15 June 2010AgResearch scientists and the team from subsidiary company, Grasslanz Technology Ltd, believe they can improve white clover (Trifolium repens) to give grazing animals a higher intake of protein, while at the same time reducing methane emissions. In addition, the genetic breakthrough could improve animal health and reduce nitrogen waste, all issues important for sustainable farming.
The key is to develop white clover that contains beneficial concentrations of ‘condensed tannins’ in their leaves. Condensed tannins are a complex group of chemical compounds that are able to bind to and protect protein from breakdown in the stomach of sheep, cattle and other ruminants. However, they exist only in trace amounts in forage plants such as white clover and are entirely absent in grasses. There are some naturally occurring forage legumes that contain significant levels of tannins, but they are not suitable for pasture as they are difficult to establish and manage and do not persist under grazing conditions.
There are over 250 different types of clover, but only two are known to accumulate high levels of condensed tannins in their leaves. By using genetic techniques as a research tool, AgResearch scientists have compared these two to white clover and uncovered a pivotal gene that increases levels of condensed tannins in white clover leaves. A related tannin gene was then located in white clover itself, although this native gene at present remains switched off. Understanding how the ‘switches’ work may result in clovers which have not been genetically modified but have a reactivated tannin gene. The technology has significant value for New Zealand but in the current regulatory environment some of the work will continue with partners offshore.
Dr Jimmy Suttie, AgResearch’s Science & Technology General Manager, Applied Biotechnologies Group says that, if realised, this huge breakthrough will benefit the environment, farmers and industry. “Currently white clover contains extremely low levels of tannins found only in the flowers, and if we can alter this to allow condensed tannins to accumulate to effective levels in leaves then we’ll have a major benefit.
“There is evidence that tannins can reduce methane emissions from ruminants, and this increases the importance of our work,” says Dr Suttie.
Another benefit may be reducing bloat in animals eating clover rich pastures. Bloat is caused by retention of gas in the stomach, which can lead to the death of the animal and is common particularly in spring when pasture growth is rapid.
The work on the genetics of tannin production in clovers has been taking place for a number of years but is now at a point where there is progress to report.