One of the main problem of preserving forages by ensiling is the high proportion of non-protein N of the silage as a consequence of the proteolitic action of plant enzymes and the consequent poor utilization of N by the ruminant.

Several procedures have been developed with the aim of reduce this protein breakdown but these methods could reduce the ammount of N available for tie rumen microbes and the N digestibility in the post-runinal tract. This study was set up to determine the rumen degradation characteristics of silages treated wit different additives.

Three silages were lade from the 3rd cut of a grass-legune mixture sward in 1 t capacity silos. The herbages were treated with either no additive (C), formic acid (4 1 of a solution of 85% foric acid/t of grass) (F) or fonaldehyde (4.9 g fonaldehyde/100 g grass CP) (FA).