In the last 20 years there has been extensive in vitro research on the effects of plant extracts and essential oils on rumen microbial fermentation. The main objectives have been to improve energy metabolism through a reduction in methane emissions and an increase in propionate production; and to improve protein metabolism by reducing proteolysis and deamination. While the positive results from in vitro studies has stimulated the release of commercial products based on blends of essential oils, there is limited in vivo evidence on the rumen fermentation and production performance effects. A literature search was conducted to select in vivo studies where information on rumen fermentation and animal performance was reported. For dairy cattle, we identified 37 studies of which 21 were adequate to test production performance. Ten studies reported increases and 3 decreases in milk yield. For beef cattle, we identified 20 studies with rumen fermentation profile and 22 with performance data. Average daily gain improved in 7 and decreased in 1 study. Only 1 out of 16 studies reported an improvement in feed efficiency. Data indicate that out of more than 500 products tested in vitro, only around 20 have been tested in vivo in different mixtures and doses. The use of statistical approaches will allow to describe the conditions, doses and responses in dairy and beef cattle performance. The search for postruminal effects offers another alternative use. Evidence for effects on the intestinal and systemic effects on the immune system and antioxidant status (i.e., capsicum, garlic, eugenol, cinnamaldehyde curcuma, catechins, anethol or pinene), and in the modulation of metabolic regulation (capsicum, cinnamaldehyde, curcuma or garlic) may open the opportunity for future applications. However, stability of the product in the GI tract, description of the mechanisms of action and the impact of these changes on performance needs to be further demonstrated.

中文翻译：

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67 植物生物活性化合物在奶牛和肉牛中的应用现状和未来展望

在过去的 20 年中，对植物提取物和精油对瘤胃微生物发酵的影响进行了广泛的体外研究。主要目标是通过减少甲烷排放和增加丙酸盐产量来改善能量代谢；并通过减少蛋白水解和脱氨基作用来改善蛋白质代谢。虽然体外研究的积极结果刺激了基于精油混合物的商业产品的发布，但关于瘤胃发酵和生产性能影响的体内证据有限。进行文献检索以选择报告瘤胃发酵和动物性能信息的体内研究。对于奶牛，我们确定了 37 项研究，其中 21 项足以测试生产性能。10 项研究报告了产奶量增加和 3 项减少。对于肉牛，我们确定了 20 项具有瘤胃发酵特征的研究和 22 项具有性能数据的研究。7 项研究的平均日增重增加，1 项研究减少。16 项研究中只有 1 项报告饲料效率有所提高。数据表明，在体外测试的 500 多种产品中，只有大约 20 种以不同的混合物和剂量进行了体内测试。统计方法的使用将允许描述奶牛和肉牛性能的条件、剂量和反应。寻找瘤后效应提供了另一种替代用途。对肠道的影响和对免疫系统和抗氧化状态的全身影响的证据（即辣椒、大蒜、丁香酚、肉桂醛姜黄、儿茶素、茴香脑或蒎烯），并且在调节代谢调节（辣椒、肉桂醛、姜黄或大蒜）方面可能为未来的应用开辟机会。然而，产品在胃肠道中的稳定性、作用机制的描述以及这些变化对性能的影响需要进一步证明。