Reducing the water footprint of finishing beef cattle through feed selection

Life cycle assessments have shown that the blue water required to finish beef cattle can be large, primarily due to the feeding of corn and corn byproducts produced using irrigated crops. Almost half of the beef cattle in the US are finished on feedlots overlying the Ogallala Aquifer where crop production relies on irrigation water obtained from the declining reserves in the aquifer. Blue water footprints (liters per unit dry matter produced) of cattle feeds were determined and used to assess the potential for reducing the blue water footprint (liters per unit of body weight gained) of finishing cattle in the Ogallala Aquifer region. Life cycle assessment was applied to simulated feedlots in Nebraska, western Kansas and the Texas Panhandle to quantify the potential reduction in the blue water footprint of finishing cattle using alternative feeds along with effects on feed cost and other environmental footprints. The blue water footprint of producing feeds varied from 2 to 2000 liters/kg DM depending upon the amount of irrigation used. When most of the base diet came from irrigated corn, substituting half of the grain with wheat or sorghum reduced the water footprint of finishing cattle by up to 38 %. In Texas, however, where much of the corn came from non-irrigated crops imported to the state, use of local wheat or sorghum, where more irrigation was used, increased the water footprint up to 39 %. Replacing alfalfa hay with sorghum forage reduced the water footprint by 7–50 % across locations depending upon the amount of irrigation required for each crop. Considering long-term relative feed prices, substitution of corn with wheat increased feed cost about 10 % while use of sorghum grain provided a similar cost. Use of sorghum hay in place of alfalfa offset the long-term increased cost of feeding wheat. Due to lower yields, feeding wheat increased the footprints of fossil energy use (20–30 %), GHG emission (4–6 %), reactive N loss (14–23 %), and land use (100–160 %) for finishing cattle in the region. Substitution of sorghum grain or forage had little effect on environmental intensities except that lower grain yield increased land use 90–150 %. A sensitivity analysis showed that differences among diets varied with changes in some important assumptions of the analysis but not enough to reverse the relative ranking of diets. Although alternative crops can be used to reduce the blue water footprint of finishing cattle, a comprehensive sustainability assessment is needed for weighing all benefits and costs of dietary changes. Due to tradeoffs among sustainability metrics, no diet can be concluded as the best long-term option for finishing cattle in the Ogallala Aquifer region. • Method developed to quantify state or regional blue water footprints of cattle feeds. • Water footprints of feeds varied from 2 to 2000 liters per kilogram of dry matter. • Potential water savings using alternative feeds for finishing cattle were determined. • Substituting wheat or sorghum for corn reduced water footprints by up to 38 %. • Use of alternative feeds often increased costs and other measures of sustainability.