Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 314

13.2.1.4 Disadvantages
1. Improper ratio of concentrate to forage feed
may result in abnormal rumen fermentation
and increase of CH 4 production.
2. The technician is required to produce the best
possible results of feed optimization.
3. Monitoring the characteristics of the forage
and concentrate is required.
The regression relationship between 4 % fat
corrected milk (FCM), yield ( Y ), and grain sup-
ply ( X ) has the equation Y = 1.962 X + 3.492. This
indicates that with every additional 1 kg of grain
feed intake, the milk production could increase
by 2 kg. The methane production for each kg of
milk decreases with the increase of the propor-
tion of dietary concentrate.
There are considerable potentials to improve
animal production performance such as yield per
unit and to reduce methane emissions by using
feed optimization techniques. Many experimen-
tal tests have shown that with the improvement of
feeding technology, CH 4 emission per unit of
livestock is reduced (Na 2010 ).
It is reported that when daily milk production
increases from 25 to 30 kg, then the CH 4 emis-
sions per unit milk product decreases by 10 %
(Yang 2000 ). When the average daily gain
increases from 0.65 to 0.80 kg, the CH 4 emitted
per unit of weight gain can be reduced by 14 %.
According to the Na ( 2010 ) studies, when milk
yield of milk cow increases from 11 to 13 kg, the
CH 4 emission per unit of milk product decreases
by around 39 %.
The regression relationship between CH 4 pro-
duction per unit of FCM and grain supply was
expressed as Y = −2.546 X + 46.442. This also
indicates that with every additional 1 kg of cereal
feed intake, the CH 4 emission per kg of FCM can
be reduced by about 2.5 l.

Then the genetically modifi ed microorganisms
are introduced back into the rumen ecosystem to
establish a relatively stable microbiota that can
replace or compete with the original pathway of
methanogenesis to reduce CH 4 synthesis in the
rumen.
Most CH 4 emissions from ruminants are syn-
thesized by methanogenic archaea in rumen. The
methanogens mainly use carbon dioxide and
hydrogen to synthesize CH 4 . Protozoa and other
microbes involved in cellulose-degrading or
glucose-metabolic pathways provide carbon diox-
ide and hydrogen and other mono carbon com-
pounds necessary for methanogens. Therefore,
the process of CH 4 synthesis is implicated with
complex symbiotic relationships of ruminal
microbes, and improper manipulation may break
metabolic homeostasis in rumen. However, the
development of modern molecular biotechnology
and gene engineering technology provides a great
opportunity for the improvement of rumen micro-
biota to bring about optimal reduction in CH 4
emissions.
With respect to the process of feed degrada-
tion and CH 4 synthesis, there are some possible
links in realizing the CH 4 -mitigating goal with
the application of developing genetically modi-
fi ed microorganisms. First, digestibility is one of
the important factors infl uencing CH 4 synthesis
in the rumen. Cellulose, semi-cellulose, and
lignin contents are high in forage, and they are
diffi cult to degrade completely, and therefore
they are positively associated with CH 4 emis-
sions. Based on mutagenic breeding methods
and transgenic technology, high-effi ciency exog-
enous genes could be introduced into microbial
genomes and then express high-effi ciency
degrading enzymes in rumen. As a consequence,
the cellulose decomposition bacteria are
strengthened to better degrade refractory carbon
structure in forage, thus resulting in high-effi cient
feed digestibility and energy use. Since more
energy is obtained from an equal quantity of feed
and animal production is improved, CH 4 emis-
sion per unit of product could be reduced.
The reaction of carbon dioxide and hydrogen
to form CH 4 is a key step to decrease the hydro-
gen partial pressure in the rumen, so fi nding new

13.2.2 Genetically Modifi ed Rumen
Bacteria

To optimize the synthetic or metabolic pathway
of microorganisms related to CH 4 synthesis is by
employing modern molecular biotechnology to
obtain genetically modifi ed microorganisms.