Agriculture Reference
In-Depth Information
Table 14.5. Summary of the literature examining grain-based versus forage-based finishing systems for
beef cattle on greenhou se gas (GHG) intensity. a
Days in feedlot on
high grain ration
GHG intensity (CO 2 e kg −1
beef live weight)
Reference
Production system
Beauchemin et al . (2011)
Extended grain finishing
210
12.8
Backgrounding and
finishing
170
13.0
Reduced grain finishing
120
13.9
Capper (2011)
Conventional feedlot
finishing
135
15
Pasture finished
0
26
Pelletier et al . (2010)
Traditional feedlot system
303
14.8
Reduced grain finishing
150
16.2
Pasture finished
0
19.2
Peters et al . (2010)
Grain finished
115
5.9
Grass finished
0
7.2
a Soil organic carbon was assumed to be at equilibrium in all studies.
CH 4 through diet supplementation, and supple-
menting with grain should be promoted as a CH 4
mitigation strategy only after careful assessment
using LCA and economic analysis. Furthermore,
grain feeding ignores the importance of rumi-
nants in converting fibrous feeds, unsuitable for
human consumption, to high-quality protein
sources such as milk and meat.
Several LCAs have examined the effects of
stocking density as a means to reduce GHG emis-
sions of pastoral-based beef production systems.
Carbon sequestration was not considered in
these analyses because equilibrium was
assumed, although it is well recognized that per-
manent grasslands can act as large C sinks
(Liebig et al ., 2010). For a traditional Irish beef
suckler system, both Casey and Holden (2006b)
and Foley et al . (2011) reported that where
stocking rates were already at moderate levels,
further increases had negative implications for
GHG intensity (CO 2 e emissions per hectare and
per live weight). This was because higher stock-
ing rates led to higher fertilizer-related emis-
sions, which were largely responsible for the
increased GHG intensity. Similarly for beef and
sheep farms in New Zealand, White et al . (2010)
observed that increased levels of N fertilizer were
necessary to support higher stocking densities,
which led to increased GHG intensities. While it
is recognized that some degree of intensification
is warranted in terms of maximizing land use
and avoiding land use change (Nguyen et al .,
2010), and deforestation in some areas such as
Brazil (Cederberg et al ., 2011), both the agricul-
tural outputs and GHG emissions as well as the
long-term impact on pasture productivity and
sustainability (Burrows et al ., 2010) need to be
considered in the analysis.
Dairy-Beef Systems
Dairy systems produce meat from culled animals
as well as surplus calves fattened for meat, and
in some parts of the world a significant portion
of the beef produced is a co-product from dairy
production. According to FAO, as much as 57%
of the global cattle meat production is from the
dairy sector (Gerber et al ., 2010) although the
global trend is towards more intensification of
milk production per cow, resulting in less meat
production per kilogram of milk (Flysjö et al .,
2011b). A number of studies have shown that
meat from integrated dairy-beef systems has a
lower GHG intensity than from traditional beef
production systems (Casey and Holden, 2006b;
Nguyen et al ., 2010). In a dairy-beef system,
the GHG emissions from the breeding stock are
allocated to both meat and milk, whereas all
emissions are allocated to the meat in a tradi-
tional beef system, and as stated previously,
minimizing the contribution of the breeding
stock to the total GHG emissions has a large
impact on GHG intensity of beef production.
Nguyen et al . (2010) compared a traditional
beef system (suckler cow-calf) with several
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