Grassland Science Research Department, Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork, Ireland.
J Dairy Sci. 2010 Oct;93(10):4976-85. doi: 10.3168/jds.2010-3245.
Increasing milk production from pasture while increasing grass dry matter intake (GDMI) and lowering methane (CH(4)) emissions are key objectives of low-cost dairy production systems. It was hypothesized that offering swards of low herbage mass with increased digestibility leads to increased milk output. A grazing experiment was undertaken to investigate the effects of varying levels of HM on CH(4) emissions, GDMI and milk production of grazing dairy cows during the mid-season grazing period (June to July). Prior to the experiment, 46 Holstein-Friesian dairy cows (46 d in milk) were randomly assigned to 1 of 2 treatments (n=23) in a randomized block design. The 2 treatments consisted of 2 target pregrazing HM: 1,000 kg of dry matter (DM)/ha (low herbage mass, LHM) or 2,200 kg of DM/ha (high herbage mass, HHM). The experimental period lasted 2 mo from June 1 until July 31. Within the experimental period, there were 2 measurement periods, measurement 1 (M1) and measurement 2 (M2), where CH(4) emissions, GDMI, and milk production were measured. Mean herbage mass throughout the measurement periods was 1,075 kg of DM/ha and 1,993 kg of DM/ha for the LHM and HHM treatments, respectively. Grass quality in terms of organic matter digestibility was significantly higher for the LHM treatment in M2 (+12 g/kg of DM). In M1, the effect of herbage mass on grass quality was approaching significance in favor of the LHM treatment. Herbage mass did not significantly affect milk production during the measurement periods. Cows grazing the LHM swards had increased GDMI in M1 (+1.5 kg of DM) compared with cows grazing the HHM swards; no difference in GDMI was observed in M2. Grazing HHM swards increased CH(4) production per cow per day (+42 g), per kilogram of milk yield (+3.5 g/kg of milk), per kilogram of milk solids (+47 g/kg of milk solids), and per kilogram of GDMI (+3.1 g/kg of GDMI) in M2. Cows grazing the HHM swards lost a greater proportion of their gross energy intake as CH(4) during both measurement periods (+0.9% and +1% for M1 and M2, respectively). It was concluded that grazing LHM swards would increase grass quality with a concurrent reduction in CH(4) emissions.
在降低成本的奶牛生产系统中，提高牧场牛奶产量，同时增加牧草干物质采食量（GDMI）并降低甲烷（CH(4)）排放是关键目标。据推测，提供具有更高消化率的低草料量的草地会导致牛奶产量增加。进行了一项放牧实验，以研究在中季放牧期间（6 月至 7 月），HM 水平的变化对放牧奶牛的 CH(4)排放、GDMI 和产奶量的影响。在实验前，将 46 头荷斯坦-弗里森奶牛（产奶 46 天）随机分配到 2 个处理（n=23）的随机区组设计中。2 种处理包括 2 种目标放牧前 HM：1000 公斤干物质（DM）/公顷（低牧草量，LHM）或 2200 公斤 DM/公顷（高牧草量，HHM）。实验期从 6 月 1 日持续到 7 月 31 日。在实验期间，有 2 个测量期，测量 1（M1）和测量 2（M2），在此期间测量 CH(4)排放、GDMI 和产奶量。在整个测量期内，LHM 和 HHM 处理的平均牧草量分别为 1075 公斤 DM/公顷和 1993 公斤 DM/公顷。在 M2 中，LHM 处理的牧草质量在有机物消化率方面明显更高（+12 克/公斤 DM）。在 M1 中，牧草质量对牧草质量的影响接近显著有利于 LHM 处理。在测量期间，牧草量对产奶量没有显著影响。与放牧 HHM 草地的奶牛相比，放牧 LHM 草地的奶牛在 M1 时 GDMI 增加（+1.5 公斤 DM）；在 M2 中未观察到 GDMI 差异。在 M2 中，放牧 HHM 草地会增加每头奶牛每天的 CH(4)产量（+42 克）、每公斤牛奶产量（+3.5 克/公斤牛奶）、每公斤牛奶固体（+47 克/公斤牛奶固体）和每公斤 GDMI（+3.1 克/公斤 GDMI）。在 M1 和 M2 期间，放牧 HHM 草地的奶牛分别有更大比例的总能量摄入以 CH(4)的形式损失（分别为+0.9%和+1%）。研究结论认为，放牧 LHM 草地会提高牧草质量，同时降低 CH(4)排放。
