Department of Animal Science, University of California, Davis, CA 95616, USA.
Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA.
J Anim Sci. 2022 Feb 1;100(2). doi: 10.1093/jas/skab374.
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.
随着公众对气候变化的担忧不断增加，以及社交媒体对小众市场牛肉的兴趣日益浓厚，草饲牛肉的需求大幅增长。然而，草饲牛肉需求的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关注，这些问题至今仍未得到解答。因此，我们采用整体方法，研究了目前加利福尼亚州牧场主正在实施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。处理方法包括 1）在牧场饲养并在饲养场育肥 128 天的牛（CON）；2）放牧 20 个月的牛（GF20）；3）放牧 20 个月并进行 45 天谷物育肥的牛（GR45）；4）放牧 25 个月的牛（GF25）。使用 R 中的混合模型程序分析数据，通过 Tukey HSD 确定处理之间的差异。使用这些系统的胴体和性能数据，在 Scalable、Process-based、Agronomically Responsive Cropping Systems 模型框架中开发了断奶至出栏生命周期评估，以确定全球变暖潜力（GWP）、可食用水使用量、能源、烟雾和土地占用足迹。处理间的最终体重差异显著（P<0.001），CON 牛育肥至 632kg，其次是 GF25 牛 570kg，GR45 牛 551kg，GF20 牛 478kg。所有处理间的屠宰率差异显著（P<0.001）。CON 的 DP 为 61.8%，其次是 GR45 的 57.5%、GF25 的 53.4%和 GF20 的 50.3%。CON 的大理石花纹评分明显高于其他所有处理（P<0.001），CON 的大理石花纹评分为 421（低选≥400）。CON、GF20、GR45 和 GF25 的收获和营销盈亏平衡成本分别为每公斤热胴体重量（HCW）6.01、8.98、8.02 和 8.33 美元。CON、GF20、GR45 和 GF25 的全球变暖潜势（GWP）分别为 4.79、6.74、6.65 和 8.31 CO2e/kg HCW。CON、GF20、GR45 和 GF25 的耗水量分别为 933、465、678 和 1250L/kg HCW。CON、GF20、GR45 和 GF25 的能源使用量分别为 18.7、7.65、13.8 和 8.85MJ/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，从而在环境和经济可持续性方面存在权衡，没有一个系统具有绝对优势。
