Dietary lipid requirement of juvenile hybrid sturgeon, Acipenser ...

Journal of

Applied Ichthyology J. Appl. Ichthyol. 27 (2011), 743–748  2011 Blackwell Verlag, Berlin ISSN 0175–8659

Received: May 29, 2010 Accepted: November 25, 2010 doi: 10.1111/j.1439-0426.2010.01633.x

Dietary lipid requirement of juvenile hybrid sturgeon, Acipenser baerii $ · A. gueldenstaedtii # By Z. Guo1,2, X. Zhu1, J. Liu1, D. Han1, Y. Yang1, S. Xie1 and Z. Lan3 1 State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, the Chinese Academy of Sciences, Wuhan, Hubei, China; 2Graduate University of the Chinese Academy of Sciences; 3Hubei Tianxia Sturgeon Co., Ltd, Yichang, Hubei, China

Summary A 10-week growth trial was conducted to determine the dietary lipid requirement of juvenile hybrid sturgeon (Acipenser baerii $ · A. gueldenstaedtii #) (initial body weight, 66.7 ± 0.11 g). Seven isonitrogenous (crude protein 370 g kg)1) diets were formulated to contain various levels of dietary lipid (40, 65, 90, 115, 140, 165 and 190 g kg)1) and each diet was fed to triplicate groups of thirty fish at 22.3 ± 0.8C in twenty one 1 m3 concrete tanks. The results showed that specific growth rate (SGR) significantly increased with dietary lipid level up to 115 g kg)1 (P < 0.05) and then kept constant (P > 0.05). Feed intake (FI) was significantly lower at 40 g kg)1 lipid diet (P < 0.05) while there was no significant difference between other diets (P > 0.05). Feed efficiency (FE), protein efficiency ratio (PER), or protein retention efficiency (PRE) showed no significant difference between diets (P > 0.05). Energy retention efficiency (ERE) was lowest in the fish fed diet with 40 g kg)1 lipid (P < 0.05). Fish serum triglyceride (TG), total cholesterol (TC), phospholipid (PL) and low density lipoprotein cholesterol (LDL-C) were positively correlated to dietary lipid level (P < 0.05). The contents of dry matter, lipid, energy in whole body, and the contents of dry matter and lipid in dorsal white muscle showed a steady increase with the increasing dietary lipid level (P < 0.05). Broken-line regression analysis indicated the dietary lipid requirement for juvenile hybrid sturgeon was 111 g kg)1. Introduction In fish, dietary lipids are almost completely digestible and favoured over carbohydrate as an energy source, especially for carnivorous species, such as rainbow trout, salmon, yellowtail and Atlantic cod, as these species have a limited ability to utilize carbohydrate (NRC, 1983). Furthermore, lipid as a nonprotein energy source shows protein sparing effects, which can reduce the nitrogen load to the environment and minimizes the use of high-priced protein sources (Watanabe, 1982; Lo´pez et al., 2009). Therefore, adequate dietary lipid not only ensures the best protein and feed utilization but also has great benefits to the environments. However, high lipid diets should be carefully evaluated since an excessive dietary lipid content in feeds may decrease feed consumption, reduce growth rate and impair functions of the viscera by fat accumulation and, even worse, it usually results in the increased fat deposition in the fish body, strongly influencing market value and flesh quality in terms of storage stability, transformation yield, organoleptic and physical properties (Watanabe, 1982; Regost et al., 2001; U.S. Copyright Clearance Centre Code Statement:

Du et al., 2008; Mohanta et al., 2008; Lo´pez et al., 2009). Therefore, estimation the dietary lipid requirement is one of most important procedure in formulation of diets for aquatic species. Sturgeon culture is growing world-wide, especially in the Caspian Sea region, Western Europe, Russia and China. China has become the largest sturgeon culture region since 2000 (Wei et al., 2004). Hybrid sturgeon culture is now favoured by many owing to their fast growth rate and strong resistance to diseases (Steffens et al., 1990; Williot et al., 2001; Wei et al., 2004). However, the available information on dietary lipid of sturgeon is limited in China. Earlier studies indicated that juvenile Acipenser sinensis showed the best growth performance when fed diets with 90 g kg)1 lipid (Xiao et al., 1999). The optimal dietary lipid level for Acipenser transmontanus larvae was found to range from 120 to 200 g kg)1 and Gawlicka et al. (2002) demonstrated it grew faster when limiting lipid in the diet to 170 g kg)1 rather than higher values (250, 330 and 420 g kg)1). However, subyearling A. transmontanus grew well when dietary lipid content ranged from 258 to 357 g kg)1 (Hung et al., 1997). It had been reported that sturgeon larvae showed high energy demands and exhibited relatively high lipase activity and lipid absorption ability during development (Gershanovich et al., 1989). Moreover, sturgeon juveniles demonstrated a high ability in absorption, digestion and utilization of high-lipid or high-energy diets (Hung et al., 1997; Gawlicka et al., 2002; Mohseni et al., 2007). Up to now the information on the dietary lipid requirement for hybrid sturgeon was scarce. The objective of this study was, therefore, to determine the dietary lipid requirement and investigate the effect of dietary lipid level on growth performance, feed utilization and tissue lipid deposition in juvenile hybrid sturgeon, Acipenser baerii $ · A. gueldenstaedtii #. Materials and methods Experimental diets

Formulation and chemical composition of the experimental diets was given in Table 1. Seven isonitrogenous (crude protein 370 g kg)1) diets were prepared with the crude lipid levels of 40, 65, 90, 115, 140, 165 and 190 g kg)1. Fish oil and soybean oil (1 : 1, v ⁄ v) was used as lipid sources. Chromic oxide (Cr2O3) (10 g kg)1) was added as inert marker for digestibility determination. Pellets with diameter of 2.0 mm were made by laboratory presser, oven dried at 60C and stored at 4C.

0175–8659/2011/2702–0743$15.00/0

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Z. Guo et al. Dietary lipid level (g kg)1)

Ingredients

40

65

Fishmeal1 300.0 300.0 Soybean meal 266.2 266.2 Fish oil 0.0 15.0 Soybean oil 0.0 15.0 a-starch 100.0 100.0 50.0 50.0 Mineral premix2 4.4 4.4 Vitamin premix3 Choline chloride 1.1 1.1 Cellulose 238.3 208.3 10.0 10.0 Cr2O3 Carboxymethyl cellulose 30.0 30.0 )1 Chemical composition (g kg in dry matter) Dry matter 911.48 922.96 Crude protein 371.74 370.56 Crude lipid 36.92 63.03 Ash 136.34 134.58 17.66 17.95 Gross energy (kJ g)1) 21.05 20.64 P ⁄ E ratio (mg kJ)1)4

90

115

140

165

190

300.0 266.2 30.0 30.0 100.0 50.0 4.4 1.1 178.3 10.0 30.0

300.0 266.2 45.0 45.0 100.0 50.0 4.4 1.1 148.3 10.0 30.0

300.0 266.2 60.0 60.0 100.0 50.0 4.4 1.1 118.3 10.0 30.0

300.0 266.2 75.0 75.0 100.0 50.0 4.4 1.1 88.3 10.0 30.0

300.0 266.2 90.0 90.0 100.0 50.0 4.4 1.1 58.3 10.0 30.0

911.90 384.99 89.79 136.29 18.91 20.36

947.38 372.47 119.74 130.68 19.28 19.32

942.55 383.16 144.25 130.65 20.46 18.73

953.18 375.20 165.24 134.07 21.62 17.35

956.37 369.98 193.90 132.59 21.69 17.05

Table 1 Formulation and chemical composition of the experimental diets (g kg)1 in dry matter)

1 Imported from Seafood Company (USA) by Coland Feed Industry Co., Ltd. (Wuhan, China) (Crude protein: 684.82 g kg)1, Crude lipid: 107.78 g kg)1). 2 Mineral premix (mg kg)1 diet): NaCl, 500; MgSO4Æ7H2O, 7500; NaH2PO4Æ2H2O, 12 500; KH2PO4, 16 000; Ca(H2PO4)2ÆH2O, 10 000; FeSO4, 1250; C6H10CaO6Æ5H2O, 1750; ZnSO4Æ7H2O, 176.5; MnSO4Æ4H2O, 81; CuSO4Æ5H2O, 15.5; CoSO4Æ6H2O, 0.5; KI, 1.5; Starch, 225. 3 Vitamin premix (mg kg)1 diet): vitamin A, 1.83; vitamin D, 0.5; vitamin E, 10; vitamin K, 10; niacin, 100; riboflavin, 20; pyridoxine, 20; thiamin, 20; D-calcium pantothenate, 50; biotin, 0.1; folacin, 5; vitamin B12, 20; ascorbic acid, 100; inositol, 100. 4 Protein to energy ratio.

Experimental fish and husbandry

Chemical analysis

The study was conducted in a closed recirculation system in Hubei Tianxia Sturgeon Co., Ltd (Yichang, Hubei, China). The system comprised 21 concrete tanks (2.7 · 0.8 · 0.45 m). Water renewal rate was four times per hour and aeration was supplied via air stones continually. During the experiment, water temperature was 22.3 ± 0.8C, pH was controlled at 7.7 ± 1.1, dissolved oxygen was >7.5 mg L)1 and ammoniaN was 0.05). Fish fed the lowest lipid diet (40 g kg)1) showed the lowest feed intake (FI) (P < 0.05) while there was no significant difference between other groups (P > 0.05). Specific growth rate (SGR) and weight gain (WG) increased significantly with dietary lipid level from 40 to 115 g kg)1 (P < 0.05) and then reached a plateau (P > 0.05). Feed efficiency (FE) increased when the dietary lipid level increased to 115 g kg)1 and then kept constant but no significant difference was found (P > 0.05). Protein efficient ratio (PER) or protein retention efficiency (PRE) was not differed significantly between treatments (P > 0.05). The energy retention efficiency (ERE) of fish fed 40 g kg)1 lipid diet was lowest and that fed 115 g kg)1 was highest (P < 0.05). Hepatosomatic index (HSI), condition factor (CF) or viscerosomatic index (VSI) showed no significant difference (P > 0.05). Based on broken-line regression analysis of SGR against dietary lipid level, the dietary lipid requirement for maximal growth of the fish was 111 g kg)1 (Fig. 1).

2.0

Specific growth rate (SGR, % day–1)

difference of means between diets. When significant difference was identified, multiple comparisons among means were conducted using Duncans procedure. Difference was regarded as significant when P < 0.05. All the statistical analyses were performed by STATISTICA 6.0 software package.

SGR = 0.0049CL + 1.1826

SGR = 1.7282

2

1.8

R = 0.9938 P 0.05). Serum chemistry

The concentration of serum triglyceride (TG) in fish fed 40, 65 and 90 g kg)1 lipid diets showed no significant difference

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Z. Guo et al.

Table 3 Effect of dietary lipid level on apparent digestibility coefficients (ADC) of juvenile hybrid sturgeon fed experimental diets for 10 weeks at 22.3 ± 0.8C* Dietary lipid level (g kg)1) 40 ADCd1 ADCp2 ADCe3

65 b

90 a

45.86 ± 0.47 88.81 ± 1.21 59.22 ± 1.48b

39.33 ± 1.78 86.72 ± 1.23 54.97 ± 0.84a

115 bc

48.71 ± 3.81 89.79 ± 0.57 62.67 ± 1.90bc

140 bc

50.09 ± 1.20 86.24 ± 0.30 65.04 ± 0.83cd

165 cd

54.46 ± 2.11 87.24 ± 1.99 68.38 ± 1.50d

190 d

56.51 ± 0.56 87.97 ± 0.82 72.50 ± 0.92e

63.48 ± 1.15e 89.94 ± 0.48 76.41 ± 1.02f

*Values are the mean ± standard error (SE) of triplicate groups. Means in the same row with different superscript are significantly different (P < 0.05). 1 Apparent digestibility coefficient of dry matter (%) = 100 · [1)(Cr2O3 in the diet ⁄ Cr2O3 in the faeces)]. 2 Apparent digestibility coefficient of protein (%) = 100 · [1)(Cr2O3 in the diet ⁄ Cr2O3 in the faeces) · (crude protein in the faeces ⁄ crude protein in the diets)]. 3 Apparent digestibility coefficient of energy (%) = 100 · [1)(Cr2O3 in the diet ⁄ Cr2O3 in the faeces) · (energy in the faeces ⁄ energy in the diet)].

Dietary lipid level (g kg)1)

Triglyceride (mmol L)1)

40 65 90 115 140 165 190

4.06 4.90 5.78 8.91 9.03 10.47 9.65

± ± ± ± ± ± ±

0.69a 0.13a 1.16a 1.32b 0.74b 1.19b 0.67b

Total cholesterol (mmol L)1) 4.20 4.65 5.09 5.78 6.01 7.08 7.03

± ± ± ± ± ± ±

0.38a 0.90a 0.88ab 0.64ab 0.26ab 0.18b 0.05b

Phospholipid (mmol L)1) 3.31 3.80 4.22 4.67 4.78 5.47 5.73

± ± ± ± ± ± ±

0.12a 0.11b 0.23b 0.18c 0.10c 0.09d 0.06d

Low density lipoprotein cholesterol (mmol L)1) 2.98 3.23 3.24 4.21 4.37 5.62 4.46

± ± ± ± ± ± ±

Table 4 Effect of dietary lipid level on serum chemistry of juvenile hybrid sturgeon fed experimental diets for 10 weeks at 22.3 ± 0.8C*

0.40a 0.81ab 0.64ab 0.66abc 0.37abc 0.57c 0.19bc

*Values are the mean ± standard error (SE) of triplicate groups with three fish from each of the replicates (nine fish total for each dietary treatment). Means in the same column with different superscript are significantly different (P < 0.05).

(P > 0.05), while these were significantly lower than that of other groups (P < 0.05; Table 4). The fish showed significantly lowest concentration of serum total cholesterol (TC) when fed diets with 40 and 65 g kg)1 lipid diets and those fed 165 and 190 g kg)1 lipid diets showed highest values (P < 0.05). The serum phospholipid (PL) concentration of the fish increased linearly with the dietary lipid level (P < 0.05). The highest content of serum low density lipoprotein cholesterol (LDL-C) was observed in the fish fed 165 g kg)1 lipid diet, followed by 190 g kg)1, and the group fed lowest lipid diet (40 g kg)1) showed the lowest value (P < 0.05). The relationship between concentration (C, mmol L)1) of TG, TC, PL, LDL-C and dietary lipid level (CL, g kg)1) was: CTG = 0.0445 CL + 2.4262 (R2 = 0.8820, P < 0.05, n = 7); CTC = 0.0204 CL + 3.347 (R2 = 0.9697, P < 0.05, n = 7); CPL = 0.0159 CL + 2.7374 (R2 = 0.9859, P < 0.05, n = 7) and CLDL-C = 0.0173 CL + 2.1117 (R2 = 0.8671, P < 0.05, n = 7), respectively.

Whole body and dorsal muscle composition

The content of dry matter, crude lipid and gross energy in the whole body increased significantly with increasing dietary lipid level (P < 0.05; Table 5). Test results showed the lowest and highest value in fish fed 40 and 190 g kg)1 lipid diets, respectively (P < 0.05). In contrast, the whole body ash content showed an inverse tendency with the dietary lipid level (P < 0.05). The crude protein of the whole body seemed to keep at constant levels between diets (P > 0.05). Dry matter and lipid content in dorsal muscle showed an increasing trend with increasing dietary lipid content (P < 0.05) but there was no significant difference in crude protein or ash content (P > 0.05).

Discussion The broken-line regression analysis suggested that, using fish oil and soybean oil (1 : 1, w ⁄ w) as lipid source, dietary lipid requirement for maximal growth of the fish was 111 g kg)1 when dietary protein level was 370 g kg)1. As a carnivorous species, sturgeon may have limited capability to utilize carbohydrate as energy source and requires as much as 100– 200 g kg)1 dietary lipid (NRC, 1983). Our result was in this range and differed slightly from that of earlier reports, such as 91 g kg)1 for juvenile of Acipenser sinensis and 170 g kg)1 for larvae of Acipenser transmontanus (Xiao et al., 1999; Gawlicka et al., 2002). The discrepance might result from the different fish body size, lipid sources, dietary formulations and experimental conditions. It had been widely reported that fish growth rate increased proportionally when dietary lipid content was up to a certain level (Pei et al., 2004; Luo et al., 2005; Mohseni et al., 2007; Ai et al., 2008; Lo´pez et al., 2009). However, when dietary lipid level was above the optimum, fish might not exhibit a further growth increment because excessive dietary lipid usually decrease the ability to digest, absorb and assimilate dietary lipid, or even reduce the feed intake. What is even worse is the fact that high lipid diets probably result in metabolic impairments in viscera by excessive lipid accumulation and an abnormal oxidative status (Gawlicka et al., 2002; Pei et al., 2004; Rueda-Jasso et al., 2004; Luo et al., 2005; Du et al., 2008). Therefore, some species showed a significant decrease in growth rate when dietary lipid was above the optimal level (Regost et al., 2001; Pei et al., 2004; Luo et al., 2005; Ai et al., 2008). SGR in our study reached a plateau when dietary lipid level was above 115 g kg)1. This indicated hybrid sturgeon might be able to tolerate relatively

Dietary lipid requirement of juvenile hybrid sturgeon

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Table 5 Effect of dietary lipid level on whole body and dorsal muscle composition (in wet weight, g kg)1) of juvenile hybrid sturgeon fed experimental diets for 10 weeks at 22.3 ± 0.8C* Dietary lipid level (g kg)1) Whole body composition1 Initial 40 65 90 115 140 165 190 Dorsal muscle composition2 40 65 90 115 140 165 190

Gross energy (kJ g)1)

Dry matter

Crude protein

Crude lipid

Ash

214.09 215.98 230.09 230.85 245.96 244.14 229.64 257.01

± ± ± ± ± ± ± ±

4.93 2.33a 9.62ab 9.28ab 4.45bc 10.71abc 4.82ab 2.23c

135.94 140.42 139.56 137.55 141.61 138.81 137.01 137.63

± ± ± ± ± ± ± ±

1.87 0.95 2.84 3.18 1.35 2.18 2.55 0.73

30.79 23.73 41.94 39.84 49.48 53.78 50.65 70.42

± ± ± ± ± ± ± ±

1.89 2.90a 7.86b 3.94b 1.22b 7.52b 0.92b 5.94c

31.36 36.23 31.94 33.52 32.66 31.43 29.49 29.31

± ± ± ± ± ± ± ±

1.76 2.14a 0.10b 0.48ab 1.24ab 1.62b 0.85b 1.32b

4.38 4.10 4.89 4.96 5.58 5.55 5.12 6.12

180.57 192.15 201.22 223.26 206.97 210.15 235.07

± ± ± ± ± ± ±

2.01a 13.41ab 10.17abc 7.19cd 2.63bc 5.53bc 2.81d

133.92 139.08 148.18 158.10 142.37 151.43 162.49

± ± ± ± ± ± ±

8.11 14.42 6.60 9.35 11.79 3.30 6.90

18.77 29.89 35.64 46.22 49.58 47.47 60.48

± ± ± ± ± ± ±

1.30a 5.75ab 5.29bc 2.44bcd 3.71cd 9.77cd 2.77d

9.97 9.20 9.89 10.18 9.22 9.48 10.20

± ± ± ± ± ± ±

0.58 0.58 0.39 0.77 0.31 0.10 0.30

– – – – – – –

± ± ± ± ± ± ± ±

0.13 0.11a 0.39ab 0.27b 0.28b 0.42bc 0.10bc 0.05c

*Means in the same column with different superscript are significantly different (P < 0.05). 1 Values are the mean ± standard error (SE) of triplicate groups with two fish from each replicate (six fish total for each dietary treatment). 2 Values are the mean ± standard error (SE) of triplicate groups with three fish from each replicate (nine fish total for each dietary treatment).

high dietary lipid. Sturgeon has been reported to show high energy demands, exhibit relatively high lipase activity and lipid absorption ability during development (Gershanovich et al., 1989). Moreover, they were found to have high capacity to adapt or utilize the high dietary non-protein energy (Kaushik et al., 1989; Medale et al., 1991; Gawlicka et al., 2002). Nevertheless, high lipid diet was disadvantageous to growth of sturgeon as long as it surpassed the tolerant threshold. For example, subyearling Acipenser transmontanus showed significantly lower growth rate and poorer feed efficiency when fed diet with 402 g kg)1 lipid than 258, 304 and 357 g kg)1 (Hung et al., 1997). Possibly, dietary lipid level over 115 but