Climate Change Mitigation - Climate Resilient Agriculture for Ensuring Food Security - page 313

13.2.1.2 Specifi c Agents and Dietary
Additives
Adding agents and/or dietary additives can also
reduce CH 4 emissions. Most of these agents or
additives aim at suppressing methanogenesis
which is the chemical process that creates
methane. A wide range of these agents or
additives have been proposed to reduce CH 4
emissions:
• Ionophores are antibiotics that can reduce CH 4
emissions, but their effect may be transitory
and they have been banned in the European
Union.
• Halogenated compounds inhibit the growth of
methanogenic bacteria (the bacteria that pro-
duce the CH 4 ), but their effects can also be
transitory and they can have side effects such
as reduced intake.
• Adding plant compounds (condensed tannins,
saponins, or essential oils) can also reduce
CH 4 emissions. However, adding such com-
pounds may have the negative side effect of
reduced digestibility of the diet.
• Probiotics have shown to result in small and
insignifi cant effects. However, selecting
strains specifi cally for CH 4 -reducing ability
might be able to improve results.
• Propionate precursors such as fumarate or
malate reduce CH 4 formation. These precur-
sors reduce CH 4 by acting as alternative
hydrogen acceptors. However, this option is
expensive due to the requirement for high
doses of precursors to elicit effect.
• Hormonal growth implants do not specifi cally
reduce CH 4 emissions by themselves, but by
improving animal performance, they can
reduce emissions per kg of animal product.
• Vaccines against methanogenic bacteria are
being developed but are not yet available
commercially.

The production of CH 4 during rumen fermen-
tation is a necessary by-product, which cannot be
completely eliminated. The control of concen-
trate to forage ratio in ruminant animals' daily
diet to reduce CH 4 emissions has certain advan-
tages and disadvantages.

13.2.1.1 Improved Feeding Practices
An animal's feed quality and feed intake affect
CH 4 emissions. In general, lower feed quality or
higher feed intake lead to higher CH 4 emissions.
Feed intake is positively related to animal size,
growth rate, and production (e.g., milk produc-
tion, wool growth, pregnancy, or work). Therefore,
feed intake varies among animal types, as well as
among different management practices for indi-
vidual animal types.
Because CH 4 emissions represent an eco-
nomic loss to the farmer, where feed is converted
to CH 4 rather than to product output, viable mit-
igation options can entail feed effi ciency
improvements to reduce CH 4 emissions per unit
of beef or milk (IPCC 2007a , b , c ). However,
these mitigation options can actually increase
CH 4 per animal.
Through replacing forages with the feeding
of more concentrates, methane emissions can
be reduced (Lovett et al. 2003 ). While the con-
centrates may increase the daily methane emis-
sions per animal, the emissions per kg of feed
intake and per kg of product are reduced. The
extent of reduced emissions per kg of feed
intake or per kg of product decreases as produc-
tion increases (IPCC 2007a , b , c ). Feeding con-
centrates' benefi ts depend on whether the
number of animals can be reduced or whether
slaughter age can be reduced. In addition, it is
important to consider how the practice affects
land use, the nitrogen content in the manure,
and the emissions from transporting and pro-
ducing the concentrates in the fi rst place (Lovett
et al. 2006 ; IPCC 2007a , b , c ).
Other practices to reduce methane emissions
are available. Adding certain oils or oilseeds to
the diet, improving pasture quality, and optimiz-
ing protein intake to reduce nitrogen excretion
and N 2 O emissions are examples (IPCC 2007a ,
b , c ).

13.2.1.3 Advantages
1. There is no additional cost of CH 4 reduction.
2. CH 4 reduction and improvement of productiv-
ity could be consistently realized.
3. The technology could be applied in any
animal production system by using feed
optimization.