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、禾本科植物和豆类牧场的奶牛的牛奶产量、氮利用率和甲烷排放量。


在不破坏环境的情况下实现高动物生产力是牧场奶牛养殖的主要目标。本研究调查了春季草料基地从草三叶草牧场改为杂草或豆类牧场对俄勒冈州西部泽西奶牛产奶量、氮利用率和甲烷排放量的影响。 27头泌乳中期奶牛被随机分配到三种牧场处理之一：以草三叶草为基础的牧场，由羊茅、高羊茅、果园草和白三叶草（草）组成；以禾本科植物为基础的牧场，由菊苣、车前草和白三叶草 (Forb) 组成；以及由红三叶草、鸟足三叶草、berseem 三叶草和巴兰萨三叶草（豆科植物）组成的豆科牧草。牧场以随机完整的区组设计排列，具有三个重复（即区块），每个重复由一组三头奶牛放牧。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。与草相比，豆类和杂草的奶牛饲料质量和干物质摄入量 (DMI) 更高 ( P ≤ 0.05)，因此牛奶和乳固体产量更高 ( P < 0.01)。与放牧其他牧场的奶牛相比，放牧福布草的奶牛牛奶中的乳糖和亚油酸含量更高（ P < 0.01），而与草场相比，放牧福布草的奶牛的体细胞计数更少（ P = 0.04）。与放牧其他牧场的奶牛相比，放牧福布的奶牛尿液、牛奶和血液中的氮含量显着减少 ( P < 0.01)，使用 MUN 计算的牛奶合成氮利用效率更高 ( P < 0.01)，但也更大 (P < 0.01)。 P < 0.01) 粪便氮含量，表明氮从尿液转移到粪便。 与草相比，草和豆类对奶牛都有利尿作用，尿液中的肌酐浓度较低 ( P < 0.01)。与其他牧场相比，在福布牧场放牧的奶牛的甲烷排放量往往较少 ( P = 0.07)。结果表明，与豆类牧场相比，福布牧场可以支持动物生产性能、牛奶质量和健康；然而，福布牧场还提供了额外的好处，即减少牧场乳制品生产对环境的影响。