Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames 50011.
J Dairy Sci. 2018 Apr;101(4):2763-2813. doi: 10.3168/jds.2017-13112. Epub 2018 Feb 4.
Several minerals are required for life to exist. In animals, 7 elements (Ca, P, Mg, Na, K, Cl, and S) are required to be present in the diet in fairly large amounts (grams to tens of grams each day for the dairy cow) and are termed macrominerals. Several other elements are termed microminerals or trace minerals because they are required in much smaller amounts (milligrams to micrograms each day). In most cases the mineral in the diet must be absorbed across the gastrointestinal mucosa and enter the blood if it is to be of value to the animal. The bulk of this review discusses the paracellular and transcellular mechanisms used by the gastrointestinal tract to absorb each of the various minerals needed. Unfortunately, particularly in ruminants, interactions between minerals and other substances within the diet can occur within the digestive tract that impair mineral absorption. The attributes of organic or chelated minerals that might permit diet minerals to circumvent factors that inhibit absorption of more traditional inorganic forms of these minerals are discussed. Once absorbed, minerals are used in many ways. One focus of this review is the effect macrominerals have on the acid-base status of the animal. Manipulation of dietary cation and anion content is commonly used as a tool in the dry period and during lactation to improve performance. A section on how the strong ion theory can be used to understand these effects is included. Many microminerals play a role in the body as cofactors of enzymes involved in controlling free radicals within the body and are vital to antioxidant capabilities. Those same minerals, when consumed in excess, can become pro-oxidants in the body, generating destructive free radicals. Complex interactions between minerals can compromise the effectiveness of a diet in promoting health and productivity of the cow. The objective of this review is to provide insight into some of these mechanisms.
有几种矿物质是生命存在所必需的。在动物中，有 7 种元素（钙、磷、镁、钠、钾、氯和硫）需要存在于饮食中，并且需要大量存在（每天几克到几十克），这些元素被称为常量矿物质。还有几种其他元素被称为微量元素或痕量矿物质，因为它们的需求量非常小（每天几毫克到几微克）。在大多数情况下，饮食中的矿物质必须通过胃肠道黏膜吸收并进入血液，才能对动物有价值。本文综述的大部分内容讨论了胃肠道用于吸收各种所需矿物质的细胞旁和细胞内机制。不幸的是，特别是在反刍动物中，饮食中的矿物质与其他物质之间可能会在消化道内发生相互作用，从而影响矿物质的吸收。本文讨论了有机或螯合矿物质的特性，这些特性可能使饮食中的矿物质能够规避抑制这些矿物质更传统无机形式吸收的因素。一旦被吸收，矿物质就会以多种方式被利用。本文的一个重点是研究常量矿物质对动物酸碱平衡状态的影响。在干奶期和泌乳期，通过操纵日粮中阳离子和阴离子的含量来改善生产性能是一种常用的方法。本文还包括了一个关于如何使用强离子理论来理解这些影响的部分。许多微量元素作为参与体内自由基控制的酶的辅助因子，在体内发挥作用，对抗氧化能力至关重要。当这些微量元素摄入过量时，它们在体内可能成为促氧化剂，产生破坏性的自由基。矿物质之间的复杂相互作用会降低饮食促进奶牛健康和生产力的效果。本文的目的是提供对这些机制的一些深入了解。
