引用本文
徐静, 杨书展, 胡边文, 张晓萌, 牛文晓, 闫安倩, 曾丹, 周荣艳, 王德贺, 陈一凡, 陈辉. 大蒜精油对产蛋后期蛋鸡生产性能及鸡肉风味物质的影响[J]. 动物营养学报, 2020, 32(1): 199-205.
XU Jing, YANG Shuzhan, HU Bianwen, ZHANG Xiaomeng, NIU Wenxiao, YAN Anqian, ZENG Dan, ZHOU Rongyan, WANG Dehe, CHEN Yifan, CHEN Hui. Effects of Garlic Essential Oil on Performance and Chicken Flavor Substance of Laying Hens during Later Period of Laying[J]. Chinese Journal of Animal Nutrition, 2020, 32(1): 199-205.
大蒜精油对产蛋后期蛋鸡生产性能及鸡肉风味物质的影响
徐静1
,
杨书展2
,
胡边文3
,
张晓萌1
,
牛文晓1
,
闫安倩1
,
曾丹4
,
周荣艳1
,
王德贺1
,
陈一凡1
,
陈辉1
1. 河北农业大学动物科技学院, 保定 071001;
2. 威县德青源农业科技有限公司, 邢台 054000;
3. 南昌市万阳生物科技有限公司, 南昌 330096;
4. 华裕农业科技有限公司, 邯郸 057150
收稿日期: 2019-06-26
基金项目: 国家蛋鸡产业技术体系(CARS-40-K20);保定市科技计划项目(18ZN015)
摘要: 本试验旨在研究饮水中添加大蒜精油对产蛋后期蛋鸡生产性能及鸡肉风味物质的影响。试验选用70周龄健康状况良好、生产性能相近的海兰灰蛋鸡512只,随机分为4组,每组8个重复,每个重复16只鸡。对照组饲喂基础饲粮,试验组在基础饲粮的基础上分别在饮水中添加0.2、0.4和0.6 mL/L的大蒜精油。试验预试期7 d,正试期56 d。结果表明:与对照组相比,0.2和0.4 mL/L大蒜精油添加组蛋鸡平均日采食量极显著降低(P < 0.01),料蛋比显著降低(P < 0.05),蛋白高度和哈氏单位极显著升高(P < 0.01);0.4 mL/L大蒜精油添加组蛋鸡鸡肉中甜味氨基酸中的丙氨酸、丝氨酸、甘氨酸和脯氨酸含量升高(P>0.05),酸味氨基酸中的谷氨酸含量升高(P>0.05),苦味氨基酸中的酪氨酸、异亮氨酸、精氨酸、亮氨酸、赖氨酸、组氨酸和缬氨酸含量下降(P>0.05),硬脂酸和亚麻酸含量下降(P>0.05),豆蔻酸、棕榈酸、棕榈油酸、油酸和亚油酸含量显著下降(P < 0.05);0.6 mL/L大蒜精油添加组蛋鸡生产性能无显著差异(P>0.05),鸡肉中甜味氨基酸中的丙氨酸、丝氨酸、甘氨酸和脯氨酸含量升高(P>0.05),酸味氨基酸中的谷氨酸含量升高(P>0.05),苦味氨基酸中的酪氨酸、异亮氨酸、亮氨酸和赖氨酸含量升高(P>0.05),组氨酸和缬氨酸含量下降(P>0.05),豆蔻酸、棕榈酸、棕榈油酸、油酸和亚油酸含量极显著下降(P < 0.01),亚麻酸含量显著下降(P < 0.05)。综上所述,在产蛋后期蛋鸡饮水中添加0.2~0.4 mL/L大蒜精油能够提高蛋鸡生产性能与鸡肉中部分鲜味和酸味氨基酸的含量,降低部分苦味氨基酸和脂肪酸含量,且适宜添加水平为0.4 mL/L。
关键词:
蛋鸡 产蛋后期 大蒜精油 生产性能 鸡肉风味物质
Effects of Garlic Essential Oil on Performance and Chicken Flavor Substance of Laying Hens during Later Period of Laying
XU Jing1
,
YANG Shuzhan2
,
HU Bianwen3
,
ZHANG Xiaomeng1
,
NIU Wenxiao1
,
YAN Anqian1
,
ZENG Dan4
,
ZHOU Rongyan1
,
WANG Dehe1
,
CHEN Yifan1
,
CHEN Hui1
1. College of Animal Science and Technology, Agricultural University of Hebei, Baoding 071001, China;
2. Weixian Deqingyuan Agricultural Technology Co., Ltd., Xingtai 054000, China;
3. Nanchang Wanyang Biotechnology Co., Ltd., Nanchang 330096, China;
4. Huayu Agricultural Technology Co., Ltd., Handan 057150, China
Abstract: This study investigated the effects of garlic essential oil offered via drinking water on performance and flavor substance in chicken of laying hens during later period of laying. A total of 512 Hy-Line Grey laying hens of 70 weeks age with good health and similar performance were used and randomly divided into 4 groups with 8 replicates in each group and 16 hens in each replicate. The control group was offered a basal diet, and the three experimental groups were offered the basal diets supplemented with 0.2, 0.4 and 0.6 mL/L garlic essential oil in drinking water, respectively. The experiment lasted for 56 days after 7 days adaption. The results showed that, compared with the control group, the average daily feed intake of laying hens in 0.2 and 0.4 mL/L garlic essential oil supplemental groups was extremely significantly decreased (P < 0.01), the feed to egg ratio was significantly decreased (P < 0.05), and the albumen height and Haugh unit were extremely significantly increased (P < 0.01). Compared with the control group, the contents of alanine, serine, glycine and proline in sweet amino acids in chicken of laying hens in 0.4 mL/L garlic essential oil supplemental group were increased (P>0.05), the glutamate content in sour amino acids was increased (P>0.05), the contents of tyrosine, isoleucine, arginine, leucine, lysine, histidine and valine in bitter amino acids were decreased (P>0.05), the contents of stearic acid and linolenic acid were decreased (P>0.05), and the contents of myristic acid, palmitic acid, palmioleic acid, oleic acid and linoleic acid were significantly decreased (P < 0.05); the performance of laying hens in 0.6 mL/L garlic essential oil supplemental group was not significantly different (P>0.05), the contents of alanine, serine, glycine and proline in sweet amino acids in chicken were increased (P>0.05), the glutamate content in sour amino acids was increased (P>0.05), the contents of tyrosine, isoleucine, leucine and lysine in bitter amino acids were increased (P>0.05), the contents of histidine and valine were decreased (P>0.05), the contents of myristic acid, palmitic acid, palmioleic acid, oleic acid and linoleic acid were extremely significantly decreased (P < 0.01), and the linolenic acid content was significantly decreased (P < 0.05). The results suggest that supplementation with 0.2 to 0.4 mL/L garlic essential oil in drinking water during later period of laying can improve the performance of laying hens and the content of some umami and sour amino acids in chicken, and reduce the contents of some bitter amino acids and fatty acids in chicken. The optimum supplemental level of garlic essential oil is 0.4 mL/L.
Key words:
laying hens later laying period garlic essential oil performance chicken flavor substance
随着生活水平的提高,人们越来越看重禽肉和禽蛋的品质与风味。实际生产中,产蛋后期蛋鸡易堆积脂肪,生产性能和蛋品质均下降,淘汰蛋鸡流入市场作肉用。因此,提高蛋鸡产蛋后期的生产性能及鸡肉风味具有重要意义。大蒜精油为乳白色液体,主要成分为大蒜素,是从大蒜鳞茎中提取的生物活性物质[1]。大量研究表明,大蒜素无毒、无副作用、无残留、无抗原性,且大蒜素能够降血脂、降血压、抗疲劳、抗凝血、抗病毒且并有较强的抑制许多细菌和真菌的活性[2-6],能够大大提高饲料转化率和改善畜禽产品品质与风味,因此大蒜素常被用作饲料添加剂[7-8]。前人研究大多将大蒜或大蒜粉混入基础饲粮中探究大蒜素对肉鸡生长性能及肉品质的影响,关于饮水中添加大蒜精油对蛋鸡鸡肉风味物质的影响的研究极少。因此本试验在饮水中添加大蒜精油,探究大蒜素对蛋鸡产蛋后期生产性能及鸡肉风味物质的影响,减少固态大蒜素不易与饲料混匀的情况,减少劳动力,为实际生产中大蒜精油的使用提供理论依据。
1 材料与方法
1.1 试验动物及材料
试验选用70周龄健康状况良好、生产性能相近的海兰灰蛋鸡512只,随机分为4组,每组8个重复,每个重复16只鸡。对照组饲喂基础饲粮,试验组在基础饲粮的基础上在饮水中分别添加0.2、0.4和0.6 mL/L的大蒜精油。预试期7 d,正试期56 d。大蒜精油由南昌市万阳生物科技有限公司提供,大蒜素含量为5%。基础饲粮参照我国农业行业标准NY/T 33—2004设计,其组成及营养水平见表 1。
表 1(Table 1)
表 1 基础饲粮组成及营养水平(风干基础)
Table 1 Composition and nutrient levels of the basal diet (air-dry basis)
% |
项目Items |
含量Content |
原料Ingredients |
|
玉米Corn |
60.80 |
豆粕Soybean meal |
22.90 |
沸石粉Zeolite powder |
2.60 |
石粉Limestone |
8.60 |
磷酸氢钙CaHPO4 |
1.53 |
花生粕Peanut meal |
1.00 |
水解羽毛粉Hydrolyzed feather powder |
1.00 |
植物油Vegetable oil |
0.80 |
食盐NaCl |
0.30 |
微量元素预混料Trace mineral premix1) |
0.20 |
蛋氨酸Met |
0.17 |
赖氨酸Lys |
0.06 |
维生素预混料Vitamin premix2) |
0.03 |
枯草芽孢杆菌Bacillus subtilis |
0.01 |
合计Total |
100.00 |
营养水平Nutrient levels3) |
|
代谢能ME/(MJ/kg) |
10.88 |
粗蛋白质CP |
15.99 |
粗纤维CF |
2.37 |
钙Ca |
3.66 |
总磷TP |
0.56 |
有效磷AP |
0.32 |
1)每千克微量元素预混料提供Every kilogram of trace mineral premix provided the following:Cu (as copper sulfate) 0.8 g,Fe (as ferrous sulfate) 6 g,Mn (as manganese sulfate) 9 g,Zn (as zinc sulfate) 6 g,I (as potassium iodide) 90 mg,Se (as sodium selenite) 21 mg。 2)每千克维生素预混料提供Every kilogram of vitamin premix provided the following:VA 330 000 IU,VB1 20 mg,VB2 500 mg,D-泛酸钙D-pantothenate calcium 1 200 mg,VB6 300 mg,VD3 82 500 IU,VE 2 000 IU,VK 180 mg,生物素biotin 14 mg,叶酸folic acid 55 mg,烟酸niacin 2 300 mg,胆碱choline 45 g。 3)代谢能为计算值,其余为实测值。ME was a calculated value, while the others were measured values.
|
|
表 1 基础饲粮组成及营养水平(风干基础)
Table 1 Composition and nutrient levels of the basal diet (air-dry basis)
|
1.2 饲养管理
试验地点在河北省邢台市威县德青源蛋鸡场。所有鸡只采用4层笼养的方式进行饲养,自由采食和饮水。光照时间为16 h/d,光照强度为16 lx,大蒜精油添加时间6 h/d。
1.3 测定指标与方法
1.3.1 生产性能
试验期间每天记录每个重复的总产蛋数、总蛋重、采食量,并计算产蛋率、平均日采食量、平均蛋重和料蛋比。
1.3.2 蛋品质
正试期第28天和第56天,分别以每个重复为单位随机取8个鸡蛋进行蛋品质测定。使用日本产FHK型蛋形指数测定仪测量鸡蛋的长径与短径,并计算蛋形指数(长径/短径);游标卡尺测定蛋壳厚度;使用以色列产EFR-01型蛋壳强度测定仪测定蛋壳强度;使用电子天平测量蛋重、蛋黄重,用蛋黄比色扇测定蛋黄颜色;使用以色列产EA-01型蛋白高度测定仪测定蛋白高度。并计算哈氏单位,计算公式为:
式中:H为蛋白高度(mm);W为蛋重(g)。
1.3.3 鸡肉中风味物质含量
正试期第28天和第56天,以重复为单位随机取2只鸡进行屠宰,取左侧胸肌和腿肌于-80 ℃冷冻保存备用。鸡肉中游离氨基酸含量由北京精益捷检测科技有限公司测定,检测依据参考GB/T 18246—2000和GB/T 15299—1994,主要仪器为气相质谱联用仪,型号为Agilent 5975C;脂肪酸含量由北京精益捷检测科技有限公司测定,检测依据为该实验室自制方法,主要仪器为气相色谱仪。
1.4 数据统计与分析
利用Excel 2016对数据进行初步整理,后应用SPSS 21.0软件中的一般线性模型进行分析,用Duncan氏法检验组间差异,数据结果以平均值±标准差表示,P<0.05表示差异显著,P<0.01表示差异极显著。
2 结果
2.1 大蒜精油对产蛋后期蛋鸡生产性能的影响
由表 2可知,饮水中添加大蒜精油对产蛋后期蛋鸡平均蛋重无显著影响(P>0.05)。与对照组相比,添加0.2和0.4 mL/L大蒜精油时,蛋鸡平均日采食量分别下降了10.15%和10.72%(P < 0.01),料蛋比分别下降了7.20%和10.40%(P < 0.05),产蛋率分别提高了3.64%和6.75%(P>0.05);添加0.6 mL/L大蒜精油时,蛋鸡产蛋率与料蛋比均升高(P>0.05)。
表 2(Table 2)
表 2 大蒜精油对产蛋后期蛋鸡生产性能的影响
Table 2 Effects of garlic essential oil on performance of laying hens during later period of laying
项目 Items |
对照 Control |
大蒜精油添加水平 Garlic essential oil supplemental level/(mL/L) |
P值 P-value |
0.2 |
0.4 |
0.6 |
平均日采食量ADFI/g |
134.62±6.60Aa |
120.95±10.30Bb |
120.19±7.89Bb |
135.12±9.34Aa |
0.009 |
平均蛋重Average egg weight/g |
59.43±5.22 |
59.53±8.16 |
59.59±5.14 |
57.66±6.67 |
0.917 |
产蛋率Laying rate/% |
80.26±6.32 |
83.18±10.12 |
85.68±6.51 |
84.34±6.06 |
0.194 |
料蛋比Feed/egg |
2.50±0.25ab |
2.32±0.45b |
2.24±0.19b |
2.67±0.27a |
0.040 |
同行数据肩标无字母或相同小写字母表示差异不显著(P>0.05),不同小写字母表示差异显著(P<0.05),不同大写字母表示差异极显著(P<0.01)。下表同。 In the same row, values with no letter or the same small letter superscripts mean no significant difference (P>0.05), while with different small letter superscripts mean significant difference (P<0.05), and with different capital letter superscripts mean extremely significant difference (P<0.01). The same as below.
|
|
表 2 大蒜精油对产蛋后期蛋鸡生产性能的影响
Table 2 Effects of garlic essential oil on performance of laying hens during later period of laying
|
2.2 大蒜精油对产蛋后期蛋鸡蛋品质的影响
由表 3可知,与对照组相比,饮水中添加0.2和0.4 mL/L大蒜精油使产蛋后期蛋鸡蛋白高度分别升高了17.92%和21.79%(P < 0.01),哈氏单位分别升高了14.63%和26.03%(P < 0.01);添加大蒜精油对产蛋后期蛋鸡蛋壳厚度、蛋壳强度和蛋黄颜色均无显著影响(P>0.05)。
表 3(Table 3)
表 3 大蒜精油对产蛋后期蛋鸡蛋品质的影响
Table 3 Effects of garlic essential oil on egg quality of laying hens during later period of laying
项目 Items |
对照 Control |
大蒜精油添加水平 Garlic essential oil supplemental level/(mL/L) |
P值 P-value |
0.2 |
0.4 |
0.6 |
蛋形指数Egg shape index |
1.30±0.02Aa |
1.29±0.02Bb |
1.32±0.01Aa |
1.30±0.01Aa |
< 0.001 |
蛋白高度Albumen height/mm |
4.13±0.82Bb |
4.87±0.83Aa |
5.03±0.65Aa |
4.51±0.81ABb |
0.009 |
哈氏单位Haugh unit |
55.86±10.30Cc |
64.03±9.48ABab |
70.40±5.59Aa |
60.93±8.56Cc |
< 0.001 |
蛋壳厚度Eggshell thickness/mm |
0.34±0.02 |
0.35±0.02 |
0.34±0.01 |
0.32±0.02 |
0.890 |
蛋壳强度Eggshell strength/N |
32.10±2.73 |
33.49±2.84 |
32.76±2.51 |
31.64±2.86 |
0.107 |
蛋黄颜色Egg yolk color |
9.16±0.37 |
9.19±0.40 |
9.16±0.69 |
9.00±0.26 |
0.342 |
|
表 3 大蒜精油对产蛋后期蛋鸡蛋品质的影响
Table 3 Effects of garlic essential oil on egg quality of laying hens during later period of laying
|
2.3 大蒜精油对产蛋后期蛋鸡鸡肉中风味物质含量的影响
由表 4可知,与对照组相比,饮水中添加0.4 mL/L大蒜精油使产蛋后期蛋鸡鸡肉中丝氨酸、甘氨酸、脯氨酸、谷氨酸和丙氨酸含量分别升高了41.53%、12.61%、10.43%、1.97%和1.91%(P>0.05),使产蛋后期蛋鸡鸡肉中酪氨酸、异亮氨酸、精氨酸、亮氨酸、赖氨酸、组氨酸和缬氨酸含量分别降低了11.76%、6.67%、4.29%、4.04%、3.90%、3.54%和2.94%(P>0.05)。
表 4(Table 4)
表 4 大蒜精油对产蛋后期蛋鸡鸡肉中氨基酸含量的影响
Table 4 Effects of garlic essential oil on amino acid contents in chicken of laying hens during later period of laying
% |
项目 Items |
对照 Control |
大蒜精油添加水平 Garlic essential oil supplemental level/(mL/L) |
P值 P-value |
0.2 |
0.4 |
0.6 |
天门冬氨酸Asp |
2.56±0.07 |
2.56±0.04 |
2.48±0.24 |
2.58±0.04 |
0.711 |
苏氨酸Thr |
1.25±0.02 |
1.26±0.03 |
1.20±0.11 |
1.26±0.02 |
0.471 |
丝氨酸Ser |
1.18±0.03 |
1.20±0.02 |
1.67±0.10 |
1.21±0.03 |
0.755 |
谷氨酸Glu |
4.07±0.08 |
4.09±0.09 |
4.15±0.08 |
4.13±0.07 |
0.662 |
甘氨酸Gly |
1.19±0.03 |
1.20±0.03 |
1.34±0.04 |
1.21±0.05 |
0.738 |
丙氨酸Ala |
1.57±0.05 |
1.58±0.01 |
1.60±0.07 |
1.59±0.03 |
0.703 |
半胱氨酸Cys |
0.64±0.02 |
0.67±0.02 |
0.65±0.01 |
0.60±0.11 |
0.479 |
缬氨酸Val |
1.36±0.07 |
1.39±0.10 |
1.32±0.13 |
1.33±0.17 |
0.821 |
蛋氨酸Met |
0.51±0.02 |
0.54±0.02 |
0.52±0.01 |
0.48±0.10 |
0.575 |
异亮氨酸Ile |
1.05±0.03 |
1.06±0.05 |
0.98±0.13 |
1.06±0.08 |
0.530 |
亮氨酸Leu |
2.23±0.05 |
2.24±0.03 |
2.14±0.21 |
2.25±0.04 |
0.481 |
酪氨酸Tyr |
0.34±0.04 |
0.33±0.03 |
0.30±0.06 |
0.35±0.02 |
0.333 |
苯丙氨酸Phe |
1.02±0.05 |
1.05±0.01 |
1.03±0.08 |
1.09±0.04 |
0.334 |
赖氨酸Lys |
2.31±0.05 |
2.34±0.04 |
2.22±0.20 |
2.35±0.05 |
0.342 |
组氨酸His |
1.13±0.08 |
1.11±0.02 |
1.09±0.11 |
1.11±0.05 |
0.907 |
精氨酸Arg |
1.40±0.05 |
1.40±0.04 |
1.34±0.19 |
1.40±0.07 |
0.765 |
脯氨酸Pro |
1.15±0.04 |
1.18±0.02 |
1.27±0.25 |
1.19±0.04 |
0.600 |
|
表 4 大蒜精油对产蛋后期蛋鸡鸡肉中氨基酸含量的影响
Table 4 Effects of garlic essential oil on amino acid contents in chicken of laying hens during later period of laying
|
由表 5可知,与对照组相比,饮水中添加0.4 mL/L大蒜精油使产蛋后期蛋鸡鸡肉中豆蔻酸、棕榈酸、棕榈油酸、油酸和亚油酸含量分别下降了22.58%、21.84%、28.75%、26.97%和23.16%(P < 0.05);添加0.6 mL/L大蒜精油使产蛋后期蛋鸡鸡肉中豆蔻酸、棕榈酸、棕榈油酸和油酸含量分别下降了40.32%、34.00%、55.63%和41.80%(P < 0.01),使鸡肉中亚油酸含量下降了36.74%(P < 0.05);添加0.6 mL/L大蒜精油使产蛋后期蛋鸡鸡肉中硬脂酸含量下降了16.01%(P < 0.05),亚麻酸含量下降了35.38%(P>0.05)。
表 5(Table 5)
表 5 大蒜精油对产蛋后期蛋鸡鸡肉中脂肪酸含量的影响
Table 5 Effects of garlic essential oil on fatty acid contents in chicken of laying hens during later period of laying
% |
项目 Items |
对照 Control |
大蒜精油添加水平 Garlic essential oil supplemental level/(mL/L) |
P值 P-value |
0.2 |
0.4 |
0.6 |
豆蔻酸C14:0 |
0.62±0.03Aa |
0.55±0.09Aa |
0.48±0.06ABb |
0.37±0.09Bb |
< 0.001 |
棕榈酸C16:0 |
14.56±1.19Aa |
12.62±2.10ABab |
11.38±1.67ABb |
9.61±1.31Bb |
< 0.001 |
棕榈油酸C16:1 |
1.60±0.17Aa |
1.25±0.24Aab |
1.14±0.34ABb |
0.71±0.04Bc |
< 0.001 |
硬脂酸C18:0 |
5.81±0.21a |
5.56±0.70a |
5.24±0.28ab |
4.88±0.37b |
0.049 |
油酸C18:1n9c |
21.84±1.66Aa |
18.06±4.25ABab |
15.95±3.31ABb |
12.71±2.12Bb |
< 0.001 |
亚油酸C18:2n9c |
19.30±1.29a |
16.62±3.72ab |
14.83±3.01b |
12.21±1.88b |
0.018 |
亚麻酸C18:3n3 |
0.65±0.08 |
0.58±0.14 |
0.53±0.13 |
0.42±0.07 |
0.065 |
花生酸C20:0 |
0.25±0.02 |
0.28±0.01 |
0.26±0.03 |
0.28±0.01 |
0.140 |
顺-11-二十碳烯酸C20:1n9 |
0.24±0.05 |
0.24±0.05 |
0.21±0.01 |
0.26±0.06 |
0.541 |
|
表 5 大蒜精油对产蛋后期蛋鸡鸡肉中脂肪酸含量的影响
Table 5 Effects of garlic essential oil on fatty acid contents in chicken of laying hens during later period of laying
|
3 讨论
3.1 大蒜精油对产蛋后期蛋鸡生产性能的影响
大蒜素具有特殊的气味,能诱食、助消化[8],同时大蒜素也能够改善肠道菌群,调节酶分泌,提高肠道的消化能力[9-10],从而提高饲料的利用率。实际生产中,产蛋后期蛋鸡耗料量增加,料蛋比升高,饲料更多的转化为脂肪。本试验中,在产蛋后期蛋鸡饮水中添加大蒜精油能够极显著降低蛋鸡的平均日采食量,提高产蛋率,显著降低料蛋比,但对平均蛋重无显著影响,这与王文利等[11]、陈承祯等[12]在蛋鸡基础饲粮中添加大蒜素的研究结果一致。但蛋鸡生产性能并不随大蒜精油添加水平的升高而升高。本试验中,0.6 mL/L大蒜精油添加组的料蛋比显著高于0.2和0.4 mL/L大蒜精油添加组;洪伟等[13]研究也表明,高剂量的大蒜素会降低产蛋率,这可能是由于高剂量的大蒜素刺激肠道作用过强,使肠道黏膜受损而影响了肠道对营养物质的消化和吸收。本试验结果表明,饮水中添加0.4 mL/L大蒜精油对产蛋后期蛋鸡生产性能的改善效果最佳。
3.2 大蒜精油对产蛋后期蛋鸡蛋品质的影响
蛋形指数和蛋白高度是衡量禽蛋品质的重要指标,除遗传因素外,蛋品质还受饲粮、光照和鸡体健康状况等因素的影响[14]。蛋白高度表示了鸡蛋鲜度和蛋白质量,哈氏单位高的鸡蛋,其蛋白的黏稠度好,蛋品质含量也高[15]。研究表明,大蒜素能够提高蛋品质。尼满等[16]在基础饲粮中添加0.1 g/kg大蒜素对产蛋后期蛋鸡哈氏单位和蛋形指数等都有所提高。Chowdhury等[17]也指出,大蒜粉能够显著提高鸡蛋的哈氏单位。本试验也得出了同样的结论,在产蛋后期蛋鸡饮水中添加0.4 mL/L的大蒜精油能够显著极显著提高蛋白高度和哈氏单位,从而提高产蛋后期蛋鸡的蛋品质。
3.3 大蒜精油对产蛋后期蛋鸡鸡肉中风味物质含量的影响
鸡肉中脂肪酸和氨基酸的种类和含量决定了鸡肉的风味。不饱和脂肪酸对机体起着重要的作用。研究表明,鸡肉中的亚油酸和亚麻酸不仅是人体所必须的不饱和脂肪酸,还是形成其气味的重要前体物质[18]。但多不饱和脂肪酸易氧化,当多不饱和脂肪酸含量升高时,鸡肉脂肪会变软从而导致鸡肉品质下降、产生异味[19]。而鸡肉中的饱和脂肪酸能够在血清中转化为胆固醇,引起动脉粥样硬化,因此降低鸡肉中的脂肪酸有利于鸡的健康[20]。前人将大蒜作为中草药添加剂探究其对肉鸡鸡肉风味的影响时发现,大蒜能够降低饱和脂肪酸中的豆蔻酸含量,提高不饱和脂肪酸中的亚油酸和亚麻酸含量[18]。在钱辉跃等[21]设计的15种不同水平复合饲料添加剂中,大蒜素含量为24.33 mg/kg时,显著降低了肌间饱和脂肪酸含量,同时增加了不饱和脂肪酸含量。这与本试验结论不完全一致,本试验中,大蒜精油使鸡肉中豆蔻酸、硬脂酸、亚油酸及亚麻酸等含量均降低,且大蒜精油添加水平越高脂肪酸含量越低,这有可能减少了脂肪沉积,但具体机制有待研究。
鸡肉中的游离氨基酸决定了鸡肉的滋味,其中呈甜味的氨基酸有甘氨酸、丙氨酸、丝氨酸、脯氨酸和苏氨酸等;呈苦味的氨基酸有亮氨酸、异亮氨酸、缬氨酸、苯丙氨酸、酪氨酸、组氨酸、赖氨酸和精氨酸等;呈酸味的氨基酸有天门冬氨酸和谷氨酸,这2种氨基酸同时也是形成鲜味物质的重要前体物质之一[22],且谷氨酸对不良气味有较好的缓冲作用[23]。鸡肉中主要的香味成分为C3H5S(O)基团,大蒜素中富含的硫醚化合物正具有这一结构[24],因而大蒜素能够刺激鸡体内香味的氨基酸的产生,增加鸡肉的香味,使其味道更加鲜美。研究发现,在鸡饲粮中添加1%~2%鲜大蒜或0.2%的大蒜粉,不仅能够消除鸡肉中由于鸡吃了含鱼粉较多的饲粮而产生的鱼腥味[25],还能使鸡肉更加细嫩多汁、香味浓郁[26]。本试验中,当饮水中添加0.4 mL/L的大蒜精油时,产蛋后期蛋鸡鸡肉中谷氨酸、丙氨酸、甘氨酸、丝氨酸和脯氨酸含量最高,且酪氨酸、异亮氨酸、精氨酸、亮氨酸、赖氨酸、组氨酸和缬氨酸含量最低。该结果说明,在产蛋后期蛋鸡饮水中添加0.4 mL/L大蒜精油能够增加鸡肉的鲜味,因而提升其市场价值。
4 结论
在饮水中添加大蒜精油能够提高产蛋后期蛋鸡的生产性能、蛋品质以及鸡肉中部分香味与鲜味氨基酸含量,降低鸡肉中部分苦味氨基酸含量和脂肪酸含量,提升产蛋后期蛋鸡淘汰后的市场价值,且适宜添加水平为0.4 mL/L。
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