Tedeschi Luis O, Muir James P, Naumann Harley D, Norris Aaron B, Ramírez-Restrepo Carlos A, Mertens-Talcott Susanne U
Department of Animal Science, Texas A&M University, College Station, TX, United States.
Texas A&M AgriLife Research, Stephenville, TX, United States.
Front Vet Sci. 2021 Mar 5;8:628445. doi: 10.3389/fvets.2021.628445. eCollection 2021.
This review provides an update of ecologically relevant phytochemicals for ruminant production, focusing on their contribution to advancing nutrition. Phytochemicals embody a broad spectrum of chemical components that influence resource competence and biological advantage in determining plant species' distribution and density in different ecosystems. These natural compounds also often act as plant defensive chemicals against predatorial microbes, insects, and herbivores. They may modulate or exacerbate microbial transactions in the gastrointestinal tract and physiological responses in ruminant microbiomes. To harness their production-enhancing characteristics, phytochemicals have been actively researched as feed additives to manipulate ruminal fermentation and establish other phytochemoprophylactic (prevent animal diseases) and phytochemotherapeutic (treat animal diseases) roles. However, phytochemical-host interactions, the exact mechanism of action, and their effects require more profound elucidation to provide definitive recommendations for ruminant production. The majority of phytochemicals of nutritional and pharmacological interest are typically classified as flavonoids (9%), terpenoids (55%), and alkaloids (36%). Within flavonoids, polyphenolics (e.g., hydrolyzable and condensed tannins) have many benefits to ruminants, including reducing methane (CH) emission, gastrointestinal nematode parasitism, and ruminal proteolysis. Within terpenoids, saponins and essential oils also mitigate CH emission, but triterpenoid saponins have rich biochemical structures with many clinical benefits in humans. The anti-methanogenic property in ruminants is variable because of the simultaneous targeting of several physiological pathways. This may explain saponin-containing forages' relative safety for long-term use and describe associated molecular interactions on all ruminant metabolism phases. Alkaloids are N-containing compounds with vast pharmacological properties currently used to treat humans, but their phytochemical usage as feed additives in ruminants has yet to be exploited as they may act as ghost compounds alongside other phytochemicals of known importance. We discussed strategic recommendations for phytochemicals to support sustainable ruminant production, such as replacements for antibiotics and anthelmintics. Topics that merit further examination are discussed and include the role of fresh forages vis-à-vis processed feeds in confined ruminant operations. Applications and benefits of phytochemicals to humankind are yet to be fully understood or utilized. Scientific explorations have provided promising results, pending thorough vetting before primetime use, such that academic and commercial interests in the technology are fully adopted.
本综述介绍了与反刍动物生产相关的生态植物化学物质的最新情况，重点关注它们在促进营养方面的作用。植物化学物质包含多种化学成分，这些成分在决定不同生态系统中植物物种的分布和密度方面影响着资源竞争力和生物优势。这些天然化合物还常常充当植物抵御捕食性微生物、昆虫和食草动物的防御性化学物质。它们可能调节或加剧胃肠道中的微生物相互作用以及反刍动物微生物群中的生理反应。为了利用它们的增产特性，人们积极研究将植物化学物质用作饲料添加剂，以控制瘤胃发酵，并确立其他植物化学预防（预防动物疾病）和植物化学治疗（治疗动物疾病）的作用。然而，植物化学物质与宿主的相互作用、确切作用机制及其效果需要更深入的阐释，以便为反刍动物生产提供明确的建议。大多数具有营养和药理意义的植物化学物质通常分为黄酮类化合物（9%）、萜类化合物（55%）和生物碱（36%）。在黄酮类化合物中，多酚类物质（如可水解单宁和缩合单宁）对反刍动物有诸多益处，包括减少甲烷（CH）排放、胃肠道线虫寄生和瘤胃蛋白水解。在萜类化合物中，皂苷和精油也能减少CH排放，但三萜皂苷具有丰富的生化结构，对人类有许多临床益处。反刍动物中的抗产甲烷特性存在差异，因为它同时针对多种生理途径。这或许可以解释含皂苷饲料长期使用的相对安全性，并描述其在反刍动物所有代谢阶段的相关分子相互作用。生物碱是含氮化合物，具有广泛的药理特性，目前用于治疗人类疾病，但它们作为反刍动物饲料添加剂的植物化学用途尚未得到开发，因为它们可能与其他已知重要的植物化学物质一起作为“幽灵化合物”起作用。我们讨论了支持反刍动物可持续生产的植物化学物质的战略建议，例如替代抗生素和驱虫药。文中还讨论了值得进一步研究的主题，包括新鲜饲料与加工饲料在圈养反刍动物养殖中的作用。植物化学物质对人类的应用和益处尚未得到充分理解或利用。科学探索已取得了有前景的成果，但在广泛应用之前还需全面审查，以便充分发挥学术界和商业界对该技术的兴趣。
