17 May 2002

Delayed cut hits silage quality

By Robert Davies

SILAGE quality can be badly reduced when cutting is delayed by as little as a week to harvest more bulk.

"You may get an extra 0.5t/ha of dry matter, but D-value could fall by three units and crude protein by 2%," researcher Chris Duller told milk producers at an Institute of Grassland and Environmental Research open day at Trawsgoed, Aberystwyth.

Going for a heavy cut could also delay regrowth and reduce sward density. To strike the correct balance between yield and quality, grass should be cut before 50% of plants had headed, giving silage with a D-value of about 67, he said.

The heading date of varieties included in seeds mixtures should match likely conservation date. It was not good enough to accept a general description such as intermediate, because among the most popular intermediate varieties there was a 17-day spread of flowering dates.

While it was important to make as much silage as stock needed, making too much was an expensive exercise, he added.

Dave Davies said the aim should be to preserve nutrients present in fresh herbage especially true protein. A good additive could make a difference by increasing the speed of acidification.

Work at IGER showed that only 51% of protein in grass was preserved when it was ensiled without an additive, while 67% remained in silage made using a live bacterial inoculant.

Dr Davies reported that five years research had isolated a lactic acid bacterium which could degrade fructan, the most important but most difficult to degrade grass sugar.

The long-chain sugar could make up 80% of the water soluble carbohydrates in ryegrass, so it was important to have a lactobacillus strain which could use it to optimise speed of fermentation.

The Aber F1 strain, being marketed as Powerstart through Genus, may also have benefits for ensiling of whole-crop cereals, in which much of the sugar is in the form of fructan, he added. &#42

Waiting to cut silage will delay regrowth, warns Chris Duller.

&#8226 Avoid delaying cut.

&#8226 Quality declines rapidly.

&#8226 Save protein with additive.