Print PageThe livestock industry has provided affordable quality products, while continually adapting to environmental change, social needs, governmental policies, and economic conditions. Reactive nitrogen (N) in the environment due to human activity has increased by ~ 12 times from 1860 to the 2005. Increased reactive N can contribute to photochemical smog, depletion of stratospheric ozone, soil acidification, loss of biodiversity, eutrophication of freshwater and coastal systems, and global climate change. Most of this anthropogenic reactive N passes through agricultural systems, about two thirds of this is related to animal production. Generally, less than 25% of the nitrogen fed to animals is stored as growth. The rest is rapidly released into the environment. Livestock are responsible for more than 60% of global anthropogenic ammonia emissions that can contribute to acidification of ecosystems. Fifty to seventy-five percent of nitrogen in livestock manure used as applied fertilizer is lost to the environment. Livestock production is likely to continue to increase rapidly as worldwide demand rises, potentially intensifying environmental impacts. We assess the livestock industry's contribution to anthropogenic nitrogen and phosphorus cycling and then suggest opportunities to lessen undesirable impacts in the near and distant future.
Results/Conclusions
The rising cost of fuel and livestock feeds, competition from biofuels, potential regulation of nitrogen, phosphorus, and greenhouse gas pollutants, and desire for improved sustainability create opportunities for change. Further refinements in feeds and feeding practices are likely to continue in order to meet, and not exceed, beef cattle nutrient requirements and to increase nutrient bioavailability. Best practices for manure management that prevent run-off from pastures by use of grazing management and hydrologic controls will further reduce these pollutants. In the long term, restructuring of industrialized livestock production could further reduce environmental impacts. For example, changing human diets, increasing fuel costs and expanding regional food systems would promote the development of diverse beef cattle breeds that are specifically adapted to local forage environments. In the northern Chihuahuan Desert, unsupplemented Desert adapted Mexican criollo cattle reach sexual maturity earlier than common British breeds (363.5 and 376.7 ± 6.3 days, respectively), with some Angus x Hereford heifers not reaching puberty during the study. Animals requiring fewer external inputs, such as supplemental feeds, are needed for locally adapted grazing systems. Regionally distributed beef cattle feeding and processing facilities for regional markets could support pasture based production while maintaining economies of scale.
