19 July 2002

Check silage DM or risk a shortfall in the clamp

By Marianne Curtis

APPEARANCES can be deceptive when it comes to silage clamps.

Those taking late first cuts in wet conditions may find they have less than expected when the polythene is rolled back this winter, warns Promar senior dairy consultant Phil Clarke.

"When silage was cut, it looked as though there was plenty, so some eased fertiliser application for second cut. However, many silages are only 16-18% dry matter, lower than the 26-28% seen in some seasons."

It is vital to assess silage dry matter rather than simply how big the heap is, he advises. "Factors are available for different silage dry matter contents, which can be multiplied by volume of silage to work out supply. This should be checked against herd requirements."

Producers on mixed farms finding themselves with insufficient grass silage could make whole-crop over the next couple of weeks, suggests Mr Clarke. "Rather than selling cereals, whole-crop could provide a valuable supplementary forage."

Even producers with plenty of silage cut in late April/early May, when the weather was more favourable, may find it difficult to get enough into cows, according to analysis results released by Frank Wright (see table). Average dry matter for its first 600 samples is 28%, 3% lower than last year, says the companys ruminant manager David Wilde.

"Cows will need to eat more to consume the same potential nutrients. Animals which consumed 35kg a day last year will need to eat an additional 4kg a day – equal to 800kg of silage over a 200-day winter – to derive the same feed value.

"But with silages having poorer intake characteristics, it will take skill to keep animal intake levels the same."

But there are some positives in early silage results. Producers will find new Feed Into Milk analysis results on silage analysis sheets for the first time and these show cows will be able to make better use of protein in silages than last year, says Mr Wilde.

"While many farms had to feed a 20% protein concentrate last year, it should be possible to use one with an 18% protein content this winter. However, feeding more concentrates may be necessary to compensate for low dry matter silages."

Concentrate type is also an issue which could vary considerably from farm to farm depending on analysis results, warns Mr Clarke. "Farms with dry but later cut mature silage will be ideally placed to take advantage of relatively cheap wheat to boost diet energy levels.

"However, where silage is wet and acidic, feeding too much wheat could lead to acidosis, so sugar beet pulp is more appropriate. Sodium bicarbonate may also need to be used as a buffer in these situations."

The new rumen stability value (RSV) being used in FiM analysis will provide valuable information about how silage acidity and fibre levels affect cows digestive function, says Mr Wilde. "The lower the RSV, the worse the silage from a rumen function point of view. Weve seen a range of RSV values from 120 which shouldnt be fed to 400 which is great silage.

"With this years wet weather quite a few RSV values are low. Take notice of any silages analysing below 260. These silages will not necessarily be unpalatable, but rumen function will be impaired meaning cows miss out on energy and protein." Seek expert rationing advice where silage has a low RSV. &#42


Dry matter 28%

Crude protein 13.7%

D-Value 68.2

ME 10.9 MJ

Source: Frank Wright.

&#8226 Variable results.

&#8226 Check dry matter.

&#8226 Poor intakes possible.