A fermentation system for rapid and accurate modelling of rumen function
Author: Stefan Muetzel
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Executive summary
Currently, New Zealand rumen microbial/nutritional scientists use a simple batch culture system to evaluate the relative quantities of fermentation gases produced from fresh forage substrates incubated with rumen contents. This technique is a static system that can only be used for short periods and is non-representative of dynamic rumen processes, since it does not allow an adaptation of the microbial community. In batch cultures, gas composition is measured at the end of the fermentation period, which does not account for the release rates. At present, batch cultures are carried out manually which severely limits the number of samples that can be handled and introduces additional analytical variation.
To address the limitations of the existing fermentation technology, we constructed a 'state of the art' continuous dual flow fermentation system for use by rumen microbiologists/rumen nutritionists comparable to the system described by Teather and Sauer (1988) (see Appendix 1). The continuous fermentation system enables solid and liquid substrates to be fed by computer control into the fermentor, where solid particles are retained longer in the raft mat than liquid components, leading to different liquid and solid turnover rates as observed in the rumen. The pH in the fermentors can be monitored and controlled by the system and the system is interfaced with gas analysers to facilitate continuous and automated monitoring of fermentation gases. This facility will speed up work on developing mitigation solutions for enteric methane emissions. In particular, this system will facilitate:
- screening of potential mitigation agents or forages;
- the assessment of dose response rates, prior to expensive animal trials;
- real-time and long term assessment and characterisation of microbial and biochemical responses;
- the testing of new tools for monitoring changes in rumen microbial populations.
In addition to speeding up development of methane mitigation strategies, the continuous flow systems will facilitate a broader range of assays allowing us to model aspects of plant cell wall degradation and microbial nitrogen utilisation. The facilities will provide the NZ animal feed industry and researchers a means to evaluate; strategies for improving feed digestibility, forages or formulations for reducing methane emissions or improved nitrogen utilisation using a dynamic rumen-like system prior to animal based evaluations or cultivation of forages for future animal studies.
Besides being a useful tool for screening of anti-methanogenic materials, the system will also allow us to study the effect of basic parameters like rumen turnover rates and pH on methane production, which cannot be controlled independently in living animals. The unit is designed as an open system to which components can be added in order to improve it, based on needs arising when the system is in use in various projects.
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