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The uses of an Artificial Rumen for in vitro studies
Figure 1: A closeup of our artificial rumen setup.
In vitro, artificial rumens offer many advantages over the use of animals for pharmaceutical and feed analysis. These advantages include a reduction in cost due to the expensive nature of purchasing ruminants, a reduction in animal use for scientific purposes, elimination of animal variability and it is often easier to set up and more convenient. There are multiple differing artificial rumen analogues ranging from simple gas collection rumens (GCRs) that can run for approximately 96 hours to complex RUSITEC systems that can run continuously for months. The main difference between a GCR and a RUSITEC is that a GCR is given a set amount of buffer and ‘feed’ to sustain the microorganisms for approximately 96 hours compared to a RUSITEC which is continuously ‘fed’ with a constant supply of artificial saliva and continuous removal of waste material.
Both systems have many uses, this ranges from measuring the gas produced by varying feedstuffs to analysing the digestibility and longevity of pharmaceuticals in a rumen environment.
Gas Collection Rumens
Figure 2: A showcase of RRLs preliminary gas collection setup using our artificial rumen.
Gas Collection Rumens (GCRs) are useful for measuring the volume of gas produced by differing feedstuffs. The gas can also be analysed downstream to characterise the types of gas produced and how the tested feedstuff has affected gas production. One of the main aims is to study methane production and how new feedstuffs can reduce methane production and help combat climate change. Several other parameters can be measured using a GCR, these include pH, volatile fatty acids and ammonia production. GCRs can also be used in the preliminary pharmaceutical discovery and formulation testing stages. GCRs allow an insight into the breakdown and digestibility of the pharmaceutical, how it precipitates within the rumen and how the microbiome of the rumen is affected by the pharmaceutical with downstream analysis.
Rumen Stimulation Technique (RUSITEC)
The RUSITEC has existed for many years and is now a well-established and tested in vitro model. RUSITEC systems are semi-continuous and due to this, they can run for weeks or even months with little downtime. They are extremely useful for investigating ruminal fermentation, digestion of feedstuff, gases produced, the microbiota of the rumen, metabolism changes and the breakdown and precipitation of pharmaceuticals.
The main advantage of a RUSITEC compared to a GCR is that a RUSITEC can run for longer periods, partly due to the continual feed of artificial saliva and a constant runoff of waste material. Also, the RUSITEC system minimises animal variability, like the GCR. However there are still some differences between in vitro models and in vivo studies, this is regarding absorptive processes, liquid and solid material ratio differences, lower short-chain fatty acid concentrations and protozoal shifts. There are disadvantages of a RUSITEC, the main one being that the equipment is expensive to purchase and maintain. In a similar way to the GCR, the liquid effluent and/or gases can be collected and analysed downstream in relation to the experiment taking place.
We are currently developing our artificial rumen with the first pharmaceutical experiments being conducted at the time of publishing this article and hope to be able to offer this in vitro service in the future.
The use of artificial rumens is a hot area of research; other types of artificial rumen are currently being developed in the industry to advance the technique, such as dual flow continuous culture. Read more here.