Fifty-two-day-old guinea grass (Panicum maximum var. maximum cv. Gatton) which received 150 kg N per hectare and 10-month-old leucaena (Leucaena leucocephala (Lam.) De Wit.) were used. There were five treatments viz., guinea grass (T1), leucaena (T2), guinea grass-leucaena (T3), guinea grass-leucaena with starch (T4) and guinea grass-leucaena with formic acid (T5). Both guinea grass and leucaena were mixed in a grass:legume ratio of 7:3 in T3, T4 and T5. Samples were stuffed into laboratory silo (1.4-1.5 kg sample) and stored for 42 days. Samples were taken at and after ensiling and analysed for total nitrogen, volatile basic nitrogen as per cent of total N, pH, lactic acid, acetic acid, butyric acid, neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, acid detergent lignin (ADL) and in vitro dry matter digestibility (IVDMD). Guinea grass had significantly lower (P