Data from 21 experiments, conducted at ADAS Research Centres during 1971-1991, were used to compare grass silage harvested with either a flail-harvester, foragewagon, double-chop or precision-chop harvester. In 15 of the experiments, formic acid was applied at 2)7, 3)1, 2)1 and 2)1 l/t, respectively. The silages were made from herbage with an average dry matter of 210 g/kg and water-soluble carbohydrate of 25 g/kg.
Criteria have previously been established for seven chemical analyses that can be used to indicate whether or not silages are well fermented. Only two of these (pH and lactic acid) out of the seven were actually met with the precision-chop harvester and only one (acetic acid) was met by the flail-harvester and forage-wagon. None was satisfied by the double-chop machine, despite the fact that more formic acid was applied to the flail-harvester and particularly forage-wagon-made silages. The foragewagon-made silage also suffered from soil contamination.
When given to young cattle, precision-chop harvested silage resulted in the highest silage DM intake, liveweight gain and best feed conversion efficiency. Silage, made with a forage-wagon had a very low silage DM intake and liveweight gain, despite the fact that the amount of barley fed was twice as high as in the other treatments. With flail and double-chop harvested silage, both silage and total DM intake were similar. Nevertheless, liveweight gain was higher with the latter treatment. With dairy cows, the type of harvester used to make silage had no significant effect upon milk production, except that silage DM intake tended to be higher with the precisionchop harvested silage, whereas liveweight loss was significantly less with the flail harvested silage.