A study of the intake potential of a range of well-preserved silages offered to lambs over several years showed that, of the many parameters considered, those with the greatest positive effect on DM intake were sugars in the grass as ensiled, residual sugars and protein nitrogen in the silage, with ethanol concentration in the silage having a negative effect (Henderson, Anderson and Phillips, 1984). In the experiments reported here ADD-F (85 per cent formic acid) from BP Chemicals International was applied to ryegrass at a rate sufficient to conserve much of the sugar (WSC) in the silage by inhibiting the growth of the micro-organisms on the grass. The initial lowering of the pH should also inhibit the activity of the plant enzymes, conserve protein nitrogen (PN) in the silage and prevent extensive deamination.

In 1986 first-cut perennial ryegrass, and in 1987 Italian/perennial ryegrass, was ensiled direct-cut, untreated or treated with 5 1 ADD-F/t grass in 100t capacity clamp silos. The grass was cut with a mower and lifted with a precision-chop forage harvester. The acid was pumped onto the grass through a dribble bar sited over the pick-up drum.