Improving environmental benefits of white clover through condensed tannin expression

Abstract

Forage legumes improve both the intake and quality of the diet in pasture-based livestock systems. However, the high protein content of these forages can lead to inefficient nitrogen utilisation in the rumen and to high nitrogen (N) losses in urine and dung. Condensed tannins in forages have been shown to significantly reduce N leaching and also methane emissions. The use of classical breeding approaches over more than 50 years has failed to elevate condensed tannins in forage legumes. However, molecular biology approaches have achieved condensed tannin expression in white clover at levels that are biologically significant (>2% of dry matter). Results from a field trial in the USA showed that while condensed tannin levels in white clover (Trifolium repens) were similar to those produced by birdsfoot trefoil (Lotus corniculatus), plants did suffer a yield penalty. Protein binding assays were conducted by incubating soluble white clover leaf CTs in a solution containing the protein bovine serum albumin (BSA). The CTs in white clover leaves efficiently precipitated BSA from the supernatant at pH 6.5, and these CT-protein complexes dissociated at pH 2.5.While the use of genetically modified organisms in New Zealand is regulated, this development has the potential to improve environmental, animal health and animal productivity outcomes from grazed pasture systems.