Formic acid as a silage additive for wet crops of cocksfoot and lucerne

SummaryCrops of lucerne and cocksfoot of high moisture content were ensiled without additive and with the addition of formic acid at up to 0·91% of the fresh crop weight in test-tube silos and in silos containing about one tonne of crop. Silages from the larger silos were fed to sheep for measurement of voluntary intake and digestibility.Silages made without formic acid were badly preserved and contained large quantities of acetic acid, butyric acid and ammonia. The addition of formic acid reduced the production of acids and ammonia. With test-tube silos differences between the minimum pH measured during the storage period and the final pH after 155 days were not significant for silages made from both crops with addition of 0·45% or more of formic acid: these silages were considered to be stable.Silages from the larger silos were generally not as well preserved as those from the test-tube silos, particularly at the higher levels of formic acid application. This difference was attributed to less effective application of additive to the larger silos and loss of formic acid in the effluent which was released from these silos but not from the test-tubes. Organic matter intake increased with increase in formic acid level, but organic matter digestibility was not significantly correlated with formic acid levels. Intake was closely related to the quantity of ammonia in the silage and it is argued that formic acid affected intake by influencing the pattern of fermentation in the silo rather than by a direct effect of formic acid itself.