Forages are a major source of nutrients for milk production, but little is known about the effects of forage species on whole-farm profitability and environmental performance. Using a whole-farm approach, the N-CyCLES (Nutrient-Cycling Crops-Livestock-Environment-Soil) optimization model, and experimentally measured data, this study aimed to compare the profitability and environmental performance of dairy farms when four alfalfa (Medicago sativa L.)-grass binary mixtures harvested and stored as silage and hay are used in ration formulation of heifers and lactating and dry cows: (a) alfalfa-timothy (Phleum pratense L.) (Al+Tim), (b) alfalfa-tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] (Al+TF), (c) alfalfa-meadow fescue fescue [Schedonorus pratensis (Huds.) P. Beauv.] (Al+MF), and (d) alfalfa-meadow bromegrass (Bromus biebersteinii Roem. & Schult.) (Al+Bro). Simulations were conducted on two virtual eastern Canadian dairy farms: southwestern (SWQ) and eastern Quebec (EQ). Comparisons were based on net income, greenhouse gas emissions, and nutrient balances. In SWQ, Al+Bro and Al+Tim led to the highest net income, but only slight differences were calculated between the four mixtures (maximum difference of 1.4%). In EQ, results suggested that Al+TF is the most viable alternative to Al+Tim mixtures as it allowed the farm to reach the highest profit (maximum difference of 8%). The choice of grass in alfalfa-grass binary mixture had little impact on the farm's total greenhouse gas emissions: the lowest total greenhouse gas emissions were with Al+ MF in SWQ and with Al+TF in EQ. In SWQ, phosphorus balance was low for the four mixtures and the lowest nitrogen balance was reached with Al+MF and Al+Tim. Finally, in EQ, the lowest phosphorus balance was reached with Al+MF, whereas the lowest nitrogen balance was reached with Al+Bro. In conclusion, despite slight differences, all grass species tested allowed the farm to reach similar profits and environmental performance.

中文翻译：

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模拟加拿大东部奶牛场四种苜蓿草二元混合物的整个农场盈利能力和环境绩效

牧草是牛奶生产营养的主要来源，但关于牧草种类对整个农场盈利能力和环境绩效的影响知之甚少。本研究采用全农场方法、N-CyCLES（营养循环作物-牲畜-环境-土壤）优化模型和实验测量数据，旨在比较四种苜蓿（Medicago sativa L.)-作为青贮饲料和干草收获和储存的草二元混合物用于小母牛和泌乳牛和干奶牛的日粮配方：(a) 苜蓿草( Phleum pratense L.) (Al+Tim)，(b) 苜蓿-高羊茅 [ Schedonorus arundinaceus (Schreb.) Dumort.] (Al+TF), (c) 苜蓿草甸羊茅 [Schedonorus pratensis (Huds.) P. Beauv.] (Al+MF) 和 (d) 苜蓿草甸雀麦草 ( Bromus biebersteinii罗姆。＆舒尔特。）（Al + Bro）。在两个虚拟的加拿大东部奶牛场进行了模拟：西南 (SWQ) 和魁北克东部 (EQ)。比较基于净收入、温室气体排放和营养平衡。在 SWQ 中，Al+Bro 和 Al+Tim 导致最高的净收入，但计算出四种混合物之间的差异很小（最大差异为 1.4%）。在 EQ 中，结果表明 Al+TF 是 Al+Tim 混合物最可行的替代品，因为它可以让农场达到最高的利润（最大差异为 8%）。在苜蓿草二元混合物中草的选择对农场的温室气体总排放量几乎没有影响：温室气体总排放量最低的是 SWQ 中的 Al+MF 和 EQ 中的 Al+TF。在 SWQ，四种混合物的磷平衡较低，Al+MF 和 Al+Tim 达到最低的氮平衡。最后，在 EQ 中，Al+MF 达到了最低的磷平衡，而 Al+Bro 达到了最低的氮平衡。总之，尽管略有不同，但所有测试的草种都使农场达到了相似的利润和环境绩效。