Agriculture Reference
In-Depth Information
they are required in the diet such as essential
amino acids (Calsamiglia et al ., 2007). Much of
the work with these compounds has been done
in vitro , though a few studies have demonstrated
reduced enteric CH 4 emissions in vivo . Mao et al .
(2010) fed lambs tea saponins and found reduced
CH 4 emissions and protozoa populations relative
to total bacteria, but the relative number of
methanogens was not affected nor was the
lamb's growth. Mohammed et al . (2004) fed
steers horseradish oil and found reduced CH 4
emissions, but Beauchemin and McGinn (2006)
fed steers a commercial mixture of essential oils
and found no effect on CH 4 emissions. Clearly,
more in vivo research is needed to understand the
effectiveness of various plant extracts, the doses
required to impact CH 4 emissions and if there
is an adaptation to the extracts over time.
Furthermore, research is needed to evaluate
their economic cost to farmers and the effects
of such compounds on milk production and
composition.
Mitigating CO 2 -eq emissions per unit of
pork can be achieved by reducing emissions
from manure and by improving production effi-
ciency (enteric CH 4 emissions from pigs will be
ignored as they are relatively minor). Anaerobic
digestion of manure can generate CH 4 gas that
can be captured for energy production use on-
farm and reduce the CO 2 -eq emissions from
swine production (Schils et al ., 2007). Cooling of
manure slurry is another way to reduce CH 4
emissions (Schils et al ., 2007); however, this may
not be cost effective for swine farmers. Nitrous
oxide emission mitigation is best achieved
through optimizing when manure is applied to
soil, as it is important to time the application
with plant's N needs for growth to minimize
the nitrification/denitrification processes of soil
microbes (Dosch and Gutser, 1996).
Chapters 2 and 3 (this volume) cover pro-
duction efficiency more extensively, however it is
worth mentioning as a proven method of reduc-
ing CO 2 -eq emissions per unit of output (Capper,
2011; Gerber et al ., 2011). Production efficiency
can be defined as achieving greater or the same
output (e.g. kg of pork) with fewer inputs. Two
of the ways to improve the production efficiency
of pork production (and likely reduce emissions
per unit of pork, though the authors are una-
ware of any published analysis) is to increase the
litter size per sow and reduce the incidence of
disease. Litter sizes in the USA have already
made impressive historical gains (the average lit-
ter rate increased from around 8.8 in 2002 to
just over 10 pigs per litter in 2011), and further
improvements will likely reduce the number of
sows required to produce each kg of pork,
thereby reducing manure and CO 2 -eq emissions
from manure per unit of pork as well (NASS,
2011). One of the major diseases that impacts
pigs is porcine reproductive and respiratory
syndrome (PRRS). The PRRS virus can cause
reproductive failure, pneumonia, reduced
growth rates and mortalities in pigs (Neumann
et al ., 2005). It is estimated the disease causes
US$560 million in losses to the US swine indus-
try each year, and, since the disease's emer-
gence in the 1980s, effective control measures
have yet to be found (Neumann et al ., 2005).
It seems likely that finding effective treatments
for diseases like PRRS would not only improve
the welfare of pigs, but also reduce the inputs
required and emissions created per unit of pork
through improved production efficiency.
VOC emission mitigation opportunities
Mitigating the VOC emissions from fermented
feeds can be achieved through using best man-
agement practices (BMPs) that are advocated
for reducing feed losses and improving feed
quality. Ultimately, these BMPs are focused
around achieving optimum fermentation pro-
cesses (for feed preservation), minimizing the
exposure of feed to the air and reducing overall
feed waste. Filling silos with harvested plant
material quickly, harvesting the crop at the
proper moisture content, packing the harvested
feed adequately, using microbial inoculants and
preservation acids, and completely sealing the
feed to prevent air exposure can all promote opti-
mum fermentation and preservation of silage
(Muck, 1988). Most of the VOC emissions occur
once the silo is opened for feed out, as the numer-
ous VOCs in the aqueous phase of the silage
(e.g. ethanol) will rapidly volatilize once exposed
to the air. Recent research has shown that VOC
emissions are far greater from 'loose' silage and
most of these emissions occur within the first
12 h of air exposure (Hafner et al ., 2010).
Therefore, the best way to reduce VOC emissions
at feed out is to minimize the size of the 'face' of
Search WWH ::




Custom Search