The role of condensed tannins in ruminant animal production: advances, limitations and future directions
The role of condensed tannins in ruminant animal production: advances, limitations and future directions
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DOI：
10.1590/s1806-92902017001200009
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发表时间：
2017-12-01
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影响因子：
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通讯作者：
Huntley, Nichole F.
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作者：
Naumann, Harley D.;Tedeschi, Luis O.;Huntley, Nichole F.
单宁是植物中含量最丰富的多酚化合物之一。单宁在自然界中以多种独特的化学物质存在。最常见的单宁通常根据化学结构分为两大类：水解性单宁(HT)或缩合单宁(CT)。可水解单宁是连接在多元醇核上的没食子酸酯或鞣花酸的酯，通常是葡萄糖。缩合单宁或原花青素由连接在一起的黄烷-3-醇亚单位组成，形成齐聚物和聚合物。HT和CT都被定义为收敛的、中到高相对分子质量的多酚化合物，其特征是结合和沉淀可溶蛋白质。本文的目的是介绍CT与反刍动物相互作用的最新进展，了解和使用CT在反刍动物生产中的局限性，以及未来研究的需要，以进一步提高我们对CT在优化反刍动物生产中的作用的认识。缩合单宁对反刍动物造成了一些抗营养问题，因为它们的收敛特性减少了饲料摄入量，从而降低了动物的生产性能。然而，反刍动物可以通过慢慢使瘤胃微生物适应CT的毒性作用以及通过释放与CT结合的唾液蛋白来耐受CT。CT的蛋白质结合能力对反刍动物有一定的好处，因为它与必需氨基酸形成络合物，防止它们在瘤胃中降解，但在较低的肠道中释放出来，供动物吸收。最近的数据表明，当给生长中的动物服用CT时，N的存留量增加。使用CT和HT驱虫有潜在的好处，因为它们能够抑制胃肠道线虫寄生虫的卵孵化和幼虫运动，特别是在小型反刍动物中。缩合单宁还能与矿物质(铝、钙、钴、铜、铁、镁、锰、磷和锌)结合。尽管对反刍动物的研究一直是相互矛盾的，但有报道称，由于CT-金属离子络合物在较宽的pH范围内是稳定的，CT可能会降低矿物的生物利用率。通过饲喂CT减少甲烷可能是对反刍动物生产最有影响的好处。已经开发了许多经验公式来预测瘤胃甲烷排放，但包括CT在内的很少。未来的研究应集中于改进评估CT生物活性的方法学，与其他植物专门化代谢物的相互作用，以及相关的对反刍动物的生理和营养影响。
Tannins represent one of the most abundant polyphenolic compounds in plants. Tannins exist as a multitude of chemically unique entities in nature. The most commonly occurring tannins are typically divided into two major classes based on chemical structure: hydrolysable (HT) or condensed tannins (CT). Hydrolysable tannins are esters of gallic or ellagic acid linked to a polyol core, typically glucose. Condensed tannins or proanthocyanidins consist of flavan-3-ol subunits linked together to form oligomers and polymers. Both HT and CT are defined as astringent, medium-to-high-molecular weight polyphenolic compounds that characteristically bind and precipitate soluble proteins. The objective of this paper was to present recent advances in CT-ruminant interactions, the limitations associated with understanding and using CT in ruminant animal production, and future needs for research to further advance our knowledge of the role of CT in optimization of ruminant animal production. Condensed tannins pose some anti-nutritional problems to ruminants due to their astringent property that reduces feed intake and, consequently, animal performance. Ruminants can, however, tolerate CT by slowly adapting the ruminal microbes to the toxic effects of CT and by releasing CT-binding salivary proteins. The protein-binding ability of CT has some benefits to the ruminant due to complexes formed with essential amino acids, preventing their degradation in the rumen, but releasing them in the lower gut for absorption by the animal. Recent data have suggested increased N retention when CT is given to growing animals. There are potential benefits of using CT and HT for anthelmintic purposes due to their ability to inhibit egg hatching and larval motility of gastrointestinal nematode parasites, especially in small ruminants. Condensed tannins also bind to minerals (Al, Ca, Co, Cu, Fe, Mg, Mn, P, and Zn). Although studies with ruminants have been contradictory, it has been reported that because the CT-metal ion complex is stable over a wide pH range, CT may reduce the bioavailability of minerals. Methane mitigation by feeding CT might be the most impactful benefit for ruminant production. Many empirical equations have been developed to predict ruminal methane emissions, but very few have included CT. Future research should focus on the improvement of methodology to assess CT biological activity, interaction with other plant-specialized metabolites, and associated physiological and nutritional impacts on ruminants.