Department of Animal and Rangeland Sciences, Oregon State University, Corvallis, OR.
Department of Plants, Soils, and Climate, Utah State University, Logan, UT.
J Anim Sci. 2020 Jul 1;98(7). doi: 10.1093/jas/skaa220.
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, bird's-foot 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 with cows grazing the other pastures, and less (P = 0.04) somatic cell counts compared with Grass. Cows grazing Forb had substantially less (P < 0.01) N in urine, milk, and blood compared with cows grazing the other pastures, with not only a greater (P < 0.01) efficiency of N utilization for milk synthesis calculated using milk urea nitrogen 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 with Grass. Methane emissions tended to be less (P = 0.07) in cows grazed on Forb vs. the other pastures. The results indicate that 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.
在牧场式奶牛养殖中，实现高产而不破坏环境是主要目标。本研究调查了在俄勒冈西部，春季将饲草基础从三叶草-草地改为杂类草或豆科草地对泽西奶牛产奶量、氮利用和甲烷排放的影响。27 头泌乳中期奶牛被随机分配到三种牧场处理之一：由 festulolium、高羊茅、果园草和白三叶草组成的三叶草草地（Grass）；由菊苣、车前草和白三叶草组成的杂类草草地（Forb）；由红三叶草、鸟足三叶草、波斯黑麦草和百脉根组成的豆科草地（Legume）。牧场采用随机完全区组设计，每个区组有三个重复（即块），每个重复由三组奶牛放牧。测定了饲草的生产性能和营养价值、动物性能、牛奶成分、氮分配和甲烷排放。与 Grass 相比，Legume 和 Forb 的饲草质量和奶牛干物质采食量（DMI）更高（P≤0.05），导致产奶量和乳固体产量更高（P＜0.01）。与放牧其他草地的奶牛相比，放牧 Forb 的奶牛的牛奶中乳糖和亚油酸含量更高（P＜0.01），体细胞计数更低（P=0.04）。与放牧其他草地的奶牛相比，放牧 Forb 的奶牛尿液、牛奶和血液中的氮含量明显更少（P＜0.01），用牛奶尿素氮计算的氮用于合成牛奶的效率更高（P＜0.01），粪便中的氮含量也更大（P＜0.01），表明氮从尿液转移到粪便。与 Grass 相比，Forb 和 Legume 都对奶牛有排利尿作用，表现为尿液中肌酐浓度更低（P＜0.01）。与放牧其他草地的奶牛相比，放牧 Forb 的奶牛的甲烷排放量有降低的趋势（P=0.07）。结果表明，与豆科草地相比，杂类草草地可以支持动物生产性能、牛奶质量和健康状况相当，但杂类草草地还具有减少牧场式奶牛生产对环境影响的额外益处。
