Variability in delivery of nutrients to lactating dairy cows
Variability in delivery of nutrients to lactating dairy cows
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DOI：
10.3168/jds.s0022-0302(98)75872-2
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发表时间：
1998-11-01
影响因子：
3.5
通讯作者：
Kertz, AF
中科院分区：
文献类型：
--
作者：
Kertz, AF
奶牛食用饲料，从中获取营养以满足其需求。水和干物质的摄入限制了整体营养素的摄入。饲料营养成分的变异性得到乳制品生产商的认可，并通过实验室分析程序加以解决。谷物、油籽和副产品的营养成分差异很大，大多数情况下低于NRC列出的值。然而，这些成分通常不会在分娩前或泌乳奶牛食用前进行分析。商业饲料是受管制的，必须提供一定浓度的主要营养素，并在饲料标签上列出成分。能量不能直接分析，但已通过体外、回归和总结性方程估计。从消化率到代谢能和净能的转换也可以简单地从系数或通过使用基于个别饲料或饮食的营养成分的经验模型来估计。必须考虑储存和处理损失，必须通过供应商或检查样品实验室分析程序解决饲料的变化。成分和膳食营养素含量的知识对于任何计算和输送营养素的方法都是必不可少的，以满足泌乳奶牛的需求。
Dairy cows consume feedstuffs from which they derive nutrients to meet their requirements. Water and dry matter intake limit overall nutrient intake. The variability in the nutrient content of forages is recognized by dairy producers and is addressed with a laboratory analysis program. Grains, oilseeds, and byproducts vary considerably in nutrient content, most often being below values listed by the NRC. Nevertheless, these ingredients are usually not analyzed prior to delivery or prior to consumption by the lactating dairy cow. Commercial feeds are regulated and must provide certain concentrations of major nutrients and list the ingredients on the feed label. Energy cannot be directly analyzed but has been estimated by in vitro, regression, and summative equations. Conversions from digestibility to metabolizable and net energy are also estimated simply from coefficients or by using empirical models based on the nutritional composition of individual feedstuffs or diets. Storage and handling losses must be accounted for, and variability in feedstuffs must be addressed through the supplier or a check sample laboratory analysis program. Knowledge of ingredients and dietary nutrient content is essential for any method of computing and delivering nutrients to meet the requirements of the lactating dairy cow.