Abstract
The environmental impact of livestock production has become an important and controversial global issue, pri- marily due to reported impacts on global warming. This concern applies to all meat animals, but especially beef cattle due to their emission of enteric methane. Livestock production contributes to global warming, but the importance of its contri- bution may be overstated. Its effect on climate is primarily through methane production, which does not have a long-term effect on the atmosphere. Global livestock numbers and emissions from their manure are increasing, so there is a short-term effect through increased rate of emission. Other effects of meat production may be of more concern for long-term sustain- ability. Through a full life cycle of meat, the dominant impact is loss and waste, which adversely effects all measures of sustainability. An important environmental concern is reactive nitrogen losses, among which ammonia emission from manure is of most concern. Global estimates suggest that 63% of all ammonia emissions come from agriculture, with 44% of the total from livestock manure. Ammonia emissions have adverse effects related to acidification of ecosystems, eutrophication of surface waters, and human toxicity through formation of small particulate matter in the air we breathe. Water consumption is another important concern. Global estimates suggest that agriculture uses about 70% of freshwater withdrawals, with 20% used for livestock feed production. Although livestock production is not a large energy consumer, fossil fuels are a limited resource, and conservation is important. Many technologies and strategies exist for mitigating environmental impacts of livestock production, but finding economical solutions is challenging. Mitigation must start with the reduction of consumer waste. Other livestock impacts are best reduced using intensive practices to produce animals in less time and with fewer resources. Diets that accurately meet animal nutrient needs are an important mitigation option for efficient and sustainable meat production.
Highlights
The global demand for livestock products is increasing (OECD/FAO, 2018)
This began with the publication of the report “Livestock’s long shadow,” which concluded that livestock production contributed more greenhouse gas (GHG) emissions globally all of transportation (Steinfeld et al, 2006)
life cycle assessment (LCA) tools are used for these evaluations, but variations in system boundaries, assumed inventory data, and functional units make comparisons across studies difficult
Summary
The global demand for livestock products is increasing (OECD/FAO, 2018). This is due to both increasing population and the need for high-quality protein in human diets, in developing countries. For all livestock, meeting nutrient needs through balanced diets normally provides optimal growth and resource use with a minimum environmental impact per unit of meat produced This is best done by feeding animals total mixed rations in confined housing facilities where diets can be controlled. For beef cattle production in the US, the combined use of ionophore, implant (estrogen/trenbolone acetatebased), and ß2-adrenergic agonist (zilpaterol) treatments was found to reduce GHG emission intensity by 9% with a 13% decrease in ammonia emission over the full life cycle of cattle (Stackhouse-Lawson et al, 2012b) These reductions occurred through an increase in rate of gain resulting in greater finish weight and less time on feed. Through a comprehensive literature review, Hristov et al (2013) compared a wide range of potential strategies for reducing GHG emissions from livestock production These included qualitative assessments of feeding, manure handling, and animal management practices. These technologies save energy and labor and provide more accurate and timely data for improving management (Berckmans, 2017)
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