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Effect of farming patterns on the nutrient composition and farming environment of loach, Paramisgurnus dabryanus
Accepted Manuscript Effect of farming patterns on the nutrient composition and farming environment of loach, Paramisgurnus dabryanus
Zhiguo Dong, Min Zhang, Sufeng Wei, Hongxing Ge, Xiaoying Li, Qiangan Ni, Qufei Ling, Yong Li PII: DOI: Reference:
S0044-8486(18)30978-5 doi:10.1016/j.aquaculture.2018.07.061 AQUA 633432
To appear in:
aquaculture
Received date: Revised date: Accepted date:
11 May 2018 27 July 2018 30 July 2018
Please cite this article as: Zhiguo Dong, Min Zhang, Sufeng Wei, Hongxing Ge, Xiaoying Li, Qiangan Ni, Qufei Ling, Yong Li , Effect of farming patterns on the nutrient composition and farming environment of loach, Paramisgurnus dabryanus. Aqua (2018), doi:10.1016/j.aquaculture.2018.07.061
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ACCEPTED MANUSCRIPT Effect of farming patterns on the nutrient composition and farming environment of loach, Paramisgurnus dabryanus
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Running Head: Effect of farming patterns on loach
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Zhiguo Dong1,2, 3*, Min Zhang1,2,3, Sufeng Wei1,2, 3, Hongxing Ge1,2,3, Xiaoying Li1,2,3,
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Qiangan Ni4, Qufei Ling5, Yong Li4
1
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Jiangsu Key Laboratory of Marine Bioresources and Eco-environment, Huaihai
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Institute of Technology, 59 Cangwu Road, Haizhou, Lianyungang, 222005, China. 2
Jiangsu Key Laboratory of Marine Biotechnology, Huaihai Institute of Technology,
Co-Innovation Center of Jiangsu Marine Bioindustry Technology, Huaihai Institute
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3
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59 Cangwu Road, Haizhou, Lianyungang, 222005, China.
of Technology, 59 Cangwu Road, Haizhou, Lianyungang, 222005, China. Siyang Fishery Technical Guidance Station, 1 Jiefang North Road, Zhongxing
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4
5
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Town, Huaian, 223700, China. Fisheries Research Institute, Soochow University, 1 Ten catalpa Street, Suzhou,
215021, China.
*
Corresponding author:
E-mail: [email protected]
ACCEPTED MANUSCRIPT Abstract This study aimed to investigate the effect of farming patterns on the farming environment and nutrient composition of loach Paramisgurnus dabryanus. Loach juveniles (2.57 ± 0.42 g) grown for 150 days were stocked with two treatments: high-
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density farming pattern (210 ind·m-2) and imitative ecological farming pattern (70
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ind·m-2). At the end of the farming experiment, the nutrient composition of the loach
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dorsal meat, the water quality, and the sediment in both farming patterns were determined. The contents of chemical oxygen demand, nitrite nitrogen, heterotrophic
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bacteria, denitrifying bacteria and organic carbon in the imitative ecological ponds
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were significantly lower than those in the high-density groups (P < 0.05), whereas the two treatments presented no significant difference in the proximate content of loach
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(P > 0.05). In addition, the two treatments displayed no significant difference in the
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unsaturated fatty acid and saturated fatty acid contents of loach (P > 0.05). The ratios of essential amino acids to total amino acids and of delicious amino acids to total
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amino acids of loach under the two treatments did not significantly differ (P > 0.05).
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The results indicated that although the nutrient compositions of the high-density and imitative ecological cultured loaches did not vary significantly, the high-density farming pattern influenced the water quality and the sediment.
Keywords: Farming pattern; Nutrients; Aquatic ecosystems; Loach
ACCEPTED MANUSCRIPT 1 Introduction Loach Paramisgurnus dabryanus, which is also known as water ginseng, belongs to the genus Paramisgurnus of the family Cobitidae (Qin et al., 2002). It is popular among Chinese, Japanese and Korean consumers because of its delicious and
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nutritious meat. In recent years, loach aquaculture has considerably grown in China,
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reaching a production volume of 4,020 million tons in 2016, which was an increase by
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9.29% from that in 2015 according to the China Fishery Statistics Yearbook (Ning, 2017). The market demand for loach has been increasing annually. At present,
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international markets, specifically Japanese and Korean, import approximately 80% of
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the farmed loach in China (Zhou et al., 2015), as wild loach resources are steadily declining due to ecological damage and overfishing; this situation has driven the
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growth of loach farming (Zhang et al., 2010). In China, loach is cultured through
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different farming patterns, such as pond farming, paddy farming, cage culture, yard culture and soilless farming (Zhang and Fan, 2011). Among them, high-density
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farming and imitative ecological farming are the most dominant patterns of artificial
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farming. High-density farming pattern is a simple and cost-effective farming pattern. In this pattern, large-sized seedlings are placed at 1250–1500 kg/(667 m2), mediumsized seedlings are placed at 1000–1250 (kg/667 m2), and small-sized seedlings are placed at 750–1000 (kg/667 m2) (Bai and Yu, 2010). Imitative ecological pattern is a comprehensive farming pattern that is mainly applied for stocking loach, raising carp, catfish, silver carp (Wang and Zhang, 2010) shrimp and crabs (Jiang et al., 2015) and so on.
ACCEPTED MANUSCRIPT Domestic and foreign scholars have extensively investigated the growth (Ding et al., 2016), environment (Zhang et al., 2008), nutrition (Pu et al., 2017), culture (Legendre et al., 2012) and feeding model of loach (Guo et al., 2015). However, many consumers unreasonably believe that the quality of loach from the wild or imitative
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ecological farmed environments is better than that of other artificial farming patterns,
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and therefore prefer wild or imitative ecological cultured loach. Several studies have
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focused on the body colour and texture (Yuan et al., 2017) as well as body composition (Song et al., 2017) of loach from wild and cultured environments.
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However, no study has comprehensively compared the meat composition and
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nutritional differences of imitative ecological cultured and high-density cultured loach. Thus, in this study, we investigated the effect of farming patterns on the
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nutrient composition and farming environment of loach to provide scientific guidance
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to consumers.
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2 Materials and methods
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2.1 Farming and sampling Loach seedlings (body length: 6.83 ± 0.53 cm; body weight: 2.57 ± 0.42 g) were acquired from Pu'nan Farm in Lianyungang, Jiangsu Province, China. The experiment consisted of two treatments, namely, high-density farming pattern and imitative ecological farming pattern, each of which has three replicates. The size of the highdensity farming pond was approximately 667 m2. The stocking density of the cultured loach was 210 ind·m-2. The size of the imitative ecological farming pond was
ACCEPTED MANUSCRIPT approximately 13340 m2. The stocking density of the cultured loach was 70 ind·m-2, and each pond contained a mixture of crucian carp and silver carp. All experimental ponds were sterilised prior to the experiment. During the experiment, the loaches were fed with compound feed containing 40% crude protein twice a day in accordance with
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the feeding situation. The imitative ecological farming ponds were operated without
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was exchanged every 15 days during the experiment.
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water exchange; whereas 20% of the total water in the high-density farming ponds
At the end of the 150-day breeding experiment, the sediment of 0–2 cm from the
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surface was collected with a dredging device from five sites in the same pond and
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combined. The middle water samples of the farming pond were also sampled using a Plexiglas water-collecting device and pooled together. The sediment and water
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samples were maintained at 4 °C and transported to the laboratory within 2 h to
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determine the relevant water quality and sediment indicators. Ten loaches were randomly collected from each pond, and those of the same group were mixed
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together, kept alive in water and immediately delivered to the laboratory.
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All loaches were sacrificed by anaesthesia. We collected the dorsal meat from each loach, placed it in corresponding Petri dishes, and preserved in a refrigerator at −80 °C. The rest of the loach samples were freeze-dried for analysis of fatty acid and amino acid composition.
2.2 Environmental factor determination
ACCEPTED MANUSCRIPT The chemical oxygen demand (COD) in the water samples was determined by acidic potassium permanganate titration (Xu, 2009). Nitrite nitrogen (NO2-N) content was measured using diazo-azo colorimetric method (Lin et al., 2010). The nitrate nitrogen (NO3-N) in the water was monitored by spectrophotometric method with
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phenol disulfonic acid (Dai, 2003). The ammonia nitrogen (NH3-N) concentration in
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the water sample was determined using Nessler's reagent spectrophotometry (Zhang et
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al., 2009). The sediment samples were analysed for organic carbon content by potassium dichromate external heating method (Xin, 2014). Molybdenum blue
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sediment extraction (Ma et al., 1996).
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colorimetric method was used for labile phosphate (PO4-P) determination during
The microorganisms in the sediment were identified by coating the sediment on
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different concentrations of heterotrophic bacteria culture medium plate, denitrifying
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bacteria culture medium plate and nitrifying bacteria culture medium plate; incubating at 30 °C; and counting on the third day. The organic carbon in the sediment was
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oxidised by sulfuric acid-potassium dichromate standard solution in a boiling water
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bath and then titrated by ferrous sulphate solution on the sulfuric acid-potassium dichromate (Kalembasa and Jenkinson, 2010).
2.3 Nutrient compositions determination Moisture and ash were measured by direct oven-drying method at 105 °C (Brendan, 2014) and direct burning method at 550 °C (Kazuki et al., 2009). The crude lipid was analysed by Soxhlet extraction (Manirakiza et al., 2001). The crude protein
ACCEPTED MANUSCRIPT content was determined by the micro-Kjeldahl method (Technical, 2009). The total sugar was calculated by subtraction method [total sugar = 100 − (moisture + ash + crude lipid + crude protein)] (Qian et al., 2010). The amino acid concentration was analysed by high-performance liquid
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chromatography (Agilent 1100; Agilent Technologies, California, USA) according to
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the method of Paramás et al. (2006). A ODS column (200 mm × 4.6 mm; pore size: 5
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μm) thermostated at 40 °C was used for all amino acids analyses. The flow rate was set to 1 mL·min-1. The UV absorbance was detected at 254 nm. Acetonitrile (solution
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A) and pH 6.5 8.2g·L-1 sodium acetate-acetate buffer solution (solution B) were used
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as the mobile phases.
The frozen material was weighed and disintegrated by crushing with a mortar.
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The experiment was performed by determining the composition of fatty acid in animal
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meat (Zhang et al., 2012). Fatty acid composition was analysed by a gas chromatograph (GC-2014; Shimadzu Corp, Kyoto, Japan) equipped with a flame
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ionisation detector (FID) and a Supelco SP-2560 fused silica capillary column (100 m
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× 0.25 mm × 0.2 μm). The column temperature was programmed to increase from 140 °C to 240 °C at a rate of 4 °C·min-1. The temperatures of the injection port and the detector were maintained at 26 °C and 280 °C, respectively. Helium was used as the carrier gas. Amino acid score (AAS), chemical score (CS) and essential amino acid index (IEAA) (Bing et al., 2005) were calculated based on the essential amino acid profile (%, dry) (Passmore, 1982) and the essential amino acid of whole egg protein profile
ACCEPTED MANUSCRIPT (%, dry) (Li et al., 2017) recommended by the WHO/FAO 1973. The formulas are as follows: ASS= Sample amino acid content (%, dry) / FAO scoring mode of the same amino acid content (%, dry)
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CS= Sample amino acid content (%, dry) / whole egg protein mode of the same amino
n
100a 100b 100c 100 j ae be ce je
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I EAA
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acid content (%, dry) (Ou et al., 2010)
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n-the number of IEAA; a, b, c… j - IEAA content (%, dry) in the protein; ae, be, ce… jeIEAA content (% dry weight) in the whole egg protein.
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F value = (valine + leucine + isoleucine) / (phenylalanine + tyrosine) (Shi et al.,
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2013).
2.4 Statistical analysis
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SPSS 20 software was used for data analysis. The average and variance of the statistical analysis were described first. Then, a normality test was performed by using
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the K-S in the non-parametric statistical analysis. Finally, an independent sample t-test was used to compare the two farming patterns and to obtain significant test values, for which P < 0.05 was considered a significant difference. The results were expressed as means ± SD.
3 Results 3.1 Environmental factors
ACCEPTED MANUSCRIPT At the end of the breeding experiment, the contents of COD, PO4-P, NH3-N and NO2-N in the high-density farming ponds were higher than those in the imitative ecological farming ponds, whereas the NO3-N content displayed an opposite trend (Table 1). The contents of COD and NO2-N in the high-density farming ponds were
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significantly higher than those in the imitative ecological farming ponds (P < 0.05).
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The numbers of heterotrophic and nitrifying bacteria in the high-density farming pond
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sediment were lower than those in the imitative ecological farming ponds, and a significant difference was found in the number of heterotrophic bacteria (P < 0.05).
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Furthermore, the number of denitrifying bacteria and the organic carbon content in the
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high-density group were significantly higher than those in the imitative ecological
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3.2 Nutrient components
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group (P<0.05).
Table 2 shows the proximate composition of the loach. The contents of crude
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protein and crude fat in the high-density group were higher than those in the imitative
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ecological group, but no significant difference was observed (P > 0.05). The two groups presented no significant difference in the contents of moisture and ash (P > 0.05). The total sugar content of the high-density group was significantly lower than that of the imitative ecological group (P < 0.05). The loaches under the two different farming patterns exhibited the same 21 types of fatty acids (Table 3): six types of saturated fatty acids (SFA), eight types of monounsaturated fatty acids and seven types of polyunsaturated fatty acids. The loaches
ACCEPTED MANUSCRIPT of the high-density group and the imitative ecological group presented no significant differences in the total saturated fatty acid (∑SFA) and the total unsaturated fatty acid content (∑UFA) (P > 0.05). The SFA/UFA values of the loach dorsal meat in the highdensity group were lower than those in the imitative ecological group, although no
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significant difference was recorded (P > 0.05).
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Four main fatty acids of the loaches from the two farming patterns were compared.
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The palmitic acid (C16:0) content of the loach in the high-density group was slightly higher than that in the imitative ecological group (P > 0.05). The stearic acid (C18:0)
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content of the high-density cultured loach was slightly lower than that of the imitative
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ecological cultured loach (P > 0.05). The EPA (C20:5n3) and DHA (C22:6n3) of the loach in the imitative ecological group were higher than those in the high-density group,
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although the difference was insignificant (P > 0.05).
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The loach under the two farming patterns presented 17 types of amino acids (except tryptophan), of which the highest and lowest contents were of lysine and
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cysteine (Table 4). The total amino acids (TAA) of the loach in the high-density group
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were higher than that in the imitative ecological group, but the difference was insignificant (P > 0.05). The contents of tyrosine and leucine of the loach in the highdensity group were lower than those in the imitative ecological group (P > 0.05). By contrast, no significant difference was found in the other amino acids. The ratio of essential amino acids (EAA) to TAA (E/T) of the loach in the highdensity group was higher than that in the imitative ecological group, but the difference was insignificant (P > 0.05). The delicious amino acids (DAA) found in the amino acids
ACCEPTED MANUSCRIPT included four types: aspartic acid, glutamic acid, glycine and alanine, and the ratios of DAA to TAA (D/T) of the imitative ecological cultured loach and the high-density cultured loach did not differ significantly (P > 0.05). Table 5 presents data on the essential amino acids. The essential amino acid
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content (except leucine) of the loach in the high-density group was higher than that in
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the imitative ecological group. The contents of amino acids, except for lysine, under the
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two farming patterns were lower than those under the whole egg protein scoring mode. According to the AAS and the CS, the first limiting amino acids of both high-density
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and imitative ecological cultured loaches were phenylalanine + tyrosine. According to
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the CS, the second limiting amino acids of both high-density and imitative ecological cultured loaches were methionine + cysteine. The essential amino acid index (IEEA) of
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the loach in the high-density group was higher than that in the imitative ecological
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group.
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4 Discussion
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COD is a key indicator of organic pollution and reduced substances on the water surface, and it is commonly used as a parameter for describing organic pollution in water environment quality assessment (Aoki et al., 2004). The COD in the highdensity farming ponds was approximately twice higher than that in the imitative ecological farming ponds. This phenomenon may be due to the strong accumulation of large amounts of residue and faeces in farming systems under high-density farming conditions, resulting in an increase in organic pollutants, which in turn led to an
ACCEPTED MANUSCRIPT excessively high COD level in the ponds. This result is consistent with the findings of Li, who found that the COD was significantly increased by organic matter (Li, 2011). Microorganism number is a variable influencing water quality that cannot be neglected. The number of heterotrophic bacteria in the high-density farming ponds
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was significantly lower than that in the imitative ecological farming ponds. The
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number of heterotrophic bacteria in the sediment was closely associated with the
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amount of dissolved oxygen in the water (Gao et al., 2003). The nitrite content in the high-density farming ponds was significantly higher than that in the imitative
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ecological farming ponds. This phenomenon may be due to the lower number of
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nitrifying bacteria in the high-density ponds or the lack of dissolved oxygen (Chen et al., 2011). The nitrogenous nitrogen content in the high-density farming ponds was
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lower than that in the imitative ecological farming ponds. The possible reason is that
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the higher feed residue in the high-density ponds led to the plankton growth in the ponds and the nitrate nitrogen uptake (Liu et al., 2008).
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The organic carbon content in the sediment of the high-density farming ponds
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was significantly higher than that in the imitative ecological farming ponds, and the total phosphorus content was also slightly higher than that in the imitative ecological farming ponds. The probable reason is that the compound feed was the main sources of nitrogen, phosphorus and carbon for the ponds (Gao et al., 2011). In the highdensity group, more compound feed was introduced to the pond, leading to an increase in nitrogen, phosphorus and carbon deposition. At the same time, the highdensity cultured loach metabolised a large amount of waste, resulting in a significant
ACCEPTED MANUSCRIPT accumulation of organic sludge. This finding is consistent with the over-density cultivation of Litopenaeus vannamei, which leads to an increased deposition of nitrogen and phosphorus in the ponds (Liu and Ma, 2004). Ten loaches were randomly collected from the high-density (body length: 11.47
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± 0.28 cm; body weight: 21.74 ± 2.26 g) and imitative ecological groups (body length:
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11.56 ± 2.57 cm; body weight: 23.24 ± 1.23 g). Protein and fat are the main nutrients
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in fish dorsal meat. The results of the general nutritional content of the loach dorsal meat were consistent with the composition of Misgurnus anguillicaudatus under
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artificial farming (Zhang et al., 2010). This result implied that the proximate
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compositions of the loach were not related to the environment of the two farming patterns. In the high-density group, the crude protein and crude fat contents were
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slightly higher than those of the loach in the imitative ecological group; however, the
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difference was insignificant. The total sugar content in the high-density group was significantly lower than that in the imitative ecological group. On the one hand, this
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phenomenon might have resulted from the increased metabolism of the loach,
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prompting the energy consumption to cope with the adverse environmental changes under unsuitable external environments (Xing et al., 2005). On the other hand, a significant error might have occurred in the subtraction method applied to determine the total sugar content, which may contain substances such as vitamins, minerals and so on. Overall, the nutrient contents in the loach dorsal meat were not significantly different. This phenomenon was possibly due to the more adequate feeding, which promoted the plankton growth in the pond and in turn supplied sufficient nutrients for
ACCEPTED MANUSCRIPT the loach (Liu et al., 2007), or it was due to the powerful environmental tolerance of the loach (Yi, 2005). Fish fat meets satisfies the physiological needs of different organisms by providing energy and the necessary fatty acids (Aras et al., 2003). The meat of
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Misgurnus anguillicaudatus under artificial farming contains 11 types of fatty acids,
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and UFA accounted for 68.15% of fatty acids (Zhang et al., 2010). In comparison, the
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Paramisgurnus dabryanus in this study was rich in fatty acid species and had a greater UFA content. The nutritional value of fatty acids was mainly reflected by the
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UFA (Zhou et al., 2000). In this study, the UFA content of the loach in the imitative
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ecological group was slightly higher than that in the high-density group; however, the difference was insignificant. Therefore, the loaches under the two kinds of farming
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patterns had similar fatty acid values. The loach cannot synthesise essential fatty acids
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by itself, and the lack of essential fatty acids can lead to adverse consequences (KrisEtherton et al., 2009). The amounts of EPA and DHA under the high-density framing
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pattern were larger than those under the imitative ecological farming pattern. In view
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of the accumulation of EPA and DHA in the body through the enrichment of the food chain (Zuo, 2012), this phenomenon may be related to the amount of compound feed and phytoplankton consumed by the loach. The fish fat quality strongly depends on the EPA and DHA contents (Xu et al., 2010). Therefore, the fatty acid quality of highdensity and imitative ecological cultured loaches was not significantly different. The content and composition of amino acids are important indexes for evaluating the nutritional value of food. The results of amino acid determination of
ACCEPTED MANUSCRIPT Paramisgurnus dabryanus were consistent with those of the loach in paddy fields and ponds in Sichuan province, implying that no obvious relationship existed between the amino acid content and the farming environment (Song et al., 2017). The EAA composition determines the nutritional value of protein (Jiang et al., 2005). The EAA
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content in the high-density and imitative ecological groups were not significantly
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different in the TAA values, and their E/T values were higher than the ideal protein
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pattern recommended by FAO/WHO (E/T≈40%). Moreover, their scores of limiting amino acid were low, such that the loaches in the high-density and imitative
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ecological groups had various amino acids with balanced proportions. One possible
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explanation for the low scores was that the compound feed used in the two treatments was the same and was rich in balanced amino acids (Lin et al., 2012). The IEEA and
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protein quality of the loach in the high-density group were higher than that in the
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imitative ecological group, because the IEEA can predict the protein biological value (Oser, 1959). The DAA content and the D/T value of the loach in the high-density
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group were not significantly different from those of the imitative ecological group,
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because the composition and content of DAA determined the degree of protein delicacy (Wu et al., 2017). Thus, the meat flavour of the loaches under the highdensity and imitative ecological farming patterns were not significantly different. However, an environmental friendly farming mode such as imitative ecological farming pattern should been advocated for producing loach in people food basket. In conclusion, the results of our study revealed that although the high-density farming pattern influenced the water quality and the sediment, the nutrient
ACCEPTED MANUSCRIPT compositions of the high-density and imitative ecological cultured loaches did not vary significantly.
Acknowledgements
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This study was approved by the ethics committee of Huahai Institute of
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Technology, China and financially supported by grants from the Project for
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Aquaculture in Jiangsu Province (Grant No. DY2012-3-6) , the Huaihai Institute of Technology start-up funds (Grant No. KQ17022) and the Priority Academic Program
Conflict of interest statement
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Development of Jiangsu Higher Education Institutions.
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The authors have declared that no competing interests exist.
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ACCEPTED MANUSCRIPT Xing, D.L., Zhang, S.F., Wu, L.X., Liu, J., Cai, X., 2005. Effects of starvation and refeeding on energy metabolism in oriental weatherfish (Misgurnus anguillicaudatus). J. Dalian Fish Univ. 4, 290-294. Xu, J.Z., 2009. Determination of COD by potassium permanganate method.
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ACCEPTED MANUSCRIPT Zhang, Y.L., Fan, Q.X., 2011. Farming mode and management techniques of loach. Anim. Farming Feed. 9, 22-24. Zhang, Y.M., Wang, Y.J., Yu, R.L., Zhou, M., 2008. Effects of heavy metals on ATPase and SOD activities of hepatopancreas in Misgurnus anguillicaudatus. J.
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and muscle nutrient components of Misgurnus anguillicaudatus under artificial
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Zhou, C.Y., 2015. Large-scale cultivation of loach prospects. New Agr. 3, 39-39.
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Zhou, J.X., Huang, Q., Wu, L.F., Yu, T., 2000. The component of fatty acid and requirement in fish. China Feed. 3, 19-20.
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1558-1561.
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Zuo, S.S., 2012. Progress in research on DHA and EPA. Chinese J. Biologicals. 11,
ACCEPTED MANUSCRIPT Table 1. Aquaculture water and sediment analysis results of two farming patterns Final value Initial value
COD (mg/L)
Imitative ecological
2.15±0.31
21.68±2.47a
9.82±0.14b
PO4-P (mg/L)
0.01±0.01
0.02±0.01a
0.011±0.011a
NH3-N (mg/L)
0.04±0.02
0.08±0.06 a
0.04±0.03a
NO2-N (mg/L)
0.01±0.21
0.013±0.004a
0.002±0.001b
NO3-N (mg/L)
0.59±0.19
0.87±0.32a
1.21±0.15a
Heterotrophic bacteria (cfu/ml)
(3.47±2.32) ×105
(2.24±0.62a)×108
(1.14±0.21 b) ×108
Nitrifying bacteria (cfu/ml)
(7.01±0.84) ×105
(0.37±0.35a)×108
Denitrifying bacteria (cfu/ml)
(5.21±0.41) ×104
(6.79±1.08a)×108
(3.79±1.39b)×108
WC.O（%）
0.96±0.08
5.49±2.55a
1.37±0.02b
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High-density
Aquaculture water
Sediment
Index
(0.98±0.31a) ×108
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significantly different (P < 0.05).
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Values are the mean ± SD (n = 3). Values in the same row with different lowercase letters are
ACCEPTED MANUSCRIPT Table 2. Proximate composition of P. dabryanus samples (g/100g) Sample
Moisture
Ash
Crude fat
Crude protein
Total sugar
High-density
77.36±0.63a
1.44±0.09a
3.34±0.12a
16.43±0.52a
1.39±0.24a
Imitative ecological
77.24±1.15a
1.48±0.31a
2.85±0.73a
15.98±0.19a
2.58±0.25b
Values are the mean ± SD (n = 3). Values in the same column with different lowercase letters are
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significantly different (p < 0.05).
ACCEPTED MANUSCRIPT Table 3. Dorsal meat fatty acids composition of P. dabryanus High-density
Imitative ecological
C14:0
0.59±0.09a
0.93±0.34a
C16:0
0.67±0.42a
0.31±0.04a
C17:0
0.56±0.09a
1.02±0.09b
C18:0
4.59±0.45a
5.23±0.75a
C20:0
0.73±0.42a
0.21±0.64a
C24:0
2.10±0.59a
4.10±0.33b
C14:1
0.43±0.19a
C15:1
18.07±0.47a
C16:1
3.23±0.67a
C17:1
0.38±0.10a
C18:1n9t
22.40±1.10b
C20:1
1.08±0.26a
C22:1n9
2.82±0.58a
C24:1
0.93±0.60a
0.97±0.28a
C18:2n6c
29.30±2.48a
22.07±3.72a
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Fatty acids
0.53±0.06a
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17.33±0.86a 5.71±2.84a 0.73±0.19a
16.47±2.31a 0.66±0.14a 5.73±1.21b
1.82±0.20a
2.68±0.71a
1.02±0.04a
1.14±0.30a
1.66±0.10a
0.95±0.39a
0.70±0.28a
1.01±0.25a
0.45±0.09a
0.47±0.09a
6.37±2.43a
11.59±2.73a
9.77±0.80a
9.24±0.80a
46.37±1.11a
48.17±4.65a
41.33±1.08a
39.97±4.43a
∑UFA
88.17±0.87a
89.70±0.75a
SFA/UFA
0.10±0.01a
0.13±0.01b
C18:3n6 C20:2 C20:3n6
C22:6n3 ∑SFA ∑MUFA
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∑PUFA
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C22:2
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C20:5n3
Values are the mean ± SD (n = 3). Values in the same row with different lowercase letters are significantly different (P < 0.05).
ACCEPTED MANUSCRIPT Table 4. Amino acids composition in dorsal meat of P. dabryanus samples (basis of dry weight) High-density
Imitative ecological
Aspartic acid *
4.47±0.24 a
4.06±0.51 a
Glutamic acid *
5.58±0.32 a
5.44±1.17 a
Serine
3.47±0.79 a
3.34±0.96 a
Glycine *
4.83±0.11 a
4.79±1.17 a
Histidine
1.38±0.04 a
1.35±0.28 a
Arginine
4.97±0.26 a
4.81±1.07 a
Threonine
4.66±0.14 a
Alanine *
2.78±0.15 a
Proline
4.77±0.68 a
Tyrosine
1.41±0.49 a
Valine
3.22±0.23 a
Methionine
2.07±0.67 a
Cystine
0.13±0.02 a
Isoleucine
4.33±2.83 a
3.88±4.65 a
Leucine
3.62±1.38 a
3.82±1.59 a
Lysine TAA
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D/T(％)
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2.53±0.77 a 4.46±0.49 a
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1.45±0.29 a 3.13±0.67 a 1.63±0.23 a 0.11±0.05 a
1.36±0.82 b
0.57±0.73 a
10.61±3.72 a
7.95±2.17 a
63.66±3.91a
57.78±12.46 a
29.87±3.39 a
25.44±6.63 a
17.66±0.63 a
16.82±3.57 a
46.92±2.55 a
44.03±2.54 a
27.74±1.61 a
29.11±0.31 a
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EAA E/T(％)
4.46±1.18 a
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Phenylalanine
DAA
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Amino acids
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*delicious amino acids; TAA-total amino acids; EAA-essential amino acids; DAA-delicious
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amino acids. Values are the mean ± SD (n = 3). Values in the same row with different lowercase letters are significantly different (P < 0.05).
ACCEPTED MANUSCRIPT Table 5. Evaluation of essential amino acids in loach dorsal meat in two different farming patterns Average of amino acid content
AAS
FA O
Whol e egg protei n
Highdensity 1.08
Parameters
Highdensit y
Imitative ecologic al
Isoleucine
2.71
2.43
2.50
3.31
Leucine
2.26
2.39
4.40
5.34
Lysine
6.63
4.97
3.40
4.41
Threonine
2.91
2.79
2.50
Valine
2.01
1.96
Methionine + Cystine
1.38
Phenylalani ne +Tyrosine
CS Imitative ecologic al
0.97
0.82
0.73
0.54
0.42
0.45
1.95
1.46
1.50
1.13
2.92
1.16
1.12
1.00
0.96
3.10
4.10
0.65
0.63
0.49
0.48
1.09
2.20
3.86
0.63
0.502
0.362
0.282
1.73
1.26
3.80
5.65
0.331
0.311
0.221
IEAA
60.08
52.18
F value
4.03
5.36
0.46 1
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2
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Highdensit y
0.51
Imitative ecologic al
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1-the first limiting amino acids; 2- the second limiting amino acids
ACCEPTED MANUSCRIPT Highlights
High-density (HD) farming pattern influences water quality.
HD farming pattern influences sediment.
Body composition of HD and imitative ecological cultured loach are
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similar.
Zhiguo Dong, Min Zhang, Sufeng Wei, Hongxing Ge, Xiaoying Li, Qiangan Ni, Qufei Ling, Yong Li PII: DOI: Reference:
S0044-8486(18)30978-5 doi:10.1016/j.aquaculture.2018.07.061 AQUA 633432
To appear in:
aquaculture
Received date: Revised date: Accepted date:
11 May 2018 27 July 2018 30 July 2018
Please cite this article as: Zhiguo Dong, Min Zhang, Sufeng Wei, Hongxing Ge, Xiaoying Li, Qiangan Ni, Qufei Ling, Yong Li , Effect of farming patterns on the nutrient composition and farming environment of loach, Paramisgurnus dabryanus. Aqua (2018), doi:10.1016/j.aquaculture.2018.07.061
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ACCEPTED MANUSCRIPT Effect of farming patterns on the nutrient composition and farming environment of loach, Paramisgurnus dabryanus
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Running Head: Effect of farming patterns on loach
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Zhiguo Dong1,2, 3*, Min Zhang1,2,3, Sufeng Wei1,2, 3, Hongxing Ge1,2,3, Xiaoying Li1,2,3,
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Qiangan Ni4, Qufei Ling5, Yong Li4
1
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Jiangsu Key Laboratory of Marine Bioresources and Eco-environment, Huaihai
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Institute of Technology, 59 Cangwu Road, Haizhou, Lianyungang, 222005, China. 2
Jiangsu Key Laboratory of Marine Biotechnology, Huaihai Institute of Technology,
Co-Innovation Center of Jiangsu Marine Bioindustry Technology, Huaihai Institute
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3
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59 Cangwu Road, Haizhou, Lianyungang, 222005, China.
of Technology, 59 Cangwu Road, Haizhou, Lianyungang, 222005, China. Siyang Fishery Technical Guidance Station, 1 Jiefang North Road, Zhongxing
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4
5
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Town, Huaian, 223700, China. Fisheries Research Institute, Soochow University, 1 Ten catalpa Street, Suzhou,
215021, China.
*
Corresponding author:
E-mail: [email protected]
ACCEPTED MANUSCRIPT Abstract This study aimed to investigate the effect of farming patterns on the farming environment and nutrient composition of loach Paramisgurnus dabryanus. Loach juveniles (2.57 ± 0.42 g) grown for 150 days were stocked with two treatments: high-
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density farming pattern (210 ind·m-2) and imitative ecological farming pattern (70
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ind·m-2). At the end of the farming experiment, the nutrient composition of the loach
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dorsal meat, the water quality, and the sediment in both farming patterns were determined. The contents of chemical oxygen demand, nitrite nitrogen, heterotrophic
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bacteria, denitrifying bacteria and organic carbon in the imitative ecological ponds
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were significantly lower than those in the high-density groups (P < 0.05), whereas the two treatments presented no significant difference in the proximate content of loach
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(P > 0.05). In addition, the two treatments displayed no significant difference in the
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unsaturated fatty acid and saturated fatty acid contents of loach (P > 0.05). The ratios of essential amino acids to total amino acids and of delicious amino acids to total
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amino acids of loach under the two treatments did not significantly differ (P > 0.05).
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The results indicated that although the nutrient compositions of the high-density and imitative ecological cultured loaches did not vary significantly, the high-density farming pattern influenced the water quality and the sediment.
Keywords: Farming pattern; Nutrients; Aquatic ecosystems; Loach
ACCEPTED MANUSCRIPT 1 Introduction Loach Paramisgurnus dabryanus, which is also known as water ginseng, belongs to the genus Paramisgurnus of the family Cobitidae (Qin et al., 2002). It is popular among Chinese, Japanese and Korean consumers because of its delicious and
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nutritious meat. In recent years, loach aquaculture has considerably grown in China,
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reaching a production volume of 4,020 million tons in 2016, which was an increase by
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9.29% from that in 2015 according to the China Fishery Statistics Yearbook (Ning, 2017). The market demand for loach has been increasing annually. At present,
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international markets, specifically Japanese and Korean, import approximately 80% of
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the farmed loach in China (Zhou et al., 2015), as wild loach resources are steadily declining due to ecological damage and overfishing; this situation has driven the
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growth of loach farming (Zhang et al., 2010). In China, loach is cultured through
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different farming patterns, such as pond farming, paddy farming, cage culture, yard culture and soilless farming (Zhang and Fan, 2011). Among them, high-density
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farming and imitative ecological farming are the most dominant patterns of artificial
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farming. High-density farming pattern is a simple and cost-effective farming pattern. In this pattern, large-sized seedlings are placed at 1250–1500 kg/(667 m2), mediumsized seedlings are placed at 1000–1250 (kg/667 m2), and small-sized seedlings are placed at 750–1000 (kg/667 m2) (Bai and Yu, 2010). Imitative ecological pattern is a comprehensive farming pattern that is mainly applied for stocking loach, raising carp, catfish, silver carp (Wang and Zhang, 2010) shrimp and crabs (Jiang et al., 2015) and so on.
ACCEPTED MANUSCRIPT Domestic and foreign scholars have extensively investigated the growth (Ding et al., 2016), environment (Zhang et al., 2008), nutrition (Pu et al., 2017), culture (Legendre et al., 2012) and feeding model of loach (Guo et al., 2015). However, many consumers unreasonably believe that the quality of loach from the wild or imitative
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ecological farmed environments is better than that of other artificial farming patterns,
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and therefore prefer wild or imitative ecological cultured loach. Several studies have
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focused on the body colour and texture (Yuan et al., 2017) as well as body composition (Song et al., 2017) of loach from wild and cultured environments.
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However, no study has comprehensively compared the meat composition and
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nutritional differences of imitative ecological cultured and high-density cultured loach. Thus, in this study, we investigated the effect of farming patterns on the
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nutrient composition and farming environment of loach to provide scientific guidance
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to consumers.
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2 Materials and methods
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2.1 Farming and sampling Loach seedlings (body length: 6.83 ± 0.53 cm; body weight: 2.57 ± 0.42 g) were acquired from Pu'nan Farm in Lianyungang, Jiangsu Province, China. The experiment consisted of two treatments, namely, high-density farming pattern and imitative ecological farming pattern, each of which has three replicates. The size of the highdensity farming pond was approximately 667 m2. The stocking density of the cultured loach was 210 ind·m-2. The size of the imitative ecological farming pond was
ACCEPTED MANUSCRIPT approximately 13340 m2. The stocking density of the cultured loach was 70 ind·m-2, and each pond contained a mixture of crucian carp and silver carp. All experimental ponds were sterilised prior to the experiment. During the experiment, the loaches were fed with compound feed containing 40% crude protein twice a day in accordance with
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the feeding situation. The imitative ecological farming ponds were operated without
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was exchanged every 15 days during the experiment.
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water exchange; whereas 20% of the total water in the high-density farming ponds
At the end of the 150-day breeding experiment, the sediment of 0–2 cm from the
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surface was collected with a dredging device from five sites in the same pond and
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combined. The middle water samples of the farming pond were also sampled using a Plexiglas water-collecting device and pooled together. The sediment and water
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samples were maintained at 4 °C and transported to the laboratory within 2 h to
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determine the relevant water quality and sediment indicators. Ten loaches were randomly collected from each pond, and those of the same group were mixed
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together, kept alive in water and immediately delivered to the laboratory.
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All loaches were sacrificed by anaesthesia. We collected the dorsal meat from each loach, placed it in corresponding Petri dishes, and preserved in a refrigerator at −80 °C. The rest of the loach samples were freeze-dried for analysis of fatty acid and amino acid composition.
2.2 Environmental factor determination
ACCEPTED MANUSCRIPT The chemical oxygen demand (COD) in the water samples was determined by acidic potassium permanganate titration (Xu, 2009). Nitrite nitrogen (NO2-N) content was measured using diazo-azo colorimetric method (Lin et al., 2010). The nitrate nitrogen (NO3-N) in the water was monitored by spectrophotometric method with
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phenol disulfonic acid (Dai, 2003). The ammonia nitrogen (NH3-N) concentration in
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the water sample was determined using Nessler's reagent spectrophotometry (Zhang et
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al., 2009). The sediment samples were analysed for organic carbon content by potassium dichromate external heating method (Xin, 2014). Molybdenum blue
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sediment extraction (Ma et al., 1996).
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colorimetric method was used for labile phosphate (PO4-P) determination during
The microorganisms in the sediment were identified by coating the sediment on
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different concentrations of heterotrophic bacteria culture medium plate, denitrifying
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bacteria culture medium plate and nitrifying bacteria culture medium plate; incubating at 30 °C; and counting on the third day. The organic carbon in the sediment was
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oxidised by sulfuric acid-potassium dichromate standard solution in a boiling water
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bath and then titrated by ferrous sulphate solution on the sulfuric acid-potassium dichromate (Kalembasa and Jenkinson, 2010).
2.3 Nutrient compositions determination Moisture and ash were measured by direct oven-drying method at 105 °C (Brendan, 2014) and direct burning method at 550 °C (Kazuki et al., 2009). The crude lipid was analysed by Soxhlet extraction (Manirakiza et al., 2001). The crude protein
ACCEPTED MANUSCRIPT content was determined by the micro-Kjeldahl method (Technical, 2009). The total sugar was calculated by subtraction method [total sugar = 100 − (moisture + ash + crude lipid + crude protein)] (Qian et al., 2010). The amino acid concentration was analysed by high-performance liquid
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chromatography (Agilent 1100; Agilent Technologies, California, USA) according to
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the method of Paramás et al. (2006). A ODS column (200 mm × 4.6 mm; pore size: 5
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μm) thermostated at 40 °C was used for all amino acids analyses. The flow rate was set to 1 mL·min-1. The UV absorbance was detected at 254 nm. Acetonitrile (solution
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A) and pH 6.5 8.2g·L-1 sodium acetate-acetate buffer solution (solution B) were used
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as the mobile phases.
The frozen material was weighed and disintegrated by crushing with a mortar.
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The experiment was performed by determining the composition of fatty acid in animal
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meat (Zhang et al., 2012). Fatty acid composition was analysed by a gas chromatograph (GC-2014; Shimadzu Corp, Kyoto, Japan) equipped with a flame
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ionisation detector (FID) and a Supelco SP-2560 fused silica capillary column (100 m
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× 0.25 mm × 0.2 μm). The column temperature was programmed to increase from 140 °C to 240 °C at a rate of 4 °C·min-1. The temperatures of the injection port and the detector were maintained at 26 °C and 280 °C, respectively. Helium was used as the carrier gas. Amino acid score (AAS), chemical score (CS) and essential amino acid index (IEAA) (Bing et al., 2005) were calculated based on the essential amino acid profile (%, dry) (Passmore, 1982) and the essential amino acid of whole egg protein profile
ACCEPTED MANUSCRIPT (%, dry) (Li et al., 2017) recommended by the WHO/FAO 1973. The formulas are as follows: ASS= Sample amino acid content (%, dry) / FAO scoring mode of the same amino acid content (%, dry)
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CS= Sample amino acid content (%, dry) / whole egg protein mode of the same amino
n
100a 100b 100c 100 j ae be ce je
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I EAA
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acid content (%, dry) (Ou et al., 2010)
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n-the number of IEAA; a, b, c… j - IEAA content (%, dry) in the protein; ae, be, ce… jeIEAA content (% dry weight) in the whole egg protein.
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F value = (valine + leucine + isoleucine) / (phenylalanine + tyrosine) (Shi et al.,
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2013).
2.4 Statistical analysis
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SPSS 20 software was used for data analysis. The average and variance of the statistical analysis were described first. Then, a normality test was performed by using
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the K-S in the non-parametric statistical analysis. Finally, an independent sample t-test was used to compare the two farming patterns and to obtain significant test values, for which P < 0.05 was considered a significant difference. The results were expressed as means ± SD.
3 Results 3.1 Environmental factors
ACCEPTED MANUSCRIPT At the end of the breeding experiment, the contents of COD, PO4-P, NH3-N and NO2-N in the high-density farming ponds were higher than those in the imitative ecological farming ponds, whereas the NO3-N content displayed an opposite trend (Table 1). The contents of COD and NO2-N in the high-density farming ponds were
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significantly higher than those in the imitative ecological farming ponds (P < 0.05).
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The numbers of heterotrophic and nitrifying bacteria in the high-density farming pond
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sediment were lower than those in the imitative ecological farming ponds, and a significant difference was found in the number of heterotrophic bacteria (P < 0.05).
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Furthermore, the number of denitrifying bacteria and the organic carbon content in the
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high-density group were significantly higher than those in the imitative ecological
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3.2 Nutrient components
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group (P<0.05).
Table 2 shows the proximate composition of the loach. The contents of crude
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protein and crude fat in the high-density group were higher than those in the imitative
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ecological group, but no significant difference was observed (P > 0.05). The two groups presented no significant difference in the contents of moisture and ash (P > 0.05). The total sugar content of the high-density group was significantly lower than that of the imitative ecological group (P < 0.05). The loaches under the two different farming patterns exhibited the same 21 types of fatty acids (Table 3): six types of saturated fatty acids (SFA), eight types of monounsaturated fatty acids and seven types of polyunsaturated fatty acids. The loaches
ACCEPTED MANUSCRIPT of the high-density group and the imitative ecological group presented no significant differences in the total saturated fatty acid (∑SFA) and the total unsaturated fatty acid content (∑UFA) (P > 0.05). The SFA/UFA values of the loach dorsal meat in the highdensity group were lower than those in the imitative ecological group, although no
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significant difference was recorded (P > 0.05).
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Four main fatty acids of the loaches from the two farming patterns were compared.
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The palmitic acid (C16:0) content of the loach in the high-density group was slightly higher than that in the imitative ecological group (P > 0.05). The stearic acid (C18:0)
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content of the high-density cultured loach was slightly lower than that of the imitative
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ecological cultured loach (P > 0.05). The EPA (C20:5n3) and DHA (C22:6n3) of the loach in the imitative ecological group were higher than those in the high-density group,
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although the difference was insignificant (P > 0.05).
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The loach under the two farming patterns presented 17 types of amino acids (except tryptophan), of which the highest and lowest contents were of lysine and
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cysteine (Table 4). The total amino acids (TAA) of the loach in the high-density group
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were higher than that in the imitative ecological group, but the difference was insignificant (P > 0.05). The contents of tyrosine and leucine of the loach in the highdensity group were lower than those in the imitative ecological group (P > 0.05). By contrast, no significant difference was found in the other amino acids. The ratio of essential amino acids (EAA) to TAA (E/T) of the loach in the highdensity group was higher than that in the imitative ecological group, but the difference was insignificant (P > 0.05). The delicious amino acids (DAA) found in the amino acids
ACCEPTED MANUSCRIPT included four types: aspartic acid, glutamic acid, glycine and alanine, and the ratios of DAA to TAA (D/T) of the imitative ecological cultured loach and the high-density cultured loach did not differ significantly (P > 0.05). Table 5 presents data on the essential amino acids. The essential amino acid
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content (except leucine) of the loach in the high-density group was higher than that in
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the imitative ecological group. The contents of amino acids, except for lysine, under the
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two farming patterns were lower than those under the whole egg protein scoring mode. According to the AAS and the CS, the first limiting amino acids of both high-density
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and imitative ecological cultured loaches were phenylalanine + tyrosine. According to
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the CS, the second limiting amino acids of both high-density and imitative ecological cultured loaches were methionine + cysteine. The essential amino acid index (IEEA) of
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the loach in the high-density group was higher than that in the imitative ecological
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group.
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4 Discussion
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COD is a key indicator of organic pollution and reduced substances on the water surface, and it is commonly used as a parameter for describing organic pollution in water environment quality assessment (Aoki et al., 2004). The COD in the highdensity farming ponds was approximately twice higher than that in the imitative ecological farming ponds. This phenomenon may be due to the strong accumulation of large amounts of residue and faeces in farming systems under high-density farming conditions, resulting in an increase in organic pollutants, which in turn led to an
ACCEPTED MANUSCRIPT excessively high COD level in the ponds. This result is consistent with the findings of Li, who found that the COD was significantly increased by organic matter (Li, 2011). Microorganism number is a variable influencing water quality that cannot be neglected. The number of heterotrophic bacteria in the high-density farming ponds
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was significantly lower than that in the imitative ecological farming ponds. The
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number of heterotrophic bacteria in the sediment was closely associated with the
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amount of dissolved oxygen in the water (Gao et al., 2003). The nitrite content in the high-density farming ponds was significantly higher than that in the imitative
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ecological farming ponds. This phenomenon may be due to the lower number of
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nitrifying bacteria in the high-density ponds or the lack of dissolved oxygen (Chen et al., 2011). The nitrogenous nitrogen content in the high-density farming ponds was
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lower than that in the imitative ecological farming ponds. The possible reason is that
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the higher feed residue in the high-density ponds led to the plankton growth in the ponds and the nitrate nitrogen uptake (Liu et al., 2008).
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The organic carbon content in the sediment of the high-density farming ponds
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was significantly higher than that in the imitative ecological farming ponds, and the total phosphorus content was also slightly higher than that in the imitative ecological farming ponds. The probable reason is that the compound feed was the main sources of nitrogen, phosphorus and carbon for the ponds (Gao et al., 2011). In the highdensity group, more compound feed was introduced to the pond, leading to an increase in nitrogen, phosphorus and carbon deposition. At the same time, the highdensity cultured loach metabolised a large amount of waste, resulting in a significant
ACCEPTED MANUSCRIPT accumulation of organic sludge. This finding is consistent with the over-density cultivation of Litopenaeus vannamei, which leads to an increased deposition of nitrogen and phosphorus in the ponds (Liu and Ma, 2004). Ten loaches were randomly collected from the high-density (body length: 11.47
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± 0.28 cm; body weight: 21.74 ± 2.26 g) and imitative ecological groups (body length:
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11.56 ± 2.57 cm; body weight: 23.24 ± 1.23 g). Protein and fat are the main nutrients
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in fish dorsal meat. The results of the general nutritional content of the loach dorsal meat were consistent with the composition of Misgurnus anguillicaudatus under
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artificial farming (Zhang et al., 2010). This result implied that the proximate
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compositions of the loach were not related to the environment of the two farming patterns. In the high-density group, the crude protein and crude fat contents were
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slightly higher than those of the loach in the imitative ecological group; however, the
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difference was insignificant. The total sugar content in the high-density group was significantly lower than that in the imitative ecological group. On the one hand, this
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phenomenon might have resulted from the increased metabolism of the loach,
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prompting the energy consumption to cope with the adverse environmental changes under unsuitable external environments (Xing et al., 2005). On the other hand, a significant error might have occurred in the subtraction method applied to determine the total sugar content, which may contain substances such as vitamins, minerals and so on. Overall, the nutrient contents in the loach dorsal meat were not significantly different. This phenomenon was possibly due to the more adequate feeding, which promoted the plankton growth in the pond and in turn supplied sufficient nutrients for
ACCEPTED MANUSCRIPT the loach (Liu et al., 2007), or it was due to the powerful environmental tolerance of the loach (Yi, 2005). Fish fat meets satisfies the physiological needs of different organisms by providing energy and the necessary fatty acids (Aras et al., 2003). The meat of
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Misgurnus anguillicaudatus under artificial farming contains 11 types of fatty acids,
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and UFA accounted for 68.15% of fatty acids (Zhang et al., 2010). In comparison, the
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Paramisgurnus dabryanus in this study was rich in fatty acid species and had a greater UFA content. The nutritional value of fatty acids was mainly reflected by the
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UFA (Zhou et al., 2000). In this study, the UFA content of the loach in the imitative
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ecological group was slightly higher than that in the high-density group; however, the difference was insignificant. Therefore, the loaches under the two kinds of farming
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patterns had similar fatty acid values. The loach cannot synthesise essential fatty acids
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by itself, and the lack of essential fatty acids can lead to adverse consequences (KrisEtherton et al., 2009). The amounts of EPA and DHA under the high-density framing
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pattern were larger than those under the imitative ecological farming pattern. In view
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of the accumulation of EPA and DHA in the body through the enrichment of the food chain (Zuo, 2012), this phenomenon may be related to the amount of compound feed and phytoplankton consumed by the loach. The fish fat quality strongly depends on the EPA and DHA contents (Xu et al., 2010). Therefore, the fatty acid quality of highdensity and imitative ecological cultured loaches was not significantly different. The content and composition of amino acids are important indexes for evaluating the nutritional value of food. The results of amino acid determination of
ACCEPTED MANUSCRIPT Paramisgurnus dabryanus were consistent with those of the loach in paddy fields and ponds in Sichuan province, implying that no obvious relationship existed between the amino acid content and the farming environment (Song et al., 2017). The EAA composition determines the nutritional value of protein (Jiang et al., 2005). The EAA
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content in the high-density and imitative ecological groups were not significantly
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different in the TAA values, and their E/T values were higher than the ideal protein
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pattern recommended by FAO/WHO (E/T≈40%). Moreover, their scores of limiting amino acid were low, such that the loaches in the high-density and imitative
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ecological groups had various amino acids with balanced proportions. One possible
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explanation for the low scores was that the compound feed used in the two treatments was the same and was rich in balanced amino acids (Lin et al., 2012). The IEEA and
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protein quality of the loach in the high-density group were higher than that in the
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imitative ecological group, because the IEEA can predict the protein biological value (Oser, 1959). The DAA content and the D/T value of the loach in the high-density
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group were not significantly different from those of the imitative ecological group,
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because the composition and content of DAA determined the degree of protein delicacy (Wu et al., 2017). Thus, the meat flavour of the loaches under the highdensity and imitative ecological farming patterns were not significantly different. However, an environmental friendly farming mode such as imitative ecological farming pattern should been advocated for producing loach in people food basket. In conclusion, the results of our study revealed that although the high-density farming pattern influenced the water quality and the sediment, the nutrient
ACCEPTED MANUSCRIPT compositions of the high-density and imitative ecological cultured loaches did not vary significantly.
Acknowledgements
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This study was approved by the ethics committee of Huahai Institute of
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Technology, China and financially supported by grants from the Project for
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Aquaculture in Jiangsu Province (Grant No. DY2012-3-6) , the Huaihai Institute of Technology start-up funds (Grant No. KQ17022) and the Priority Academic Program
Conflict of interest statement
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Development of Jiangsu Higher Education Institutions.
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The authors have declared that no competing interests exist.
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ACCEPTED MANUSCRIPT Table 1. Aquaculture water and sediment analysis results of two farming patterns Final value Initial value
COD (mg/L)
Imitative ecological
2.15±0.31
21.68±2.47a
9.82±0.14b
PO4-P (mg/L)
0.01±0.01
0.02±0.01a
0.011±0.011a
NH3-N (mg/L)
0.04±0.02
0.08±0.06 a
0.04±0.03a
NO2-N (mg/L)
0.01±0.21
0.013±0.004a
0.002±0.001b
NO3-N (mg/L)
0.59±0.19
0.87±0.32a
1.21±0.15a
Heterotrophic bacteria (cfu/ml)
(3.47±2.32) ×105
(2.24±0.62a)×108
(1.14±0.21 b) ×108
Nitrifying bacteria (cfu/ml)
(7.01±0.84) ×105
(0.37±0.35a)×108
Denitrifying bacteria (cfu/ml)
(5.21±0.41) ×104
(6.79±1.08a)×108
(3.79±1.39b)×108
WC.O（%）
0.96±0.08
5.49±2.55a
1.37±0.02b
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High-density
Aquaculture water
Sediment
Index
(0.98±0.31a) ×108
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significantly different (P < 0.05).
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Values are the mean ± SD (n = 3). Values in the same row with different lowercase letters are
ACCEPTED MANUSCRIPT Table 2. Proximate composition of P. dabryanus samples (g/100g) Sample
Moisture
Ash
Crude fat
Crude protein
Total sugar
High-density
77.36±0.63a
1.44±0.09a
3.34±0.12a
16.43±0.52a
1.39±0.24a
Imitative ecological
77.24±1.15a
1.48±0.31a
2.85±0.73a
15.98±0.19a
2.58±0.25b
Values are the mean ± SD (n = 3). Values in the same column with different lowercase letters are
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significantly different (p < 0.05).
ACCEPTED MANUSCRIPT Table 3. Dorsal meat fatty acids composition of P. dabryanus High-density
Imitative ecological
C14:0
0.59±0.09a
0.93±0.34a
C16:0
0.67±0.42a
0.31±0.04a
C17:0
0.56±0.09a
1.02±0.09b
C18:0
4.59±0.45a
5.23±0.75a
C20:0
0.73±0.42a
0.21±0.64a
C24:0
2.10±0.59a
4.10±0.33b
C14:1
0.43±0.19a
C15:1
18.07±0.47a
C16:1
3.23±0.67a
C17:1
0.38±0.10a
C18:1n9t
22.40±1.10b
C20:1
1.08±0.26a
C22:1n9
2.82±0.58a
C24:1
0.93±0.60a
0.97±0.28a
C18:2n6c
29.30±2.48a
22.07±3.72a
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Fatty acids
0.53±0.06a
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17.33±0.86a 5.71±2.84a 0.73±0.19a
16.47±2.31a 0.66±0.14a 5.73±1.21b
1.82±0.20a
2.68±0.71a
1.02±0.04a
1.14±0.30a
1.66±0.10a
0.95±0.39a
0.70±0.28a
1.01±0.25a
0.45±0.09a
0.47±0.09a
6.37±2.43a
11.59±2.73a
9.77±0.80a
9.24±0.80a
46.37±1.11a
48.17±4.65a
41.33±1.08a
39.97±4.43a
∑UFA
88.17±0.87a
89.70±0.75a
SFA/UFA
0.10±0.01a
0.13±0.01b
C18:3n6 C20:2 C20:3n6
C22:6n3 ∑SFA ∑MUFA
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∑PUFA
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C22:2
D
C20:5n3
Values are the mean ± SD (n = 3). Values in the same row with different lowercase letters are significantly different (P < 0.05).
ACCEPTED MANUSCRIPT Table 4. Amino acids composition in dorsal meat of P. dabryanus samples (basis of dry weight) High-density
Imitative ecological
Aspartic acid *
4.47±0.24 a
4.06±0.51 a
Glutamic acid *
5.58±0.32 a
5.44±1.17 a
Serine
3.47±0.79 a
3.34±0.96 a
Glycine *
4.83±0.11 a
4.79±1.17 a
Histidine
1.38±0.04 a
1.35±0.28 a
Arginine
4.97±0.26 a
4.81±1.07 a
Threonine
4.66±0.14 a
Alanine *
2.78±0.15 a
Proline
4.77±0.68 a
Tyrosine
1.41±0.49 a
Valine
3.22±0.23 a
Methionine
2.07±0.67 a
Cystine
0.13±0.02 a
Isoleucine
4.33±2.83 a
3.88±4.65 a
Leucine
3.62±1.38 a
3.82±1.59 a
Lysine TAA
PT E
D/T(％)
RI
2.53±0.77 a 4.46±0.49 a
SC
1.45±0.29 a 3.13±0.67 a 1.63±0.23 a 0.11±0.05 a
1.36±0.82 b
0.57±0.73 a
10.61±3.72 a
7.95±2.17 a
63.66±3.91a
57.78±12.46 a
29.87±3.39 a
25.44±6.63 a
17.66±0.63 a
16.82±3.57 a
46.92±2.55 a
44.03±2.54 a
27.74±1.61 a
29.11±0.31 a
D
EAA E/T(％)
4.46±1.18 a
NU
MA
Phenylalanine
DAA
PT
Amino acids
CE
*delicious amino acids; TAA-total amino acids; EAA-essential amino acids; DAA-delicious
AC
amino acids. Values are the mean ± SD (n = 3). Values in the same row with different lowercase letters are significantly different (P < 0.05).
ACCEPTED MANUSCRIPT Table 5. Evaluation of essential amino acids in loach dorsal meat in two different farming patterns Average of amino acid content
AAS
FA O
Whol e egg protei n
Highdensity 1.08
Parameters
Highdensit y
Imitative ecologic al
Isoleucine
2.71
2.43
2.50
3.31
Leucine
2.26
2.39
4.40
5.34
Lysine
6.63
4.97
3.40
4.41
Threonine
2.91
2.79
2.50
Valine
2.01
1.96
Methionine + Cystine
1.38
Phenylalani ne +Tyrosine
CS Imitative ecologic al
0.97
0.82
0.73
0.54
0.42
0.45
1.95
1.46
1.50
1.13
2.92
1.16
1.12
1.00
0.96
3.10
4.10
0.65
0.63
0.49
0.48
1.09
2.20
3.86
0.63
0.502
0.362
0.282
1.73
1.26
3.80
5.65
0.331
0.311
0.221
IEAA
60.08
52.18
F value
4.03
5.36
0.46 1
NU
MA
RI
SC
2
PT
Highdensit y
0.51
Imitative ecologic al
AC
CE
PT E
D
1-the first limiting amino acids; 2- the second limiting amino acids
ACCEPTED MANUSCRIPT Highlights
High-density (HD) farming pattern influences water quality.
HD farming pattern influences sediment.
Body composition of HD and imitative ecological cultured loach are
AC
CE
PT E
D
MA
NU
SC
RI
PT
similar.