17 November 1995

Heat is on in clamps as dry matter disappears

By Jessica Buss

DRY matter losses are occurring from aerobic spoilage in some maize and whole-crop forage clamps.

Evidence comes from Wolverhampton-based independent nutrition consultant Stuart Jones who has been measuring the temperature of open silage clamps.

He cautions that ensiled material is particularly prone to spoilage this year because much was harvested at high dry matters making it more difficult to consolidate in the clamp.

"Unless chop length was good and short, under such conditions consolidation would have been difficult," he says.

Poor consolidation allows air to penetrate back through the face faster once it is opened, causing spoilage (see p40).

Mr Jones uses a 60cm (2ft) temperature probe to measure heat behind the open clamp face.

He claims that when the silage temperature is more than 5C (10F) above the ambient temperature DM losses are significant.

This year Mr Jones has recorded three clamps with temperatures of 50C (122F) behind the face (warmer than bath-water). Three other clamps have also shown readings over 5C (10F) above ambient temperature.

"One of these farms was cutting back 2ft blocks and going across the face once every five days as the clamp was 15m wide," he says. "This should have been enough to prevent heating because more than the conventional six inches a day was being used. But the silage was still heating up.

"On the shoulders and upper layers it was very hot – the highest temperature was 55C; in the middle of the clamp 5cm behind the face it was 30-32C; 35cm behind the face it was 48C and 60cm behind the face it was 40C." Air was drawn in through the face, activating yeasts and producing heat before silage could be used.

"The only solution in this case was to spray the newly exposed surface with a propionic acid additive every day."

This helped reduce spoilage although there was still some heating."

Mr Jones also advises increasing the amount fed to stock, when this can be done without affecting animal performance, so that the clamp can be used more quickly, he adds.

Nutrition consultant Stuart Jones uses a 60cm (2ft) temperature probe to measure heat behind the open clamp face. When silage temperature is more than 5C(10F) above ambient, DMlosses will be significant, he says. For advice on how to avoid waste through spoilage, see p40.