畜牧兽医学报  2017, Vol. 48 Issue (6): 1054-1065. DOI: 10.11843/j.issn.0366-6964.2017.06.010    PDF    
饲粮n-6/n-3多不饱和脂肪酸配比对北极狐冬毛期体脂沉积、体脂肪酸组成及血液生化指标的影响
钟伟, 张婷, 罗婧, 王卓, 岳志刚, 刘学庆, 李光玉     
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实验室, 长春 130112
摘要:本试验旨在研究饲粮n-6/n-3多不饱和脂肪酸(PUFA)配比对冬毛生长期雄性北极狐体脂沉积、体脂肪酸组成及血液生化指标的影响。试验选取48只157日龄,平均体重为(5 658±47)g的健康雄性北极狐,随机分成4组(每组12个重复,每个重复1只),分别饲喂n-6/n-3 PUFA配比为3、18、41和136的试验饲粮,试验饲粮对应添加的油脂为12%鱼油和2%豆油(Ⅰ组),9.38%玉米油和4.62%豆油(Ⅱ组),12%玉米油和2%豆油(Ⅲ组),1.5%鱼油和12.5%玉米油(Ⅳ组)。预饲期7 d,试验期40 d。结果表明:1)饲粮n-6/n-3 PUFA配比极显著影响北极狐肝体指数(P<0.01),Ⅳ组极显著高于Ⅱ和Ⅲ组(P<0.01),与Ⅰ组差异不显著(P>0.05),对肝脂肪含量、肝脂率、皮下脂肪重、皮脂率均无显著影响(P>0.05);2)饲粮n-6/n-3 PUFA配比显著或极显著影响北极狐肌内脂肪饱和脂肪酸(SFA)、单不饱和脂肪酸(MUFA)、PUFA、n-6和n-3 PUFA含量(P<0.05或P<0.01),Ⅰ组SFA显著高于Ⅱ组(P<0.05),与Ⅲ和Ⅳ组差异不显著(P>0.05),Ⅰ组MUFA显著高于Ⅲ和Ⅳ组(P<0.05),与Ⅱ组差异不显著(P>0.05),Ⅱ组PUFA极显著高于Ⅰ和Ⅳ组(P<0.01),与Ⅲ组差异不显著(P>0.05),Ⅰ和Ⅲ组n-3极显著高于Ⅱ和Ⅳ组(P<0.01),Ⅲ组n-6极显著高于Ⅰ和Ⅳ组(P<0.01),与Ⅱ组差异不显著(P>0.05);饲粮n-6/n-3 PUFA配比极显著影响皮下脂肪中的MUFA,PUFA,n-3和n-6 PUFA(P<0.01),而对SFA无显著影响(P>0.05),Ⅰ组MUFA极显著高于Ⅱ、Ⅲ和Ⅳ组(P<0.01),Ⅱ和Ⅲ组PUFA极显著高于Ⅰ和Ⅳ组(P<0.01),Ⅰ和Ⅲ组n-3极显著高于Ⅱ和Ⅳ组(P<0.01),Ⅱ组n-6极显著高于Ⅰ和Ⅳ组(P<0.01),与Ⅲ组差异不显著(P>0.05);3)饲粮n-6/n-3 PUFA配比显著影响了北极狐血清中的高密度脂蛋白(HDL-C)、低密度脂蛋白(LDL-C)和补体4(C4)(P<0.05),而对血清中的TG、TC和GLU、IgA、IgM、IgG、补体3、TNF和IL-2无显著影响(P>0.05),Ⅰ组HDL-C显著高于Ⅱ、Ⅲ和Ⅳ组(P<0.05),Ⅰ组LDL-C显著高于Ⅲ和Ⅳ组(P<0.05),与Ⅱ组差异不显著(P>0.05),Ⅳ组C4显著高于Ⅱ和Ⅲ组(P<0.05),与Ⅰ组差异不显著(P>.05)。饲粮n-6/n-3 PUFA配比为41时,降低了肝体指数,动员了肌内脂肪和皮下脂肪中不饱和脂肪酸(UFA)含量,利于机体SFA的沉积,降低了血脂中高密度脂蛋白(HDL-C)和低密度脂蛋白(LDL-C)含量,保证了北极狐机体的健康。
关键词n-6/n-3    北极狐    体脂沉积    体脂肪酸    血液生化指标    
Effects of Dietary n-6/n-3 PUFA Ratio on the Body Fat Deposition, Body Fatty Acid Composition and Serum Biochemical Parameters in Male Arctic Foxes during the Winter Fur-growing Period
ZHONG Wei, ZHANG Ting, LUO Jing, WANG Zhuo, YUE Zhi-gang, LIU Xue-qing, LI Guang-yu     
Jilin Province Key Laboratory of Special Economic Animal Molecular Biology, Institute of Special Animal and Plant Sciences of Chinese Academy of Agricultural Sciences, Changchun 130112, China
Abstract: This experiment was conducted to study the effect of dietary n-6/n-3 PUFA ratio on body fat deposition, body fatty acid composition and serum biochemical parameters of male Arctic foxes during the winter fur-growing period. Forty-eight male Arctic foxes of 157-day-old with average body weight of(5 658±47) g were randomly divided into 4 groups with 12 replicates per group and 1 fox per replicate, and they were fed experimental diets containing n-6/n-3 PUFA ratio for 3, 18, 41, 136, respectively. The composition and proportion of oil were 12% fish oil and 2% soybean oil (Group Ⅰ), 9.38% corn oil and 4.62% soybean oil (Group Ⅱ), 12% corn oil and 2% soybean oil (Group Ⅲ), 1.5% fish oil and 12.5% corn oil (Group Ⅳ), respectively. The experiment was 7 days for adaption and 40 days for trial period. The results showed as follows: 1) Dietary n-6/n-3 PUFA ratio extremely significantly affected hepatic somatic index(P < 0.01), but no significant effect on hepatic fat content, liver fat percentage, subcutaneous fat weight and subcutaneous fat percentage(P > 0.05) during the winter fur-growing period. The hepatic somatic index in group Ⅳ was extremely significantly higher than that in group Ⅱ and Ⅲ (P > 0.01), while no significant difference between group Ⅰ and Ⅳ (P > 0.05). 2) Dietary n-6/n-3 PUFA ratio extremely significantly or significantly affected SFA, MUFA, PUFA, n-3 and n-6 contents in intramuscular fat (P < 0.01 or P < 0.05) in Arctic fox. SFA in intramuscular fat in group Ⅰ was significantly higher than that in group Ⅱ (P < 0.05), while there were no significant difference among group Ⅰ, Ⅲ and Ⅳ (P > 0.05). MUFA in intramuscular fat in group Ⅰ was significantly higher than that in group Ⅲ and Ⅳ (P < 0.05), while there was no significant difference between group Ⅰ and Ⅱ (P > 0.05).PUFA in intramuscular fat in group Ⅱ was extremely significantly higher than that in group Ⅰ and Ⅳ (P < 0.01), while there was no significant difference between group Ⅱ and Ⅲ (P > 0.05). n-3 in intramuscular fat in group Ⅰ and Ⅲ were extremely significantly higher than that in group Ⅱ and Ⅳ (P < 0.01). n-6 in intramuscular fat in group Ⅲ was extremely significantly higher than that in group Ⅰ and Ⅳ (P < 0.01), while there was no significant difference between group Ⅲ and Ⅱ (P > 0.05).Dietary n-6/n-3 PUFA ratio extremely significantly affected MUFA, PUFA, n-3 and n-6 contents in subcutaneous fat (P < 0.01), but no significant effect on SFA (P > 0.05). MUFA in subcutaneous fat in group Ⅰ was extremely significantly higher than that in group Ⅱ, Ⅲ and Ⅳ(P < 0.01). PUFA in subcutaneous fat in group Ⅱ and Ⅲ was extremely significantly higher than that in group Ⅰ and Ⅳ(P < 0.01). n-3 in subcutaneous fat in group Ⅰ and Ⅲ was extremely significantly higher than that in group Ⅱ and Ⅳ(P < 0.01). n-6 in subcutaneous fat in group Ⅱ was extremely significantly higher than that in group Ⅰ and Ⅳ(P < 0.01), while there was no significant difference between group Ⅱ and Ⅲ (P > 0.05). 3) Dietary n-6/n-3 PUFA ratio significantly affected the serum HDL-C, LDL-C and complement 4(P < 0.05), but no significant effect on serum TG, TC, GLU, IgA, IgM, IgG, complement 3, TNF and IL-2(P > 0.05). Serum HDL-C in group Ⅰ was significantly higher than that in group Ⅱ, Ⅲ and Ⅳ (P < 0.05). Serum LDL-C in group Ⅰ was significantly higher than that in group Ⅲ and Ⅳ(P < 0.05), while there was no significant difference between group Ⅰ and Ⅱ(P > 0.05).Serum C4 in group Ⅳ was significantly higher than that in group Ⅱ and Ⅲ(P < 0.05), while there was no significant difference between group Ⅳ and Ⅰ (P > 0.05). The ratio of n-6/n-3 PUFA is 41 (12% corn oil + 2% soybean oil), the hepatic somatic index is reduced, UFA in intramuscular fat and subcutaneous fat are mobilized, more SFA is deposed and serum lipid level is reduced, which make Arctic fox more healthy.
Key words: n-6/n-3     Arctic fox     body fat deposition     body fatty acid composition     serum biochemical parameters    

多不饱和脂肪酸(Polyunsaturated fatty acids,PUFA)与动物体脂沉积、机体免疫,以及心血管疾病都有一定的关联[1-3]。大量试验证实,毛皮动物体脂肪酸组成与饲粮脂肪酸组成存在一定的对应关系[4-6],而且不同组织中脂肪酸组成有差异[7]。喻礼怀[8]研究表明, 饲粮n-6/n-3 PUFA配比显著影响扬州鹅的体脂沉积和血脂代谢,适宜配比可以降低扬州鹅早期腹脂沉积,对血糖和血脂也有一定改善作用。研究表明,适宜n-6/n-3 PUFA配比能提高动物机体的免疫性能[9-10]。北极狐(Alopex lagopus),又称蓝狐,是世界珍贵的毛皮动物之一,属于食肉目犬科动物,原产于亚洲、欧洲、北美洲北部和接近北冰洋地带。北极狐在耐受脂肪方面与其他单胃动物存在不同[11],在脂肪酸分配与沉积、血脂代谢及免疫性能方面尚未见研究报道。

本试验旨在研究饲粮n-6/n-3多不饱和脂肪酸配比对冬毛期北极狐体脂沉积、体脂肪酸组成及血液生化指标的影响,以期为北极狐脂肪代谢规律研究提供基础数据。

1 材料与方法 1.1 试验动物、试验设计与饲养管理

本试验在中国农业科学院特产研究所毛皮动物试验基地完成。选用的北极狐是地产芬系北极狐,即引进的芬兰种狐经过多年改良所形成的地方品种。选取157日龄48只平均体重为(5 658±47) g的健康雄性北极狐,随机分成4组,每组设12个重复,每个重复1只北极狐。每组饲喂不同油脂配比的饲粮,每组饲粮除油脂组成和配比不同外,其他原料一致,Ⅰ组饲粮中添加12%鱼油和2%豆油,n-6/n-3为3;Ⅱ组饲粮中添加9.38%玉米油和4.62%豆油,n-6/n-3为18;Ⅲ组饲粮中添加12%玉米油和2%豆油,n-6/n-3为41;Ⅳ组饲粮中添加1.5%鱼油和12.5%玉米油,n-6/n-3为136。

试验动物单笼饲养。试验从2014年10月13日开始至2014年12月1日结束,预饲期7 d,正式试验期40 d,每天08:00和15:00各饲喂1次,自由饮水。

1.2 试验日粮

以膨化玉米、豆粕、玉米蛋白粉、干酒糟及其可溶物(DDGS)、鱼粉、肉粉、油等为主要原料,同时添加由矿物质元素、维生素等组成的营养性添加剂配制的试验饲粮;饲粮中脂肪酸需求量参照FEDIAF(EUROPEAN PET FOOD INDUSTRY FEDERATION,2011)[12],通过改变饲粮中的油脂配比来调配脂肪酸的配比,不同组别饲粮组成、营养水平及脂肪酸组成详见表 1表 2

表 1 饲粮组成及营养水平(风干基础) Table 1 Composition and nutrient levels of the diets (air-dry basis)
表 2 试验饲粮脂肪酸组成 Table 2 Fatty acid composition of experimental diets
1.3 样品采集

试验期末屠宰称体重,每组随机选取7只北极狐,后肢静脉采血5 mL,用于血液生化指标检测。之后注射5 mL的琥珀乙酰胆碱处死,分别取大腿内侧肌肉、皮下腹部脂肪各50 g用生理盐水冲洗掉血迹,放入自封袋,-20 ℃冰箱冷藏待测脂肪酸组成;分别测定肝、皮下脂肪的重量,肝采集的样品在65 ℃下烘干至恒重,测定初水分,用索氏提取法测定脂肪含量。

体脂沉积指标计算公式:

肝体指数(%)=肝鲜重/体重×100%;

肝脂率(%)=肝中脂肪重量/肝鲜重×100%;

皮脂率(%)=皮下脂肪重量/体重×100%。

1.4 测定指标及方法 1.4.1 饲料养分的测定

测定基础饲粮中干物质、粗蛋白质、粗脂肪、粗灰分、钙、磷含量。干物质含量采用105 ℃烘干法测定,参照GB/T 6435-2006;粗蛋白质含量采用凯氏定氮法测定,参照GB/T 6432-94;粗脂肪含量采用索氏抽提法测定,参照GB/T 6433-94;粗灰分含量采用550 ℃灼烧法测定,参照GB/T 6438-92;钙含量采用乙二胺四乙酸(EDTA)络合滴定法测定,参照GB/T 6436-92;磷含量采用钒钼酸铵比色法测定,参照GB/T6437-92;氨基酸采用全自动氨基酸分析仪(HITACHI,L-8900,日本)进行测定。

1.4.2 饲粮、肌肉和皮下脂肪脂肪酸的测定

脂肪酸前处理采用甲酯化方法,参照GB/T 21514-2008,测试采用外标法。脂肪酸测定采用气质联用仪(Agilent7890A-7000B),具体测定条件参考陈小燕等[13]的方法。

1.4.3 血液生化指标测定

血清中的血糖采用罗氏试剂盒己糖激酶法测试。甘油三酯采用酶法检测,胆固醇采用胆固醇氧化酶法检测,高密度脂蛋白胆固醇采用酶法检测,低密度脂蛋白胆固醇采用遮蔽法检测,血清中糖脂类生化指标的检测均通过罗氏试剂盒分析检测。血清中的免疫球蛋白IgA、IgG、IgM、补体3和补体4采用免疫透射比浊法测定,白介素-2和肿瘤坏死因子采用化学发光法测定,血清中免疫生化指标的检测均通过罗氏试剂盒检测。

1.5 数据整理与统计分析

试验数据采用EXCEL 2003进行整理,采用SPASS 9.13软件中GLM程序进行统计分析,多重比较采用Ducan氏法进行,其中P<0.01为差异极显著,P<0.05为差异显著,P>0.05为差异不显著,结果以“平均值±标准差”表示。

2 结果 2.1 饲粮n-6/n-3 PUFA配比对冬毛期北极狐体脂沉积的影响

表 3可知,饲粮n-6/n-3 PUFA配比极显著影响北极狐肝体指数(P<0.01),Ⅳ组极显著高于Ⅱ和Ⅲ组(P<0.01),与Ⅰ组差异不显著(P>0.05),Ⅰ、Ⅱ和Ⅲ组间差异不显著(P>0.05)。饲粮n-6/n-3 PUFA配比对北极狐肝脂肪含量、肝脂率、皮下脂肪重、皮脂率均无显著性影响(P>0.05)。

表 3 饲粮n-6/n-3 PUFA配比对冬毛期北极狐体脂沉积的影响 Table 3 Effects of dietary n-6/n-3 PUFA ratio on body fat deposition traits of Arctic fox during the winter fur-growing peroid
2.2 饲粮n-6/n-3 PUFA配比对冬毛期北极狐体脂肪酸组成的影响

表 4可知,饲粮n-6/n-3 PUFA配比显著影响肌内脂肪中SFA和MUFA(P<0.05),Ⅰ组SFA显著高于Ⅱ组(P<0.05),与Ⅲ和Ⅳ组差异不显著(P>0.05),Ⅱ、Ⅲ和Ⅳ组间差异不显著(P>0.05);Ⅰ组MUFA显著高于Ⅲ和Ⅳ组(P<0.05),与Ⅱ组差异不显著(P>0.05),Ⅱ、Ⅲ和Ⅳ组间差异不显著(P>0.05)。饲粮n-6/n-3 PUFA配比极显著影响肌内脂肪中PUFA、n-3 PUFA和n-6 PUFA含量(P<0.01),Ⅱ组PUFA极显著高于Ⅰ和Ⅳ组(P<0.01),与Ⅲ组差异不显著(P>0.05),Ⅲ和Ⅳ组极显著高于Ⅰ组(P<0.01);Ⅰ和Ⅲ组n-3 PUFA显著高于Ⅱ和Ⅳ组(P<0.01),Ⅰ和Ⅲ组间差异不显著(P>0.05),Ⅱ和Ⅳ组间差异不显著(P>0.05);Ⅲ组n-6 PUFA显著高于Ⅰ和Ⅳ组(P<0.01),与Ⅱ组差异不显著(P>0.05),Ⅱ组和Ⅳ组n-6极显著高于Ⅰ组(P<0.01),但两组间差异不显著(P>0.05)。

表 4 饲粮n-6/n-3 PUFA配比对北极狐肌内脂肪脂肪酸组成的影响(占总脂肪酸配比) Table 4 Effects of dietary n-6/n-3 PUFA ratio on fatty acid profiles in intramuscular fat of Arctic fox during the winter fur-growing period (proportion of total fatty acid)

表 5可知,饲粮n-6/n-3 PUFA配比极显著影响皮下脂肪中的MUFA和PUFA(P<0.01),Ⅰ组MUFA极显著高于Ⅱ、Ⅲ和Ⅳ组(P<0.01),Ⅱ、Ⅲ和Ⅳ组间差异不显著(P>0.05);Ⅱ和Ⅲ组PUFA极显著高于Ⅰ组和Ⅳ组(P<0.01),Ⅳ组极显著高于Ⅰ组(P<0.01),Ⅱ和Ⅲ组间差异不显著(P>0.05)。饲粮n-6/n-3 PUFA配比极显著影响皮下脂肪n-3和n-6 PUFA(P<0.01),Ⅰ和Ⅲ组皮下脂肪的n-3 PUFA极显著高于Ⅱ和Ⅳ组(P<0.01),Ⅰ和Ⅲ组间差异不显著(P>0.05),Ⅱ和Ⅳ组间差异不显著(P>0.05);Ⅱ组n-6极显著高于Ⅰ和Ⅳ组(P<0.01),与Ⅲ组差异不显著(P>0.05),Ⅲ组极显著高于Ⅰ组(P<0.01),与Ⅳ组差异不显著(P>0.05),Ⅳ组极显著高于Ⅰ组(P<0.01)。饲粮n-6/n-3 PUFA配比对皮下脂肪中SFA无显著性影响(P>0.05)。

表 5 饲粮n-6/n-3 PUFA配比对北极狐皮下脂肪脂肪酸组成的影响(占总脂肪酸配比) Table 5 Effects of dietary n-6/n-3 PUFA ratio on fatty acid profiles in subcutaneous fat of Arctic fox during the winter fur-growing period (proportion of total fatty acid)
2.3 饲粮n-6/n-3 PUFA配比对冬毛期北极狐血液生化指标的影响 2.3.1 饲粮n-6/n-3 PUFA配比对冬毛期北极狐血脂生化指标的影响

表 6可知,饲粮n-6/n-3 PUFA配比对血清中HDL-C和LDL-C影响显著(P<0.05),Ⅰ组HDL-C显著高于Ⅱ、Ⅲ和Ⅳ组(P<0.05),而Ⅱ、Ⅲ和Ⅳ组间差异不显著(P>0.05);Ⅰ组LDL-C显著高于Ⅲ和Ⅳ组(P<0.05),与Ⅱ组差异不显著(P>0.05),Ⅱ组与Ⅲ、Ⅳ组间无显著差异(P>0.05),Ⅲ和Ⅳ组无显著差异(P>0.05);饲粮n-6/n-3 PUFA配比对TG、TC和GLU无显著影响(P>0.05),但Ⅰ组TG、TC均略高于其他组。

表 6 饲粮n-6/n-3 PUFA配比对冬毛期北极狐血清中血脂指标的影响 Table 6 Effects of dietary n-6/n-3 PUFA ratio on serum lipid parameters of Arctic fox during the winter fur-growing period
2.3.2 饲粮n-6 /n-3 PUFA配比对冬毛期北极狐血液免疫生化指标的影响

表 7可知,饲粮n-6/n-3 PUFA配比对血清C4影响显著(P<0.05),Ⅳ组显著高于Ⅱ和Ⅲ组(P<0.05),与Ⅰ组差异不显著(P>0.05),Ⅰ、Ⅱ和Ⅲ组间差异不显著(P>0.05);饲粮n-6/n-3 PUFA配比对血清中IgA、IgM、IgG、补体3、TNF和IL-2均无显著影响(P>0.05)。

表 7 饲粮n-6/n-3 PUFA配比对冬毛期北极狐血清免疫指标的影响 Table 7 Effects of dietary n-6/n-3 PUFA ratio on serum immune parameters of Arctic fox during the winter fur-growing period
3 讨论 3.1 饲粮n-6/n-3 PUFA配比对冬毛期北极狐体脂沉积的影响

饲料中添加不同的脂类会影响动物对脂肪的消化吸收和利用,从而影响动物体脂的沉积速度和沉积量[14]。多数研究证明不同脂肪源对猪体脂沉积产生不同影响[15-16]。R.E.Newman等[17]和J.Luo等[18]分别报道,PUFA能降低鸡和鼠的体脂沉积,n-3 PUFA能调控脂类氧化从而降低鸡的体脂沉积。N.Tous等[19]研究表明,共轭亚油酸能降低体脂沉积,增加肝重量。耿业业等[20]研究报道,饲粮脂肪水平在12%~40%范围内,肝脂率和肝体指数受脂肪水平的影响不显著,而当脂肪水平增加到54%时,肝脂率和肝体指数高于其他各组。R.Takada等[21]发现,小鼠饲粮中添加PUFA能够通过抑制一些生脂酶的活性使脂肪合成减少,同时能提高脂肪酸氧化酶活性,促进脂肪降解,从而降低体脂沉积。研究表明,PUFA对脂肪合成酶和动物体脂沉积的影响程度受其不饱和程度及双键位置的影响[22],当第一个双键位于n-3时,对脂肪和脂肪酸合成酶的抑制作用比n-6强[23]。本试验结果显示,随饲粮n-6/n-3 PUFA配比增加,北极狐肝体指数呈先降低后升高趋势,说明高配比的n-6/n-3 PUFA影响了肝的质量,但其他体脂沉积指标未受影响,主要由于各组饲粮的脂肪水平一致,Ⅱ、Ⅲ和Ⅳ组的饲粮PUFA水平基本接近,Ⅰ组虽然与Ⅱ、Ⅲ和Ⅳ组相差较大,但其n-3含量要高于其他3组,这可能是导致各组北极狐体脂沉积无明显变化的主要原因,与上述文献报道基本一致。

3.2 饲粮n-6/n-3 PUFA配比对冬毛期北极狐体脂肪酸组成的影响

鱼体组织中脂肪酸组成在很大程度上受饲料中脂肪酸成分的影响,并在一定程度上能反映饲料中的脂肪酸组成[24]。R.E.Newman等[17]研究表明,日粮中n-3和n-6 PUFA调控动物机体脂类沉积和氧化,从而影响组织中的脂肪酸组成,相似的结果已在人和鼠上得到了证实[25-26]。M.Sobol等[27]研究表明,n-3 PUFA和n-6/n-3 PUFA配比调控猪机体脂肪酸的组成和沉积方式。本试验结果显示,北极狐肌内脂肪脂肪酸的组成变化趋势与饲粮脂肪酸含量直接相关,与上述文献报道一致,北极狐肌内脂肪中SFA、MUFA和PUFA含量分别是28.52%、42.5%和28.73%,饲粮中SFA、MUFA和PUFA含量分别是8.01%、29.96%和62.04%,与饲粮脂肪酸相比,北极狐肌内脂肪中SFA、MUFA含量均有增加,而PUFA含量减少,表明北极狐从饲粮中摄入的PUFA,在机体内发生了脂肪酸的转化和分配,导致肌内脂肪酸的沉积方式差异。

张婷等[28]研究报道,银狐皮下脂肪SFA、MUFA和PUFA不受饲粮中的脂肪水平影响,分别是25.65%、42.97%和31.34%。本试验结果显示,北极狐皮下脂肪SFA未受饲粮n-6/n-3 PUFA配比影响,而MUFA和PUFA变化趋势与饲粮中脂肪酸组成呈正相关,SFA、MUFA和PUFA的比例分别是22.44%、41.20%和35.66%,与银狐皮下脂肪脂肪酸组成相近,饲粮中SFA、MUFA和PUFA含量分别是8.01%、29.96%和62.04%,相较饲粮,SFA和MUFA分别上升,而PUFA下降,说明北极狐为抵御冬季严寒,要消耗能量维持自身代谢,其皮下的PUFA相对SFA更利于氧化分解以供其能量代谢的需求[29]

3.3 饲粮n-6/n-3 PUFA配比对冬毛期北极狐血液生化指标的影响 3.3.1 饲粮n-6/n-3 PUFA配比对冬毛期北极狐血脂生化指标的影响

目前心脑血管疾病已成为引起人类死亡的主要疾病之一[30],研究表明,提高机体血脂水平是增加心脑血管疾病的主要原因之一[31-32],高脂血症就是增加了血液中的甘油三酯浓度,升高了LDL浓度,降低了HDL浓度[33]。在人和动物上已研究证明n-3 PUFA能有效降低血浆中甘油三酯浓度[34-36]。J.J.A.Ferguson等[37]研究证明了老年人长期服用n-3 PUFA会降低其血脂水平,减少患心脑血管疾病的风险。R.J.Nicolosi等[38]研究报道,日粮添加PUFA同添加SFA相比,不管饲粮中是否存在胆固醇均显著降低大鼠血浆中LDL和HDL中胆固醇的含量。本试验结果显示,随饲粮中n-6/n-3 PUFA配比升高,北极狐血清中LDL和HDL的含量有降低趋势,与文献报道相一致。本试验各组饲粮的脂肪水平和能量含量均一致,随饲粮中n-6/n-3,PUFA配比升高,n-6含量呈增加趋势,n-3含量呈逐渐降低趋势,n-6/n-3 PUFA配比未对TG、TC和GLU产生影响与S.P.S.Lee等[39]研究报道一致,高配比和低配比n-6/n-3 PUFA未对血脂指标产生影响,适宜配比的n-6/n-3 PUFA及长期饲喂能降低血脂指标,并有降低患心脑血管疾病的风险。Ⅰ组的TG和TC略高于其他组,可能由于该组饲粮所含SFA含量相对较高,引起北极狐血脂指标较高的变化。

3.3.2 饲粮n-6/n-3 PUFA配比对冬毛期北极狐血液免疫指标的影响

血液免疫指标是指机体的免疫性能水平,能间接反映动物机体健康状况。大量研究显示,鱼油中含有的n-3 PUFA对动物机体的免疫性能具有促进作用[40-41],n-6 PUFA则在体内代谢合成类二十烷酸,具有较强的促血管收缩、血小板聚集和细胞趋化等作用,进而产生一定的免疫抑制作用[42]。研究表明,不同n-6/n-3配比对AA肉鸡免疫功能产生显著影响[9-10]。本试验随饲粮n-6/n-3 PUFA配比升高,n-3含量逐渐降低,n-6含量逐渐升高,由于n-3和n-6 PUFA在脱饱和酶上存在竞争,在影响机体免疫机制方面发生竞争效应,可能是导致北极狐血液免疫指标未发生变化的主要原因。本试验结果显示,当饲粮n-6/n-3 PUFA为136和3时,血清C4水平相对较高,说明Ⅳ组(相对高含量的n-6与相对低含量的n-3) 具有的抑制作用与Ⅰ组(相对低含量的n-6与相对高含量的n-3) 对血清C4发挥的作用相近,具体机理还有待于进一步研究。

4 结论

从本试验结果综合分析,当饲粮n-6/n-3 PUFA配比为41时(即饲喂12%玉米油与2%豆油混合油脂),降低了肝体指数,动员了肌内脂肪和皮下脂肪中不饱和脂肪酸(UFA)含量,更有利于氧化分解满足北极狐能量的需求,降低了血脂中高密度脂蛋白(HDL-C)和低密度脂蛋白(LDL-C)含量,保证了北极狐的健康。

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