Feed conversions, ration compositions, and land use efficiencies of major livestock products in US agricultural systems

A sustainability transition will require a clear understanding of the environmental impacts of human food needs. To this end, accurate data on the feed requirements of livestock production are essential. Unfortunately, approaches used to estimate overall feed conversion ratios per unit output of livestock product vary and the reported values used in environmental analyses may be inconsistent. This paper presents a spreadsheet model for determining the aggregate, herd (flock) level feed needs of six major livestock commodities (beef, chicken, dairy, eggs, pork, and turkey) based on contemporary U.S. production practices. In this model, each system is represented as a set of stocks and flows, each of which is estimated based on performance metrics, such as reproduction and mortality rates. Parameter estimates were made primarily from U.S. government surveys or comparable peer-reviewed literature. Nutritional needs of livestock were based primarily from National Research Council reports. The model estimates the feed intake and ration composition for each life stage of each livestock system. Results were summarized as feed conversion ratios per unit output, herd (flock) average ration composition, and land use requirements for all feed ingredients. The findings confirm conventional wisdom that the total feed use efficiency of livestock products varies widely across livestock systems. However, the differences appear more subtle when the requirements for individual feed ingredients are considered. Similarly, the land requirements of livestock production also vary widely, but the differences are more nuanced when viewed in light of the land quality required to supply each feed ingredient. While the findings are consistent with some other past efforts to determine feed and land use efficiency of livestock production, greater transparency and consistency is needed in this area of research. (C) 2014 Elsevier Ltd. All rights reserved.