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首页> 外文期刊>Animal Feed Science and Technology >Estimating greenhouse gas emissions from New Zealand dairy systems using a mechanistic whole farm model and inventory methodology
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Estimating greenhouse gas emissions from New Zealand dairy systems using a mechanistic whole farm model and inventory methodology

机译：使用机械化整体农场模型和清单方法估算新西兰奶业系统的温室气体排放量

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The strategy for New Zealand dairy farming (DairyNZ, 2009) formulates targets for increased national milk production and a reduction in greenhouse gas (GHG) emissions, but acknowledges these two targets conflict because GHG typically increase with increased milk output. Our objective was to determine if both targets could be achieved by implementing combinations of five mitigations. A farm scale computer model, which includes a mechanistic cow model, was used to model a typical pasture based New Zealand dairy farm as the baseline farm. The five mitigations were: (1) improved reproductive performance of the herd resulting in lower replacement rates, (2) increased genetic merit of the cows combined with lower stocking rate and longer lactations, (3) keeping lactating cows on a loafing pad for 12 h/day for 2 mo during autumn, (4) growing low protein crops of grains and/or silages of maize, barley and oats on a portion of the farm and feeding this to lactating cows, (5) reducing fertilizer N use and replacing some of this with nitrification inhibitors and the plant growth stimulant gibberellins. No single mitigation strategy achieved both targets of increasing production by 10-15% and reducing GHG emissions by 20%, but when all were simultaneously implemented in the baseline farm, milk production increased by 15-20% to 1200 kg milk fat + protein/ha, and absolute GHG emissions decreased by 15-20% to 0.8 kg CO2-equivalents (CO2-e)/kg fat and protein corrected milk (FPCM), which is equivalent to a decrease from 11.7 to 8.2 kg CO2-e/kg fat + protein. The synergies of the mitigations resulted in reduced dry matter intake and enteric CH4 emissions, a reduction in N input and N dilution in feed, and, therefore, reduced urinary N excretion onto pastures, and an increase in feed conversion efficiency (i.e., more feed was used for production and less for maintenance). Mechanistic CH4 models as part of farm scale models are important because current GHG inventory methodology cannot properly evaluate CH4 emissions for a range of potential mitigation strategies. There is also a need to develop capabilities in farm scale models to accurately simulate urine patches and N2O emissions from these patches. This paper is part of the special issue entitled: Greenhouse Gases in Animal Agriculture Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X Hao, S. McGinn and Editor for Animal Feed Science and Technology, PH. Robinson
机译：新西兰奶牛养殖战略（DairyNZ，2009年）制定了提高全国牛奶产量和减少温室气体（GHG）排放的目标，但承认这两个目标存在冲突，因为温室气体通常随着牛奶产量的增加而增加。我们的目标是确定是否可以通过实施五个缓解措施的组合来实现两个目标。农场规模的计算机模型（包括机械牛模型）被用来对基于新西兰牧场的典型牧场作为基线农场进行建模。这五项缓解措施是：（1）提高牛群的繁殖性能，从而降低替代率;（2）增加母牛的遗传价值，同时降低放牧率和延长泌乳时间;（3）将哺乳期的母牛在垫子上保持12头秋季每天2个小时的小时/天，（4）在农场的一部分上种​​植低蛋白的谷类和/或玉米，大麦和燕麦青贮饲料，并将其喂给泌乳母牛，（5）减少肥料氮的使用并更换其中一些与硝化抑制剂和植物生长刺激物赤霉素有关。没有一个单一的缓解策略能够同时实现将产量提高10-15％和减少温室气体排放20％的目标，但是当在基准农场同时实施所有措施时，牛奶产量增加了15-20％，达到1200公斤乳脂+蛋白质/公顷，绝对温室气体排放量减少15-20％，降至0.8千克二氧化碳当量（CO2-e）/ kg脂肪和蛋白质校正乳（FPCM），相当于从11.7千克减少至8.2千克CO2-e / kg脂肪+蛋白质。缓解措施的协同作用导致减少了干物质的摄入和肠内CH4的排放，减少了饲料中氮的输入和氮的稀释，因此减少了草场中尿液氮的排泄，并提高了饲料转化效率（即增加了饲料量）用于生产，较少用于维护）。机械CH4模型作为农场规模模型的一部分非常重要，因为当前的温室气体清单方法无法针对一系列潜在的缓解策略正确评估CH4排放量。还需要开发农场规模模型中的功能，以准确模拟尿斑和这些斑中的N2O排放。该论文是《农业农业中的温室气体在食物和排放之间找到平衡》一期特刊的一部分，由T.A.撰写。麦卡利斯特（McAllister），客座编辑：K.A。 Beauchemin，X Hao，S. McGinn，动物饲料科学与技术编辑，PH。罗宾逊

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