Atmospheric methane levels increased over geological formations in Northern Siberia following a heat wave in 2020, suggesting that permafrost thaw releases methane from reservoirs.
Image credit: Wikimedia Commons.
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Edited by David H. Baker, University of Illinois at Urbana–Champaign, Urbana, IL, and approved May 2, 2008 (received for review March 12, 2008)
Abstract
The environmental impact of using recombinant bovine somatotropin (rbST) in dairy production was examined on an individual cow, industry-scale adoption, and overall production system basis. An average 2006 U.S. milk yield of 28.9 kg per day was used, with a daily response to rbST supplementation of 4.5 kg per cow. Rations were formulated and both resource inputs (feedstuffs, fertilizers, and fuels) and waste outputs (nutrient excretion and greenhouse gas emissions) calculated. The wider environmental impact of production systems was assessed via acidification (AP), eutrophication (EP), and global warming (GWP) potentials. From a producer perspective, rbST supplementation improved individual cow production, with reductions in nutrient input and waste output per unit of milk produced. From an industry perspective, supplementing one million cows with rbST reduced feedstuff and water use, cropland area, N and P excretion, greenhouse gas emissions, and fossil fuel use compared with an equivalent milk production from unsupplemented cows. Meeting future U.S. milk requirements from cows supplemented with rbST conferred the lowest AP, EP, and GWP, with intermediate values for conventional management and the highest environmental impact resulting from organic production. Overall, rbST appears to represent a valuable management tool for use in dairy production to improve productive efficiency and to have less negative effects on the environment than conventional dairying.
Footnotes
- §To whom correspondence should be addressed. E-mail: deb6{at}cornell.edu
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Author contributions: J.L.C., E.C.-G., R.A.C., and D.E.B. designed research; J.L.C., E.C.-G., R.A.C., and D.E.B. performed research; J.L.C., E.C.-G., R.A.C., and D.E.B. contributed new reagents/analytic tools; J.L.C., E.C.-G., R.A.C., and D.E.B. analyzed data; and J.L.C., E.C.-G., R.A.C., and D.E.B. wrote the paper.
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↵†Present address: Nestlé Research Center, Ver-Chez-les-Blanc Case Postale 44, 1000 Lausanne 26, Switzerland.
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Conflict of interest statement: R.A.C. is a full-time employee of Monsanto, holding the position of Technical Project Manager for POSILAC rbST with the primary responsibility of ensuring the scientific integrity of Monsanto publications about POSILAC; he also owns Monsanto stock. D.E.B. consults for Monsanto in areas outside the environmental impact area and owns no Monsanto stock. J.L.C. and E.C.-G. have no conflict of interest.
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This article is a PNAS Direct Submission.
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↵¶ Toride Y, Expert Consultation and Workshop, April 23–May 3, 2002, Bangkok, Thailand.
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↵‖ Brugger M, American Society of Agricultural and Biological Engineers, Annual International Meeting, July 9–12, 2006, Portland, OR, paper no. 064035.
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Freely available online through the PNAS open access option.
- © 2008 by The National Academy of Sciences of the USA
The environmental impact of recombinant bovine somatotropin (rbST) use in dairy production
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