Achieving high animal productivity without degrading the environment is the primary target in pasture based-dairy farming. This study investigated the effects of changing the forage base in spring from grass-clover pastures to forb or legume-based pastures on milk yield, N utilization and methane emissions of Jersey cows in Western Oregon. Twenty-seven mid-lactation dairy cows were randomly assigned to one of three pasture treatments: grass-clover based pasture composed of festulolium, tall fescue, orchardgrass, and white clover (Grass); forb-based pasture composed of chicory, plantain, and white clover (Forb); and legume-based pasture composed of red clover, birdsfoot trefoil, berseem clover and balansa clover (Legume). Pastures were arranged in a randomized complete block design with three replicates (i.e., blocks) with each replicate grazed by a group of three cows. Production and nutritive quality of the forages, animal performance, milk components, nitrogen partitioning, and methane emissions were measured. Feed quality and dry matter intake (DMI) of cows were greater (P ≤ 0.05) for Legume and Forb vs. Grass, with consequent greater milk and milk solids yields (P < 0.01). Cows grazing Forb also had more (P < 0.01) lactose and linoleic acid in milk compared to cows grazing the other pastures, and less (P = 0.04) somatic cell counts compared to Grass. Cows grazing Forb had substantially less (P < 0.01) N in urine, milk, and blood compared to cows grazing the other pastures, with a greater (P < 0.01) efficiency of N utilization for milk synthesis calculated using MUN but also a larger (P < 0.01) fecal N content, indicating a shift of N from urine to feces. Both Forb and Legume had a diuretic effect on cows, as indicated by the lower (P < 0.01) creatinine concentration in urine compared to Grass. Methane emissions tended to be less (P = 0.07) in cows grazed on Forb vs. the other pastures. The results indicate Forb pasture can support animal performance, milk quality, and health, comparable to Legume pasture; however, Forb pasture provides the additional benefit of reduced environmental impact of pasture-based dairy production.

中文翻译：

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放牧草，牧草和豆类牧场的奶牛的牛奶产量，氮利用率和甲烷排放量。

在不损害环境的前提下实现高动物生产率是牧场奶牛养殖的主要目标。这项研究调查了春季将草料基地从草三叶草牧场改为草皮或豆类牧场对俄勒冈州西部泽西奶牛的牛奶产量，氮利用和甲烷排放的影响。二十七头哺乳中期的奶牛被随机分配到三种牧场处理方法之一：草草三叶草组成的牧场，由草木，高羊茅，果园和白三叶草组成（草）；由菊苣，车前草和白三叶草组成的基于福布的牧场（福布）；以及以豆科植物为主的草场，由红三叶草，鸟足三叶草，伯尔西姆三叶草和巴兰萨三叶草（Legume）组成。牧场按照随机完整的街区设计进行布置，一式三份（即 街区），每个副本由一组三头母牛放牧。测量了草料的产量和营养质量，动物性能，牛奶成分，氮分配和甲烷排放。母牛的饲料质量和干物质摄入量（DMI）更高（P ≤0.05）为豆科和FORB与草，具有随之而来的较大的牛奶和奶固体的产率（P <0.01）。与放牧其他牧场的母牛相比，放牧Forb的母牛的牛奶中的乳糖和亚油酸含量更高（P <0.01），并且与草相比，体细胞数量更少（P = 0.04）。与放牧Forb的母牛相比，在其他牧场放牧的牛的尿，牛奶和血液中的N含量要少得多（P <0.01），使用MUN计算得出的牛奶合成中的氮利用效率更高（P <0.01），但更大（P <0.01）粪中N含量，表明N从尿液转移到粪便。Forb和豆科植物均对母牛有利尿作用，与草相比，尿液中的肌酐浓度P <0.01）。与其他牧场相比，在福布斯（Forb）放牧的奶牛的甲烷排放量往往较少（P = 0.07）。结果表明，Forb牧场可与豆类牧场相比，可支持动物的生产性能，牛奶质量和健康。但是，Forb牧场带来的其他好处是减少了基于牧场的乳制品生产对环境的影响。