Data from: Starch and dextrose at 2 levels of rumen-degradable protein in iso-nitrogenous diets: Effects on lactation performance, ruminal measurements, methane emission, digestibility, and nitrogen balance of dairy cows

This feeding trial was designed to investigate two separate questions. The first question is, “What are the effects of substituting two non-fiber carbohydrate (NFC) sources at two rumen-degradable protein (RDP) levels in the diet on apparent total-tract nutrient digestibility, manure production and nitrogen (N) excretion in dairy cows?”. This is relevant because most of the N ingested by dairy cows is excreted, resulting in negative effects on environmental quality. The second question is, “Is phenotypic residual feed intake (pRFI) correlated with feed efficiency, N use efficiency, and metabolic energy losses (via urinary N and enteric CH4) in dairy cows?”. The pRFI is the difference between what an animal is expected to eat, given its level of productivity, and what it actually eats. The goal was to determine whether production of CH4, urinary N or fecal N is a driver of pRFI.
This experiment was conducted at the Dairy Cattle Center of University of Wisconsin-Madison. The use and care of animals was approved by the University of Wisconsin-Madison Research Animal and Resource Committee.

本饲养试验旨在探究两个独立的问题。第一个问题是，在饲料中用两种非纤维碳水化合物（NFC）来源替代两种瘤胃降解蛋白（RDP）水平，对奶牛的表观总消化率、粪便产生和氮（N）排泄有何影响？这一问题具有重要意义，因为奶牛摄入的大多数氮最终以排泄物的形式排出，对环境质量产生负面影响。第二个问题是，表型残余采食量（pRFI）是否与饲料效率、氮利用效率以及代谢能量损失（通过尿液中的氮和肠道中的甲烷）相关？pRFI是指动物在给定生产力水平下预期采食量与实际采食量之间的差异。研究目标在于确定甲烷、尿液氮或粪便氮的产生是否是pRFI的驱动因素。该实验在威斯康星大学麦迪逊分校奶牛研究中心进行。动物的使用与照料已获得威斯康星大学麦迪逊分校研究动物和资源委员会的批准。