Condensed tannin expression in white clover leaves for enhanced animal health benefits

Abstract

Rapid consumption of lush white clover foliage can cause bloat which, in severe cases, can lead to animal death. One way of mitigating against this is to provide a moderate level of condensed tannins (CTs) in the diet. Unfortunately, CTs are largely absent in white clover leaves. Insertion of a transcription factor gene that encodes a CT ‘master switch’ from a distantly related clover species enabled stable production of biologically significant levels of CTs in white clover leaves. Leaf CTs reduced methane emissions in rumen fluid in vitro, however, in high CT producing genotypes, a yield penalty of up to 50% was incurred. To alleviate this issue, genotypes with good herbage yield and CT levels >1.5% of DM were backcrossed to the elite cultivar Mainstay over several generations. Recurrent plant selections, both in the glasshouse and the field, have delivered white clover with commercially acceptable herbage yield combined with a biologically significant level of leaf CTs. Under laboratory conditions clover leaves containing CTs >2.0% DM effectively reduced frothy foam and biofilm formation (P<0.01). Since these are indicators of bloat incidence, this development has the potential to enhance animal health in addition to reducing greenhouse gas emissions.