牛至精油是从中草药牛至中提取出的一种精油，因其具有抗菌、调味等作用常作为食品的保鲜剂、调味剂、保鲜剂或功能性成分。牛至精油是农业农村部批准使用的饲料添加剂， 被广泛应用于畜禽养殖领域，具有提高动物采食量、促生长、抗菌、抗炎症、抗寄生虫等功能，与传统饲料添加剂相比更加安全高效，且易被机体吸收、无残留，是一种绿色饲料添加剂，应用和发展潜力巨大。
本研究以异育银鲫（Carassius auratus gibebio） 为对象， 设计了 7 个牛至精油添加组进行养殖实验，分别为 N0 （0 mg/kg， 空白对照组）、N1 （25 mg/kg）、N2（50 mg/kg）、N3（100 mg/kg）、 N4（200 mg/kg）、 N5（400 mg/kg）和 N6（800 mg/kg）， 养殖周期为 8 周， 旨在探讨基础日粮中添加不同含量的牛至精油对异育银鲫生长性能、 消化酶活性、肠道形态、肠道菌群、 抗氧化和非特异性免疫的影响， 并采用嗜水气单胞菌攻毒， 分析牛至精油对异育银鲫抗病原菌感染能力的影响。 本文主要内容和研究结果如下：
1. 牛至精油对异育银鲫生长性能、消化酶活性的影响
室外网箱养殖 8 周后采样测定异育银鲫生长性能和肠道消化酶活性。结果表明，基础饲料中添加 400、 800 mg/kg 牛至精油组异育银鲫的增重率、肥满度和特定生长率显著高于空白对照组（P＜0.05），且饵料系数显著降低（P＜0.05）； 与空白对照组相比， 添加剂量为 200、 400 mg/kg 的实验组鱼体胰蛋白酶、脂肪酶和α -淀粉酶活性显著升高（P＜0.05）。
2. 牛至精油对异育银鲫肠道形态、 肠道菌群和肝功能的影响
添加剂量为 200、 400 mg/kg 的实验组鱼体后肠肠壁厚度、肠绒毛高度、 肠绒毛宽度和杯状细胞数量均显著高于空白对照组（P＜0.05）；而在肠道菌群分析中，不同添加量的牛至精油均未影响肠道菌群的丰富度（P＞0.05）。 各实验组的胆固醇（TC）和甘油三酯（TG）与空白对照组相比均无显著性差异（P＞0.05）；添加剂量为 200、 400、800 mg/kg 的实验组尿素（UREA）含量显著降低（P＜0.05）。
3. 牛至精油对异育银鲫抗氧化功能、 非特异性免疫和抗病原菌感染能力的影响
各实验组的异育银鲫的超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、总抗氧化能力(T-AOC)、丙二醛(MDA)含量等指标与空白对照组无显著差异（P＞0.05）； 添加剂量为 200、 400 mg/kg 的实验组鱼体血清总蛋白、白蛋白和补体 C3 均显著高于空白对照组（P＜0.05）； 嗜水气单胞菌攻毒后， 添加量为 200、 400 和 800 mg/kg 的实验组异育银鲫存活率显著高于空白对照组， 400 和 800 mg/kg 组异育银鲫的感染保护率显著高于 25、 50 和 100 mg/kg 组（P＜0.05）。

Oregano essential oil is a kind of essential oil extracted from the Chinese traditonal drug-origanum vulgare. Because of its antibacterial and flavouring properties, it is often used as a food preservative, flavouring agent, preservative or functional ingredient. Oregano essential oil is a feed additive approved by the Ministry of Agriculture and Rural Affairs and is widely used in livestock and poultry breeding. It has the functions of increasing animal feed intake, promoting growth, antibacterial, anti-inflammatory, and anti-parasitic. It is safer and more efficient than
traditional feed additives, and it is easily absorbed by the body and has no residue. Itis a green feed additive with huge application and development potential.
In this study, gibel carp (Carassius auratus gibebio) as the object, 7 oregano essential oil supplement groups were designed for breeding experiments, namely N0(0 mg/kg， the control group)、 N1(25 mg/kg)、 N2(50 mg/kg)、 N3(100 mg/kg)、
N4(200 mg/kg)、 N5(400 mg/kg) and N6(800 mg/kg), the experimental period is 8 weeks. In order to explore the effects of adding different amounts of oregano essential oil in the basal diet on the growth performance, digestive enzyme activity, intestinal
morphology, intestinal flora, antioxidant and non-specific immunology of gibel carp, and Aeromonas hydrophila was used to challenge to analyze the effect of oregano essential oil on the ability of gibel carp against pathogen infection. The main content
and experimental results of this article are as follows:
1. The effect of oregano essential oil on the growth performance and digestive enzyme activity of gibel carp

Sampling after 8 weeks of breeding experiment, the growth performance and intestinal digestive enzyme activity of gibel carp were measured. The results showed
that the weight gain, condition factor and specific growth rate of gibel carp with 400 mg/kg group and 800 mg/kg group were significantly higher than those of the control group (P＜ 0.05), and the feed coefficient was significantly reduced (P＜ 0.05);Compared with the control group, trypsin, lipase and α-amylase activities in the 200 mg/kg group and 400 mg/kg group were significantly increased (P＜0.05);
2. The effect of oregano essential oil on the intestinal morphology, intestinal flora and liver function of gibel carp

The thickness of the posterior intestinal wall, villus height, villi width and the
number of goblet cells in the experimental group with the addition doses of 200 and 400 mg/kg were significantly higher than those in the control group (P<0.05); In the analysis of intestinal flora, the experimental groups with different dosages did not affect the abundance of intestinal flora (P＞0.05). There was no significant difference in total cholesterol (TC) and triglyceride (TG) in each experimental group compared with the control group (P＞0.05); the content of urea (UREA) in the experimental group at 200 mg/kg group, 400 mg/kg group and 800 mg/kg group was significantly reduced（P＜0.05） .
3. The effect of oregano essential oil on the antioxidant function, non-specific immunity and anti-pathogenic infection of gibel carp

Antioxidant indexes such as superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC) and malondialdehyde (MDA) content of gibel carp in the experimental group were no significant difference from those in the control group (P＞0.05); The total protein, albumin and complement C3 of 200 mg/kg group and 400 mg/kg group were significantly higher than those of the control group (P＜0.05); After Aeromonas hydrophila challenged, the survival rate of 200, 400 and 800 mg/kg
group was significantly higher than that of the control group and the relative percent survival of 400 and 800 mg/kg group was significantly higher than that of 25, 50, 100 mg/kg group (P＜0.05).

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