Maxgrass is a silage additive consisting of a premixture of carboxylic acids containing ammonium hexamethanoate (68%) and ammonium hexapropanoate (10%). In theory, this additive when used on grass for ensiling at a high rate (6.0 1/t) should restrict fermentation, thereby reducing the level of VFA and lactic acid production and increasing the amount of residual WSC in the silage. It is claimed that silage with these characteristics should result in higher dry matter intakes and better animal performance. The objective of this experiment was to compare the performance of dairy cows fed either maxgrass or formic acid treated silages at two levels of concentrate supplementation.

Silage was harvested unwilted from a primary growth sward of perennial ryegrass on May 21 and 22, 1990. The additive treatments applied through the harvester were: (i) Maxgrass - 6 1/t grass and (ii) formic acid - 2 1/t grass. Cows calving between mid-September 1990 and early January 1991 were used to evaluate the silages.