Agriculture Reference
In-Depth Information
the total emissions attributed to the breeding
stock was reduced. It should be pointed out that
feeding cattle to a heavier carcass weight only
decreases GHG intensity of beef production
when both the cow-calf and fattening system
are included in the system boundary. For exam-
ple, Ogino
et al
. (2004) examined a Japanese beef
fattening system that only included the calves.
The heavier carcass weight obtained by increas-
ing the feeding length from 26 to 28 months did
not offset the additional GHG produced.
Strategies that improve the efficiency and
productivity of the cow herd by reducing the use
of feed resources or increasing the weaning per-
centage can have a significant impact on reduc-
ing the GHG intensity of producing beef, because
the breeding stock contribute the greatest pro-
portion of the C-footprint of beef (Beauchemin
et al
., 2010). However, some have suggested that
opportunities for significant further improve-
ment in animal productivity may be restricted
mainly to developing countries, because animal
productivity is already high in most OECD coun-
tries (Henderson
et al
., 2011).
using canola seed as a source of lipids. The study
included the emissions associated with growing
the canola seed. Feeding canola seed to the cow
calf herd reduced GHG emission intensity by 8%,
while feeding it to backgrounding cattle reduced
GHG emission intensity of beef production by
1% and feeding it to finishing cattle reduced
intensity by 2%. The reduction was due to lower
enteric CH
4
emissions because of the reduced
DMI of the higher energy diet containing canola
and a lower Ym of lipid-supplemented diets.
Grain versus Forage Finishing
Within beef fattening systems, increasing the
duration of grain feeding while decreasing the
duration of forage feeding (using conserved
forages or pasture) decreases GHG intensity, as
shown in a number of studies (Table 14.5).
Similarly, pasture-finished cattle have a higher
GHG intensity than do grain-finished cattle
(Pelletier
et al
., 2010; Peters
et al
., 2010;
Capper, 2011; Cederberg
et al
., 2011). Forage
feeding tends to decrease average daily gain,
thereby prolonging the time to slaughter
(which increases emissions), but not animal
product (live weight) if calves are marketed at
the same weight. Furthermore, enteric CH
4
emissions increase because of the higher Ym
of forage-based diets compared with grain-
based diets, and higher maintenance energy
requirements of pastured cattle due to
increased activity during grazing. Manure
emissions are usually increased because more
manure is excreted in the longer time to
slaughter and the N
2
O emission factor for
manure deposited on pasture is higher than
that for deep-bedded manure (Beauchemin
et al
., 2011). Thus, while increased grazing of
cattle may be advantageous for reasons such
as consumer preference, fatty acid profile of
the meat, animal welfare, maintenance of pas-
toral land, cost of production and other rea-
sons, this is not the case for GHG emissions.
Nutrition
Alterations in diet composition have been pro-
posed as a means of reducing GHG emissions
from beef cattle (Johnson and Johnson, 1995;
Beauchemin
et al
., 2009; Martin
et al
., 2010;
Grainger and Beauchemin, 2011). As previ-
ously discussed for dairy cows, improving the
nutritive value of the diet can lower enteric CH
4
emissions. In a farm LCA of beef production,
Beauchemin
et al
. (2011) showed that feeding
more highly digestible forages to the cow herd
lowered GHG emission intensity of beef produc-
tion by 5%. Energy density of the ration affects
the quantity of feed required to meet the ani-
mals' energy requirements, and enteric CH
4
is
proportional to DMI (Grainger
et al
., 2007) and
GEI (IPCC, 2006). Thus, feeding energy-dense
feeds to mature beef cows can reduce CH
4
emis-
sions, as these animals are typically limit-fed to
meet energy requirements.
Another proposed approach to lowering
CH
4
emissions has been supplementation of
diets with lipids. Beauchemin
et al
. (2011)
showed the potential to decrease GHG emission
intensity through fat supplementation of diets
Pasture Stocking Rate
In most parts of the world, beef production is
partly or entirely pasture-based. Pastoral sys-
tems have limited potential to decrease enteric
