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Dietary vitamin B6 requirement of juvenile sea cucumber Apostichopus japonicus Selenka

  • Corresponding author: Jiying WANG, ytwjy@126.com
  • Received Date: 2018-09-11
    Accepted Date: 2019-03-25
  • The present trial was conducted to investigate the dietary vitamin B6 requirement of sea cucumber Apostichopus japonicas Selenka juveniles. The experimental diets were formulated with graded levels of vitamin B6 (1.23, 5.29, 9.35, 17.47, 33.71, 66.17 mg/kg), and named D1, D2, D3, D4, D5 and D6 group. Each diet was randomly assigned with triplicate sea cucumber juvenile with initial body weight (12.23±0.11) g for 12 weeks. The results showed that weight gain rate and specific growth rate presented an increasing firstly and then decreasing afterwards, and got maximum in D5 group (33.73 mg/kg). Crude protein of body wall was increased firstly by dietary vitamin B6 and then decreased, and crude protein of D6 group was significantly lower than other groups; Crude lipid of D1 group was significantly lower than other groups. All of activities of glucose 6-phosphatede hydrogenase, isocitrate dehydrogenase, acetyl coA carboxylase, and nitric oxide synthesis were increased firstly and then decreased afterwards, activity of D6 group was significantly lower than other groups. With the increasing of dietary vitamin B6, both protease and amylase were increased, and cellulase was decreased by dietary vitamin B6, while the height of villus; MC and the thickness of muscularis were increased significantly. With the weight gain rate as the evaluation indictor, regression analysis showed that the optimum dietary vitamin B6 for sea cucumber juveniles were 45 mg/kg.
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Dietary vitamin B6 requirement of juvenile sea cucumber Apostichopus japonicus Selenka

    Corresponding author: Jiying WANG, ytwjy@126.com
  • Shandong Marine Resourse and Environment Research Institute, Shandong Provincial Key Laboratory of Restoration for Marine Ecology, Yantai,    264006, China

Abstract: The present trial was conducted to investigate the dietary vitamin B6 requirement of sea cucumber Apostichopus japonicas Selenka juveniles. The experimental diets were formulated with graded levels of vitamin B6 (1.23, 5.29, 9.35, 17.47, 33.71, 66.17 mg/kg), and named D1, D2, D3, D4, D5 and D6 group. Each diet was randomly assigned with triplicate sea cucumber juvenile with initial body weight (12.23±0.11) g for 12 weeks. The results showed that weight gain rate and specific growth rate presented an increasing firstly and then decreasing afterwards, and got maximum in D5 group (33.73 mg/kg). Crude protein of body wall was increased firstly by dietary vitamin B6 and then decreased, and crude protein of D6 group was significantly lower than other groups; Crude lipid of D1 group was significantly lower than other groups. All of activities of glucose 6-phosphatede hydrogenase, isocitrate dehydrogenase, acetyl coA carboxylase, and nitric oxide synthesis were increased firstly and then decreased afterwards, activity of D6 group was significantly lower than other groups. With the increasing of dietary vitamin B6, both protease and amylase were increased, and cellulase was decreased by dietary vitamin B6, while the height of villus; MC and the thickness of muscularis were increased significantly. With the weight gain rate as the evaluation indictor, regression analysis showed that the optimum dietary vitamin B6 for sea cucumber juveniles were 45 mg/kg.

  • 维生素B6(Vitamin B6)又称吡哆素,包括吡哆醇、吡哆醛及吡哆胺3种化学形式,在体内以磷酸酯的形式存在,是一种水溶性维生素。维生素B6是140多种酶的辅酶,参与多种代谢反应,尤其是和氨基酸代谢有密切关系,是维持动物正常生理功能的一种必需营养素[1]。此外,维生素B6还参与糖异生、不饱和脂肪酸(UFA)代谢,参与神经介质、核酸的合成[2]。研究表明:饲料中添加适宜的维生素B6会提高斑节对虾(Penaeus monodon)[3]、尼罗罗非鱼(Oreochromis niloticus)[4]和印度囊鳃鲇(Heteropneustes fossilis)[5]生长性能,促进皱纹盘鲍(Haliotis discus hannai Ino)[6]、中华绒螯蟹(Eriocheir sinensis)[7]和凡纳滨对虾(Litopenaeus vannamei)[8]对饲料蛋白质的利用,增加虹鳟(Oncorhynchus mykiss)[9]肌肉中二十二碳六烯酸(DHA)的沉积。

    仿刺参(Apostichopus japonicus)属棘皮动物门(Echinodermata),海参纲(Holothuroidea),是我国名贵的海珍品之一,也是我国重要的海水养殖动物之一。研究报道仿刺参对饲料中蛋白质[10]、脂肪[11]及碳水化合物[12]的需求量均较低,这与其消化道分化程度及摄食选择能力较低有关。维生素B6是动物体内蛋白质、脂肪、糖类代谢必需的一种营养素,对营养素的吸收及利用影响巨大,目前未见仿刺参对饲料维生素B6需求量的报道。因此,本实验通过在基础饲料中添加不同梯度的维生素B6,饲喂仿刺参幼参,研究对其生长、体腔液代谢酶活性及消化生理的影响,从而得出仿刺参幼参对饲料中维生素B6的需求量,以期为仿刺参代谢生理及饲料配制提供参考。

1.   材料与方法
  • 以藻粉、鱼粉及小麦粉为主要原料,设计粗蛋白含量为16%、粗脂肪含量为2%的基础饲料配方[11]。在基础饲料中分别添加0、5、10、20、40和80 mg/kg的磷酸吡哆醇(江西百盈生物技术有限公司,纯度≥99%),制作维生素B6实测含量分别为1.23、5.29、9.35、17.47、33.71和66.17 mg/kg的6组等氮等能的实验饲料,命名为D1、D2、D3、D4、D5和D6组。饲料配方及基本成分含量见表1。各原料粉碎过80目标准筛,按配比称重,逐级混匀,加入蒸馏水,用小型饲料挤压机制作成条状饲料,自然风干后,用饲料破碎机破碎,筛取20~40目标准筛之间的颗粒,−20 °C保存备用。

    组别 groups
    D1D2D3D4D5D6
    原料 ingredients
    海泥/% sea mud 35.9 35.9 35.9 35.9 35.9 35.9
    维生素B6/(mg/kg) vitamin B6 0 5 10 20 40 80
    鱼粉/% fishmeal 12 12 12 12 12 12
    藻粉/% algae powder 36 36 36 36 36 36
    小麦粉/% wheat flour 10 10 10 10 10 10
    多维/% vitamin mixa 1 1 1 1 1 1
    多矿/% minerals mixa 1 1 1 1 1 1
    谷朊粉/% wheat gluten 3 3 3 3 3 3
    抗氧化剂/% antioxidant 0.1 0.1 0.1 0.1 0.1 0.1
    大豆卵磷脂/% soy lecithin 1 1 1 1 1 1
    合计 total 100 100 100 100 100 100
    营养成分(干重) approximate composition (DM)
    粗蛋白/% crude protein 16.21 15.83 15.94 15.84 15.61 16.06
    粗脂肪/% crude lipid 2.08 2.13 2.04 1.97 2.01 2.09
    粗灰分/% crude ash 49.20 50.14 50.25 49.40 50.19 50.23
    能量/(kJ/g) energy 12.17 11.95 12.00 11.98 12.01 12.02
    维生素B6/(mg/kg) vitamin B6 1.23 5.29 9.35 17.47 33.71 66.17
    注:a. 多维多矿配方参见文献[13],多维中不含维生素B6
    Notes: a. formulas of vitamins and minerals are the same as reference [13], and vitamin B6 free in the mix

    Table 1.  Formulation and composition of experimental diets

  • 养殖实验在室内养殖系统中进行。实验用仿刺参购自山东安源水产股份有限公司。实验开始前,将1 000头体质量约12 g的仿刺参放养于养殖系统中,饲喂D1组配合饲料,使其适应实验环境。21 d后,饥饿24 h,挑选体质量相近、肉刺坚挺的仿刺参幼参540头,平均放置于18个养殖水槽中(Ф 65 cm×80 cm),水槽水深60 cm,每个水槽放置仿刺参养殖筐一个。每种饲料随机投喂3个水槽,每日饱食投喂1次(16:00),初始投喂量约为仿刺参体质量的3%,饲料投喂前加入适量水润湿,泼洒投喂。每天观察仿刺参摄食情况,调整次日投喂量。实验采用流水养殖,控制水流速约为2 L/min;每隔2日用虹吸法将残饵粪便吸出,每隔20天更换养殖筐1次。养殖期间,水温14~17 °C,pH 7.8~8.2,盐度30,DO>6 mg/L,氨氮、亚硝酸氮<0.05 mg/L,养殖实验持续84 d。

  • 养殖实验结束后,停饲48 h。将每个水槽中仿刺参全部捞出计数,放置在洁净的白瓷盘上,待其恢复自然体长时称总重,然后随机选取15头,测量体长和体质量后解剖,收集体壁、肠道和体腔液,测量体壁质量和肠道质量,计算成活率、增重率、特定生长率、脏壁比及肠壁比。体腔液在4 °C、500 r/min离心10 min后收集上清液,超声波细胞破碎仪破碎5 min后过0.45 μm滤膜;肠道用0.75 %生理盐水冲洗干净。所有样品置于−20 °C保存、待测。

    在仿刺参肠道前1/3处截取0.3 cm,用波恩试液(Bone’s)固定,用于肠道组织切片的制作。

  • 饲料及体壁中水分用105 °C恒重法测定(GB/T6435-2006),粗蛋白含量用凯氏定氮法(GB/T6432-2006),粗脂肪用乙醚浸提法测定(GB/T6433-2006),粗灰分用马弗炉灼烧法测定(GB/T6438-2006),能量用燃烧法测定(IKA,C6000,Germany),饲料中维生素B6用高效液相色谱法测定(GB/T14702-2002)。

    体腔液中葡萄糖-6-磷酸脱氢酶(glucose 6-phosphatede hydrogenase, G6PD),乳酸脱氢酶(lactate dehydrogenase, LDH),异柠檬酸脱氢酶(isocitrate dehydrogenase, ICD),乙酰辅酶A羧化酶(acetyl coA carboxylase, ACC),一氧化氮合酶(nitric oxide synthesis, NOS),谷丙转氨酶(alanine aminotransferase, ALT),谷草转氨酶(aspartate aminotransferase, AST)采用Elisa试剂盒测定(上海纪宁实业有限公司),酶活性单位设定及测定方法见说明书。

    肠道粗酶液采用吴永恒等[14]的方法制备;蛋白酶(Protease)、脂肪酶(Lipase)、淀粉酶(Amylase)及纤维素酶(Cellulase)活性采用南京建成生物工程研究所试剂盒测定,酶液中粗蛋白含量采用考马斯亮蓝法测定,酶活性单位设定及测定方法见说明书。

  • 固定后的样品经梯度酒精脱水、透明、进蜡(Leica TP1020)后包埋,在室温下切成7 um厚的切片,苏木精-伊红(HE)染色后,中性树脂封片。在×20物镜下观测切片,选择典型视野,采用Leica DM500图像采集系统统计肠壁厚度及绒毛长度,每个样品观察10个非连续性的纵切片,其中肠壁厚度为肠外部至肌层与粘膜下层交接处的距离,绒毛长度为所有绒毛长度的平均值。

  • 成活率(survival rate, SR, %)= Nt/N0×100%;

    增重率(weight gain rate, WGR, %)=(WtW0)/W0×100%;

    特定生长率(specific growth rate, SGR, %/d)=(lnWt−lnW0)/t×100%;

    脏壁比(ratio of visceral weight to body wall weight, VBR, %)=Wv/Wb×100%;

    肠壁比(ratio of intestine weight to body wall weight, IBR, %)= Wi/Wb×100%;

    式中,Nt为终末头数,N0为初始头数,Wt为终末体质量(g),W0为初始体质量(g),t为实验天数(d),Wv为内脏团质量,Wb为体壁质量,Wi为肠道质量。

  • 实验所得数据采用Microsoft Excel 2007及SPSS®(SPSS, Inc, Chicago, IL)11.0软件进行单因素方差分析(One-Way ANOVA),结果以平均值±标准差(mean±SD)表示,差异显著(P<0.05)时用Duncan氏检验进行多重比较分析。

2.   结果
  • 饲料中维生素B6含量对实验仿刺参成活率无显著影响(P>0.05)。随着饲料中维生素B6含量的增加,实验仿刺参的终末体质量、增重率和特定生长率均呈先上升后下降的趋势,D1组显著低于其他组(P<0.05)。脏壁比和肠壁比均先升高后平稳,D3至D6组无显著差异(P>0.05)(表2)。

    指标 
    indices 
    组别 groups
    D1D2D3D4D5D6
    初始体质量/g W0 12.25±0.23 12.26±0.12 12.24±0.07 12.22±0.08 12.21±0.12 12.18±0.07
    终末体质量/g Wt 16.91±0.77a 19.28±0.33b 20.24±0.17c 21.25±0.63d 22.33±0.31e 21.59±0.54de
    增重率/% WGR 38.01±3.79a 57.29±1.18b 65.32±0.76c 73.91±4.45d 82.89±2.61e 77.23±4.11d
    特定生长率/(%/d) SGR 0.58±0.05a 0.81±0.01b 0.91±0.01c 0.99±0.04d 1.08±0.03e 1.02±0.04de
    脏壁比/% VBR 16.30±1.10a 18.66±0.96b 19.62±0.63bc 20.42±1.52c 20.96±0.55c 20.95±0.42c
    肠壁比/% IBR 3.49±0.22a 4.05±0.21b 4.45±0.13c 4.37±0.09c 4.51±0.17c 4.40±0.14c
    成活率/% SR 93.33±3.34 95.56±1.93 96.67±3.34 95.56±1.93 95.56±3.85 97.78±1.92
    注:同行上标字母不同,表示二者之间差异显著(P<0.05),下同
    Notes: in the same column with different letters indicated significantly different (P<0.05),the same below

    Table 2.  Effects of dietary vitamin B6 on growth performances of sea cucumber A. japonicus juveniles

    以增重率为评价指标,经一元二次回归分析得出,体质量为12.23 g的仿刺参幼参饲料中维生素B6的适宜含量为45 mg/kg饲料(图1)。

    Figure 1.  Relationship between WGR and dietary vitamin B6 contents

  • 饲料中维生素B6含量对实验仿刺参体壁中水分和粗灰分含量无显著影响(P>0.05),粗蛋白含量先升高后降低,D1组粗脂肪含量显著低于其他各组(P<0.05),其他各组之间无显著差异(P>0.05)(表3)。

    指标
    indices
    组别 groups
    D1D2D3D4D5D6
    水分 moisture 90.75±0.12 90.67±0.18 90.59±0.23 90.48±0.31 90.72±0.41 90.59±0.34
    粗蛋白 crude protein 4.14±0.10ab 4.20±0.14ab 4.41±0.07c 4.37±0.08bc 4.18±0.04b 4.06±0.06a
    粗脂肪 crude lipid 0.13±0.01a 0.16±0.01b 0.18±0.01b 0.17±0.00b 0.17±0.01b 0.15±0.00b
    粗灰分 crude ash 3.10±0.07 3.30±0.28 3.08±0.06 3.29±0.21 3.18±0.25 3.41±0.23

    Table 3.  Effects of dietary vitamin B6 on body composition of sea cucumber A. japonicus juveniles

  • 实验仿刺参体腔液中葡萄糖-6-磷酸脱氢酶、异柠檬酸脱氢酶、乙酰辅酶A羧化酶及一氧化氮合酶的活性均随维生素B6含量的升高呈先升高后降低的趋势,D6组显著低于其他组(P<0.05);乳酸脱氢酶、谷丙转氨酶和谷草转氨酶活性均随维生素B6含量的升高呈上升趋势,D5、D6组显著高于其他组(P<0.05),二组之间差异不显著(P>0.05)(表4)。

    指标
    indices
    组别 groups
    D1D2D3D4D5D6
    葡萄糖-6-磷酸脱氢酶/(IU/L) G-6-PD 5.57±0.73bc 6.08±0.42c 5.47±0.39bc 5.41±0.54ab 5.01±0.32ab 4.92±0.42a
    乳酸脱氢酶/(mg/L) LDH 2.48±0.23a 2.85±0.28ab 3.02±0.40b 3.14±0.52b 3.74±0.15c 4.14±0.42c
    异柠檬酸脱氢酶/ (mIU/L) ICD 730.14±33.945b 753.33±57.63bc 807.40±61.55bc 829.34±10.18c 582.08±14.79a 599.06±55.92a
    乙酰辅酶A羧化酶/(ng/L) ACC 90.10±5.17c 113.36±7.81d 105.87±11.01d 107.69±8.13d 79.57±5.38b 65.17±7.43a
    一氧化氮合酶/(umol/L) NOS 10.07±0.35a 11.13±0.58b 13.08±0.71c 12.24±0.69b 10.12±0.52a 9.53±0.25a
    谷丙转氨酶/(U/L) ALT 2.05±0.31a 2.26±0.11ab 2.41±0.15b 2.35±0.23b 2.83±0.19c 2.71±0.19c
    谷草转氨酶/(U/L) AST 4.54±0.49a 4.91±0.48a 5.09±0.23a 5.13±0.32a 6.10±0.39b 5.77±0.49b

    Table 4.  Effects of dietary vitamin B6 on physiological enzyme activities of coelomic fluid of sea cucumber A. japonicus juveniles

  • 实验仿刺参肠道中蛋白酶、淀粉酶活性均随维生素B6含量的升高而升高,D4~D6组蛋白酶活性显著高于其他组(P<0.05),3组之间无显著差异(P>0.05);D5、D6组淀粉酶活性显著高于其他组(P<0.05),但二者之间差异不显著(P>0.05);D1组脂肪酶活性显著低于其他组(P<0.05),其他各组之间差异不显著(P>0.05);纤维素酶活性随维生素B6含量的升高而降低(P<0.05)(表5)。

    指标
    indices
    组别 groups
    D1D2D3D4D5D6
    蛋白酶 protease 44.85±3.58a 58.74±3.25b 63.29±4.71c 74.52±4.96d 73.94±5.33d 75.39±5.50d
    脂肪酶 lipase 0.38±0.04a 0.61±0.05b 0.64±0.04b 0.66±0.07b 0.63±0.05b 0.65±0.04b
    淀粉酶 amylase 5.58±0.57a 6.69±0.71b 8.34±0.78c 10.25±0.46d 11.91±0.83e 12.08±0.95e
    纤维素酶 cellulase 2.04±0.57e 1.91±0.37e 1.65±0.28d 1.46±0.33c 1.25±0.19b 1.04±0.41a

    Table 5.  Effects of dietary vitamin B6 on digestive enzyme activities of intestine of sea cucumber A. japonicus juveniles

  • 随着饲料中维生素B6含量的增加,仿刺参肠道肠壁厚度及绒毛长度均显著升高,D5组显著高于其他组(P<0.05)(表6)。

    指标
    indices
    组别 groups
    D1D2D3D4D5D6
    肠壁厚度/um MC 3.25±0.46a 3.88±0.52a 5.17±0.34b 7.41±0.69c 8.45±0.72d 7.37±0.59c
    绒毛长度/um VH 78.84±12.19a 74.35±15.27a 96.77±18.57b 112.46±25.91c 143.80±21.34d 129.88±17.22c

    Table 6.  Effects of dietary vitamin B6 on digestive enzyme activities of intestine of sea cucumber A. japonicus juveniles

    饲料中缺乏维生素B6时,肠道绒毛长度变短、宽度变窄、数量变少,粘膜下层出现异常。随着饲料中维生素B6含量的增加,实验仿刺参肠道绒毛变得致密、规则,肠壁厚度增大(D5组);当饲料中维生素B6含量过多时(D6组),仿刺参肠道黏膜下层、中央乳糜管均出现异常(图2)。

    Figure 2.  Effects of dietary FBSM on intestinal morphology of sea cucumber A. japonicus juveniles

3.   讨论
  • 本实验,饲料中维生素B6含量对仿刺参的成活率无显著影响,但显著影响增重率,表明维生素B6缺乏会抑制仿刺参的生长,但无致死性。在鱼类、甲壳动物及贝类上的研究均表明,饲料中缺乏维生素B6会影响动物的生长性能[3-8]。鱼类对维生素B6的需求量为1~15 mg/kg[4-5, 15],而斑节对虾对维生素B6的需求量为72~89 mg/kg[3],中华绒螯蟹对维生素B6的需求量为81.675~85.74 mg/kg[7],皱纹盘鲍饲料中维生素B6的最佳含量为40 mg/kg[16],本实验得出仿刺参对维生素B6的需求量为45 mg/kg,均远高于鱼类的需求量[5, 15, 17]。这可能体现了动物种属之间的差异,但更重要的是与动物的摄食习性有关,大部分鱼类摄食较为迅速,而虾蟹贝参的摄食速度较慢,相当一部分维生素B6在水中溶失,导致实验出现偏差。本实验中,随着饲料中维生素B6含量的增加,实验仿刺参的增重率有下降趋势,这可能与高剂量的维生素B6引起的细胞凋亡有关[2]。此外,仿刺参体内不具备完善的吸收及转运系统,水管系统和血窦系统在营养物质的吸收及转运中起着重要作用[18],因此其对营养物质的吸收利用效率较低,由此导致机体对维生素B6的较高生理需求量。

  • 维生素B6是动物体内蛋白质、脂肪代谢酶的重要辅酶,广泛参与机体营养代谢。研究表明,饲料中适宜的维生素B6含量能显著提高组织粗蛋白、粗脂肪的含量[6-7, 19]。本实验,仿刺参体壁中粗蛋白含量先升后降,粗脂肪含量先升后平稳,表明维生素B6影响了仿刺参体内蛋白质、脂肪的沉积。D6组粗蛋白含量显著低于其他组,可能与维生素B6的生理毒性有关,维生素B6含量过高,引起了细胞凋亡,因此降低了蛋白质代谢酶活性,减少了体壁蛋白质的沉积;而D1组粗蛋白含量与D2组无显著差异,可能与实验开始前,仿刺参体内储备的维生素B6有关。在中华绒螯蟹上的研究表明,饲料中适宜含量的维生素B6可以促进机体脂肪的沉积[7],这可能与维生素B6促进机体蛋白质利用有关,当蛋白质超出其需求量时,部分氨基酸脱氨基代谢为α-酮酸,继而转化为脂肪储存体内[20]。但仿刺参与脊椎动物的营养需求及代谢机理存在较大差异,饲料及机体中粗脂肪的含量均较低,因此其机体粗脂肪含量的升高更倾向于维生素B6提高了机体脂肪利用能力,从而提高了机体粗脂肪的沉积。

  • 葡萄糖-6-磷酸脱氢酶参与磷酸戊糖途径,通过调控NADPH的含量维持细胞的能量;乳酸脱氢酶参与糖酵解和糖异生过程,催化乳酸生成丙酮酸和NADH;异柠檬酸脱氢酶催化异柠檬酸生成α-酮戊二酸,是TCA循环的限速酶;这3种酶均与糖及能量的代谢有关[20]。本实验,随着饲料中维生素B6含量的增加葡萄糖-6-磷酸脱氢酶、异柠檬酸脱氢酶的活性,而乳酸脱氢酶的活性则呈上升趋势,表明饲料中维生素B6含量的改变直接影响了仿刺参体内磷酸戊糖途径、三羧酸循环、糖酵解及糖异生等生物过程的效率,从而影响蛋白质、脂肪及糖三大类营养物质的代谢。当饲料中维生素B6含量缺乏时,葡萄糖会被用来氧化供能;当维生素B6含量超过其需求量时,部分蛋白质或脂肪可能被用来氧化供能,而糖类被沉积下来;只有饲料中维生素B6含量适宜时,才能维持机体蛋白质、脂肪、糖三大类营养物质的正常代谢。乙酰辅酶A羧化酶催化乙酰辅酶A生成丙二酰辅酶A,是脂肪酸合成的关键酶[20]。随着饲料中维生素B6含量的增加,仿刺参脂肪酸合成能力先提高后下降。但从本实验测得的糖酵解或TCA循环酶活推测,可能是由于维生素B6提高了脂肪酸β-氧化功能的比例,从而降低了脂肪酸合成的能力。

    谷丙转氨酶和谷草转氨酶是氨基酸代谢的2个重要酶类,它们的辅酶均为5′-磷酸吡哆醛(PLP)[21]。本实验中,随着维生素B6含量的增加,仿刺参体腔液中谷丙转氨酶和谷草转氨酶的活性均显著上升,同样的现象在斑节对虾[3]、皱纹盘鲍[6]、中华绒螯蟹[7]上均有报道,表明维生素B6能够显著提高仿刺参体内氨基酸的代谢。但随着维生素B6含量的升高,2种转氨酶活性出现一定程度的下降,这可能与维生素B6的细胞毒性有关[2]

    一氧化氮合酶催化精氨酸生产NO,NO是重要的生物信使分子,在心脑血管调节、神经、免疫调节等方面有着十分重要的生物学作用[22-23]。本实验中,随着饲料中维生素B6含量的增加,一氧化氮合酶活性有了一定程度的上升,这可能与底物精氨酸的浓度有关。维生素B6含量的增加,增强了仿刺参体内氨基酸代谢,提供了更多的精氨酸[24]。但当维生素B6含量超过一定数值后,一氧化氮合酶活性降低,这在其他动物上尚未见报道,其机理也待更深入的研究。

  • 有研究报道,维生素B6可以通过促进消化器官的生长发育,增强消化酶的分泌能力,从而提高消化吸收能力[25]。仿刺参不具有专门的消化酶分泌器官,且主要消化酶位于肠道粘膜层的柱状细胞内。随着饲料中维生素B6的添加,仿刺参肠道粘膜层环形褶皱逐渐致密,肠壁厚度逐渐增大,表明维生素B6促进了仿刺参肠道的发育,维持了肠道结构完整性和功能的正常性。一方面,肠道发育良好可以促进消化酶的分泌,提高仿刺参的消化能力;另一方面,仿刺参消化能力的提高,促进了机体对营养物质的利用能力,提高了机体对营养物质的需求,刺激了消化酶的合成与分泌。本实验中,从D3组开始,肠道蛋白酶和淀粉酶活性有了较大的提高,与肠道组织结构变化相吻合,表明仿刺参对饲料中维生素B6的需求量高于9.35 mg/kg,D4、D5肠道形态结构与吴永恒[14]等报道的仿刺参正常肠道结构形态类似,表明仿刺参对饲料中维生素B6的需求量为17.47~33.71 mg/kg,与本实验回归分析得出的结论较为符合。

4.   结论
  • 饲料中适宜含量的维生素B6可以促进仿刺参的生长,促进肠道发育,提高机体营养物质的代谢能力。分别以增重率为评价指标,仿刺参幼参配合饲料中适宜的维生素B6含量为45 mg/kg。

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