Formic acid as a silage additive

Abstract

SummaryPure swards of cocksfoot and perennial ryegrass cut on three occasions and of lucerne cut on two occasions were ensiled in test-tube silos after three treatments: (i) unwilted without additive, (ii) unwilted after the addition of formic acid at 0-23 % of fresh weight, and (iii) wilted to a water content of about 70 %, with no additive. Replicate silos were opened at intervals up to 105 days in order to follow the course of fermentation.Silages from the final sampling could be divided into two clearly defined groups. Those where the lactic acid content, expressed as a percentage of total fermentation acids (L %T), was over 60 (19 silages) were considered stable while those with a value less than 20 (5 silages) were considered unstable.The addition of formic acid resulted in a reduction in pH of the ensiled material from 5–86 + 0–12 to 4–60 ±0–11. This value changed little during the first 6 days after ensiling but then fell as lactic and acetic acids were formed. Stable silages made from unwilted crops without additive contained more lactic acid than those made with formic acid, but the converse was true for unstable silages. The ammonia content of silages made from unwilted material was always lower when formic acid had been applied. Wilting before ensiling gave stable silages from all crops.