动物营养学报    2021, Vol. 33 Issue (8): 4478-4490    PDF    
牛至精油对平凉红牛生长性能、血液生理指标、肉品质及肌肉脂肪酸的影响
李佳龙1 , 张瑞1 , 吴建平2 , 张科3 , 豆思远4 , 曾金焱5 , 刘婷1 , 宫旭胤2,6 , 王建福1 , 雷赵民1     
1. 甘肃农业大学动物科学技术学院, 兰州 730070;
2. 甘肃省农业科学院, 兰州 730070;
3. 西北农林科技大学动物科技学院, 杨凌 712100;
4. 甘肃省动物疫病预防控制中心, 兰州 730046;
5. 甘肃农业职业技术学院, 兰州 730020;
6. 甘肃省农业科学院畜草与绿色农业研究所, 兰州 730070
摘要: 本试验旨在研究牛至精油对平凉红牛生长性能、血液生理指标、肉品质及肌肉脂肪酸的影响。选取12月龄左右、体重为(270.74±26.24)kg的健康平凉红牛(阉牛)9头,随机分为3组(每组3头),对照组(CON组)饲喂基础饲粮,试验组分别在基础饲粮中添加10(L组)、20 g/(d·头)(H组)牛至精油。饲喂584 d(预试期14 d,正试期570 d)后屠宰。结果表明:1)试验组的终末体重、平均日增重、宰前活重、净肉重、眼肌面积显著高于CON组(P < 0.05),L组的皮下脂肪厚度和H组的胴体胸深显著高于CON组(P < 0.05),且L组和H组的平均日增重较CON组分别提高了16.07%、21.43%。2)试验组的白细胞计数、淋巴细胞计数、单核细胞计数、粒细胞计数、血红蛋白浓度显著高于CON组(P < 0.05),L组的血小板计数、血小板压积显著高于CON组(P < 0.05)。3)试验组的肌肉pH45 min、pH24 h、剪切力显著低于CON组(P < 0.05);L组的大理石花纹评分和H组的熟肉率显著高于CON组(P < 0.05),H组的蒸煮损失显著低于CON组(P < 0.05)。4)对于肌肉脂肪酸组成和含量,试验组饱和脂肪酸含量显著低于CON组(P < 0.05),不饱和脂肪酸含量显著高于CON组(P < 0.05);CON组和L组的C8:0、C13:0、C20:2含量显著低于H组(P < 0.05),试验组的C18:0和C18:1n9c含量显著高于CON组(P < 0.05);n-3多不饱和脂肪酸、n-6多不饱和脂肪酸、多不饱和脂肪酸/饱和脂肪酸值各组间差异均不显著(P>0.05),但L组和H组的多不饱和脂肪酸/饱和脂肪酸值较CON组分别提高了16.67%和33.33%。综上所述,饲粮中添加牛至精油可以提高平凉红牛的生长性能及产肉量,改善牛肉品质,改变肌肉脂肪酸的组成和含量,提升机体的健康状态。
关键词: 牛至精油    平凉红牛    生长性能    血液生理指标    肉品质    肌肉脂肪酸    
Effects of Oregano Essential Oil on Growth Performance, Blood Physiological Indices, Meat Quality and Muscle Fatty Acids of Pingliang Red Cattle
LI Jialong1 , ZHANG Rui1 , WU Jianping2 , ZAHNG Ke3 , DOU Siyuan4 , ZENG Jinyan5 , LIU Ting1 , GONG Xuyin2,6 , WANG Jianfu1 , LEI Zhaomin1     
1. College of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070, China;
2. Gansu Academy of Agricultural Sciences, Lanzhou 730070, China;
3. College of Animal Science and Technology, Northwest A&F University, Yangling 712100, China;
4. Animal Disease Prevention and Control Centre of Gansu Province, Lanzhou 730046, China;
5. Gansu Agricultural Vocational and Technical College, Lanzhou 730020, China;
6. Animal Husbandry, Pasture and Green Agriculture Institute, Gansu Academy of Agricultural Science, Lanzhou 730070, China
Abstract: This experiment was conducted to study the effects of oregano essential oil on growth performance, blood physiological indices, meat quality and muscle fatty acids of Pingliang red cattle. A total of 9 healthy Pingliang red cattle (steers) about 12 months of age and weighing (270.74±26.24) kg were randomly divided into 3 groups (3 heads per group). The cattle in control group (CON group) were fed a basal diet, and the cattle in experimental groups were fed the basal diet supplemented with 10 (L group) and 20 g/(d·head) (H group) oregano essential oil, respectively. The animals were fed for 584 days (pre-trial period was 14 days, and trial period was 570 days). The results showed as follows: 1) the final weight and average daily gain (ADG), live weight before slaughter, meat weight and eye muscle area of the experimental groups were significantly higher than those of CON group (P < 0.05), the thickness of subcutaneous fat of L group and the carcass chest depth of H group were significantly higher than those of CON group (P < 0.05), the ADG of L group and H group was 16.07% and 21.43% higher than that of CON group. 2) The white blood cell (WBC) count, lymphocyte (LYM) count, monocyte (MON) count, granulocyte (GRA) count and hemoglobin (HGB) concentration of experimental groups were significantly higher than those of CON group (P < 0.05), and the platelet (PLT) count and plateletcrit (PCT) of L group were significantly higher than those of CON group (P < 0.05). 3) The muscle pH45 min, pH24 h and shear force were significantly lower than those of CON group (P < 0.05); the marbling score of L group and the cooked meat rate of H group were significantly higher than those of CON group (P < 0.05), and the cooking loss of H group was significantly lower than that of CON group (P < 0.05). 4) For the composition and content of fatty acids in muscle, the content of saturated fatty acid (SFA) of experimental groups was significantly lower than that of CON group (P < 0.05), and the content of unsaturated fatty acid (UFA) was significantly higher than that of CON group (P < 0.05); the contents of C8:0, C13:0 and C20:2 of CON group and L group were significantly lower than those of H group (P < 0.05), and the contents of C18:0 and C18:1n9c of experimental groups were significantly higher than those of CON group (P < 0.05); there were no significant differences in n-3 polyunsaturated fatty acid (PUFA), n-6PUFA, PUFA/SFA (P/S) value among groups (P>0.05), but the P/S value of L group and H group were 16.67% and 33.33% higher than those of CON group. In conclusion, adding oregano essential oil into the diet can improve the growth performance and meat production of Pingliang red cattle, also can improve the quality of beef, change the composition and contents of fatty acids in muscle, and improve the health of the body.
Key words: oregano essential oil    Pingliang red cattle    growth performance    blood physiological indices    meat quality    muscle fatty acids    

兽用抗生素的使用可追溯到20世纪50年代,因其可以促进动物生长[1]、提高畜禽生产效率和维持畜禽健康,被认为是动物健康的保障,同时为养殖业带来了巨大的经济效益。但是随着研究的深入,使用抗生素产生的一系列弊端逐渐暴露,尤其是药物残留问题严重威胁到了动物和人类健康以及环境安全。研究发现,在饲粮中长期添加低剂量抗生素更易使动物机体产生具有耐药性的超级细菌[2];同时,抗生素滥用将导致抗生素抗性基因的富集,这些抗性基因最终转移到人类致病菌中并危害人类健康[3]。因此,寻找健康有效的抗生素替代品越来越受到人们的重视。植物精油(essential oil)是以植物为原料提取的有特征气味的植物源次生代谢产物,用作饲料添加剂时,可以通过调节肠道消化酶活性来促进营养物质的消化吸收[4],进而提高饲料效率;同时,可以通过抑制有害微生物的生长,刺激有益微生物繁殖来改善肠道微生态环境[5]。Khattak等[6]研究表明,饲粮中添加植物精油可明显改善肉仔鸡的生长性能。Herawati等[7]研究表明,在饲粮中添加薰衣草精油可以促进肉鸡生长,提高饲料转化率和机体抗炎能力。牛至精油是从植物牛至中通过化学工艺萃取出的次级代谢物,主要成分是香芹酚和百里酚,具有芳香味以及广谱的抗菌和抗氧化活性,对革兰氏阳性菌与阴性菌和真菌均有抑制作用[8],能够促进动物生长,提高动物机体免疫力,无耐药性,是一种天然、环保、安全的抗生素替代品,也是我国农业农村部批准使用的饲料添加剂[9-10]。有研究发现牛至精油可抑制全混合日粮中霉菌、细菌和大肠杆菌生长,保证饲粮的新鲜度,从而提高动物的采食量[11]。徐方华[12]研究表明,牛至精油可通过调节反刍动物瘤胃微生物发酵来改变胃肠道微生物组成,促进对营养物质的消化吸收。本课题组前期研究发现,牛至精油可以促进河西绒山羊、肉羊和荷斯坦公牛的生长,并改善肉品质,提高机体的免疫能力及疾病预防能力[13-18]。平凉红牛是中国黄牛品种的一个类群,是平凉当地黄牛与利木赞、南德温经过多年杂交选育改良形成的,具有耐粗饲、适应性强、脂肪沉积率高、大理石花纹明显等特点,是优质高档肉牛新类群。在全球人口增加及经济发展的驱动下,人们对牛肉尤其是优质高档牛肉的需求量逐年增加,生产能够满足人们需求的优质高档牛肉是畜牧生产者追求的目标。因此,本试验拟通过在饲粮中添加牛至精油,研究其对平凉红牛生长性能、血液生理指标、肉品质及肌肉脂肪酸的影响,以此为牛至精油作为抗生素的替代品提供理论依据,并为其在生产中的应用提供一定的参考。

1 材料与方法 1.1 试验材料

本试验所用牛至精油采用超临界萃取法进行制备,并将提取物超微化处理,呈暗绿色粉末状,纯度为1.3%,载体主要为碳酸硅、碳酸钙、硅藻土等;饲粮及试验动物均由甘肃省平凉红牛繁育中心提供。

1.2 试验设计

选取12月龄左右、体重为(270.74±26.24) kg的健康平凉红牛(阉牛)9头,随机分为3组,每组3头。对照组(CON组)饲喂基础饲粮,试验组分别在基础饲粮中添加10(L组)、20 g/(d·头)(H组)牛至精油。试验期为584 d,其中预试期14 d,正试期570 d,每30 d为1个阶段,共19个阶段(Ⅰ~Ⅺ Ⅹ),每30 d早上空腹称重,根据称重记录及NRC(2003)肉牛营养标准按阶段设计全价配合饲料,各阶段基础饲粮组成及营养水平如表 1所示。试验采用全混合日粮(TMR)模式饲喂,于07:00、15:00各饲喂1次,自由采食和饮水,饲养试验开始前对牛舍进行全面消毒,所有参试牛进行常规检查,体内驱虫、免疫并编号。

表 1 基础饲粮组成及营养水平(干物质基础) Table 1 Composition and nutrient levels of basal diets (DM basis)  
1.3 测定指标与方法 1.3.1 生长性能

正试期第1天和试验结束第2天早上对试验牛空腹称重1次,记录数据,并计算每头牛的平均日增重(ADG)。

体尺测定:参照昝林森[19]所编写《牛生产学》中关于肉牛体尺测量的方法于每次称重时对各组试验牛的体高、体直长、体斜长进行测量。

体高:自鬓甲最高点到地面的垂直高度。

体直长:从肩胛前缘(肱骨突)至同侧坐骨结节后缘间的水平距离。

体斜长:从肩胛前缘(肱骨突)到同侧坐骨结节后缘间的距离。

1.3.2 屠宰性能和胴体性状

饲养试验结束后,试验牛全部进行屠宰,屠宰前禁食24 h、禁水8 h,参照昝林森[19]所编写《牛生产学》中“肉牛屠宰实验”的方法测定屠宰性能和胴体性状,屠宰性能包括每头牛的宰前活重、净肉重、屠宰率、净肉率、胴体产肉率、肉骨比。试验牛屠宰后分为左右两半胴体,选取每头试验牛左半侧胴体进行胴体性状测定,包括胴体长、胴体深、胴体胸深、背膘厚度、皮下脂肪厚度和眼肌面积。

1.3.3 血液生理指标

饲喂试验结束后,禁食12 h后,对所有试验牛颈静脉采血5 mL,肝素钠抗凝保存,24 h内测定血液生理指标。血液生理指标送至平凉市奥斯咔动物医院使用迈瑞BC-1800三分类血球仪测定。

1.3.4 肉品质

肉品质测定参考刘婷等[20]的方法。试验牛屠宰后,在每头试验牛左半侧胴体选取背最长肌6 kg,测定色泽、pH、滴水损失、蒸煮损失、失水率、嫩度和大理石花纹评分;另选取腰大肌500 g,测定熟肉率。

大理石花纹评分:按照美国牛肉大理石花纹等级图谱分制,从a~f分别为大理石花纹丰富、较丰富、适量、较少、少、微量或无,数据分析时定义为a=6、b=5、c=4、d=3、e=2、f=1。

1.3.5 肌肉脂肪酸组成和含量

试验牛屠宰后,取左半侧胴体背最长肌50 g,用铝箔袋真空包装、编号,-20 ℃保存,用于脂肪酸组成的测定。甲酯化处理参考Liu等[21]的方法。采用气相色谱-串联质谱(GC-MS)分析仪测定脂肪酸组成和含量。

1.3.5.1 色谱条件

色谱柱:安捷伦DB-23(30 m×0.25 mm×0.25 μm),载气:高纯氦气(He),升温条件:初温50 ℃,保持4 min,以10 ℃/min升温至150 ℃,保持3 min;再以4 ℃/min升温至230 ℃,保持5 min。进样口温度:260 ℃,分流比:50 ∶ 1。

1.3.5.2 质谱条件

传输带温度:230 ℃,离子源温度:150 ℃,电离方式:电轰击电离(EI),电离电压:70 eV,扫描方式为全扫描,质荷比(m/z)扫描范围:35~550。

1.4 数据统计与分析

试验数据经Excel 2010初步整理后,利用SPSS 19.0软件的单因素方差分析(one-way ANOVA)模型进行分析,对有显著差异(P < 0.05)的数据采用Duncan氏法进行多重比较,结果用“平均值±标准差”表示。

2 结果与分析 2.1 生长性能

表 2可知,初始体重各组间无显著差异(P>0.05);L组和H组的终末体重和平均日增重较CON组分别提高了6.51%、8.78%和16.07%、21.43%,且具有显著差异(P < 0.05),同时体尺指标(体高、体直长、体斜长)也显著高于CON组(P < 0.05)。

表 2 牛至精油对平凉红牛生长性能的影响 Table 2 Effects of oregano essential oil on growth performance of Pingliang red cattle
2.2 屠宰性能和胴体性状

表 3可知,L组和H组的宰前活重、净肉重显著高于CON组(P < 0.05);屠宰率、净肉率、胴体产肉率、肉骨比各组间均没有显著差异(P>0.05),屠宰率均在68%左右,净肉率均在52%左右,胴体产肉率均在77%左右,但L组和H组在数值上均高于CON组;L组的皮下脂肪厚度、眼肌面积显著高于CON组(P < 0.05);H组的胴体胸深、眼肌面积显著高于CON组(P < 0.05);胴体长、胴体深、背膘厚度各组间均没有显著差异(P>0.05)。

表 3 牛至精油对平凉红牛屠宰性能和胴体性状的影响 Table 3 Effects of oregano essential oil on slaughter performance and carcass traits of Pingliang red cattle
2.3 血液生理指标

表 4可知,L组和H组的白细胞计数、淋巴细胞计数、单核细胞计数、粒细胞计数、血红蛋白浓度显著高于CON组(P < 0.05),L组的血小板计数、血小板压积显著高于CON组(P < 0.05),其他血液生理指标各组间差异不显著(P>0.05)。

表 4 牛至精油对平凉红牛血液生理指标的影响 Table 4 Effects of oregano essential oil on blood physiological indices of Pingliang red cattle
2.4 肉品质

表 5可知,L组和H组pH45 min和pH24 h均显著低于CON组(P < 0.05),L组和H组的剪切力显著低于CON组(P < 0.05),H组的蒸煮损失显著低于CON组(P < 0.05),L组的大理石花纹评分显著高于CON组(P < 0.05),H组的熟肉率显著高于CON组(P < 0.05),L组和H组的亮度、红度值均高于CON组,而黄度值、失水率、滴水损失均低于CON组,但差异不显著(P>0.05)。

表 5 牛至精油对平凉红牛肉品质的影响 Table 5 Effects of oregano essential oil on meat quality of Pingliang red cattle
2.5 肌肉脂肪酸组成和含量

表 6可知,利用气相色谱-串联质谱分析仪对肌肉样品中的脂肪酸组成及含量进行检测分析,共检测出33种脂肪酸,其中饱和脂肪酸(saturated fatty acid, SFA)15种,单不饱和脂肪酸(monounsaturated fatty acid, MUFA)9种,多不饱和脂肪酸(polyunsaturated fatty acid, PUFA)9种。33种脂肪酸中,C14 ∶ 0、C16 ∶ 0、C18 ∶ 0、C14 ∶ 1、C16 ∶ 1、C18 ∶ 1n9c、C18 ∶ 2n6c含量均高于1%,其中以C18 ∶ 1n9c含量最高,各组均在45%左右,C16 ∶ 0含量次之,各组均在25%左右,C18 ∶ 0含量再次之,各组均在13%左右。L组和H组的SFA含量显著低于CON组(P < 0.05);L组和H组的饱和脂肪酸(UFA)含量显著高于CON组(P < 0.05);MUFA和PUFA含量各组间差异均不显著(P>0.05),但L组和H组在数值上均高于CON组。SFA中,CON组和L组的C8 ∶ 0、C13 ∶ 0含量显著低于H组(P < 0.05),L组和H组的C18 ∶ 0含量显著高于CON组(P < 0.05),L组和H组的C14 ∶ 0和C16 ∶ 0含量均低于CON组,但差异不显著(P>0.05);MUFA中,L组和H组的C18 ∶ ln9c含量显著高于CON组(P < 0.05);PUFA中,CON组和L组的C20 ∶ 2含量显著低于H组(P < 0.05),L组和H组的C18 ∶ 2n6c含量均高于CON组,但差异不显著(P>0.05)。各组间n-3 PUFA、n-6 PUFA含量与PUFA/SFA值差异均不显著(P>0.05),但L组和H组的PUFA/SFA值较CON组分别提高16.67%、33.33%。

表 6 牛至精油对平凉红牛肌肉脂肪酸组成及含量的影响 Table 6 Effects of oregano essential oil on composition and contents of fatty acids in muscle of Pingliang red cattle
3 讨论 3.1 牛至精油对平凉红牛生长性能、屠宰性能和胴体性状的影响

牛至精油的主要成分是酚类物质,具有芳香气味,能够刺激畜禽食欲,增加采食量[22];其抗菌活性能够抑制饲粮中病原微生物的增殖,可长时间保持饲粮的新鲜度,增加适口性[11];同时,牛至精油可增加胃肠道上皮细胞分化与增殖,维持肠道屏障完整性,也可通过调节胃肠道发酵来改变微生物组成,促进营养物质的消化吸收,进而促进畜禽生长及提高饲料利用率[23-24]。姚喜喜等[25]研究表明,全混合日粮中添加牛至精油能够显著提高泌乳期荷斯坦奶牛的干物质采食量和产奶量。孔繁云等[26]的饲养试验(90 d)表明,饲粮中添加牛至精油可显著提高绵羊的平均日增重。本研究结果显示,L组和H组的平均日增重、体高、体直长、体斜长显著高于CON组,这与上述研究结果一致,说明牛至精油提高了平凉红牛的生长性能。

屠宰性能直接反映出动物的生长性能,是评价畜禽饲养管理水平和屠宰加工效益的重要依据;胴体性状是评价肉牛育肥性能的重要指标,是动物经济价值的直观表现。其中,宰前活重、屠宰率、净肉率和肉骨比是衡量动物产肉性能的重要指标,背膘厚度、皮下脂肪厚度、眼肌面积可以反映肉牛的肥育效果。本研究中,L组和H组的宰前活重、净肉重均显著高于CON组,屠宰率、净肉率、胴体产肉率、肉骨比较CON组均有所提高,L组的皮下脂肪厚度、眼肌面积显著高于CON组,H组的胴体胸深、眼肌面积显著高于CON组。这与王雅静[27]和白云鹏等[28]的研究结果一致,说明饲粮中添加牛至精油可以提高平凉红牛的屠宰性能和胴体性状,这与生长性能的变化趋势相一致。

3.2 牛至精油对平凉红牛血液生理指标的影响

血液生理指标是反映机体生理机能及代谢状况的重要指标,血液通过循环系统与全身各组织器官相连,参与机体呼吸、营养和氧气运输、防御病毒侵袭、调节酸碱平衡等各项生理活动,机体的生理病理变化都能在血液的细胞成分和可溶成分中体现[29]。白细胞具有参与吞噬、产生抗体、细胞免疫、传递免疫信息等功能[30];在机体的免疫应答过程中,淋巴细胞是发挥主要作用的免疫细胞,反映机体免疫功能水平的高低;单核细胞和粒细胞具有趋化、吞噬和消化作用,参与机体的炎症反应和免疫防御机制;血红蛋白是动物血液运输氧气的直接载体,它能通过红细胞和血红蛋白的共同作用,反映机体运动能力、呼吸及营养状况、环境适应性和肉质。本试验中,L组和H组的白细胞计数、淋巴细胞计数、单核细胞计数、粒细胞计数、血红蛋白浓度显著高于CON组。这与王娟[31]在山羊上的研究结果一致。柏妍等[32]研究表明,饲粮中添加牛至精油能够提高犊牛的免疫力和抗氧化能力。上述结果说明牛至精油可以增强机体免疫功能,提高机体运输氧气、代谢产物的能力,增强机体代谢,最终促进机体生长,维持机体健康。

3.3 牛至精油对平凉红牛肉品质和肌肉脂肪酸的影响

肉品质是一个综合性状,包括一系列的评定指标和判断标准,其中肌肉红度值主要由肌红蛋白的不同变化形式决定,是影响消费者感官评价的第1道门槛[33]。饲喂牛至精油后,血液中肌红蛋白浓度显著提高,增加了运氧能力,使肌肉呈现更加鲜艳的红色,亮度值和黄度值则与肌肉脂肪含量相关,本研究中L组大理石花纹评分显著高于CON组。pH主要反映宰后胴体的肌糖原酵解速率,与肉的嫩度、色泽等有一定关系[34],宰后一般表现为先下降后升高的趋势,本研究中pH45 min和pH24 h均表现为L组和H组显著低于CON组,说明牛至精油加速了宰后24 h内肌糖原酵解速率。剪切力是评定肉的嫩度的重要口感指标,与肌肉pH显著相关,饲喂牛至精油后显著降低了肌肉剪切力,这与pH的变化相一致,说明牛至精油可以通过改变肌肉糖原酵解来改善肉的嫩度。滴水损失、蒸煮损失、失水率都与肉的系水力能力相关,是反映肉品多汁性的重要指标,同时影响肉的嫩度和营养价值[35-36];熟肉率指胴体肉质烹饪时的损失程度,熟肉率越高则表示肉品质越好[37]。本试验中,L组和H组的失水率、滴水损失低于CON组,但差异不显著,H组的蒸煮损失显著低于CON组,熟肉率显著高于CON组,说明牛至精油可以减少牛肉的汁液损失,提高肉品质。上述研究结果与白云鹏等[28]的研究结果相似。

肌肉中的脂肪酸不仅是风味物质形成的前体[38-39],其中的n-3 PUFA和n-6 PUFA更是具有抗癌、降脂、预防心血管疾病等功能,被称为功能性脂肪酸,对人体健康起着重要作用[40-42]。反刍动物肌肉脂肪含量和脂肪酸组成直接影响其嫩度、风味等食用品质和贮藏性能[43]。大量研究发现膳食中SFA占总脂肪酸的比例与心血管疾病及直肠癌、前列腺癌、乳腺癌的发病率之间有很强的相关性[44]。UFA是肉品香味的前体物,也是人体重要的营养物质。其中MUFA具有保护心脏、降血糖、调节血脂、防止记忆力下降等生理功能[45],PUFA有助于防治心脑血管疾病, 能够降低血脂、抑制血小板聚集和抗自身免疫反应,并可促进机体的生长发育[46]。本研究中,饲喂牛至精油后,L组和H组的SFA含量显著低于CON组,较CON组分别降低了2.21%和2.49%,L组和H组的UFA含量显著高于CON组,较CON组分别提高了2.89%和2.22%,牛至精油对MUFA和PUFA含量没有显著影响,但L组和H组的MUFA和PUFA含量在数值上均高于CON组;PUFA/SFA值是衡量肉品营养的一个重要指标,L组和H组的PUFA/SFA值较CON组分别提高了16.67%、33.33%。刘立山等[47]对荷斯坦奶公牛的研究表明,牛至精油可以使牛肉中SFA含量降低,UFA含量升高,PUFA/SFA值升高,这与本研究结果相似。C14 ∶ 0、C16 ∶ 0和C18 ∶ 0是主要的SFA,其中C14 ∶ 0和C16 ∶ 0含量与血液中胆固醇含量呈显著正相关,而C18 ∶ 0含量不能升高血液中胆固醇含量[48-49]。本研究中,饲喂牛至精油对C14 ∶ 0和C16 ∶ 0含量没有显著影响,但L组和H组的C14 ∶ 0和C16 ∶ 0含量均低于CON组,其中L组和H组C14 ∶ 0含量较CON组分别降低了7.39%和27.09%,C16 ∶ 0含量较CON组分别降低了6.01%和3.87%,而L组和H组的C18 ∶ 0含量显著高于CON组,较CON组分别提高了6.48%和2.11%。C18 ∶ 1n9c能够降低血液中脂质、胆固醇及低密度脂蛋白胆固醇(LDL-C)含量,是良性MUFA之一[50],本研究中,饲喂牛至精油后C18 ∶ 1n9c含量显著升高,其中L组和H组较CON组分别提高了2.62%和3.91%。上述结果与刘婷等[20]在高山细毛羊上研究结果相似。C18 ∶ 2n6c是主要的n-6 PUFA,是人体必需脂肪酸,具有明显降低胆固醇的作用。本研究中,饲喂牛至精油对C18 ∶ 2n6c含量没有显著影响,但L组和H组的C18 ∶ 2n6c含量均高于CON组。夏广军等[51]对延边黄牛的研究表明,混合植物油可以使牛肉中C18 ∶ 2n6c含量显著提高;另有研究表明,通过控制饲粮脂肪酸组成可以使长链PUFA在动物体组织的储存最大化[46]。通过以上结论可推断牛至精油有改善肌肉脂肪酸含量的潜力,其原因可能是牛至精油可以改善牛瘤胃的菌群环境,抑制有害菌的数量,提高肠道对饲粮中营养物质的消化吸收能力,从而从饲粮中获取更多的脂肪酸用于机体的代谢,牛至精油对于肌肉脂肪酸的调控机制还有待进一步深入研究。

4 结论

饲粮中添加牛至精油促进了平凉红牛增重,提高了屠宰性能和胴体性状,提升了机体的免疫性能,同时改善了牛肉的嫩度和多汁性,增加了肌内脂肪的沉积量,提高了肌肉中利于人体健康的UFA的含量。综上所述,牛至精油可以作为替抗产品用于生长育肥牛生产。

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