22 June 2001

High sugar grass faces clamp test

HIGH sugar experimental grass retains much of its sugar content when ensiled, which should improve rumen efficiency when fed to stock. But when ensiled with red clover, more research is needed to assess the effect of its sugar content on clover protein levels.

The Institute for Grassland and Environmental Research made high sugar silage using 1kg jars as mini-silos, are designed to replicate what occurs in silage clamps.

Compared with Aberelan, a variety currently on the market, preliminary results show silage made from IGERs experimental grass retains much more sugar, says senior research scientist David Davies.

At the time of ensiling, sugar content of the experimental grass is higher than when grazed – 6.3% fresh matter for the IGER variety and 2.8% for Aberelan. After ensiling, the high sugar silage retained 5% DM of sugar, compared with 1% DM for Aberelan.

This sugar content is beneficial for additional milk production and the environment, says Dr Davies. "Retaining more sugar after rapid ensiling will mop up rapidly digested nitrogen in the rumen, making microbial protein production more efficient. This could reduce concentrate use – improving dairy unit profits and lower nitrogen losses to the environment."

However, high sugar silage may be aerobically unstable when being fed because it provides an energy source for moulds and yeasts, warns Dr Davies.

Red clover was added to the equation to boost silage protein levels. Results showed this silage retained sugar, but at a lower level than when ensiled on its own. Compared with Aberelan, it also helped to preserve clover protein.

"Red clover is difficult to ensile on its own as it contains little sugar for rapid fermentation. By adding sugar, red clover is preserved more quickly as pH is lowered faster. However, further research is needed to establish whether faster fermentation affects red clovers feed value.

"Is it better to ensile grass and clover together or feed them separately?" he asks.

Research also looked at additive treatments and their effect on retained sugar and protein in silage.

The high sugar grass consistently produced higher levels of sugar content in the end silage than Aberelan. But, although formic acid best preserves sugar content, it did not protect protein fraction in silage as effectively as inoculant. &#42