动物营养学报    2020, Vol. 32 Issue (1): 99-108    PDF    
柑橘提取物对仔猪免疫功能的影响
崔艺燕 , 田志梅 , 邓盾 , 王刚 , 鲁慧杰 , 陈卫东 , 马现永     
广东省农业科学院动物科学研究所, 畜禽育种国家重点实验室, 农业部华南动物营养与饲料重点实验室, 广东省畜禽育种与营养研究重点实验室, 广东畜禽肉品质量安全控制与评定工程技术研究中心, 广州 510640
摘要: 本试验旨在研究柑橘提取物对仔猪血清、肝脏以及十二指肠、空肠黏膜免疫功能的影响。选取144头28日龄(8.39±1.06)kg的"杜×长×大"健康仔猪,按体重随机分配到3个组,每个组6个栏(重复),每个栏8头猪,公母各占1/2。3个组分别为:对照组,饲喂基础饲粮;抗生素组,在基础饲粮上添加75 g/t金霉素;柑橘提取物组,在基础饲粮上添加300 mL/t柑橘提取物。试验期28 d。结果表明:1)与对照组相比,抗生素组和柑橘提取物组仔猪血清免疫球蛋白G(IgG)含量分别显著提高了11.27%和14.01%(P < 0.05);与抗生素组和对照组相比,柑橘提取物组仔猪血清白细胞介素-6(IL-6)和免疫球蛋白A(IgA)含量有提高趋势(0.05 ≤ P < 0.10);柑橘提取物组仔猪血清肿瘤坏死因子-α(TNF-α)含量较对照组显著提高了12.13%(P < 0.05),与抗生素组差异不显著(P>0.05)。2)与对照组相比,柑橘提取物组和抗生素组仔猪肝脏免疫球蛋白M和IgG含量显著下降(P < 0.05);与对照组和柑橘提取物组相比,抗生素组仔猪肝脏TNF-α含量显著降低(P < 0.05),肝脏IgA含量有降低趋势(0.05 ≤ P < 0.10)。3)3组间仔猪十二指肠黏膜免疫指标差异不显著(P>0.05)。4)与对照组相比,柑橘提取物和抗生素有提高仔猪空肠黏膜白细胞介素-2和IL-6含量的趋势(0.05 ≤ P < 0.10),抗生素组仔猪空肠黏膜白细胞介素-8含量显著提高(P < 0.05);柑橘提取物组仔猪空肠黏膜分泌型免疫球蛋白A含量最高,较对照组提高了19.35%(0.05 ≤ P < 0.10)。由此可见,柑橘提取物和抗生素提高了仔猪血清和空肠黏膜的细胞因子和免疫球蛋白含量,增强了仔猪免疫功能。
关键词: 柑橘提取物    仔猪    免疫    
Effects of Citrus Extract on Immunity of Piglets
CUI Yiyan , TIAN Zhimei , DENG Dun , WANG Gang , LU Huijie , CHEN Weidong , MA Xianyong     
Guangdong Engineering Technology Research Center of Animal Meat Quality and Safety Control and Evaluation, Guangdong Key Laboratory of Animal Breeding and Nutrition, The Key Laboratory of Animal Nutrition and Feed Science(South China) of Ministry of Agriculture, State Key Laboratory of Livestock and Poultry Breeding, Institute of Animal Science, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China
Abstract: This experiment was conducted to investigate the effects of citrus extract on immune function in serum, liver, duodenal and jejunal mucosa of piglets. One hundred and forty-four 28-day-old (8.39±1.06) kg Duroc×Landrace×Large White pigs were randomly assigned to 3 groups with 6 pens (replicates) per group and 8 pigs per pen (half male and half female). Three groups were:control group, fed a basal diet; antibiotic group, fed the basal diet supplemented with 75 g/t chlortetracycline; citrus extract group, fed the basal diet supplemented with 300 mL/t citrus extract. The experiment lasted for 28 days. The results showed as follows. 1) compared with the control group, the serum immunoglobulin G (IgG) content of piglets in the antibiotic group and the citrus extract group was significantly increased by 11.27% and 14.01%, respectively (P < 0.05); compared with the antibiotic group and the control group, the contents of serum interleukin-6 (IL-6) and immunoglobulin G (IgA) of piglets in the citrus extract group were tended to be increased (0.05 ≤ P < 0.10); the serum tumor necrosis factor-α (TNF-α) content of piglets in the citrus extract group was significantly increased by 12.13% compared with the control group (P < 0.05), but not significantly different from that in the antibiotic group (P>0.05). 2) Compared with the control group, the contents of liver immunoglobulin M and IgG of piglets in the citrus extract group and the antibiotic group were significantly decreased (P < 0.05). Compared with the control group and the citrus extract group, the liver TNF-α content of piglets in the antibiotic group was significantly decreased (P < 0.05), and liver IgA content had a decreasing trend (0.05 ≤ P < 0.10). 3) There was no significant difference in indices of duodenal mucosal immunity among three groups (P>0.05). 4) Compared with the control group, the citrus extract and antibiotic had a trend to increase contents of interleukin-2 and IL-6 in jejunal mucosa of piglets (0.05 ≤ P < 0.10), and the IL-8 content in jejunal mucosa of piglets in the antibiotic group was significantly increased (P < 0.05). The secretory immunoglobulin A content in jejunal mucosa of piglets in the citrus extract group was the highest, which was 19.35% higher than that in the control group (0.05 ≤ P < 0.10). In brief, citrus extract and antibiotic can improve the contents of cytokines and immunoglobulins in serum and jejunal mucosa, thus enhance the immunity of piglets.
Key words: citrus extract    piglets    immunity    

断奶是养猪业生产的关键时期。断奶会导致仔猪肠道和免疫系统功能障碍,饲粮摄入减少,生长减慢,小肠结构萎缩,肠炎性细胞因子上调,从而导致免疫功能下降,患病率增加[1-2]。通过在饲粮中添加预防性抗生素可减少断奶应激引起的发病率,提高免疫功能[3]。然而,抗生素滥用会促进多药耐药细菌和重金属在环境中的积累。因此,人们正在努力寻找改善断奶仔猪机体免疫功能的天然抗生素替代品。

柑橘黄酮类化合物及其代谢产物具有多种生物活性,如抗癌[4]、抗利什曼原虫[5]、抗诱变[6]、抗菌[6-7]和抗氧化活性[7-8]。饲粮添加50 mg/kg柚皮苷可以显著提高仔猪的体重和饲料转化率,改善生长性能[9]。Alhidary等[10]研究了热环境条件下添加柚皮苷对羔羊抗氧化能力和免疫反应的影响,发现与对照组相比,每周添加7 g柚皮苷可使羔羊平均日增重和增重饲料比显著增加。不过,Kamboh等[11]没有观察到橙皮苷对肉鸡增重及饲料转化率的改善效果。本课题组前期结果表明,在仔猪饲粮中添加柑橘提取物提高了饲料转化率。可见,柑橘提取物或其纯化成分具有一定的促生长效果。抗生素的益处主要来自肠道健康,包括提高消化率、改变消化道分泌物、维持和改善肠道组织学[12]以及减少菌落数量及发酵产物(包括氨和生物胺)[13]。植物提取物与抗生素的促生长作用是相似的,植物提取物在动物消化道中起作用以改善食欲并调节微生物群[14],减少微生物毒素,这会减少炎症,提高机体免疫力,使得更多的蛋白质分配用于生长[12]

免疫系统是重要的生理防御系统。在饲粮中补充适宜剂量的功能物质可以调节仔猪的免疫功能,提高抗病力,减少断奶期疾病发生或免疫应激的危害[15]。橙皮苷可预防小鼠肠道炎症,对辐射诱导的炎症具有抗炎作用[16]。用柚皮苷或橙皮苷喂养蛋鸡,炎症免疫反应受到抑制[17]。橙皮苷通过抑制肝细胞氧化应激、产生细胞因子以及激活T细胞来保护小鼠免受刀豆球蛋白A诱导的肝损伤[18]。柑橘提取物通过调节机体免疫因子的产生来改善免疫功能,从而有利于提高动物抗病力。然而,目前未见有柑橘提取物在仔猪生产中的相关研究报道,尚不清楚柑橘提取物能否提高仔猪血清、肝脏和肠道黏膜中的细胞因子和免疫球蛋白的含量,也并不了解柑橘提取物与抗生素对仔猪免疫功能影响的异同。因此,本试验旨在通过研究柑橘提取物对仔猪血清、肝脏和肠道黏膜免疫指标的影响,为生产上应用柑橘提取物提高仔猪免疫功能,减少患病率提供理论依据。

1 材料与方法 1.1 试验材料

15%金霉素购自广东新南都饲料科技有限公司,柑橘提取物由广东润森环保科技发展有限公司提供。柑橘提取物含有3.04%维生素C、2.38%维生素E、2.89%柠檬酸和20.77%总黄酮。

1.2 试验动物和试验设计

选取144头28日龄(8.39±1.06) kg“杜×长×大”仔猪,按体重随机分配到3个组,每个组6个栏(重复),每个栏8头猪,公母各占1/2。试验期为28 d。3个组分别为:对照组,饲喂基础饲粮;抗生素组,在基础饲粮上添加75 g/t金霉素;柑橘提取物组,在基础饲粮上添加300 mL/t柑橘提取物。

1.3 试验饲粮

基础饲粮组成及营养水平见表 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 basal diets (air-dry basis) 
1.4 饲养管理与屠宰采样

试验在广东省新兴县丰利田农业发展有限公司猪场进行,根据猪场常规程序进行饲养管理。试验结束后,每栏选取接近平均体重的2头仔猪(1公1母),进行前腔静脉采血。血液经3 500 r/min、4 ℃离心10 min,收集血清,-80 ℃保存。采血后进行屠宰试验,取肝脏(右下叶),用载玻片刮取十二指肠和空肠黏膜,-80 ℃保存。

1.5 组织匀浆制备

取约0.1 g肝脏/肠道黏膜,加入9倍体积0.9%生理盐水制成10%匀浆液,4 ℃、3 500 r/min离心15 min,取上清液测定免疫指标。

1.6 免疫指标测定

测定血清、肝脏和肠道黏膜中总蛋白、白细胞介素-2(IL-2)、白细胞介素-6(IL-6)、白细胞介素-8(IL-8)、肿瘤坏死因子-α(TNF-α)、免疫球蛋白A(IgA)、免疫球蛋白M(IgM)、免疫球蛋白G(IgG)和分泌型免疫球蛋白A(sIgA)含量,测试盒购于北京方程生物科技有限公司,具体测定步骤按说明书进行。

1.7 数据处理

试验数据用Excel 2010进行整理,用SPSS 19.0进行单因素方差分析(one-way ANOVA),并用Duncan氏法进行多重比较。试验结果用平均值±标准误表示,P < 0.05为差异显著,0.05≤P < 0.10为有显著趋势。

2 结果 2.1 柑橘提取物对仔猪血清免疫指标的影响

表 2可知,与抗生素组和对照组相比,柑橘提取物组仔猪血清IL-6含量分别提高了11.92%和12.52%(0.05≤P < 0.10)。柑橘提取物组仔猪血清TNF-α含量比对照组显著提高了12.13%(P < 0.05),比抗生素组提高了6.33%(P>0.05)。与对照组相比,抗生素组和柑橘提取物组仔猪血清IgG含量分别显著提高了11.27%和14.01%(P < 0.05),柑橘提取物组与抗生素组之间差异不显著(P>0.05)。柑橘提取物组仔猪血清IgA含量比对照组和抗生素组分别提高了9.93%和4.89%(0.05≤P < 0.10)。与抗生素组和对照组相比,柑橘提取物组仔猪血清IL-2、IL-8和IgM含量均有所提高,但差异不显著(P>0.05)。

表 2 柑橘提取物对仔猪血清免疫指标的影响 Table 2 Effects of citrus extract on immune indices in serum of piglets
2.2 柑橘提取物对仔猪肝脏免疫指标的影响

表 3可知,与对照组相比,柑橘提取物组和抗生素组仔猪肝脏IgM含量分别降低了15.72%和21.87%(P < 0.05),柑橘提取物组仔猪肝脏IgM含量较抗生素组提高了7.86%(P>0.05)。对照组仔猪肝脏IgG含量显著高于抗生素组和柑橘提取物组(P < 0.05),柑橘提取物组仔猪肝脏IgG含量比抗生素组显著提高了17.18%(P < 0.05)。柑橘提取物与对照组仔猪肝脏IgA含量分别比抗生素组提高了10.73%和13.73%(0.05≤P < 0.10)。与对照组和柑橘提取物组相比,抗生素组仔猪肝脏TNF-α含量分别显著降低了13.81%和10.67%(P < 0.05)。

表 3 柑橘提取物对仔猪肝脏免疫指标的影响 Table 3 Effects of citrus extract on immune indices in liver of piglets
2.3 柑橘提取物对仔猪十二指肠黏膜免疫指标的影响

表 4可知,与对照组相比,柑橘提取物组和抗生素组仔猪十二指肠黏膜IL-2、IL-6、IL-8和sIgA含量无显著差异(P>0.05)。

表 4 柑橘提取物对仔猪十二指肠黏膜免疫指标的影响 Table 4 Effects of citrus extract on immune indices in duodenum mucosa of piglets
2.4 柑橘提取物对仔猪空肠黏膜免疫指标的影响

表 5可知,与对照组相比,柑橘提取物组和抗生素组仔猪空肠黏膜IL-2和IL-6含量有提高的趋势(0.05≤P < 0.10),抗生素组仔猪空肠黏膜IL-2和IL-6含量比柑橘提取物组分别提高了11.52%和9.46%(0.05≤P < 0.10)。抗生素组仔猪空肠黏膜IL-8含量比对照组显著提高(P < 0.05),与柑橘提取物组相比差异不显著(P>0.05)。柑橘提取物组仔猪空肠黏膜sIgA含量最高,较对照组和抗生素组分别提高了19.35%和3.22%(0.05≤P < 0.10)。

表 5 柑橘提取物对仔猪空肠黏膜免疫指标的影响 Table 5 Effects of citrus extract on immune indices in jejunum mucosa of piglets
3 讨论 3.1 柑橘提取物对仔猪血清、肝脏和肠道黏膜细胞因子含量的影响

细胞因子是免疫系统的关键调控分子。白细胞介素在免疫细胞的激活和分化以及增殖、成熟、迁移和黏附中起重要作用[19]。IL-2主要作用是促进T淋巴细胞增殖和分化[19],其血液含量增加可预防自身免疫[20]。IL-6参与调节免疫反应,启动和维持炎症反应[17],刺激B淋巴细胞分化和急性期蛋白的产生[19]。IL-8是炎症过程中的关键因子,急性肝损伤可产生高水平IL-8[21]。TNF-α是炎症反应的主要细胞因子之一,通过刺激肝脏产生急性期蛋白参与急性期反应[20]。正常情况下,这些炎性细胞因子的产生是机体应对异物入侵或组织损伤的有益反应,但过度提高则预示着机体产生过度的免疫反应,损伤组织。

橙皮苷、柚皮苷是柑橘类水果中的主要黄酮类化合物[22-24],橙汁、橙皮苷、柚皮苷可以通过调节促炎性细胞因子、抗炎性细胞因子及其基因表达来降低炎症或增强免疫功能[25-26]。柑橘皮水提取物能够降低肿瘤小鼠血清和小鼠结肠癌细胞(CT-26)培养基上清液的IL-6、TNF-α和白细胞介素-1β(IL-1β)含量[4]。柑橘皮提取物能够降低刀豆蛋白A诱导肝损伤小鼠血清TNF-α含量和调节性T细胞的水平,增加白细胞介素-10(IL-10)含量,保护肝脏[27]。口服柑橘水提取物可抑制血清炎症细胞因子(TNF-α和IL-6)水平,并提高全身炎症模型小鼠的存活率[28]。本试验与上述研究有所不同,与对照组相比,柑橘提取物显著提高了仔猪血清TNF-α含量,有提高血清IL-6含量的趋势。原因可能是:以往研究多在荷瘤小鼠以及免疫刺激的条件下进行,这与动物生产中的应用条件不同,由此结果也不一致。本试验中,柑橘提取物组与抗生素组相比,仔猪血清IL-6和TNF-α含量也提高了,抗生素组仔猪血清细胞因子含量介于柑橘提取物组与对照组之间,这些因子水平适度的提高对机体有益。但二者提高细胞因子的作用机制尚不清楚。研究发现饲粮添加金霉素不改变仔猪血清细胞因子水平[29],与本试验一致。Zanotti等[25]发现橙汁与橙皮苷在先天免疫反应方面呈现出不同模式。橙汁支持免疫反应,增强巨噬细胞与抗菌活性相关的效应功能;而橙皮苷减弱免疫反应,防止炎症进程。橙皮素衍生物通过增强单核细胞白血病THP-1细胞的巨噬细胞吞噬作用,促进一氧化氮、IL-6和IL-1β的释放参与免疫应答[30]。因此,后续需要研究柑橘提取物在仔猪免疫反应的作用模式,以解释试验结果。

柑橘提取物应用于动物生产的研究较少,不同植物提取物的作用效果差别较大。陈丽[31]研究发现,黄褐毛忍冬提取物(黄酮类)与抗生素对仔猪血液和肝脏的IL-6、IL-2和TNF-ɑ含量的影响没有显著差异。Li等[32]用灵芝提取物(多糖)处理饲粮,较基础饲粮提高了猪血清IgG和IL-2含量。Xi等[33]也报道,黄芪茎叶提取的超细粉末(黄酮类)饲喂鸡,比基础饲粮显著提高了血清IL-2和干扰素-γ(IFN-γ)含量。这些研究结果与本试验结果存在矛盾,可能受到不同提取物的成分、添加剂量以及实施方案(对照是否添加抗生素)的影响。不同黄酮类化合物作用效果差异较大,另外,不同提取物中主成分与其他成分的协作作用对机体免疫效果也不同,如黄酮类化合物与维生素C[15]

断奶会改变仔猪肠道免疫稳态。抗炎因子通过保留屏障功能,减弱或防止肠道炎症[34]。促炎因子可增加肠上皮细胞的通透性[34],过量产生会损坏肠道完整性和上皮功能[35]。柚皮苷能减轻败血症引起的肠黏膜损伤,改善肠道通透性损伤,抑制TNF-α和IL-6释放[36]。橙皮苷降低大鼠(甲氨蝶呤诱导的肠损伤)空肠的诱导型一氧化氮合酶和IL-8水平[37]。橙皮苷降低葡聚糖硫酸钠诱导的小鼠结肠中TNF-α和IL-6含量,并增加IL-10和干扰素-α(IFN-α)含量[38]。另外,有研究报道,大鼠小肠中白细胞介素-4(IL-4)、IL-10和TNF-α含量不受橙皮苷影响[22]。柑橘提取物是否对肠屏障发挥保护作用仍未得到研究。本试验中,柑橘提取物未能降低十二指肠、空肠促炎因子的含量与以往研究[37-38]不一致,这主要与动物种属、引起肠损伤应激大小和时间长短以及柑橘黄酮类化合物种类有关。本试验中,与对照组相比,柑橘提取物和抗生素均提高了仔猪空肠黏膜细胞因子含量,且抗生素组大部分细胞因子含量高于柑橘提取物组;但二者对仔猪十二指肠黏膜细胞因子含量无显著影响,这表明添加柑橘提取物与抗生素改善了断奶仔猪空肠细胞因子分泌能力,而不影响十二指肠的分泌能力,且抗生素的效果优于柑橘提取物。不同的肠段位置出现不同的细胞因子水平,这是可能的。细胞因子水平的变化可能与柑橘黄酮类化合物有关。柑橘提取物成分在不同位置发挥的效果是不一样的,即柑橘黄酮类化合物在不同胃肠道的生物利用度不一样[39]。另外,柑橘提取物中混合黄酮类化合物与单一黄酮化合物的效果是不同的。橙皮苷、柚皮苷在柑橘提取物中的含量与其研究含量也影响试验结果,本试验没有确认柑橘提取物中橙皮苷、柚皮苷等含量,因此其他因素可能对所得结果有贡献。柑橘提取物调控细胞因子分泌的具体机制需要进一步研究。

3.2 柑橘提取物对仔猪血清、肝脏和肠道黏膜免疫球蛋白含量的影响

免疫球蛋白是由浆细胞产生的糖蛋白。提高免疫球蛋白含量能够增强机体免疫能力。IgG是血清和组织液中最丰富的免疫球蛋白,占血浆蛋白的10%~20%和总免疫球蛋白的70%~75%[40],是参与免疫记忆的关键分子[41]。IgA占总血清免疫球蛋白的10%~15%,是黏膜表面的主要抗体同种型[41],与黏膜免疫密切相关。IgA通过免疫排斥、病原体中和和抗原排泄提供被动免疫[42]。IgM约占血清免疫球蛋白的10%[43],主要产生于对感染因子或抗原的初级免疫应答[44]

本试验通过测定血清IgG、IgA和IgM的含量来评估柑橘提取物对免疫系统的影响,发现抗生素、柑橘提取物能够提高仔猪血清免疫球蛋白含量。大鼠灌胃橙皮苷(200 mg/kg BW)4周后,血清IgM含量显著增加,但不影响血清IgG和IgA含量[22]。橙皮苷增加腹腔免疫大鼠肠道黏膜IgA含量,对血清IgA含量无影响[45]。Pourhossein等[46]发现,随着甜橙皮提取物的增加,小鸡血清IgG和IgM含量也显著增加。本试验与以往研究结果一致,提示柑橘提取物能够改善仔猪机体免疫功能,促进机体健康。本试验中柑橘提取物组仔猪血清免疫球蛋白的含量均高于抗生素组,可见柑橘提取物的免疫效果优于抗生素。

肝脏由于其独特的位置和血液供应,不断暴露于各种肠源性抗原,受到黏膜免疫反应和微生物群改变的影响[47]。肝脏在先天免疫中起主导作用,在宿主防御和维持免疫平衡中起重要作用[48]。肝脏能够合成IgM、IgG和IgA[49]。本试验中,抗生素组和柑橘提取物组仔猪肝脏免疫球蛋白含量低于对照组。IgM是机体初次体液免疫应答最早出现的免疫球蛋白[44],可能是对照组仔猪断奶应激强度大,其他仔猪得到抗生素或柑橘提取物的补充使得应激强度降低,导致肝脏免疫球蛋白含量降低。柑橘提取物含丰富的活性物质,上述效应可能受到当中黄酮类化合物和维生素的作用。研究发现,大鼠口服50 mg/kg BW的橘皮素后,在肝脏中发现最高浓度的橘皮素[39]。因此,肝脏免疫球蛋白含量与血清和肠道黏膜的不一致,可能是柑橘提取物成分在组织中的分布和代谢特点造成的。有炎症疾病肝脏的免疫球蛋白含量均升高[50],肝硬化/纤维化IgG含量升高[51]。另外,有研究发现IgA能够引发免疫复合物形成,触发IgA Fc受体与各种其他受体协同以扩增炎症反应,参与各种慢性炎症疾病[42]。从这个角度看,仔猪肝脏免疫球蛋白含量降低有利于减少炎症的发生。抗生素组肝脏免疫球蛋白含量均低于柑橘提取物组,以上说法提示抗生素对肝脏免疫力的效果优于柑橘提取物。但是,肝脏作为机体重要的器官,功能复杂,不同添加剂的作用机制不一致,需要进一步验证柑橘提取物对肝脏免疫的机理。

为了维持肠道平衡,肠黏膜释放抗微生物肽和分泌性免疫球蛋白[52]。sIgA是肠道中主要的免疫球蛋白,其分泌水平反映了黏膜免疫的成熟状况,是肠道免疫屏障的重要贡献者[53]。sIgA在肠道中具有多种功能,例如调节微生物群组成、保护肠上皮免于病原微生物以及促进免疫系统发育[52]。橙皮苷可增加大鼠小肠IgA含量[22]。然而,目前还没有关于柑橘提取物对仔猪肠道黏膜免疫的影响的报道。本试验表明,柑橘提取物和抗生素均提高了仔猪空肠黏膜sIgA的含量,且柑橘提取物组sIgA的含量高于抗生素组。抗生素的抗菌作用可改变肠道微生态系统,继而改变肠道免疫。柑橘提取物与抗生素作用机理相似。研究发现,柑橘含有丰富的黄酮类化合物、维生素C、维生素E,柑橘提取物可以增加抗体产生,通过其抗病毒和抗菌作用间接改善免疫系统[46]。另外,本试验中,仔猪十二指肠黏膜sIgA含量各组间无显著差异,也许由于sIgA分布受消化部位的影响,不同处理和不同免疫时期均可改变sIgA分布。Hung等[39]研究发现,大鼠口服橘皮素,胃和小肠中橘皮素在4 h时含量最高,盲肠、结肠和直肠中橘皮素在12 h时达到最高含量。此外,柑橘黄酮及其代谢物能够影响微生物群的组成和活性,并对肠屏障功能和胃肠道炎症产生有益作用[24]。未来,有必要研究柑橘提取物对肠道微生物代谢的影响。

4 结论

① 柑橘提取物和抗生素通过提高仔猪血清和空肠黏膜的细胞因子和免疫球蛋白含量,增强仔猪免疫功能。

② 柑橘提取物对仔猪血清免疫的增强效果优于抗生素,对仔猪空肠黏膜免疫的增强效果低于抗生素。

③ 柑橘提取物和抗生素降低了仔猪肝脏免疫球蛋白含量,对十二指肠黏膜免疫指标无显著影响。

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