Tackling the future challenges of Organic Animal Husbandry - vTI

! Agriculture and Forestry Research, Special Issue No 362 (Braunschweig, 2012) ISSN 0376-0723
Download: www.vti.bund.de/en/startseite/vti-publications/landbauforschung-special-issues.html
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Shades of green – Global implicatons of choises for
dairy systems in the United States
CHARLES BENBROOK 1 , BRIAN BAKER 1
1 The Organic Center, USA, bbaker@organic-center.org, www.organic-center.org
Key words: Dairy, Greenhouse Gas Emissions, Comparative Studies, Integrated Farming Systems,
Methane.
Introduction
Conventional dairy production in the United States has intensified rapidly since the introduction of
recombinant bovine somatatropin (rbST), corn-based Total Mixed Rations (TMRs) and the concentration
of animals in freestall barns. These changes have been coupled with heavy reliance on drugbased
therapies to combat disease and improve the efficacy of artificial insemination-based breeding
programs, as well as the movement of cattle into facilities allowing little or no access to pasture.
Over the same period, the demand for organic milk has grown rapidly in response to concerns related
to the animal health and environmental impacts caused by intensified dairy production.
Studies have either directly measured or projected the environmental footprint of dairy farms. A
controversial 2008 study concluded that high-production, input-intensive dairy farm management
systems release fewer GHGs than organic dairy farms (Capper et al., 2008). Other studies concluded
that organic dairy farms have smaller environmental footprint than conventional ones (Benbrook
et al., 2010; Haas et al., 2001; Arsenault et al., 2009). Still other studies consider the differences in
emissions by the two farming systems insignificant and inconclusive (Olesen et al., 2006).
The different results reached by past efforts to model environmental performance result from the
assumptions made, factors and variables specified, the data used and how the results are reported.
One major concern over the life cycle of the animals is their production of greenhouse gas (GHG)
emissions. The GHG of greatest concern is methane (CH4). Methane is 25-times more potent than
CO2 in terms of global warming potential. Cows emit methane directly through digestive processes
(enteric) and indirectly by excretion (manure). Enteric methane accounts for most of the CH4 emitted
by grazing-based dairy farms, while manure methane can approach one-half of total methane on
farms where manure is managed using daily flushes and anaerobic lagoons.
Methods and materials
The Shades Of Green (SOG) calculator is an Excel spreadsheet-based simulation model that projects
the impacts of management practices on several indicators of dairy farm performance: milk
and meat production, feedstuffs required, crop production inputs, cow health and longevity, several
measures of milk production, environmental performance, and gross revenues. It is designed to
compare the environmental footprint of dairy operations under scenarios that differ in one, a few or
many parameters.
Unlike other models and studies, SOG takes into account the many impacts of dairy farm management
on animal health, reproductive performance, and cow longevity, as well as financial performance.
The structure and equations in the SOG calculator are fully explained and referenced in a
user-manual document (Benbrook et al., 2010).
Four different farms were used to model the methane release caused by dairy production. Two were
grass-based organic dairy farms, one was a hypothetical dairy farm designed and managed to minimize
methane emissions per unit of milk produced, one reflected a typical high-production conven-