ECOSYSTEMS, SUSTAINABILITY, AND ANIMAL AGRICULTURE

The long-term sustainability of animal agriculture is examined in an e cological context. As an aid to defining agriculture, animal agricultu re, and sustainable agriculture, a broad overview of the structural an d functional aspects of ecosystems is presented. Energy output/cultura l energy input ratios were then calculated for 11 beef cattle manageme nt systems as relative measures of their long-term sustainability. Ene rgy output was estimated by direct conversion of whole body mass of st eers to caloric values. Cultural energy inputs were estimated using pu blished forage and cereal grain production budgets in combination with estimated organic matter intakes. Cultural energy inputs included raw materials, manufacturing, distribution, maintenance, and depreciation of all equipment and products used in a 250-animal cow-calf farm/ranc h operation. Management systems evaluated included 1) spring calving w ith slaughter beginning at either weaning (age of calf approximate to 6 mo) or after 84, 168, or 252 d in postweaning finishing lot; 2) spri ng calving with slaughter beginning at about 18 mo of age after either 0, 42, 84, or 126 d in finishing lot; and 3) fall calving with slaugh ter beginning at about 14 mo of age after either 63, 126, or 189 d in finishing lot. Estimated efficiencies were < 1.0 in all treatments, ev en when assumed marketed calf crop was 100%. Product energy output/cul tural energy input ratios ranged from a high of .40 in the spring calv ing --> stocker --> 126 d in finishing lot treatment to a low of .23 i n the spring calving --> slaughter at weaning treatment. The low level s of efficiency were found to be largely the result of the interaction effects of the high levels of cultural energy required to maintain a productive cow herd and grow and finish calves in the rather harsh env ironment of the Northern Great Plains. Results pointedly reveal the hi gh level of dependency of the U.S. beef cattle industry on fossil fuel s. These findings in turn bring into question the ecological and econo mic risks associated with the current technology driving North America n animal agriculture.