Abstract

Between increasing public concerns over climate change and heightened interest of niche market beef on social media, the demand for grass-fed beef has increased considerably. However, the demand increase for grass-fed beef has raised many producers’ and consumers’ concerns regarding product quality, economic viability, and environmental impacts that have thus far gone unanswered. Therefore, using a holistic approach, we investigated the performance, carcass quality, financial outcomes, and environmental impacts of four grass-fed and grain-fed beef systems currently being performed by ranchers in California. The treatments included 1) steers stocked on pasture and feedyard finished for 128 d (CON); 2) steers grass-fed for 20 mo (GF20); 3) steers grass-fed for 20 mo with a 45-d grain finish (GR45); and 4) steers grass-fed for 25 mo (GF25). The data were analyzed using a mixed model procedure in R with differences between treatments determined by Tukey HSD. Using carcass and performance data from these systems, a weaning-to-harvest life cycle assessment was developed in the Scalable, Process-based, Agronomically Responsive Cropping Systems model framework, to determine global warming potential (GWP), consumable water use, energy, smog, and land occupation footprints. Final body weight varied significantly between treatments (P < 0.001) with the CON cattle finishing at 632 kg, followed by GF25 at 570 kg, GR45 at 551 kg, and GF20 478 kg. Dressing percentage differed significantly between all treatments (P < 0.001). The DP was 61.8% for CON followed by GR45 at 57.5%, GF25 at 53.4%, and GF20 had the lowest DP of 50.3%. Marbling scores were significantly greater for CON compared to all other treatments (P < 0.001) with CON marbling score averaging 421 (low-choice ≥ 400). Breakeven costs with harvesting and marketing for the CON, GF20, GR45, and GF25 were $6.01, $8.98, $8.02, and $8.33 per kg hot carcass weight (HCW), respectively. The GWP for the CON, GF20, GR45, and GF25 were 4.79, 6.74, 6.65, and 8.31 CO₂e/kg HCW, respectively. Water consumptive use for CON, GF20, GR45, and GF25 were 933, 465, 678, and 1,250 L/kg HCW, respectively. Energy use for CON, GF20, GR45, and GF25 were 18.7, 7.65, 13.8, and 8.85 MJ/kg HCW, respectively. Our results indicated that grass-fed beef systems differ in both animal performance and carcass quality resulting in environmental and economic sustainability trade-offs with no system having absolute superiority.

中文翻译：

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草饲与谷饲牛肉系统：性能、经济和环境权衡

摘要

在公众对气候变化的日益关注和社交媒体上对利基市场牛肉的兴趣增加之间，对草饲牛肉的需求大幅增加。然而，对草饲牛肉的需求增加引起了许多生产者和消费者对产品质量、经济可行性和环境影响的担忧，这些担忧迄今尚未得到解决。因此，我们使用整体方法调查了加州牧场主目前正在执行的四种草饲和谷饲牛肉系统的性能、胴体质量、财务结果和环境影响。处理包括 1) 在牧场和饲料场饲养 128 天的阉牛（CON）；2) 饲养草食 20 个月 (GF20)；3) 用 45 天的谷粒完成 20 个月的草饲饲养 (GR45)；和 4) 用草饲牛 25 个月 (GF25)。使用 R 中的混合模型程序分析数据，处理之间的差异由 Tukey HSD 确定。使用来自这些系统的屠体和性能数据，在可扩展的、基于过程的、对农艺有反应的作物系统模型框架中开发了断奶到收获的生命周期评估，以确定全球变暖潜能值（GWP )、消耗用水、能源、烟雾和土地占用足迹。不同处理之间的最终体重差异显着 ( P < 0.001)，CON 牛最终体重为 632 公斤，其次是 GF25 570 公斤、GR45 551 公斤和 GF20 478 公斤。所有处理之间的屠宰率差异显着 ( P < 0.001)。CON 的 DP 为 61.8%，其次是 GR45 的 57.5%，GF25 的 53.4%，GF20 的 DP 最低，为 50.3%。与所有其他治疗相比，CON 的大理石花纹分数显着更高 ( P < 0.001)，CON 大理石花纹分数平均为 421（低选择 ≥ 400）。CON、GF20、GR45 和 GF25 的收割和营销成本为每公斤热胴体重量 6.01 美元、8.98 美元、8.02 美元和 8.33 美元（HCW）， 分别。CON、GF20、GR45 和 GF25 的 GWP 分别为 4.79、6.74、6.65 和 8.31 CO ₂ e/kg HCW。CON、GF20、GR45 和 GF25 的耗水量分别为 933、465、678 和 1,250 L/kg HCW。CON、GF20、GR45 和 GF25 的能量消耗分别为 18.7、7.65、13.8 和 8.85 MJ/kg HCW。我们的结果表明，草饲牛肉系统在动物性能和胴体质量方面存在差异，导致环境和经济可持续性权衡，没有任何系统具有绝对优势。