Table 13.

Proportion (in %) of changes in the environmental footprint [acidifying emissions, eutrophying emissions, greenhouse gas (GHG) emissions, and cumulative energy demand (CED)] of egg production in the United States in 2010 compared with 1960 attributable to changes in background systems, feed composition, or bird performance due to improved husbandry and genetics

Footprint change attributable to changes in	Acidifying emissions	Eutrophying emissions	GHG emissions	CED
Background systems (%)	27	30	28	−116
Feed composition (%)	30	35	44	93
Bird performance (%)	43	35	28	123