8 24.6 21.8 23.0
a
66% crude protein, 3% crude lipid. 61.5% crude protein, 13% crude lipid. c From menhaden. d g/kg mineral premix: KH2PO4 320; NaH2PO4, 250; Ca(H2PO4)2, 200; MgSO4.7H2O, 150; calcium lactate, 35; ferric citrate, 25; NaCl, 10, ZnSO4.7H2O, 3.53; MnSO4.H2O, 1.62; CuSO4.5H2O, 0.31; CoCl2.6H2O, 0.01. e g/kg vitamin premix: inositol, 256.39; choline chloride, 149.78; niacin, 51.28; riboflavin; ρ-amino benzoic acid, 25.53; pantothenic acid, 17.92; β-carotene, 9.39; menadione, 6.11; thiamin-HCl, 3.85; pyridoxine, 3.06; folic acid, 0.96; biotin, 0.39; cholecalciferol, 25793IU, α-tocopherol, 25643 IU; vitamin B12, 5.59 mg. f Butylatedhydroxytoluene + α-tocopherol. g Nitrogen free extract (NFE) + crude fiber = 100- (% crude protein + % total lipid + % ash). h Gross Protein:Gross Energy ratio (mg kJ− 1). b
the experimental diets are presented in Table 1. Freeze-dried white fish muscle meal and krill meal were the major dietary protein sources. Cod liver oil and corn starch were used as lipid and carbohydrate sources, respectively. All ingredients were blended in a mixer (Kitchen Aid, Hobart, Troy, OH, USA), to produce a homogeneous mixture. The wet mixture was pelleted through a 3-mm die in a commercial meat grinder and pellets were dried in a convection oven for 8 h at 65 °C. The dry pellets were placed in sealed plastic bags and stored at −20 °C until use. The commercial diet (CD, Table 1) was a commercially available marine fish grower feed (Skretting, Vancouver, British Columbia, Canada) currently used at the hatchery for production of white seabass. 2.2. Animals and husbandry The experimental culture was performed at the hatchery of HubbsSeaWorld Research Institute, Carlsbad, CA. A total of 1272 white seabass fingerlings (25 days old, 1.7± 0.13 g, 30.2 ± 0.3 mm) were randomly distributed among 24 square plastic tanks at a stocking density of 53 fish
per tank. Each tank of 65 L was supplied with recirculated seawater at a flow-rate of 1.5 L min− 1. The photoperiod and temperature of the seawater in the tanks were maintained at 14:10 h (light: dark, with fluorescent light) and 21.7 ± 0.1 °C, respectively. Salinity in the system remained relatively constant at 33 ± 0.6‰. Fish were acclimated in the system for two weeks before beginning the feeding trial. During this period, the fingerlings were fed with the CD. Each dietary treatment was replicated four times in a completely randomized block design. Fish were fed by hand to visual satiety, four times per day (0700, 1200, 1700 and 2200 h), every day for 50 days, except prior to weighing when no feed was fed for 12 h. The length of the pellet was increased and fed as the fish grew. Fish in each tank were weighed (g) and measured (mm) individually at day 0, 25 and 50. At the start and end of the trial, sub-samples of 10 fish from each tank were euthanized and the liver and white muscle were excised, weighed and frozen at −70 °C for future analysis. Daily feed intake (DFI) was calculated from the mean daily averages of feed consumed on a dry weight basis. The amount of feed provided was recorded and uneaten feed was siphoned 20 min after feeding, dried at 100 °C for 12 h and weighed. The pellets were well bound and highly stable in the water during this time. Uneaten feed from each tank was subtracted from the total feed fed for each tank to calculate feed intake. 2.3. Analytical methods The dry weights of whole body, muscle and liver samples were measured from triplicate samples per dietary treatment after freezedrying (VIRTIS 12EL Freezmobile, Köln, Germany) for 48 h. Mean total N content was determined from samples analyzed by the micro-Kjeldhal method (AOAC, 1995), and crude protein was calculated as %N × 6.25. Total lipid was determined by extraction using chloroform–methanol (2:1 v/v) following the method of Folch et al. (1957). Ash content was determined gravimetrically after ashing the sample at 500 °C for 8 h. Carbohydrate as nitrogen free extract (NFE) plus crude fiber were calculated as the difference of the total sample weight less crude protein, total lipid and ash (Jobling, 2001). Gross energy content was determined using an adiabatic bomb calorimeter (PARR 1281, Moline, IL, USA). The main performance variables were calculated using the following formulae: Daily feed intake (DFI) = total dry feed consumed (g) × 100 / [(final body wet weight + initial body wet weight (g)) × days fed / 2]. Feed conversion ratio (FCR) = Dry weight of feed consumed (g) × wet weight gain of animal (g)– 1 Nitrogen retention efficiency (NRE %) = 100 × g nitrogen gain (g/fish) / g nitrogen intake (g/fish) where the N gain was calculated from the weight increase and the N of the initial and final samples of fish. The feed N was calculated from feed intake and the nitrogen content in the feed.
Table 2 Survival and growth performance of juvenile white seabass fed the experimental and commercial diets for 50 days Diet
2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
Survival (%) Initial BW (g) Final BW (g) Weight gain (g) Length gain (mm) DFI (% day− 1) FCR NRE
89.3 ± 1.0b 1.7 ± 0.1 12.6 ± 0.2d 10.9 ± 0.2d 63.4 ± 1.9d 8.5 ± 0.10a 2.9 ± 0.2d 10.4 ± 0.2f
100 ± 0.0a 1.6 ± 0.1 23.4 ± 0.2c 21.7 ± 0.4c 81.9 ± 0.8c 7.2 ± 0.09c 2.2 ± 0.2b 12.4 ± 0.4e
97.8 ± 1.3a 1.7 ± 0.1 24.1 ± 0.4c 22.3 ± 0.4c 81.9 ± 0.9c 7.6 ± 0.05b 2.3 ± 0.1b 14.1 ± 0.4d
96.0 ± 2.2a 1.7 ± 0.1 30.5 ± 0.2a 28.8 ± 0.7a 93.2 ± 1.6ab 4.2 ± 0.04d 1.3 ± 0.1a 28.1 ± 0.3b
99.3 ± 0.8a 1.7 ± 0.1 31.6 ± 0.7a 30.0 ± 0.6a 95.6 ± 1.0a 3.5 ± 0.08e 1.1 ± 0.1a 34.4 ± 0.3a
89.0 ± 1.6b 1.8 ± 0.1 26.4 ± 0.5b 24.8 ± 0.2b 90.4 ± 1.0b 8.6 ± 0.03a 2.5 ± 0.1c 15.6 ± 0.2c
Means ± SE. Body wet weight (BW). Daily feed intake (DFI) = total dry feed intake (g) × 100 / [(final body wet weight + initial body wet weight (g)) × days fed / 2]. Feed conversion ratio (FCR): total feed intake (g) × total wet weight gain of animal (g)− 1. Nitrogen retention efficiency (NRE): 100 ×g nitrogen gain (g/fish) / g nitrogen intake (g/fish). Means in the same column with different superscript are significantly different (P b 0.05).
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Table 3 Proximate composition (wet weight) of juvenile white seabass fed the experimental and a commercial diets for 50 days Initial Whole body Moisture Crude protein Crude lipid Ash Muscle Moisture Crude protein Crude lipid Ash Liver Moisture Crude protein Crude lipid Ash
Diet 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
73.4 18.4 3.2 3.5
74.8 ± 0.5a 17.8 ± 0.1c 1.6 ± 0.0c 4.7 ± 0.1c
74.3 ± 0.4a 17.9 ± 0.1c 1.8 ± 0.0c 4.6 ± 0.1c
69.7 ± 1.0c 20.6 ± 0.3b 3.3 ± 0.1b 5.3 ± 0.1b
68.1 ± 0.5c 21.4 ± 0.1b 3.7 ± 0.0b 5.2 ± 0.1b
65.2 ± 0.6d 22.8 ± 0.3a 4.7 ± 0.1a 5.8 ± 0.0a
71.5 ± 0.4b 18.9 ± 0.2bc 3.7 ± 0.2ab 4.4 ± 0.1c
81.5 15.4 1.2 1.0
83.2 ± 0.6a 14.2 ± 0.2 0.7 ± 0.0c 1.2 ± 0.0c
82.9 ± 0.5a 14.7 ± 0.3 0.7 ± 0.0c 1.2 ± 0.0c
82.3 ± 0.3a 15.1 ± 0.1 0.9 ± 0.0c 1.1 ± 0.0d
81.5 ± 0.2b 15.6 ± 0.2 1.3 ± 0.0b 1.3 ± 0.0b
81.1 ± 0.2b 15.5 ± 0.2 1.4 ± 0.0a 1.3 ± 0.0b
80.4 ± 0.3b 16.4 ± 0.1 1.3 ± 0.0b 1.4 ± 0.0a
72.9 7.2 13.3 1.7
80.5 ± 1.2a 8.3 ± 0.2b 7.4 ± 0.2e 1.2 ± 0.0c
78.5 ± 0.8a 9.3 ± 0.1a 8.2 ± 0.2d 1.5 ± 0.1b
74.5 ± 0.5b 7.5 ± 0.1c 10.5 ± 0.1c 2.0 ± 0.1a
71.7 ± 0.7c 6.9 ± 0.1d 14.0 ± 0.3b 1.1 ± 0.1d
70.1 ± 0.7c 6.2 ± 0.1e 16.1 ± 0.5a 1.0 ± 0.1d
70.1 ± 0.6c 5.7 ± 0.2e 16.2 ± 0.2a 1.1 ± 0.1d
Means ± SE, n = 3.
Fatty acid methyl esters (FAME) from fatty acids (FA) of diets and fish tissue samples were prepared according to Christie (1993). FAME were analyzed in a Hewlett Packard 5890II gas chromatograph equipped with a flame ionization detector and a capillary column (Omegawax™ 320 by Supelco/Sigma-Aldrich: 30 m × 0.32 mm, film thickness 0.25 μm) using hydrogen as the carrier gas. FA was identified by comparing retention times to those of standards mixtures (37 Component FAME Mix, Supelco/Sigma-Aldrich; GLC 87, GLC 96, Nu-Chek Prep) and samples of marine oils (PUFA1 and PUFA3, Supelco/Sigma-Aldrich). Each FA concentration was calculated from the corresponding chromatogram area by using an internal standard (19:0) and a software package, HP ChemStation rev. A.06 for Windows. 2.4. Statistical analysis All data were subjected to one-way analysis of variance (ANOVA). Differences were considered statistically significant at P b 0.05. Means were compared after analysis of variance by Tukey range tests. All statistical analyses were carried out by using the Minitab program version 13.2 (Minitab Inc., State College, PA, USA). The results are presented as mean ± standard error of the mean (S.E.M.). 3. Results The survival, growth and feeding performances of white seabass fingerlings fed the experimental diets and a commercial diet (GP:GE ratio: 34.3 to 28.1 and 23.0 mg kJ− 1, respectively) for 50-day feeding trial are presented in Table 2. Fish survival throughout the growth trial was between 89.0 and 100%, where diets 2.6 L and CD were significantly lower than the rest of the diets (P b 0.05). Final mean body weight, weight gain, and NRE were significantly higher for diets 15.3 L and 19.4 L (P b 0.05) and the FCR was significantly lower (1.3 and 1.1, respectively) than the rest of the treatments. The DFI were variable (3.5 ± 0.08 to 8.6 ± 0.03) and significantly affected by dietary treatment (P b 0.05). Fish fed the highest gross energy diet (19.4 L, 23.7 kJ g− 1) ingested the lowest amount of fed (30.7 g) during the 50-day trial and showed the lowest DFI (3.5 ± 0.08% day− 1). The effect of dietary treatments on body composition is presented in Table 3. Significant differences (P b 0.05) of experimental diets on the whole body composition were observed. Lipid content of whole body increased in direct proportion to dietary lipid level and achieved the highest level in fish fed the 19.4 L diet. A concurrent decrease in moisture content to the increase in lipid content was observed. Protein and ash contents of whole body decreased with the increase in dietary lipid levels (P b 0.05). However, the dietary lipid level had no
significant effect on the relative protein content in muscle but ash content showed a declining trend with increasing dietary lipid level (P b 0.05). Lipid content of muscle significantly increased with increasing dietary lipid level (P b 0.05). Protein and ash contents in liver were inversely correlated with dietary lipid concentration (P b 0.05). Lipid content in liver increased with the increase in dietary lipid (P b 0.05) and moisture decreased with increasing dietary lipid level (Table 3). The FA composition of the experimental and commercial diet is presented in Table 4. In summary, the FAs 16:0, 16:1n−7, 18:1n−9, 20:5n−3 and 22:6n−3 were the most abundant of the saturated, mono and polyunsaturated FAs, in the experimental diets. In addition to the FAs listed above, the commercial diet was very high in 18:2n−6 and had the lowest n−3/n−6 ratio among all diets. The FA content of the total lipid of muscle tissue is shown in Table 5. In the initial sample, the FAs 16:0, 18:0, 18:1n−9, 18:2n−3, 20:5n−3 and 22:6n−3 were the most abundant with the lowest n−3/n−6 ratio. Samples of whole fish fed the experimental and commercial diet showed high levels of 16:0, 18:0, 18:1n−9, 20:5n−3 and 22:6n−3, and had significantly lower levels of 18:2n−6 (P b 0.05) than observed in the initial sample. The FA composition in liver is shown in Table 6, where the initial and final samples from fish fed the experimental and commercial diets, The FAs 16:0, 16:1n−7, 18:0, 18:1n−9, 18:1n−7, 18:2n−6, 20:5n−3,
Table 4 FA composition (mg of FA per g of dry weight) of the experimental and commercial diets (CD) Fatty acid
2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
14:0 16:0 16:1n−7 18:0 18:1n−9 18:1n−7 18:2n−6 18:3n−3 18:4n−3 20:0 20:1n−9 20:4n−6 20:4n−3 20:5n−3 22:0 22:5n−3 22:6n−3 HUFA n−3 n−3/n−6
1.46 4.76 2.02 1.14 3.54 1.38 0.79 0.16 0.30 0.30 0.28 0.26 0.14 2.31 0.28 0.32 1.78 4.55 5.06
3.34 12. 94 4.46 3.38 9.20 3.18 1.71 0.46 0.71 0.82 1.62 1.07 0.33 6.16 1.22 1.30 8.31 16.10 6.21
5.50 18.63 7.79 4.58 15.45 4.86 2.79 0.81 1.36 1.36 3.69 1.24 0.66 9.59 1.82 2.31 11.58 24.14 6.53
7.49 23.43 9.67 5.98 18.66 5.90 3.35 1.01 2.07 1.69 5.88 1.49 1.26 12.70 2.46 4.13 14.91 33.00 7.45
9.86 29.33 12.45 7.36 24.28 7.48 4.24 1.30 2.71 2.10 8.10 1.74 1.66 16.16 3.04 4.00 17.72 39.54 7.28
5.38 26.45 6.27 6.96 18.90 4.75 16.29 2.48 1.80 1.17 4.03 1.05 0.58 9.24 1.84 1.24 11.75 22.81 1.56
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Table 5 FA composition (mg of FA per g of dry weight) of muscle tissue of juvenile white seabass at the beginning and end of the feeding trial Fatty acid 14:0 16:0 16:1n−7 18:0 18:1n−9 18:1n−7 18:2n−6 18:3n−3 18:4n−3 20:0 20:1n−9 20:4n−6 20:4n−3 20:5n−3 22:0 22:5n−3 22:6n−3 n−3/n−6
Q 0.9 ± 0.1b 13.1 ± 0.5a 2.6 ± 0.1a 6.0 ± 0.3a 7.9 ± 0.1a 2.8 ± 0.0a 5.5 ± 0.0a 0.5 ± 0.0a 0.2 ± 0.0c 0.8 ± 0.1ab 0.9 ± 0.0a 0.8 ± 0.1de 0.2 ± 0.0b 5.4 ± 0.3a 0.9 ± 0.0e 1.4 ± 0.1b 6.3 ± 0.6d 0.7 ± 0.0e
Diet 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
0.8 ± 0.0c 7.9 ± 0.1d 3.4 ± 0.4a 4.3 ± 0.1d 5.4 ± 0.0d 1.7 ± 0.1d 1.3 ± 0.0b 0.2 ± 0.0c 0.1 ± 0.0d 0.5 ± 0.0c 0.5 ± 0.0c 0.5 ± 0.0f 0.1 ± 0.0d 2.5 ± 0.1d 0.6 ± 0.0f 0.7 ± 0.1c 3.9 ± 0.0e 1.4 ± 0.0d
0.7 ± 0.0c 7.6 ± 0.1d 1.7 ± 0.0b 3.3 ± 0.1f 3.3 ± 0.1f 1.7 ± 0.0d 0.8 ± 0.0d 0.2 ± 0.0c 0.2 ± 0.0d 0.4 ± 0.0d 0.4 ± 0.0d 0.7 ± 0.0e 0.2 ± 0.0c 2.8 ± 0.1d 0.9 ± 0.0e 0.8 ± 0.1c 6. 6 ± 0.3d 2.4 ± 0.1c
0.6 ± 0.1c 9.5 ± 0.2c 1.9 ± 0.1b 3.9 ± 0.1e 4.5 ± 0.1e 1.9 ± 0.1c 0.8 ± 0.0d 0.2 ± 0.0c 0.2 ± 0.0c 0.5 ± 0.0c 0.5 ± 0.1c 0.9 ± 0.0d 0.2 ± 0.0b 3.4 ± 0.2c 1.2 ± 0.0d 0.7 ± 0.0c 8.4 ± 0.1c 2.7 ± 0.0bc
1.3 ± 0.3a 13.1 ± 0.2a 2.9 ± 0.3a 5.1 ± 0.0c 6.1 ± 0.2c 2.5 ± 0.1b 1.1 ± 0.0c 0.4 ± 0.1a 0.4 ± 0.1a 0.7 ± 0.0a 0.8 ± 0.0b 1.2 ± 0.0c 0.4 ± 0.0a 5.0 ± 0.2b 1.7 ± 0.0b 2.2 ± 0.1a 12.4 ± 0.6b 3.1 ± 0.2ab
1.2 ± 0.0a 14.0 ± 0.1a 3.0 ± 0.0a 5.5 ± 0.1b 6.5 ± 0.1b 2.6 ± 0.0b 1.1 ± 0.0c 0.4 ± 0.0a 0.4 ± 0.0a 0.8 ± 0.0a 0.9 ± 0.0a 1.3 ± 0.0b 0.4 ± 0.0a 5.2 ± 0.1a 1.8 ± 0.0a 2.1 ± 0.1a 13.9 ± 0.1a 3.1 ± 0.0a
1.2 ± 0.1ab 12.0 ± 0.2b 2.2 ± 0.1b 4.8 ± 0.0d 6.2 ± 0.1bc 1.9 ± 0.0c 2.9 ± 0.1b 0.3 ± 0.0b 0.3 ± 0.0b 0.6 ± 0.0b 0.6 ± 0.0c 1.5 ± 0.1a 0.3 ± 0.0b 4.7 ± 0.2b 1.3 ± 0.1c 1.1 ± 0.1b 11.3 ± 0.5b 1.4 ± 0.1d
Means ± SE, n = 3. Means in the same row with different superscript are significantly different (P b 0.05).
22:5n−3 and 22:6n−3 were the most abundant and the n−6 and n−3 FA contents were higher than those found in the experimental diets. The initial sample showed the highest level of 18:2n−6 and the lowest 22:6n−3 level, as well as the lowest n−3/n−6 ratio. 4. Discussion Like several other species of marine carnivorous fish (e.g. red drum, European sea bass, Asian sea bass and cobia), an increase in dietary lipid effected the performance of white seabass. Thus, it is important to formulate diets with the proper lipid level to meet the energy and FA requirements for these species (Craig et al., 1999; Peres and OlivaTeles, 1999; Williams et al., 2003; Wang et al., 2005). The results of this study based on feeding dietary lipid levels from 2.6 to 19.4%, indicate that the most favorable inclusion level was similar to the levels of 15 to 18% reported previously for white seabass based on survival, growth and feed nutrient utilization (López et al., 2006). Growth, FCR and NRE of juvenile white seabass improved with the increase of lipid supplement in the diet. Diets 15.3 L and 19.4 L with 29 and 28.1 mg kJ− 1 GP:GE ratio, respectively, produced the best growth, FCR (1.3 and 1.1) and NRE (28.1 and 34.4), and these fish ingested the lest amount of feed (35.0 and 30.7 g, respectively), which
is likely because DFI is closely related to FCR. These findings are consistent with several other reports that the overall performance of some species of marine carnivorous fish is improved by increasing the lipid level in the diet (Craig et al., 1999; Peres and Oliva-Teles, 1999; Williams et al., 2003). In the study conducted by Peres and Oliva-Teles (1999) to determine the lipid requirement of European sea bass juveniles, a DP:DE ratio of 21 to 33 mg kJ− 1 showed the best growth. In the current study, the best performance of white seabass juveniles was observed when the GP:GE ratio was from 28.1 to 29 mg kJ− 1. When fish are fed a diet containing insufficient lipid, all performances may be reduced due to a deficient amount of energy and essential fatty acids. White seabass fed the 2.6 L diet (2.6% lipid) had only about one third the growth response observed in juveniles fed 15 or 19% lipid. Even though white seabass have been produced for more than 20 years by feeding a variety of commercial diets, in this study, the fish fed the CD (50% protein, 14.7% lipid and 21.8 kJ g− 1 energy) required a DFI of 8.6% day− 1, had a FCR of 2.5 and the NRE was only 15.6. This information demonstrates that the formulation of the CD may be improved by studying the nutrient requirements of white seabass. Proximate analyses demonstrated that dietary lipid levels influenced the body composition including the FA composition in muscle
Table 6 FA composition (mg of FA per g of dry weight) of liver tissue of juvenile white seabass at the beginning and end of the feeding trial Fatty acid 14:0 16:0 16:1n−7 18:0 18:1n−9 18:1n−7 18:2n−6 18:3n−3 18:4n−3 20:0 20:1n−9 20:4n−6 20:4n−3 20:5n−3 22:0 22:5n−3 22:6n−3 n−3/n−6
Initial 9.1 ± 0.1e 81.0 ± 2.1c 39.8 ± 0.8d 42.7 ± 0.4a 87.2 ± 1.7a 29.3 ± 0.3a 52.1 ± 2.2a 4.9 ± 0.2b 2.3 ± 0.0c 3.6 ± 0.0e 9.2 ± 0.4b 2.1 ± 0.1d 1.0 ± 0.0e 14.6 ± 0.3d 2.2 ± 0.1c 12.9 ± 5.0a 13.0 ± 0.3c 0.3 ± 0.0d
Diet 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
5.7 ± 0.1f 71.1 ± 0.3d 27.3 ± 0.6f 46.7 ± 7.7a 61.8 ± 1.2b 22.0 ± 1.1c 11.4 ± 0.1d 1.3 ± 0.0e 0.6 ± 0.3d 3.9 ± 0.1d 12.5 ± 0.9a 4.8 ± 0.4c 0.6 ± 0.3e 12.4 ± 0.5d 4.7 ± 0.3b 5.5 ± 0.5b 27.8 ± 2.9b 1.0 ± 0.0b
8.9 ± 0.2e 73.3 ± 1.2d 30.2 ± 0.2e 21.0 ± 0.1bc 39.5 ± 0.3d 22.7 ± 0.2c 9.6 ± 0.1e 2.3 ± 0.1d 2.0 ± 0.0c 3.5 ± 0.3de 5.1 ± 0.2e 6.7 ± 0.2ab 1.7 ± 0.0d 21.9 ± 0.5c 7.2 ± 0.2a 9.1 ± 1.2a 50.3 ± 2.9a 1.8 ± 0.0a
12.5 ± 1.0d 72.2 ± 0.1d 42.2 ± 0.9cd 19.6 ± 1. 7c 45.3 ± 2.5c 23.4 ± 0.3bc 9.7 ± 0.1e 3.3 ± 0.0c 3.5 ± 0.4b 4.1 ± 0.1d 5.7 ± 0.7e 5.6 ± 0. 6b 2.9 ± 0.25c 25.4 ± 0.5b 6.9 ± 0.5a 10.8 ± 1.3a 44.9 ± 3.7a 2.0 ± 0.1a
18.2 ± 0.4b 84.3 ± 0.4c 51.4 ± 0.4b 20.6 ± 1.5c 60.0 ± 0.8b 25.7 ± 0.1b 12.6 ± 0.4c 4.7 ± 0.0b 5.5 ± 0.2a 4.7 ± 0.0c 6.7 ± 0.1d 5.4 ± 0.2b 3.9 ± 0.1b 30.8 ± 0.8a 6.9 ± 0.1a 10.7 ± 0.1a 42.4 ± 0.4a 1. 8 ± 0.15a
22.4 ± 0.3a 94.0 ± 3.8b 59.9 ± 1.6a 20.8 ± 1.2c 64.4 ± 1.9b 27.0 ± 0.9b 13.3 ± 0.1c 5.3 ± 0.1a 6.4 ± 0.4a 5.4 ± 0.2ab 7.6 ± 0.2c 5.1 ± 0.3b 4.5 ± 0.2a 32.7 ± 2.5a 7.3 ± 0.4a 10.4 ± 0.5a 43.2 ± 2.4a 1.9 ± 0.1a
15.4 ± 1.1c 102.8 ± 1.1a 46.9 ± 3.2c 32.1 ± 2.9b 83.1 ± 6.4a 25.0 ± 1.5b 39.4 ± 2.1b 4.0 ± 0.8bc 2.3 ± 0.6c 4.8 ± 0.3bc 8.4 ± 0.6c 8.3 ± 1.2a 1.7 ± 0.4d 25.2 ± 6.1abc 6.3 ± 1.2a 9.1 ± 1.5a 42.1 ± 8.5a 0.6 ± 0.1c
Means ± SE, n = 3. Means in the same row with different superscript are significantly different (P b 0.05).
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and liver tissue as suggested by several authors (Oku and Yogata, 2000; Sargent et al., 2002; Solberg, 2004; Miller et al., 2005: Kucska et al., 2006). As shown in other marine fish, we demonstrated that high dietary levels of lipid lead to increased deposition of lipid on soft tissues. The lipid level in muscle suggests a limited capacity for juvenile white seabass to accumulate lipid, which is in agreement with a previous report (López et al., 2006). The propensity of white seabass to deposit high levels of lipid in the liver rather than muscle tissue is consistent with lean body muscle growth characteristic of sedentary demersal species (McGoogan and Gatlin, 1999; Lee et al., 2002). It is well known that the FA composition of tissues is determined mainly by their dietary lipid, and that marine fish have a specific requirement for the HUFAs 20:5n−3, 22:6n−3 and 20:4n−6 (Sargent et al., 1999, 2002; Bell and Sargent, 2003). Lipid composition of white seabass tissues in the present study was reflective of levels present in each experimental diet. The prevalent HUFAs [20:4n−6, 20:5n−3, 22:5n−3 and 22:6n−3] in the dietary treatments, from menhaden oil, were found in muscle and liver of white seabass in increasing levels according to dietary lipid level. Fish tissue, in general, had much higher concentrations of n−3 HUFA than 20:4n−6 but both are required for normal growth, development and reproduction (Sargent et al., 1999; Tocher, 2003). Diets with the same FA composition but different lipid level can induce modifications in FA composition and enzyme activity in intestinal brush border membranes of fish, affecting physicochemical characteristics of the membrane and the digestive functions of the intestine (Cahu et al., 2000; Gawlicka et al., 2002). However, further research will be needed to determine the dietary FA requirements of white seabass. In conclusion, our results suggest that white seabass fingerlings (25 days old, 1.7± 0.13 g, 30.2 ± 0.3 mm) perform well with a dietary lipid level between 15 to 19% when protein inclusion was 66.4%. Increased growth and NRE were evident when dietary energy increased from 19.8 to 23.7 kJ g− 1 and the GP:GE ratio varied from 28.1 to 29 mg kJ− 1. Acknowledgements This work was supported by the National Council for Science and Technology (CONACyT) of México, Project 2003-CO1-206 and by Autonomous University of Baja California (UABC) Mexico, internal project. The authors would also like to acknowledge the skillful assistance of Paul Curtis, Gabriela LaChance, and Dave Jirsa from Hubbs-SeaWorld Research Institute, San Diego, CA. References AOAC (Association of Official and Analytical Chemists), 1995. 16th ed. Official Methods of Analysis of AOAC, vol. 1. Association of Official Analytical Chemists, Arlington, VA. Bell, J.G., Sargent, J.R., 2003. Arachidonic acid in aquaculture feeds: current status and future opportunities. Aquaculture 218, 491–499. Cahu, C.L., Zambonino-Infante, J.L., Corraze, G., Coves, D., 2000. Dietary lipid level affects fatty acid composition and hydrolase activities of intestinal brush border membrane in seabass. Fish Physiol. Biochem. 23, 165–172. Cho, S.H., Lee, S.M., Lee, S.M., Lee, J.H., 2005. Effect of dietary protein and lipid levels on growth and body composition of juvenile turbot (Scophthalmus maximus L) reared under optimum salinity and temperature conditions. Aquac. Nutr. 11, 235–240. Christie, W.W., 1993. Preparation of ester derivatives of fatty acids for chromatographic analysis. In: Christie, W.W. (Ed.), Advances in Lipid Methodology, vol. 2. Oily Press, Dundee, pp. 69–111. Craig, S., Washburn, B., Gatlin, D., 1999. Effects of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus. Fish Physiol. Biochem. 21, 249–255. Donohoe, C.J., 1999. Age, growth, distribution, and food habits of recently settled white seabass, Atractoscion nobilis, off San Diego County, California. Fish. Bull. 95, 709–721. Drawbridge, M., Kent, A., Forster, D.B., 1999. Commercialization of white seabass aquaculture, pilot program out-grow to market. A Publication of Hubb– Sea World
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Research Institute Pursuant to National Oceanic and Atmospheric Administration. 45 pp. Du, Z.-Y., Liu, Y.-J., Tian, L.-X., Wang, J.-T., Wang, Y., Liang, G.-Y., 2005. Effect of dietary lipid level on growth, feed utilization and body composition by juvenile grass carp (Ctenopharyngodon idella). Aquac. Nutr. 11, 139–146. Folch, J., Lees, M., Sloane- Stanley, G.H., 1957. A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 226, 497–509. Gawlicka, A., Herold, M.A., Barrows, F.T., de la Noüve, J., Hung, S.S.O., 2002. Effects of dietary lipids on growth, fatty acid composition, intestinal absorption and hepatic storage in white sturgeon (Acipenser transmontanus R.) larvae. J. Appl. Ichthyol. 18, 673–681. Jobling, M., 2001. Nutrition partitioning and the influence of feed composition on body composition. In: Houlihan, D., Boujard, T., Jobling, M. (Eds.), Food Intake in Fish. Blackwell Science, UK, pp. 354–375. Kent, D.B., Ford, R.F., Drawbridge, M.A., 2001. Experimental culture and evaluation of enhancing marine fishes in Southern California. Annual Progress Report prepared for The California Department of Fish and Game and The Ocean Resources Enhancement and Hatchery Program Advisory Panel. Hubbs-Sea World Research Institute/San Diego State University, San Diego, CA. 66 pp. Kucska, B., Pál, L., Müller, T., Bódis, M., Bartos, A., Wágner, L., Husvéth, F., Bercsényi, M., 2006. Changing of fat content and fatty acid profile of reared pike (Esox lucius) fed two different diets. Aquac. Res. 37, 96–101. Lee, S.M., Jeon, I.G., Lee, J.Y., 2002. Effects of digestible protein and lipid levels in practical diets on growth, protein utilization and body composition of juvenile rockfish (Sebastes schlegeli). Aquaculture 211, 227–239. López, L.M., Torres, A.I., Durazo, E., Drawbridge, M., 2004. The energy and protein requirements for optimum growth and performance of the fingerlings of white seabass, Atractoscion nobilis. In: Adams, S., Olafsen, J.A. (Eds.), Biotechnologies for Quality, Proc. Aquaculture Europe, vol. 34. European Aquaculture Society Special Publ, Barcelona, Spain, pp. 496–497. López, L.M., Torres, A.L., Durazo, E., Drawbridge, M., Bureau, D.P., 2006. Effects of lipid on growth and feed utilization of white seabass (Atractoscion nobilis) fingerlings. Aquaculture 253, 557–563. Luo, Z., Liu, Y.-J., Mai, K.-S., Tian, L.-X., Liu, D.-H., Tan, X.-Y., Lin, H.-Z., 2005. Effect of dietary lipid level on growth performance, feed utilization and body composition of grouper Epinephelus coioides juveniles fed isonitrogenous diets in floating netcages. Aquac. Int. 13, 257–269. Martins, D.A., Valente, L.M.P., Lall, S.P., 2007. Effects of dietary lipid level on growth and lipid utilization by juvenile Atlantic halibut (Hippoglossus hippoglossus, L.). 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Contents lists available at ScienceDirect
Aquaculture j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a q u a - o n l i n e
Effect of dietary lipid levels on performance, body composition and fatty acid profile of juvenile white seabass, Atractoscion nobilis Lus M. López a,⁎, Eduardo Durazo a, María Teresa Viana b, Mark Drawbridge c, Dominique P. Bureau d a
Facultad de Ciencias Marinas, Universidad Autónoma de Baja California (UABC), PO Box 453, Ensenada BC 22860, Mexico Instituto de Investigaciones Oceanológicas, UABC, PO Box 453, Ensenada BC 22860, Mexico Hubbs-SeaWorld Research Institute, 2595 Ingraham St., San Diego, CA 92109, USA d Fish Nutrition Research Laboratory, Dept. of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada N1G 2W1 b c
a r t i c l e
i n f o
Article history: Received 24 September 2008 Received in revised form 31 December 2008 Accepted 4 January 2009 Keywords: White seabass Formulated diet Dietary lipids Growth Fatty acids
a b s t r a c t The objective of this study was to determine the optimum dietary lipid level of white seabass, Atractoscion nobilis, which is one of the most important species in California and Baja California for sport and commercial fisheries. Triplicate groups of fish were fed for 50 days with isonitrogenous experimental diets formulated with increasing lipid levels (2.6, 7.4, 11.6, 15.3 and 19.4% lipid) using menhaden oil as the lipid source. A commercial diet (CD, 49.9% crude protein, 14.7% lipid) was also fed to triplicate groups of fish. Survival throughout the growth trial ranged from 89 to 100% but the survival of fish fed the 2.6% lipid and the commercial diet was significantly less than the rest of the diets. Final mean body weight, feed conversion ratio (FCR), and nitrogen retention efficiency (NRE: N gain/N intake) were significantly greater for diets 15.3 L and 19.4 L compared to the rest of the treatments. Daily feed intake (DFI) was variable (3.5 ± 0.08 to 8.6 ± 0.03) and significantly affected by dietary treatment. Lipid content of whole body, muscle and liver increased with increasing dietary lipid levels. Muscle and liver fatty acid (FA) composition reflected dietary FA profiles. Tissue n−3 and n−6 highly unsaturated fatty acids (HUFAs) content increased in direct proportion to dietary lipid levels. Published by Elsevier B.V.
1. Introduction White seabass, Atractoscion nobilis, is an important recreational and commercial species found in waters off the coasts of southern California, USA and northern Baja California, Mexico (Donohoe, 1999; Vojkovich and Crooke, 2001). Due to their large size, quality flesh and high market value this species had been over-exploited and in a condition of severe depletion in California until a program for stock enhancement started in the early 1980s (Drawbridge et al., 1999). Efforts have been focused on the culture of this fish species to support stock replenishment but there is also great interest in evaluating the feasibility of farming this species under commercial conditions. Although some information has been published concerning the nutrient requirement for white seabass (Kent et al., 2001; López et al., 2004, 2006), basic studies concerning its nutritional requirements are still lacking. It is well known that marine carnivorous fish preferentially utilize protein as an energy source but lipids are a source of dietary energy and essential fatty acids (EFA) and can spare protein in the diet of many fish species (Wang et al., 2005; Martins et al., 2007; Schuchardt et al., 2008). Within certain limits, increasing the dietary lipid level ⁎ Corresponding author. Tel.: +52 646 1744570; fax: +52 646 1744103. E-mail address: [email protected] (L.M. López). 0044-8486/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.aquaculture.2009.01.003
has been shown to improve the feed efficiency of marine fish species (Cho et al., 2005; Du et al., 2005). Studies conducted in our laboratory have indicated that diets with high lipid inclusion (over 22%, provided by fish oil) produce poorer performance in white seabass than diets with lower lipid levels (15 to 18%, López et al., 2006). Many studies have analyzed the effects of dietary lipid level on growth performance and body composition in marine fish, like European sea bass (Peres and Oliva-Teles, 1999), red sea bream and Japanese yellowtail (Oku and Yogata, 2000), haddock (Nanton et al., 2001), grouper (Luo et al., 2005), cobia (Wang et al., 2005) and Atlantic halibut (Martins et al., 2007). Although the dietary FA profile is generally reflected in fish tissue, the influence of dietary lipid level on white seabass FA profiles has not been studied. Thus, the aim of the present study was to evaluate the effects of varied levels of dietary lipid on growth performance, body composition, and FA profile of whole body, muscle and liver of white seabass fingerlings. 2. Materials and methods 2.1. Diet formulation Five isonitrogenous experimental diets (67.06 ± 0.33%, CP) were formulated to contain five lipid levels (2.6, 7.4, 11.6, 15.3 and 19.4% of dry matter). Ingredients, proximate composition and gross energy of
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Table 1 Ingredient and chemical composition of the experimental and a commercial diets (CD) on a dry weight basis Ingredient (g/100 g) Fish meala Krill mealb Corn starch Fish oilc Gelatin Minerals mixtured Vitamin mixturee Sodium benzoate Antioxidantf
Diets 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
60.0 13.0 12.9 0.0 8.0 4.0 2.0 0.1 0.01
60.0 13.0 11.2 1.7 8.0 4.0 2.0 0.1 0.02
58.5 14.5 7.2 5.7 8.0 4.0 2.0 0.1 0.02
59.0 13.0 4.3 9.6 8.0 4.0 2.0 0.1 0.03
58.0 14.3 0.0 13.6 8.0 4.0 2.0 0.1 0.03
67.0 11.6 7.6 13.8 22.1 30.2
66.4 15.3 7.6 10.7 23.0 29.0
66.4 19.4 6.5 7.7 23.7 28.1
Proximate composition (% of dry matter basis) Crude protein 68.2 67.3 Crude lipid 2.6 7.4 Ash 8.3 8.1 NFE + crude fiberg 20.9 17.2 19.8 21.2 Gross energy (kJ g− 1) −1 h GP:GE ratio (mg kJ ) 34.3 31.9
CD
49.9 14.7 10.8 24.6 21.8 23.0
a
66% crude protein, 3% crude lipid. 61.5% crude protein, 13% crude lipid. c From menhaden. d g/kg mineral premix: KH2PO4 320; NaH2PO4, 250; Ca(H2PO4)2, 200; MgSO4.7H2O, 150; calcium lactate, 35; ferric citrate, 25; NaCl, 10, ZnSO4.7H2O, 3.53; MnSO4.H2O, 1.62; CuSO4.5H2O, 0.31; CoCl2.6H2O, 0.01. e g/kg vitamin premix: inositol, 256.39; choline chloride, 149.78; niacin, 51.28; riboflavin; ρ-amino benzoic acid, 25.53; pantothenic acid, 17.92; β-carotene, 9.39; menadione, 6.11; thiamin-HCl, 3.85; pyridoxine, 3.06; folic acid, 0.96; biotin, 0.39; cholecalciferol, 25793IU, α-tocopherol, 25643 IU; vitamin B12, 5.59 mg. f Butylatedhydroxytoluene + α-tocopherol. g Nitrogen free extract (NFE) + crude fiber = 100- (% crude protein + % total lipid + % ash). h Gross Protein:Gross Energy ratio (mg kJ− 1). b
the experimental diets are presented in Table 1. Freeze-dried white fish muscle meal and krill meal were the major dietary protein sources. Cod liver oil and corn starch were used as lipid and carbohydrate sources, respectively. All ingredients were blended in a mixer (Kitchen Aid, Hobart, Troy, OH, USA), to produce a homogeneous mixture. The wet mixture was pelleted through a 3-mm die in a commercial meat grinder and pellets were dried in a convection oven for 8 h at 65 °C. The dry pellets were placed in sealed plastic bags and stored at −20 °C until use. The commercial diet (CD, Table 1) was a commercially available marine fish grower feed (Skretting, Vancouver, British Columbia, Canada) currently used at the hatchery for production of white seabass. 2.2. Animals and husbandry The experimental culture was performed at the hatchery of HubbsSeaWorld Research Institute, Carlsbad, CA. A total of 1272 white seabass fingerlings (25 days old, 1.7± 0.13 g, 30.2 ± 0.3 mm) were randomly distributed among 24 square plastic tanks at a stocking density of 53 fish
per tank. Each tank of 65 L was supplied with recirculated seawater at a flow-rate of 1.5 L min− 1. The photoperiod and temperature of the seawater in the tanks were maintained at 14:10 h (light: dark, with fluorescent light) and 21.7 ± 0.1 °C, respectively. Salinity in the system remained relatively constant at 33 ± 0.6‰. Fish were acclimated in the system for two weeks before beginning the feeding trial. During this period, the fingerlings were fed with the CD. Each dietary treatment was replicated four times in a completely randomized block design. Fish were fed by hand to visual satiety, four times per day (0700, 1200, 1700 and 2200 h), every day for 50 days, except prior to weighing when no feed was fed for 12 h. The length of the pellet was increased and fed as the fish grew. Fish in each tank were weighed (g) and measured (mm) individually at day 0, 25 and 50. At the start and end of the trial, sub-samples of 10 fish from each tank were euthanized and the liver and white muscle were excised, weighed and frozen at −70 °C for future analysis. Daily feed intake (DFI) was calculated from the mean daily averages of feed consumed on a dry weight basis. The amount of feed provided was recorded and uneaten feed was siphoned 20 min after feeding, dried at 100 °C for 12 h and weighed. The pellets were well bound and highly stable in the water during this time. Uneaten feed from each tank was subtracted from the total feed fed for each tank to calculate feed intake. 2.3. Analytical methods The dry weights of whole body, muscle and liver samples were measured from triplicate samples per dietary treatment after freezedrying (VIRTIS 12EL Freezmobile, Köln, Germany) for 48 h. Mean total N content was determined from samples analyzed by the micro-Kjeldhal method (AOAC, 1995), and crude protein was calculated as %N × 6.25. Total lipid was determined by extraction using chloroform–methanol (2:1 v/v) following the method of Folch et al. (1957). Ash content was determined gravimetrically after ashing the sample at 500 °C for 8 h. Carbohydrate as nitrogen free extract (NFE) plus crude fiber were calculated as the difference of the total sample weight less crude protein, total lipid and ash (Jobling, 2001). Gross energy content was determined using an adiabatic bomb calorimeter (PARR 1281, Moline, IL, USA). The main performance variables were calculated using the following formulae: Daily feed intake (DFI) = total dry feed consumed (g) × 100 / [(final body wet weight + initial body wet weight (g)) × days fed / 2]. Feed conversion ratio (FCR) = Dry weight of feed consumed (g) × wet weight gain of animal (g)– 1 Nitrogen retention efficiency (NRE %) = 100 × g nitrogen gain (g/fish) / g nitrogen intake (g/fish) where the N gain was calculated from the weight increase and the N of the initial and final samples of fish. The feed N was calculated from feed intake and the nitrogen content in the feed.
Table 2 Survival and growth performance of juvenile white seabass fed the experimental and commercial diets for 50 days Diet
2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
Survival (%) Initial BW (g) Final BW (g) Weight gain (g) Length gain (mm) DFI (% day− 1) FCR NRE
89.3 ± 1.0b 1.7 ± 0.1 12.6 ± 0.2d 10.9 ± 0.2d 63.4 ± 1.9d 8.5 ± 0.10a 2.9 ± 0.2d 10.4 ± 0.2f
100 ± 0.0a 1.6 ± 0.1 23.4 ± 0.2c 21.7 ± 0.4c 81.9 ± 0.8c 7.2 ± 0.09c 2.2 ± 0.2b 12.4 ± 0.4e
97.8 ± 1.3a 1.7 ± 0.1 24.1 ± 0.4c 22.3 ± 0.4c 81.9 ± 0.9c 7.6 ± 0.05b 2.3 ± 0.1b 14.1 ± 0.4d
96.0 ± 2.2a 1.7 ± 0.1 30.5 ± 0.2a 28.8 ± 0.7a 93.2 ± 1.6ab 4.2 ± 0.04d 1.3 ± 0.1a 28.1 ± 0.3b
99.3 ± 0.8a 1.7 ± 0.1 31.6 ± 0.7a 30.0 ± 0.6a 95.6 ± 1.0a 3.5 ± 0.08e 1.1 ± 0.1a 34.4 ± 0.3a
89.0 ± 1.6b 1.8 ± 0.1 26.4 ± 0.5b 24.8 ± 0.2b 90.4 ± 1.0b 8.6 ± 0.03a 2.5 ± 0.1c 15.6 ± 0.2c
Means ± SE. Body wet weight (BW). Daily feed intake (DFI) = total dry feed intake (g) × 100 / [(final body wet weight + initial body wet weight (g)) × days fed / 2]. Feed conversion ratio (FCR): total feed intake (g) × total wet weight gain of animal (g)− 1. Nitrogen retention efficiency (NRE): 100 ×g nitrogen gain (g/fish) / g nitrogen intake (g/fish). Means in the same column with different superscript are significantly different (P b 0.05).
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Table 3 Proximate composition (wet weight) of juvenile white seabass fed the experimental and a commercial diets for 50 days Initial Whole body Moisture Crude protein Crude lipid Ash Muscle Moisture Crude protein Crude lipid Ash Liver Moisture Crude protein Crude lipid Ash
Diet 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
73.4 18.4 3.2 3.5
74.8 ± 0.5a 17.8 ± 0.1c 1.6 ± 0.0c 4.7 ± 0.1c
74.3 ± 0.4a 17.9 ± 0.1c 1.8 ± 0.0c 4.6 ± 0.1c
69.7 ± 1.0c 20.6 ± 0.3b 3.3 ± 0.1b 5.3 ± 0.1b
68.1 ± 0.5c 21.4 ± 0.1b 3.7 ± 0.0b 5.2 ± 0.1b
65.2 ± 0.6d 22.8 ± 0.3a 4.7 ± 0.1a 5.8 ± 0.0a
71.5 ± 0.4b 18.9 ± 0.2bc 3.7 ± 0.2ab 4.4 ± 0.1c
81.5 15.4 1.2 1.0
83.2 ± 0.6a 14.2 ± 0.2 0.7 ± 0.0c 1.2 ± 0.0c
82.9 ± 0.5a 14.7 ± 0.3 0.7 ± 0.0c 1.2 ± 0.0c
82.3 ± 0.3a 15.1 ± 0.1 0.9 ± 0.0c 1.1 ± 0.0d
81.5 ± 0.2b 15.6 ± 0.2 1.3 ± 0.0b 1.3 ± 0.0b
81.1 ± 0.2b 15.5 ± 0.2 1.4 ± 0.0a 1.3 ± 0.0b
80.4 ± 0.3b 16.4 ± 0.1 1.3 ± 0.0b 1.4 ± 0.0a
72.9 7.2 13.3 1.7
80.5 ± 1.2a 8.3 ± 0.2b 7.4 ± 0.2e 1.2 ± 0.0c
78.5 ± 0.8a 9.3 ± 0.1a 8.2 ± 0.2d 1.5 ± 0.1b
74.5 ± 0.5b 7.5 ± 0.1c 10.5 ± 0.1c 2.0 ± 0.1a
71.7 ± 0.7c 6.9 ± 0.1d 14.0 ± 0.3b 1.1 ± 0.1d
70.1 ± 0.7c 6.2 ± 0.1e 16.1 ± 0.5a 1.0 ± 0.1d
70.1 ± 0.6c 5.7 ± 0.2e 16.2 ± 0.2a 1.1 ± 0.1d
Means ± SE, n = 3.
Fatty acid methyl esters (FAME) from fatty acids (FA) of diets and fish tissue samples were prepared according to Christie (1993). FAME were analyzed in a Hewlett Packard 5890II gas chromatograph equipped with a flame ionization detector and a capillary column (Omegawax™ 320 by Supelco/Sigma-Aldrich: 30 m × 0.32 mm, film thickness 0.25 μm) using hydrogen as the carrier gas. FA was identified by comparing retention times to those of standards mixtures (37 Component FAME Mix, Supelco/Sigma-Aldrich; GLC 87, GLC 96, Nu-Chek Prep) and samples of marine oils (PUFA1 and PUFA3, Supelco/Sigma-Aldrich). Each FA concentration was calculated from the corresponding chromatogram area by using an internal standard (19:0) and a software package, HP ChemStation rev. A.06 for Windows. 2.4. Statistical analysis All data were subjected to one-way analysis of variance (ANOVA). Differences were considered statistically significant at P b 0.05. Means were compared after analysis of variance by Tukey range tests. All statistical analyses were carried out by using the Minitab program version 13.2 (Minitab Inc., State College, PA, USA). The results are presented as mean ± standard error of the mean (S.E.M.). 3. Results The survival, growth and feeding performances of white seabass fingerlings fed the experimental diets and a commercial diet (GP:GE ratio: 34.3 to 28.1 and 23.0 mg kJ− 1, respectively) for 50-day feeding trial are presented in Table 2. Fish survival throughout the growth trial was between 89.0 and 100%, where diets 2.6 L and CD were significantly lower than the rest of the diets (P b 0.05). Final mean body weight, weight gain, and NRE were significantly higher for diets 15.3 L and 19.4 L (P b 0.05) and the FCR was significantly lower (1.3 and 1.1, respectively) than the rest of the treatments. The DFI were variable (3.5 ± 0.08 to 8.6 ± 0.03) and significantly affected by dietary treatment (P b 0.05). Fish fed the highest gross energy diet (19.4 L, 23.7 kJ g− 1) ingested the lowest amount of fed (30.7 g) during the 50-day trial and showed the lowest DFI (3.5 ± 0.08% day− 1). The effect of dietary treatments on body composition is presented in Table 3. Significant differences (P b 0.05) of experimental diets on the whole body composition were observed. Lipid content of whole body increased in direct proportion to dietary lipid level and achieved the highest level in fish fed the 19.4 L diet. A concurrent decrease in moisture content to the increase in lipid content was observed. Protein and ash contents of whole body decreased with the increase in dietary lipid levels (P b 0.05). However, the dietary lipid level had no
significant effect on the relative protein content in muscle but ash content showed a declining trend with increasing dietary lipid level (P b 0.05). Lipid content of muscle significantly increased with increasing dietary lipid level (P b 0.05). Protein and ash contents in liver were inversely correlated with dietary lipid concentration (P b 0.05). Lipid content in liver increased with the increase in dietary lipid (P b 0.05) and moisture decreased with increasing dietary lipid level (Table 3). The FA composition of the experimental and commercial diet is presented in Table 4. In summary, the FAs 16:0, 16:1n−7, 18:1n−9, 20:5n−3 and 22:6n−3 were the most abundant of the saturated, mono and polyunsaturated FAs, in the experimental diets. In addition to the FAs listed above, the commercial diet was very high in 18:2n−6 and had the lowest n−3/n−6 ratio among all diets. The FA content of the total lipid of muscle tissue is shown in Table 5. In the initial sample, the FAs 16:0, 18:0, 18:1n−9, 18:2n−3, 20:5n−3 and 22:6n−3 were the most abundant with the lowest n−3/n−6 ratio. Samples of whole fish fed the experimental and commercial diet showed high levels of 16:0, 18:0, 18:1n−9, 20:5n−3 and 22:6n−3, and had significantly lower levels of 18:2n−6 (P b 0.05) than observed in the initial sample. The FA composition in liver is shown in Table 6, where the initial and final samples from fish fed the experimental and commercial diets, The FAs 16:0, 16:1n−7, 18:0, 18:1n−9, 18:1n−7, 18:2n−6, 20:5n−3,
Table 4 FA composition (mg of FA per g of dry weight) of the experimental and commercial diets (CD) Fatty acid
2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
14:0 16:0 16:1n−7 18:0 18:1n−9 18:1n−7 18:2n−6 18:3n−3 18:4n−3 20:0 20:1n−9 20:4n−6 20:4n−3 20:5n−3 22:0 22:5n−3 22:6n−3 HUFA n−3 n−3/n−6
1.46 4.76 2.02 1.14 3.54 1.38 0.79 0.16 0.30 0.30 0.28 0.26 0.14 2.31 0.28 0.32 1.78 4.55 5.06
3.34 12. 94 4.46 3.38 9.20 3.18 1.71 0.46 0.71 0.82 1.62 1.07 0.33 6.16 1.22 1.30 8.31 16.10 6.21
5.50 18.63 7.79 4.58 15.45 4.86 2.79 0.81 1.36 1.36 3.69 1.24 0.66 9.59 1.82 2.31 11.58 24.14 6.53
7.49 23.43 9.67 5.98 18.66 5.90 3.35 1.01 2.07 1.69 5.88 1.49 1.26 12.70 2.46 4.13 14.91 33.00 7.45
9.86 29.33 12.45 7.36 24.28 7.48 4.24 1.30 2.71 2.10 8.10 1.74 1.66 16.16 3.04 4.00 17.72 39.54 7.28
5.38 26.45 6.27 6.96 18.90 4.75 16.29 2.48 1.80 1.17 4.03 1.05 0.58 9.24 1.84 1.24 11.75 22.81 1.56
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Table 5 FA composition (mg of FA per g of dry weight) of muscle tissue of juvenile white seabass at the beginning and end of the feeding trial Fatty acid 14:0 16:0 16:1n−7 18:0 18:1n−9 18:1n−7 18:2n−6 18:3n−3 18:4n−3 20:0 20:1n−9 20:4n−6 20:4n−3 20:5n−3 22:0 22:5n−3 22:6n−3 n−3/n−6
Q 0.9 ± 0.1b 13.1 ± 0.5a 2.6 ± 0.1a 6.0 ± 0.3a 7.9 ± 0.1a 2.8 ± 0.0a 5.5 ± 0.0a 0.5 ± 0.0a 0.2 ± 0.0c 0.8 ± 0.1ab 0.9 ± 0.0a 0.8 ± 0.1de 0.2 ± 0.0b 5.4 ± 0.3a 0.9 ± 0.0e 1.4 ± 0.1b 6.3 ± 0.6d 0.7 ± 0.0e
Diet 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
0.8 ± 0.0c 7.9 ± 0.1d 3.4 ± 0.4a 4.3 ± 0.1d 5.4 ± 0.0d 1.7 ± 0.1d 1.3 ± 0.0b 0.2 ± 0.0c 0.1 ± 0.0d 0.5 ± 0.0c 0.5 ± 0.0c 0.5 ± 0.0f 0.1 ± 0.0d 2.5 ± 0.1d 0.6 ± 0.0f 0.7 ± 0.1c 3.9 ± 0.0e 1.4 ± 0.0d
0.7 ± 0.0c 7.6 ± 0.1d 1.7 ± 0.0b 3.3 ± 0.1f 3.3 ± 0.1f 1.7 ± 0.0d 0.8 ± 0.0d 0.2 ± 0.0c 0.2 ± 0.0d 0.4 ± 0.0d 0.4 ± 0.0d 0.7 ± 0.0e 0.2 ± 0.0c 2.8 ± 0.1d 0.9 ± 0.0e 0.8 ± 0.1c 6. 6 ± 0.3d 2.4 ± 0.1c
0.6 ± 0.1c 9.5 ± 0.2c 1.9 ± 0.1b 3.9 ± 0.1e 4.5 ± 0.1e 1.9 ± 0.1c 0.8 ± 0.0d 0.2 ± 0.0c 0.2 ± 0.0c 0.5 ± 0.0c 0.5 ± 0.1c 0.9 ± 0.0d 0.2 ± 0.0b 3.4 ± 0.2c 1.2 ± 0.0d 0.7 ± 0.0c 8.4 ± 0.1c 2.7 ± 0.0bc
1.3 ± 0.3a 13.1 ± 0.2a 2.9 ± 0.3a 5.1 ± 0.0c 6.1 ± 0.2c 2.5 ± 0.1b 1.1 ± 0.0c 0.4 ± 0.1a 0.4 ± 0.1a 0.7 ± 0.0a 0.8 ± 0.0b 1.2 ± 0.0c 0.4 ± 0.0a 5.0 ± 0.2b 1.7 ± 0.0b 2.2 ± 0.1a 12.4 ± 0.6b 3.1 ± 0.2ab
1.2 ± 0.0a 14.0 ± 0.1a 3.0 ± 0.0a 5.5 ± 0.1b 6.5 ± 0.1b 2.6 ± 0.0b 1.1 ± 0.0c 0.4 ± 0.0a 0.4 ± 0.0a 0.8 ± 0.0a 0.9 ± 0.0a 1.3 ± 0.0b 0.4 ± 0.0a 5.2 ± 0.1a 1.8 ± 0.0a 2.1 ± 0.1a 13.9 ± 0.1a 3.1 ± 0.0a
1.2 ± 0.1ab 12.0 ± 0.2b 2.2 ± 0.1b 4.8 ± 0.0d 6.2 ± 0.1bc 1.9 ± 0.0c 2.9 ± 0.1b 0.3 ± 0.0b 0.3 ± 0.0b 0.6 ± 0.0b 0.6 ± 0.0c 1.5 ± 0.1a 0.3 ± 0.0b 4.7 ± 0.2b 1.3 ± 0.1c 1.1 ± 0.1b 11.3 ± 0.5b 1.4 ± 0.1d
Means ± SE, n = 3. Means in the same row with different superscript are significantly different (P b 0.05).
22:5n−3 and 22:6n−3 were the most abundant and the n−6 and n−3 FA contents were higher than those found in the experimental diets. The initial sample showed the highest level of 18:2n−6 and the lowest 22:6n−3 level, as well as the lowest n−3/n−6 ratio. 4. Discussion Like several other species of marine carnivorous fish (e.g. red drum, European sea bass, Asian sea bass and cobia), an increase in dietary lipid effected the performance of white seabass. Thus, it is important to formulate diets with the proper lipid level to meet the energy and FA requirements for these species (Craig et al., 1999; Peres and OlivaTeles, 1999; Williams et al., 2003; Wang et al., 2005). The results of this study based on feeding dietary lipid levels from 2.6 to 19.4%, indicate that the most favorable inclusion level was similar to the levels of 15 to 18% reported previously for white seabass based on survival, growth and feed nutrient utilization (López et al., 2006). Growth, FCR and NRE of juvenile white seabass improved with the increase of lipid supplement in the diet. Diets 15.3 L and 19.4 L with 29 and 28.1 mg kJ− 1 GP:GE ratio, respectively, produced the best growth, FCR (1.3 and 1.1) and NRE (28.1 and 34.4), and these fish ingested the lest amount of feed (35.0 and 30.7 g, respectively), which
is likely because DFI is closely related to FCR. These findings are consistent with several other reports that the overall performance of some species of marine carnivorous fish is improved by increasing the lipid level in the diet (Craig et al., 1999; Peres and Oliva-Teles, 1999; Williams et al., 2003). In the study conducted by Peres and Oliva-Teles (1999) to determine the lipid requirement of European sea bass juveniles, a DP:DE ratio of 21 to 33 mg kJ− 1 showed the best growth. In the current study, the best performance of white seabass juveniles was observed when the GP:GE ratio was from 28.1 to 29 mg kJ− 1. When fish are fed a diet containing insufficient lipid, all performances may be reduced due to a deficient amount of energy and essential fatty acids. White seabass fed the 2.6 L diet (2.6% lipid) had only about one third the growth response observed in juveniles fed 15 or 19% lipid. Even though white seabass have been produced for more than 20 years by feeding a variety of commercial diets, in this study, the fish fed the CD (50% protein, 14.7% lipid and 21.8 kJ g− 1 energy) required a DFI of 8.6% day− 1, had a FCR of 2.5 and the NRE was only 15.6. This information demonstrates that the formulation of the CD may be improved by studying the nutrient requirements of white seabass. Proximate analyses demonstrated that dietary lipid levels influenced the body composition including the FA composition in muscle
Table 6 FA composition (mg of FA per g of dry weight) of liver tissue of juvenile white seabass at the beginning and end of the feeding trial Fatty acid 14:0 16:0 16:1n−7 18:0 18:1n−9 18:1n−7 18:2n−6 18:3n−3 18:4n−3 20:0 20:1n−9 20:4n−6 20:4n−3 20:5n−3 22:0 22:5n−3 22:6n−3 n−3/n−6
Initial 9.1 ± 0.1e 81.0 ± 2.1c 39.8 ± 0.8d 42.7 ± 0.4a 87.2 ± 1.7a 29.3 ± 0.3a 52.1 ± 2.2a 4.9 ± 0.2b 2.3 ± 0.0c 3.6 ± 0.0e 9.2 ± 0.4b 2.1 ± 0.1d 1.0 ± 0.0e 14.6 ± 0.3d 2.2 ± 0.1c 12.9 ± 5.0a 13.0 ± 0.3c 0.3 ± 0.0d
Diet 2.6 L
7.4 L
11.6 L
15.3 L
19.4 L
CD
5.7 ± 0.1f 71.1 ± 0.3d 27.3 ± 0.6f 46.7 ± 7.7a 61.8 ± 1.2b 22.0 ± 1.1c 11.4 ± 0.1d 1.3 ± 0.0e 0.6 ± 0.3d 3.9 ± 0.1d 12.5 ± 0.9a 4.8 ± 0.4c 0.6 ± 0.3e 12.4 ± 0.5d 4.7 ± 0.3b 5.5 ± 0.5b 27.8 ± 2.9b 1.0 ± 0.0b
8.9 ± 0.2e 73.3 ± 1.2d 30.2 ± 0.2e 21.0 ± 0.1bc 39.5 ± 0.3d 22.7 ± 0.2c 9.6 ± 0.1e 2.3 ± 0.1d 2.0 ± 0.0c 3.5 ± 0.3de 5.1 ± 0.2e 6.7 ± 0.2ab 1.7 ± 0.0d 21.9 ± 0.5c 7.2 ± 0.2a 9.1 ± 1.2a 50.3 ± 2.9a 1.8 ± 0.0a
12.5 ± 1.0d 72.2 ± 0.1d 42.2 ± 0.9cd 19.6 ± 1. 7c 45.3 ± 2.5c 23.4 ± 0.3bc 9.7 ± 0.1e 3.3 ± 0.0c 3.5 ± 0.4b 4.1 ± 0.1d 5.7 ± 0.7e 5.6 ± 0. 6b 2.9 ± 0.25c 25.4 ± 0.5b 6.9 ± 0.5a 10.8 ± 1.3a 44.9 ± 3.7a 2.0 ± 0.1a
18.2 ± 0.4b 84.3 ± 0.4c 51.4 ± 0.4b 20.6 ± 1.5c 60.0 ± 0.8b 25.7 ± 0.1b 12.6 ± 0.4c 4.7 ± 0.0b 5.5 ± 0.2a 4.7 ± 0.0c 6.7 ± 0.1d 5.4 ± 0.2b 3.9 ± 0.1b 30.8 ± 0.8a 6.9 ± 0.1a 10.7 ± 0.1a 42.4 ± 0.4a 1. 8 ± 0.15a
22.4 ± 0.3a 94.0 ± 3.8b 59.9 ± 1.6a 20.8 ± 1.2c 64.4 ± 1.9b 27.0 ± 0.9b 13.3 ± 0.1c 5.3 ± 0.1a 6.4 ± 0.4a 5.4 ± 0.2ab 7.6 ± 0.2c 5.1 ± 0.3b 4.5 ± 0.2a 32.7 ± 2.5a 7.3 ± 0.4a 10.4 ± 0.5a 43.2 ± 2.4a 1.9 ± 0.1a
15.4 ± 1.1c 102.8 ± 1.1a 46.9 ± 3.2c 32.1 ± 2.9b 83.1 ± 6.4a 25.0 ± 1.5b 39.4 ± 2.1b 4.0 ± 0.8bc 2.3 ± 0.6c 4.8 ± 0.3bc 8.4 ± 0.6c 8.3 ± 1.2a 1.7 ± 0.4d 25.2 ± 6.1abc 6.3 ± 1.2a 9.1 ± 1.5a 42.1 ± 8.5a 0.6 ± 0.1c
Means ± SE, n = 3. Means in the same row with different superscript are significantly different (P b 0.05).
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and liver tissue as suggested by several authors (Oku and Yogata, 2000; Sargent et al., 2002; Solberg, 2004; Miller et al., 2005: Kucska et al., 2006). As shown in other marine fish, we demonstrated that high dietary levels of lipid lead to increased deposition of lipid on soft tissues. The lipid level in muscle suggests a limited capacity for juvenile white seabass to accumulate lipid, which is in agreement with a previous report (López et al., 2006). The propensity of white seabass to deposit high levels of lipid in the liver rather than muscle tissue is consistent with lean body muscle growth characteristic of sedentary demersal species (McGoogan and Gatlin, 1999; Lee et al., 2002). It is well known that the FA composition of tissues is determined mainly by their dietary lipid, and that marine fish have a specific requirement for the HUFAs 20:5n−3, 22:6n−3 and 20:4n−6 (Sargent et al., 1999, 2002; Bell and Sargent, 2003). Lipid composition of white seabass tissues in the present study was reflective of levels present in each experimental diet. The prevalent HUFAs [20:4n−6, 20:5n−3, 22:5n−3 and 22:6n−3] in the dietary treatments, from menhaden oil, were found in muscle and liver of white seabass in increasing levels according to dietary lipid level. Fish tissue, in general, had much higher concentrations of n−3 HUFA than 20:4n−6 but both are required for normal growth, development and reproduction (Sargent et al., 1999; Tocher, 2003). Diets with the same FA composition but different lipid level can induce modifications in FA composition and enzyme activity in intestinal brush border membranes of fish, affecting physicochemical characteristics of the membrane and the digestive functions of the intestine (Cahu et al., 2000; Gawlicka et al., 2002). However, further research will be needed to determine the dietary FA requirements of white seabass. In conclusion, our results suggest that white seabass fingerlings (25 days old, 1.7± 0.13 g, 30.2 ± 0.3 mm) perform well with a dietary lipid level between 15 to 19% when protein inclusion was 66.4%. Increased growth and NRE were evident when dietary energy increased from 19.8 to 23.7 kJ g− 1 and the GP:GE ratio varied from 28.1 to 29 mg kJ− 1. Acknowledgements This work was supported by the National Council for Science and Technology (CONACyT) of México, Project 2003-CO1-206 and by Autonomous University of Baja California (UABC) Mexico, internal project. The authors would also like to acknowledge the skillful assistance of Paul Curtis, Gabriela LaChance, and Dave Jirsa from Hubbs-SeaWorld Research Institute, San Diego, CA. References AOAC (Association of Official and Analytical Chemists), 1995. 16th ed. Official Methods of Analysis of AOAC, vol. 1. Association of Official Analytical Chemists, Arlington, VA. Bell, J.G., Sargent, J.R., 2003. Arachidonic acid in aquaculture feeds: current status and future opportunities. Aquaculture 218, 491–499. Cahu, C.L., Zambonino-Infante, J.L., Corraze, G., Coves, D., 2000. Dietary lipid level affects fatty acid composition and hydrolase activities of intestinal brush border membrane in seabass. Fish Physiol. Biochem. 23, 165–172. Cho, S.H., Lee, S.M., Lee, S.M., Lee, J.H., 2005. Effect of dietary protein and lipid levels on growth and body composition of juvenile turbot (Scophthalmus maximus L) reared under optimum salinity and temperature conditions. Aquac. Nutr. 11, 235–240. Christie, W.W., 1993. Preparation of ester derivatives of fatty acids for chromatographic analysis. In: Christie, W.W. (Ed.), Advances in Lipid Methodology, vol. 2. Oily Press, Dundee, pp. 69–111. Craig, S., Washburn, B., Gatlin, D., 1999. Effects of dietary lipids on body composition and liver function in juvenile red drum, Sciaenops ocellatus. Fish Physiol. Biochem. 21, 249–255. Donohoe, C.J., 1999. Age, growth, distribution, and food habits of recently settled white seabass, Atractoscion nobilis, off San Diego County, California. Fish. Bull. 95, 709–721. Drawbridge, M., Kent, A., Forster, D.B., 1999. Commercialization of white seabass aquaculture, pilot program out-grow to market. A Publication of Hubb– Sea World
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