Effectiveness of S. jonesii inoculum for cattle grazing leucaena

Summary

The thrust of the work was to investigate the effectiveness of the S. jonesii inoculum produced in anaerobic fermenters by QPIF for distribution to graziers utilizing leucaena grass pastures. A second objective was to produce a quantitative real time PCR assay that specifically identifies and enumerates S. jonesii.
When using recommended and modified synthetic media for degradation studies, frozen QPIF inoculum and frozen rumen fluid collected from one property did not degrade the toxins 3,4-DHP and 2,3-DHP which are by-products of the breakdown of mimosine. However, fresh rumen fluid collected from another property did successfully degrade the toxins in the same modified media. Also fresh fermenter fluid which is the basis of the QPIF inoculum degraded both toxins when used in an undiluted form to evaluate metabolism of added toxin.
A quantitative real time PCR assay was developed for detection of S. jonesii in the rumen but the target gene is identical between all isolated strains of S. jonesii which precludes the differentiation of individual strains by this approach.
These experiments demonstrate that the ability of S. jonesii to degrade the toxin (DHP) in vitro is not always predictable and the efficiency of DHP degradation is likely to be regulated by the environment in which S. jonesii is growing. Thus the efficacy of the inoculum once established in animals cannot be inferred from these experiments. Isolation and evaluation of the DHP degrading bacteria (presumably S. jonesii strains) in Australian cattle would aid in the evaluation of the effectiveness of these naturalised microorganisms. Furthermore, the development of methods for the production and distribution of pure strains of S. jonesii to graziers may add to the quality control for the distribution of the inoculum.