A COMPARISON OF FORMIC-ACID AND AN ACID-SALT TYPE ADDITIVE ON THE PERFORMANCE OF DAIRY-COWS IN EARLY LACTATION

Perennial ryegrass, harvested as second-cut material on 10 and 11 July 1990, was treated with either formic acid at 31 t-1 or an acid-salt type additive at 61 t-1 and ensiled in roofed 150 t bunker silos. Subsequently both silages underwent a predominantly lactic fermentation. Nevertheless the acid-salt-treated silage had a significantly higher quantity of formic acid (19 vs 12 g kg DM-1) and significantly lower levels of lactic (98 vs 118 g kg DM-1) and acetic acid (11 vs 17 g kg DM-1) compared with formic acid-treated silage. In-silo losses and effluent production were similar. Each silage was individually fed to 10 October-calving Friesian dairy cows (average weight 565 kg) from weeks 2 to 15 of lactation, together with 3 kg d-1 of a compound feed containing 190 g kg DM-1 crude protein and with an estimated metabolizable energy content of 12.6 MJ kg DM-1. The acid-salt additive had no significant effect on silage DM intake, daily milk yield, milk protein or cow liveweight change, but significantly increased milk butterfat content compared with formic acid-treated silage. It is concluded that the acid-salt type additive produced little difference in terms of either silage fermentation or animal performance compared with formic acid treatment.