Life cycle assessment (LCA) is widely regarded as a useful tool for comparing the environmental impacts of multiple livestock production systems. While LCA results are typically communicated in the form of environmental burdens per mass unit of the end product, it is increasingly becoming recognized that the product quality also needs to be accounted for to truly understand the value of a farming system to society. To date, a number of studies have examined environmental consequences of different food consumption patterns at the diet level; however, few have addressed nutritional variations of a single commodity attributable to production systems, leaving limited insight into how on‐farm practices can be improved to better balance environment and human nutrition. Using data from seven livestock production systems encompassing cattle, sheep, pigs, and poultry, this paper proposes a novel framework to incorporate nutritional value of meat products into livestock LCA. The results of quantitative case studies demonstrate that relative emissions intensities associated with different systems can be dramatically altered when the nutrient content of meat replaces the mass of meat as the functional unit, with cattle systems outperforming pig and poultry systems in some cases. This finding suggests that the performance of livestock systems should be evaluated under a whole supply chain approach, whereby end products originating from different farm management strategies are treated as competing but separate commodities.

中文翻译：

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畜牧生产系统生命周期评估框架，以考虑最终产品的营养质量。

生命周期评估（LCA）被广泛认为是比较多个畜牧生产系统对环境影响的有用工具。虽然 LCA 结果通常以最终产品每质量单位的环境负担的形式传达，但人们越来越认识到，还需要考虑产品质量，才能真正了解农业系统对社会的价值。迄今为止，许多研究已经在饮食层面检验了不同食物消费模式对环境的影响；然而，很少有人关注生产系统导致的单一商品的营养变化，因此对如何改进农场实践以更好地平衡环境和人类营养的了解有限。本文利用牛、羊、猪和家禽等七个畜牧生产系统的数据，提出了一个将肉制品的营养价值纳入畜牧生命周期评价的新框架。定量案例研究的结果表明，当肉类的营养成分取代肉类质量作为功能单位时，与不同系统相关的相对排放强度可能会发生巨大变化，在某些情况下，牛系统的表现优于猪和家禽系统。这一发现表明，畜牧系统的绩效应在整个供应链方法下进行评估，其中来自不同农场管理策略的最终产品被视为竞争但独立的商品。