Agriculture Reference
In-Depth Information
Veysset
et al
., 2010). Higher GHG intensities have
been reported for a Japanese system that relies
on imported grains (14.56 kg CO
2
e kg
−1
live
weight, converted from 36.4 kg CO
2
e kg
−1
carcass
with 40% dressing percentage; Ogino
et al
., 2004,
2007) and for pasture-based systems in Brazil
(Cederberg
et al
., 2011; converted from carcass
weight assuming a 60% dressing percentage;
17 kg CO
2
e kg
−1
live weight not including land use
change and 284 kg CO
2
e kg
−1
live weight after
accounting for land use change). The variation in
GHG intensity of beef production reflects differ-
ences in the beef production systems used in
different geographical areas, but also can be attrib-
uted to differences in the scope, boundary and
methodology of the individual LCAs, which can
differ. Thus, it is not justifiable to compare GHG
intensity across studies with the aim of identifying
more GHG efficient production systems. Rather,
an LCA of a particular beef production system can
be useful for determining the impact of diet, ani-
mal husbandry and other management decisions
on GHG intensity for that particular system.
Methane from enteric and manure sources
usually represents 55-70% of the total GHG
emissions of beef production. The cow-calf
phase emits about 75-90% of the total emissions
associated with beef production (Johnson
et al
.,
2003; Beauchemin
et al
., 2010), thus partial
LCAs that only examine GHG attributed to the
fattening phase are very limited in scope. When
examined over a number of studies, some impor-
tant findings for beef production arise as dis-
cussed below.
growth promotants (Cooprider
et al
., 2011) and
improved calf survival (Beauchemin
et al
., 2011).
For example, Cooprider
et al
. (2011) reported
that use of growth promotants and ionophores
during the feedlot phase lowered GHG by 22%,
due to increased average daily gain and fewer
days to market. Assuming that the feedlot finish-
ing phase accounts for about 12% of the total
GHG intensity of producing beef in the North
American system (Beauchemin
et al
., 2010), the
GHG intensity of beef production to the farm
gate could be reduced by about 2-3% due to the
use of these growth promoting technologies.
Of course, adoption of such management prac-
tices is driven primarily by farm profitability
(and legislation in the case of growth-enhancing
technologies, which are restricted in some
areas) and not GHG intensity.
The impact of improved animal productiv-
ity on GHG intensity of beef production is illus-
trated in an industry-wide study by Capper
(2011) that examines the long-term changes in
the US industry (from 1977 to 2007). Over the
30-year period, days to slaughter reduced from
602 days in 1977 to 482 days in 2007, while
carcass yield increased from 274 to 351 kg dur-
ing the same period. Increased carcass yield per
animal reduced the size of the supporting cow
herd required, which in turn reduced resource
use. The net result was a 16% decrease in GHG
intensity of beef production during this period.
Similarly, a study of the Canadian beef industry
(including livestock, feed and manure) reported
that between 1981 and 2001, GHG emissions
per kg of live weight decreased by 36% (from
16.4 to 10.4 kg of CO
2
e) (Vergé
et al
., 2008). This
reduction in GHG was attributed to increased
technical efficiency and improved animal perfor-
mance due to genetics, nutrition and manage-
ment. A LCA of French beef production systems
showed a range in GHG intensity (range of 14.6-
19.0 kg CO
2
e kg
−1
live weight) with the lowest
intensity for an intensive system using maize
silage producing 17-month-old bulls and
33-month-old fattened heifers and the highest
intensity for a farm selling younger (15-16
months) and lighter weight calves (Veysset
et al
.,
2010). In the latter case, emissions from the
breeding stock represented a greater proportion
of the total emissions. This is why increasing the
live weight at slaughter of the progeny decreased
GHG intensity, because the relative proportion of
Production efficiency
Improved animal productivity and enhanced
efficiency of production lower GHG intensity
of beef production, mainly through increased
animal output with more efficient use of
resources. Improved animal rate of gain reduces
GHG intensity because animals reach market
weight at a younger age, and thus are fed
fewer days, so emissions over the feeding
period decrease without a change in product
output. Efficiency of producing beef can be
increased through improved herd management
(Beauchemin
et al
., 2011), better reproductive
efficiency (Garnsworthy
et al
., 2004), use of
