Manipulation of rumen function through modification of rumen microbial flora is a promising method to enhance feed utilisation in ruminants. Previous studies have proved that it is possible to alter rumen function by infusion of specific bacterial species, and also to transfer from goats to sheep bacterial populations capable of improving productivity on tannin containing feeds. It is expected that wild ruminants naturally browsing tanniniferous shrubs will have developed an association with ruminal microflora that is different from domesticated animals. Several animals in Africa, for example the Greater Kudu and the Giraffe are strict browsers and are known to browse tannin-rich plants such as Acacia. These animals survive and perform well on what appears to be low quality feed. It is planned to compare rumen fluid from wild herbivores with that from domesticated cattle and goats to assess, in-vitro, digestibility of tannin containing feeds. Where there is improved digestibility, rumen fluid will be transferred from the wild animal to domesticated animals to check whether this improvement persists in vivo. Where improved digestibility is demonstrated, the crude rumen samples will be fractionated into single microbial species which can be purified and characterised. This will have to be done in Africa for quarantine reasons. Pure bacterial cultures will then be sent to Australia for further analysis. Enzyme studies and DNA-DNA hybridisation work will be done to compare African microorganisms with those isolated previously in Australia and Indonesia. Gene or antibody probes may also be prepared against specific organisms so that their populations can be readily quantified in persistence-ecology studies. Ultimately, this work will lead to the identification of bacterial species which, when working together in the rumen, will promote enhanced digestibility and improved productivity on tannin-containing tropical forages.
During the first year rumen fluid was obtained from animals (Borana cows, calves, sheep) at the ILRI Debe Zeit Station, and free ranging sheep and goats. An experimental protocol for sampling rumen fluid of animals thought to be potential sources of useful rumen organisms was developed. Standard samples of rumen liquor were prepared, analysed and distributed to the collaborators to allow uniform evaluation of these sources across the experimental zones. Using the protocol, in vitro gas production was used to estimate digestibility of a number of plant samples (Calliandra spp, Leucaena spp, Acacia angustissima and Tephrosia bracteolata). Results have suggested that free ranging indigenous domestic ruminants sampled may have developed rumen microbial populations capable of tolerating or degrading tannin-containing feeds. Isolation of tannin tolerant/degrading microbes from these rumen fluid sources is underway. The results also showed that A.angustissima may contain not only tannin but also other poisonous compounds inhibiting the growth of most rumen microorganisms. These poisonous compounds in A.angustissima will be extracted and identified. Specific compounds will then be used to isolate microorganisms capable of detoxifying them. This work is being planned under the followup ILRI Rumen Ecology Project.
Links:
[1] http://www.aciar.gov.au/country/Indonesia
[2] http://www.aciar.gov.au/iarc/International Livestock Research Institute
[3] http://www.aciar.gov.au/programarea/Animal Health