25 July 1997

Variable silages show potentialwinter savings

By Jonathan Riley and Jessica Buss

ANALYSIS of first-cut silage has shown varying quality caused by worsening weather during cutting and highlighted areas where careful feed management will be needed this winter.

Genus Management nutrition consultant Andrew Marlow says the first 150 silages analysed are of high quality, reflecting the sunny weather early in the season, and could enable producers to reduce concentrates next winter.

"Sugars average 3.16% compared with 1.85% last year. This years sugar levels indicate high sugar contents in the sward or that fermentation is not extensive and should lead to silages with high intake potential," he says.

Total acids average 13g/kg lower this year, at 97g/kg, with a good lactic to acetic acid ratio indicating a good fermentation.

"With these silages dairy cows could produce 12 litres a day from forage alone enabling large reductions in concentrate feed to be made. For example when a cow averages 8 litres a day from forage, savings of 2kg a head of concentrate a day – worth £50 a cow – could be made," claims Mr Marlow.

But most of these high quality samples are likely to come from silage cut during dry weather in May, he warns.

ADAS has analysed 600 samples, according to senior nutritionist Bruce Cottrill, who is concerned about aerobic stability.

"Earliest cuts had high dry matters of 29% with high sugar levels. But not all of that sugar has been fermented to acid, needed to preserve the silages feed value."

This is supported by the relatively high average pH figures at 4.2 in ADAS samples. This shows that fermentation is not extensive, with ammonia nitrogen at 7.9%. Fermentation acids are also low at 80-85g/kg when these would typically average 110-120g/kg with a 22% dry matter silage, he adds.

Higher dry matter silages on some farms – where fermentation is less extensive – may still have fermentable material and open clamps will be prone to spoilage if not managed carefully.

He suggests using a block cutter when possible to keep clamp faces tidy and reduce air penetration.

Commenting on nearly 1500 silage sample analyses, BOCM Pauls national ruminant adviser, Bruce Woodacre, agrees that the first samples through had excellent quality. But as cutting progressed and wetter, colder weather predominated so quality began to fall.

Sugar levels dropped from 3% down to 1% and dry matter levels fell from 32% to 20% with a reduction in effective fermentable energy from 8.3 to 7.7MJ/kg DM.

"This figure is still better than last year, but represents an average buoyed up by the excellent quality of the earlier samples," says Mr Woodacre.

But even for some of the later first-cuts compound feeds could be reduced next winter if the compound has enough fermentable energy to help stock break down the poorer quality material.n