Agriculture Reference
In-Depth Information
Conclusions
but reported a significant correlation between
16S rRNA gene sequence relatedness and cross-
reactivity for the methanogens (
R
2
= 0.90). Upon
closer inspection, it would appear that the vac-
cine affected the diversity and composition of
the methanogen population. This suggests that
a highly specific vaccine can be made to target
specific strains of methanogens, and that a more
broad-spectrum approach is needed to be suc-
cessful in the rumen. Williams
et al
. (2009) also
reported that methanogens take longer than
4 weeks to adapt to dietary changes, which calls
into question the validity of experimental results
involving methanogens that were based upon
2-4-week acclimatization period normally
observed for bacteria. Further studies are now
warranted properly to assess the acclimatization
period for the methanogenic archaea.
An additional vaccine has recently been
developed using subcellular fractions of
Metha-
nobrevibacter ruminantium
(Wedlock
et al
., 2010).
Twenty sheep were vaccinated and then re-
vaccinated 3 weeks later and the antisera were
found to cause agglutination of methanogens
and decrease growth and methane production
in vitro
. To the best of our knowledge,
in vivo
test-
ing of the efficacy of the newest vaccines against
methanogens has not yet been conducted.
Although this technology is high risk, it provides
many options for long-term enteric methane
abatement, as well as being a simple and cost-
effective approach. Microorganisms which provide
either hydrogen to methanogens (i.e. protozoa)
or compete for hydrogen with methanogens
(i.e. acetogens) are possible vaccine targets for
the reduction of methane emissions.
Current mitigation strategies, in various stages of
research, are focusing upon decreasing the hydro-
gen upon which methanogens are dependent,
using alternative hydrogen sinks (Joblin, 1999),
discovering anti-methanogenic compounds, elim-
inating the protozoa from the rumen and develop-
ing vaccine technologies against methanogens.
While some of these approaches have been incon-
sistent or failed because of a lack of knowledge of
the composition, function and microbial interac-
tions within the ecosystem, other strategies, such
as dietary lipids, have proved relatively successful.
The increasing demand for food from animal
sources, particularly in the developing countries
of the world, will lead to a continued high interest
in the interaction of livestock with the environ-
ment. As a result, agriculture has the opportu-
nity to help mitigate the challenge as well as
adapt to the changes that will occur. Achieving
meaningful reductions in methane emissions
should be possible with advances in our knowl-
edge of the intricacies of this complex ecosystem.
New technologies are rapidly coming on line,
which promise greatly to enhance the rate with
which our knowledge of the ecosystem and its
interrelationships will advance. High-throughput
sequencing methodologies will greatly improve
the rate of knowledge acquisition, which will
enhance the ability to unravel species inter-
relationships. Novel options for reducing meth-
ane emissions, through control or elimination of
methanogens, or other microorganisms, are likely
to be developed through this improved under-
standing of the rumen microbiome.
References
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