Eastridge M L, Bucholtz H F, Slater A L, Hall C S
Department of Animal Sciences, Ohio State University, Columbus 43210, USA.
J Dairy Sci. 1998 Nov;81(11):3049-62. doi: 10.3168/jds.S0022-0302(98)75870-9.
The first edition of the Nutrient Requirements of Dairy Cattle was published by the National Research Council (NRC) in 1945. The current document is the sixth revised edition, published in 1989, and it appears that we are a few years from another edition being in print. Software designed to evaluate and formulate rations for dairy cattle commonly determine nutrient requirements using the NRC as a standard. However, the generation of new knowledge in dairy nutrition occurs more rapidly than the release of the NRC publication, and the developers of the software often modify the requirements based on more recently published research, geographical peculiarities, or factors not explicitly considered by NRC. The first step in evaluating or formulating rations is the prediction of dry matter intake (DMI). The primary variables used by NRC to predict DMI are body weight (BW) and fat-corrected milk (FCM) yield; however, developers of software programs often use different equations based on personal preference, availability of research data with given equations, and incorporation of other factors in addition to BW and FCM yield. The additional factors are included to provide a more dynamic estimation of DMI and, therefore, reduce the difference between predicted and actual DMI. Nutrients required for maintenance, lactation, and growth must be consumed in adequate quantities (e.g., kilograms or calories), but the dietary concentration of nutrients for a given animal group may differ because of DMI. Even when nutrients are fed above the requirements, dietary concentrations of nutrients may be important in some situations to minimize the risk of underfeeding caused by variability in the nutrient composition of feedstuffs and to account for interactions of certain nutrients (e.g., minerals). New research discoveries need to be incorporated into ration formulation strategies promptly, and the strategies used for ration formulation need to be dynamic.
《奶牛营养需求》第一版由美国国家研究委员会（NRC）于1945年出版。当前版本是1989年出版的第六次修订版，看起来距离下一版付梓还有几年时间。用于评估和制定奶牛日粮配方的软件通常以NRC标准来确定营养需求。然而，奶牛营养领域新知识的产生速度比NRC出版物的发布速度更快，软件开发者常常根据最新发表的研究、地域特点或NRC未明确考虑的因素来修改营养需求。评估或制定日粮配方的第一步是预测干物质采食量（DMI）。NRC用于预测DMI的主要变量是体重（BW）和脂肪校正乳（FCM）产量；然而，软件程序开发者常常根据个人偏好、特定公式的研究数据可用性以及除BW和FCM产量之外纳入其他因素，使用不同的公式。纳入这些额外因素是为了更动态地估计DMI，从而减少预测DMI与实际DMI之间的差异。维持、泌乳和生长所需的营养物质必须摄入足够的量（例如，千克或卡路里），但由于DMI的原因，给定动物群体日粮中营养物质的浓度可能会有所不同。即使提供的营养物质超过需求，在某些情况下，日粮中营养物质的浓度对于将饲料原料营养成分变异性导致的采食不足风险降至最低以及考虑某些营养物质（例如矿物质）之间的相互作用可能也很重要。新的研究发现需要迅速纳入日粮配方策略中，并且用于日粮配方的策略需要具有动态性。
