8 March 2002

Two-edged sword warning

USING silage inoculant can be a double-edged sword, warn French researchers who have discovered that lactic acid needed for silage fermentation could also suppress animal performance.

Frederique Chaucheyras-Durand, of Lallemand, says there are two common sources of lactic acid – preserved forage and as a by-product of rumen fermentation.

"We have identified two isomers or types of lactic acid. The L (+) isomer is thought to be more easily used by microbes in the rumen than the D (-) isomer. This can cause the accumulation of D (-) isomer in blood and tissue cells, leading to acidosis."

Research shows the different types of lactic acid are not produced in the same quantity. And equally of concern, if rumen conditions fall below pH6, the activity of microbes using the D (-) lactate falls.

"Lactic acid bacteria have proven their ability in rapidly lowering pH in the silo. This can help control the development of undesirable bacteria, such as listeria and also help make silage stable.

"Researchers are looking at different strains of bacteria which have characteristics to improve silage quality and produce less of the D (-) isomer," she says. &#42

lConference report continues on p49.