动物营养学报  2015, Vol. 27 Issue (3): 795-803   PDF (1112 KB)    
饲粮铜源及水平对育成期雄性水貂生长性能、营养物质表观消化率及氮、铜代谢的影响
吴学壮1,2, 高秀华1 , 杨福合2, 张铁涛2, 崔虎1, 刘志1, 郭俊刚1, 邢秀梅2    
1. 中国农业科学院饲料研究所, 北京 100081;
2. 中国农业科学院特产研究所, 吉林省特种经济动物 分子生物学省部共建重点实验室, 长春 130112
摘要:本试验旨在研究饲粮铜源及水平对育成期雄性水貂生长性能、营养物质表观消化率及氮、铜代谢的影响。采用3×3+1双因素试验设计,设3种铜源(硫酸铜、碱式氯化铜、蛋氨酸铜)和3个铜添加水平(10、25、40 mg/kg),1个对照组。选择60日龄健康、体重接近的美国短毛黑雄性水貂120只,随机分成10组,每组12个重复,每个重复1只貂。预试期7 d,正试期45 d。结果表明:1)水貂的平均日采食量随饲粮铜添加水平的增加呈极显著线性增加(P<0.01),并且平均日增重随饲粮铜添加水平的增加也呈线性增加(P=0.053)。2)水貂的粗脂肪表观消化率随饲粮铜添加水平的增加呈极显著线性增加(P<0.01),并且粗蛋白质表观消化率随饲粮铜添加水平的增加也呈显著线性增加(P<0.05)。3)水貂铜摄入量、粪铜排泄量、尿铜排泄量以及铜沉积量均随饲粮铜添加水平的增加呈极显著线性增加(P<0.01),然而铜的表观吸收率却随饲粮铜添加水平的增加呈极显著线性降低(P<0.01)。水貂对碱式氯化铜和蛋氨酸铜的表观吸收率极显著高于对硫酸铜的表观吸收率(P<0.01)。水貂氮沉积量随饲粮铜添加水平的增加而呈显著线性增加(P<0.05)。由此可见,基础饲粮中铜含量为8.05 mg/kg时,饲粮添加40 mg/kg的铜能改善育成期雄性水貂生长性能,提高水貂粗脂肪表观消化率;育成期雄性水貂对碱式氯化铜和蛋氨酸铜的表观吸收率高于对硫酸铜的表观吸收率。
关键词水貂     蛋氨酸铜     碱式氯化铜     硫酸铜     生长性能     营养物质表观消化率    
Effects of Dietary Copper Sources and Levels on Growth Performance, Nutrient Apparent Digestibility and Copper and Nitrogen Metabolism of Male Minks in Late Growing Period
WU Xuezhuang1,2, GAO Xiuhua1 , YANG Fuhe2, ZHANG Tietao2, CUI Hu1, LIU Zhi1, GUO Jungang1, XING Xiumei2    
1. Institute of Feed Research, Chinese Academy of Agriculture Science, Beijing 100081, China;
2. State Key Laboratory for Molecular Biology of Special Economic Animals, Institute of Economic Animal and Plant Science, Chinese Academy of Agriculture Science, Changchun 130112, China
Abstract: This experiment was conducted to study the effects of dietary copper sources and levels on growth performance, nutrient apparent digestibility and copper and nitrogen metabolism of male minks in late growing period. The experiment was used in a 3×3+1 factorial experiment based on a completely randomized design, minks in the control group were fed a basal diet, and minks in other nine groups were fed the basal diets supplemented with 3 sources (copper sulfate, tribasic copper chloride and copper methionine) and 3 levels (10, 25, and 40 mg/kg). The pre-test period lasted for 7 days, and the trial lasted for 45 days. The results showed as follows: 1) the average daily feed intake of minks was significantly linear increased with dietary copper supplemental level increased (P<0.01), and average daily gain of minks was linear increased with dietary copper supplemental level increased (P=0.053). 2) The apparent digestibility of ether extract and crude protein of minks was significant linear increased with dietary copper supplemental level increased (P<0.01 or P<0.05). 3) The copper intake, fecal copper excretion, Urinary copper excretion and copper retention of minks were significant linear increased with dietary copper supplemental level increased (P<0.01), but the copper apparent absorption was significant linear decreased with dietary copper supplemental level increased (P<0.01). The tribasic copper chloride and copper methionine apparent absorption of minks was significantly higher than copper sulfate apparent absorption (P<0.05). The nitrogen retention was significant linear increased with dietary copper supplemental level increased (P<0.05). In conclusion, when copper content is 8.05 mg/kg in the basal diet, dietary supplemented with 40 mg/kg copper can improve growth performance of minks in late growing period, and improve the ether extract apparent digestibility. Tribasic copper chloride and copper methionate apparent absorption of minks is higher than copper sulfate apparent absorption.
Key words: minks     copper methionate     tribasic copper chloride     copper sulfate     growth performance     nutrient apparent digestibility    

铜作为水貂的必需微量元素之一,在水貂生长性能和毛皮色素沉积方面发挥着重要作用[1]。Aulerich等[2]研究表明,饲喂铜添加水平为25 mg/kg饲粮组的雄性水貂日增重显著大于0和50 mg/kg饲粮组。Dove等[3]与Dove[4]报道,在断奶仔猪饲粮中添加250 mg/kg铜,可以提高粗脂肪表观消化率和脂肪的利用率。水貂饲粮的脂肪水平远高于猪饲粮的脂肪水平,因此水貂饲粮中添加铜比仔猪更有益。动物对不同的铜源的吸收利用不同。从铜的消化吸收和体内代谢情况来分析,国内外专家认为,氨基酸鳌合铜比无机铜(硫酸铜、氧化铜)有更高的消化吸收率和独特的生理作用,更强的促生长作用[5, 6, 7, 8]。此外,铜的添加水平越多,排泄量也越大。大量的铜随粪便排出,当粪便作为肥料使用时,增加了土壤的潜在负荷,使土壤和植物中铜含量大大增加,一方面自然环境受到污染;另一方面使采食这类牧草的对铜敏感的反刍动物发生铜中毒。因此,筛选出一些生物学利用率较好的铜源,具有更广阔的应用前景。本试验旨在研究饲粮铜源及水平对育成期水貂生长性能、营养物质表观消化率及氮、铜代谢的影响,筛选出育成期水貂适宜的铜源及水平,为指导实际生产提供理论依据。 1 材料与方法 1.1 试验设计

试验采用3×3+1试验设计,设1个对照组[饲喂基础饲粮,不添加铜],3种铜源(硫酸铜、碱式氯化铜、蛋氨酸铜)和3个铜添加水平(10、25、40 mg/kg)。基础饲粮铜含量为8.05 mg/kg,硫酸铜组铜含量分别为18.66、24.32和48.12 mg/kg,碱式氯化铜组铜含量分别为17.86、23.83和48.39 mg/kg,蛋氨酸铜组铜含量分别为19.16、23.94和48.69 mg/kg,以上均为干物质基础。在农业部长白山野生生物资源重点野外科学观测试验站的毛皮动物生产基地随机选择健康、体重[(1 100±70 g)]相近的(60±3)日龄美国短毛黑雄性水貂120只,随机分成10个组,每组12个重复,每个重复1只水貂,试验处理与动物分组见表1。

表1 试验处理与动物分组 Table 1 Experimental treatments and animal grouping

试验水貂均单笼(40 cm×40 cm×60 cm)饲养,每日07:30与15:30各饲喂1次,自由采食,自由饮水,每日记录实际采食量,常规免疫。预试期7 d,正试期45 d。水貂目前没有统一的饲养标准,参照国内近几年水貂营养需要量的研究[9, 10, 11],配制育成期水貂基础饲粮,其组成及营养水平见表2。 1.2 消化代谢试验

正试期开始30 d后,每组挑选8只体重相近的水貂进行消化代谢试验,水貂消化代谢试验时间为4 d,采用全收粪法。消化代谢试验期间饲养管理与日常饲养管理完全相同。每天收集的尿液中每100 mL加入10 mL的10%硫酸溶液,将试验期间收集的尿液混合均匀后取样,加4滴甲苯用于防腐,保存于-20 ℃备用。每天收集的粪便称重后按鲜重的5%加入10%硫酸溶液,并加少量甲苯防腐,保存于-20 ℃备用。将试验期间收集的粪混合均匀后取样,其中粪样先在80 ℃下杀菌2 h,然后降到65 ℃烘干至恒重,磨碎过40目筛,制成风干样本,以备实验室分析。 1.3 测定指标及方法

正试期开始后,第1天称重作为初重,试验结束后称重作为末重,计算每只水貂的日增重以及每组的平均日增重(average daily gain,ADG)。记录每只水貂每天的给料量和残余料量,计算每只水貂的采食量以及每组的平均日采食量(average daily feed intake,ADFI),计算料重比(feed to gain,F/G)。

样品分析:饲料及排泄物中的干物质含量测定采用105 ℃烘干法测定(GB/T 6435—2006)[12];索氏浸提法测定粗脂肪的含量,参考GB/T 6433—2006[13];凯氏定氮法测定粗蛋白质含量,参考GB/T 6432—1994[14];钙和总磷含量的测定分别采用滴定法和比色法测定;原子吸收光谱方法测定铜离子含量,参考GB/T 13885—2003[15]

营养物质表观消化率计算公式如下:

干物质表观消化率(%)=[(干物质采食量-干物质排出量)/干物质采食量]×100;
粗蛋白质表观消化率(%)=[(蛋白质摄入量—蛋白质排出量)/蛋白质摄入量]×100;
粗脂肪表观消化率(%)=[(脂肪摄入量-脂肪排出量)/脂肪摄入量]×100;
铜的表观吸收率(%)=[(铜摄入量—铜排出量)/铜摄入量]×100;
氮沉积(g/d)=食入氮-粪氮-尿氮。

表2 基础饲粮组成及营养水平(风干基础) Table 2 Composition and nutrient levels of the basal diet (air-dry basis)
1.4 数据处理

结果以平均值和平均值标准误差表示,试验数据采用SAS 9.13软件进行统计分析,采用双因素方差分析(two-way ANOVA)进行差异显著性检验,组间差异采用邓肯氏法多重比较进行检验,再采用GLM程序对数据进行多因子统计分析,其中P<0.05为差异显著,P<0.01为差异极显著。 2 结 果 2.1 饲粮铜源及水平对育成期水貂生长性能的影响

饲粮铜源及水平对育成期水貂生长性能影响的结果见表3。各组水貂的初重差异不显著(P=1.000)。水貂的平均日采食量随饲粮铜添加水平的增加呈极显著线性增加(P<0.01),并且平均日增重随饲粮铜添加水平的增加也呈线性增加(P=0.053)。饲粮添加3种铜源对末重、平均日增重、平均日采食量和料重比影响不显著(P>0.05)。

表3 饲粮铜源及水平对育成期水貂生长性能的影响 Table 3 Effects of dietary Cu sources and levels on growth performance of minks in late growing period
2.2 饲粮铜源及水平对育成期水貂营养物质表观消化率的影响

饲粮铜源及水平对育成期水貂营养物质表观消化率影响的结果见表4。水貂的粗脂肪表观消化率随饲粮铜添加水平的增加呈极显著线性增加(P<0.01),并且粗蛋白质表观消化率随饲粮铜添加水平的增加也呈显著线性增加(P=0.047)。饲粮添加3种铜源对营养物质表观消化率影响不显著(P>0.05),饲粮铜添加水平对干物质、粗蛋白质和粗灰分表观消化率影响也不显著(P>0.05)。

表4 饲粮铜源及水平对育成期水貂营养物质表观消化率的影响 Table 4 Effects of dietary Cu sources and levels on nutrient apparent digestibility of minks in late growing period
2.3 饲粮铜源及水平对育成期水貂铜、氮代谢的影响

饲粮铜源及水平对育成期水貂铜、氮代谢影响的结果见表5。水貂铜摄入量、粪铜排泄量、尿铜排泄量以及铜沉积量都是随饲粮铜添加水平的增加呈极显著线性增加(P<0.01),然而铜的表观吸收率却随饲粮铜添加水平的增加呈极显著线性降低(P<0.01)。水貂摄入的铜51%~76%通过粪便排出体外,仅有4%~6%通过尿液排出。水貂对碱式氯化铜和蛋氨酸铜的表观吸收率极显著高于对硫酸铜的表观吸收率(P<0.01)。水貂氮沉积量随饲粮铜添加水平的增加而呈显著线性增加(P=0.011),而铜源对水貂氮代谢各项指标影响不显著(P>0.05)。

表5 饲粮铜源及水平对育成期水貂铜、氮代谢的影响 Table 5 Effects of dietary Cu sources and levels on Cu and N metabolism of minks in late growing period
3 讨 论

铜是人和动物的必需微量元素之一。作为一般必需营养元素,单胃动物对铜的需要量一般在4~8 mg/kg[16]。但自英国学者Braude[17]1945年首次发现饲粮添加高剂量铜对育成猪有促生长作用以来,专家学者关于高铜对猪的促生长效应已做了大量研究。多数试验表明,猪饲粮中添加150~250 mg/kg铜[18, 19, 20],家禽饲粮中添加25~120 mg/kg铜[21, 22, 23],家兔饲粮中添加40~80 mg/kg铜[24, 25],对畜禽有明显的促生长效应,特别是对于断奶仔猪效果尤其明显。本试验结果表明,水貂的平均日采食量和平均日增重都是随饲粮铜添加水平的增加呈线性增加,这与Aulerich等[2]的研究一致。水貂的采食量主要取决于饲粮的适口性和能量水平。本试验各组动物的基础饲粮组成和能量水平相同,消除了饲粮的适口性和能量水平对水貂采食量的影响。学者证实铜对动物的促生长作用与其采食量的增加有密切关系[3, 26, 27, 28, 29]。但是,铜是如何提高动物的采食量的,至今其作用机理尚不明了。Pau等[30]报道,家兔静脉注射醋酸铜可以快速刺激下丘脑释放神经肽Y激素,同时也刺激下丘脑释放促性腺激素释放激素(GnRH),而神经肽Y激素是一种已知的强烈促进猪采食量的激素[31, 32, 33]。因此,高铜通过刺激神经肽Y激素从动物下丘脑的分泌,进而引起动物采食量增加是可能的。但尚需在不同动物上做进一步的直接研究。

本试验结果表明,水貂的粗脂肪和粗蛋白质表观消化率随饲粮铜添加水平的增加呈线性增加。许多研究表明,饲粮中添加高铜显著提高动物对饲粮脂肪消化利用[3, 4, 34]。Luo等[18]首次发现,添加250 mg/kg硫酸铜来源的铜显著提高了断奶仔猪小肠脂肪酶和磷脂酶A的活性。冷向军等[35]研究表明,断奶仔猪饲粮添加高铜提高了十二指肠脂肪酶活性和粗脂肪表观消化率。体外试验研究表明,适宜的铜离子浓度能激活胃蛋白酶,增加蛋白质的水解[36]。众所周知,胃泌素可以激活胃蛋白酶,促进胰酶分泌,加强胃运动,提高营养物质表观消化率[37]。梅绍锋[20]报道,高铜显著提高断奶仔猪胃蛋白酶和胰淀粉酶活性。可见,动物饲粮中添加铜可以提高消化酶的活性,进而增加营养物质的消化吸收,促进动物生长。实际生产中,水貂饲粮脂肪水平远高于猪饲粮脂肪水平,因此水貂饲粮中添加铜比仔猪更有益。此外,铜主要通过胆汁排出体外,本试验表明水貂摄入的铜51%~76%通过粪便排出体外。研究表明,铜可以促进胆汁的分泌[38, 39],胆汁的基本功能是乳化脂肪,进而促进脂肪的消化吸收。

Luo等[18]发现,饲粮添加250 mg/kg铜显著提高了断奶仔猪的氮表观沉积率,与本试验结果一致。体蛋白质的合成受生长激素及相关生长因子的影响。铜通过刺激促生长激素轴激素的合成与分泌并抑制生长抑制激素(SS)的合成与分泌[41, 42],进而促进蛋白质的合成,减少氨基酸的分解,使机体氮贮留增加,呈正氮平衡,最终促进动物的生长是可能的。

一些学者认为动物可以更好的吸收利用有机铜,并且有机铜与其他元素很少有拮抗[42],然而,也有一些学者报道有机铜与无机铜饲喂动物没有显著差异[43, 44]。本研究表明,水貂对碱式氯化铜和蛋氨酸铜的表观吸收率高于对硫酸铜的表观吸收率。水貂铜摄入量、粪铜排出量、尿铜排泄量以及铜在体内的沉积量都是随饲粮铜添加水平的增加呈极显著线性增加,与Mejborn[45]和Wu等[46]的试验结果一致。评估矿物质元素的吸收是一个复杂的问题,需要考虑到多种元素交互影响。此外,内源性的排泄,如胆汁和消化道分泌物以及肠道黏膜细胞的脱落也应考虑。迄今为止,关于水貂铜的吸收和体内平衡代谢报道很少,有待于做进一步的研究。 4 结 论

① 基础饲粮中铜含量为8.05 mg/kg时,饲粮添加40 mg/kg的铜能改善育成期雄性水貂生长性能,提高水貂粗脂肪表观消化率。

② 育成期雄性水貂对碱式氯化铜和蛋氨酸铜的表观吸收率高于对硫酸铜的表观吸收率。

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