Novel methane assessment in ruminants
Executive summary
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The research presented here is a pilot study to investigate the suitability of two novel, independent methods of direct methane assessment in cattle rumens.
The first 'arm' is the investigation of use of a portable methane sensor used in environmental research adapted for use as an indwelling rumen probe via the cannula in rumen fistulated cattle. The second method is the use of microbial metabolic 'proxies' of methane production in rumen contents, which has been previously used in such digesta for other end products of microbial metabolism, but not methane.
This preliminary study concludes that the METS methane sensor technology used is capable of measuring small changes in methane concentration in rumen liquid phase in vivo over time intervals as low as 30 minutes. This represents a solid advance in rumen methane research capacity, opening opportunities in detailed rumen methanogenesis studies.
There was also an apparent positive relationship between recorded methane concentration in the liquid phase and the rumen pH/ redox environment (r2 = 0.91). If this relationship was demonstrated by future research to be consistent across diet treatments, it represents a potential 'proxy' for methanogenesis that is far more easily obtained. The other 'proxies' for short interval methanogenesis investigated - real time polymerase chain reactions (RT-PCR) enumeration of methanogen populations and mRNA quantification - gave mixed results. PCR enumeration suggested the methanogen populations were relatively slow to shift, which in turn suggests that it is their metabolic activity rather than population size that determines methane production in short interval measurement periods. However, due to technical difficulties with the development of the method, assessment of this activity by mRNA quantification was not achieved in the time frame of this project.
The results of this project suggest there are several possible methods suitable for direct assessment of rumen methanogenesis across short interval periods.
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