About 12-week-old napier grass Pennisetum purpureum Schumach) and 10-month-old Leucaena (Leucaena leucocephala (Lam.) de Wit.) both from a naturalized field and chopped to about 3.5 cm were used. The grass and legume were combined in a grass:legume ratio of 7:3. There were five treatments viz., napier grass (T1), leucaena (T2), napier grass-leucaena (T3), napier grass-leucaena with starch added (50 g starch/kg fresh mixed forage) (T4) and napier grass-leucaena with formic acid added (2.3 ml per kg fresh mixed forage) (T5). Each of the treatment sample was stuffed into a two-litre laboratory silo (1.4-1.5 kg sample) and stored for 42 days. Samples were taken at the time of silo filling and after ensiling and analyzed for total nitrogen (T-N), volatile basic nitrogen (VBN) as per cent of total N, neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, acid detergent lignin (ADL) and in vitro dry matter digestibility (IVDMD). Napier grass (T1) had significantly lower (P